13 Congenital Neck Masses (Non-vascular)A.W.DuNCAN

CONTENTS

13.1 Introduction 17513.2 Imaging Investigations 17613.3 Lymphangioma 17713.3.1 Embryology of the Lymphatic system 17713.3.2 Types of Lymphangioma 17713.4 Thyroglossal Duct Cyst 18113.5 Thornwaldt's Cyst 18313.6 Branchial Cleft Anomalies 18313.7 Piriform Sinus Fistula (Abscess) 18513.8 Thymic Cyst 18613.9 Cervical Extension of the Mediastinal Thymus 18713.10 Dermoid/Epidermoid Cyst 18713.11 "Plunging" Ranula 18813.12 Ectopic Thyroid Gland 18813.13 Sternomastoid "Tumour" 190

13.14 Congenital Teratoma 19113.15 Cervical Neuroblastoma 19213.16 Laryngocele 19313.17 Lung Herniation 19313.18 Thyroid Gland Hemiagenesis 19413.19 Midline Cervical Cleft 19413.20 Bronchogenic Cyst 19513.21 Lingual Thyroid Gland 19513.22 Congenital Vascular Lesions 19513.22.1 Haemangioma 19513.22.2 Varix of the Jugular Vein 19513.22.3 Carotid Artery Aneurysm 19513.22.4 Cervical Aortic Arch 19613.23 Rare Congenital Tumours, Cysts and Infections 19613.24 Summary 196

References 196

13.1Introduction

Neck masses are common in the paediatric age group.Most are congenital or inflammatory in origin, theremaining are vascular or, rarely, malignant lesions.The site and age at presentation can strongly aid diag-

A.W.DuNCANConsultant Paediatric Radiologist, Senior Clinical Lecturer inPaediatric Radiology, University of Bristol, Bristol Royal Hos­pital for Children, Paul O'Gorman Building, Upper MaudlinStreet, Bristol, BS2 8BJ, UK

nosis. Malignant lesions are rarely present at birth,although occasionally cervical neuroblastoma maypresent at this time. Most congenital masses presentin infancy and early childhood. They may presentbecause they have become infected. The site alonecan indicate the probable diagnosis. As a general rule,most midline lesions are benign. The site is deter­mined by the embryology, and even a limited knowl­edge of the embryology helps to determine the prob­able diagnosis. Branchial abnormalities develop frompaired branchial arches, and therefore lie laterally,usually in relation to the anterior border of the ster­nomastoid muscle. Piriform sinus fistula, which maydevelop into an abscess, is a paired structure andtherefore lies laterally. Similarly the rare lung hernia­tion, bronchogenic cyst, sternomastoid tumour andcongenital sympathetic chain neuroblastoma, arisefrom paired structures and will lie laterally. The thy­roid gland, although lying more medial than theabove structures, is a paired structure and a lesionarising from one lobe will lie lateral to the midline.The embryology of a central structure such as thethymus and thyroid, which descend into the neck,results in pathology along the midline track. Der­moid cysts can lie anywhere, but usually those inthe central nervous system and in the neck are mid­line. Fig. 13.1 shows the locations of these congenitalanomalies.

The presentation of the lesion is also an aid to thediagnosis. Many congenital lesions will present in thenewborn period or early years, although some havea delayed appearance, becoming symptomatic dueto enlargement or infection. Inflammatory lesionsrarely present at birth but develop in early childhood,and some of them may be secondarily infected con­genital lesions. Malignant lesions are extremely rarein the neck at birth and usually present in older chil­dren and adolescents. Inflammatory lesions tend tobe painful and tender with erythema, whereas malig­nant lesions tend to be painless solid masses.

Masses that present in older children can oftenbe differentiated on the basis of the history, withcongenital masses being present for a considerable

S. J. King et al. (eds.), Pediatric ENT Radiology© Springer-Verlag Berlin Heidelberg 2003

176

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Fig. 13.1. The anatomical sites of congenitalneck masses

period, inflammatory masses for a few days, and neo­plastic lesions for a few months.

The most common neck mass in a young child islymphatic malformation or cystic hygroma.

13.2Imaging Investigations

A tentative diagnosis can be made with a fair degreeof accuracy on the basis of history and clinical exami­nation, but the imaging investigations add confir­matory evidence and also avoid potentially seriouserrors such as removal of the patient's only thyroidtissue in an ectopic thyroid gland.

The first line of investigation is usually ultraso­nography, which can differentiate cystic from solidmasses and is invaluable since most congenitaland inflammatory lesions have a cystic component(TELANDER and FILSTON 1992). It can also showthe extent of the lesion if small, but larger lesionsare better evaluated by magnetic resonance imaging(MRI). Calcifications and bone erosion can be betteridentified by plain films or computed tomography(CT), but these are rarely of any clinical value, whileboth CT and plain radiography add less in termsof spatial relationships than MRI and also irradiatethe child. However, if MRI is not available then CTcan show the lesion. Contrast enhancement is usuallyonly necessary in CT for showing the vessels, as most

congenital lesions will show very little enhancementunless there is infection; in the latter case there will beenhancement of the capsule or surrounding tissues.In general terms, for MRI, T1 weighting gives goodspatial relationships and T2 will show any oedema.STIR sequences with fat suppression show oedemato greater advantage, but will also confirm the fat­containing structures seen in teratomas. Contrastenhancement is usually not necessary. Coronal andaxial scans will show most lesions, although midlinelesions are better seen with the sagittal sections.Cystic lesions usually have a low signal on T1 and ahigh signal on T2 consistent with fluid, although thismay be modified if there has been haemorrhage. Thewall of the cyst and surrounding tissue is usually oflow signal on T2 but can be high if there is inflam­mation, and may at times be difficult to differentiatefrom a neoplastic lesion.

Occasionally it may be necessary to perform con­trast studies if there is encroachment on the alimen­tary tract causing dysphagia or there are lesions asso­ciated with a sinus tract. Lesions associated with apercutaneous tract ending blindly can be shown bywater-soluble contrast, but it is usually consideredmeddlesome to do this as it has the potential forintroducing infection.

In most cases small lesions can be adequatelyassessed by ultrasound. They are described below inrelative descending frequency which will vary withage of the child.

Congenital Neck Masses (Non-vascular)

13.3Lymphangioma

These are congenital lymphatic malformations (LM's),usually of a localised nature, and involve dilated lym­phatic spaces. They can occur anywhere in the bodybut are most common in the head, neck and axilla.LM's can be characterized by the size of the cysts pres­ent into microcystic, macrocystic or mixed lesions(MULLIKEN et al. 2000). Conventionally LM's havebeen subdivided into 1) cystic hygroma, 2) cavernouslymphangioma, 3) capillary lymphangioma, 4) vascu­lolymphatic lymphangiohaemangioma and they willbe discussed under these subheadings.

Most lymphangiomas present at birth, and 90%within the first 2 years oflife. 75% oflymphangiomasoccur in the neck, most commonly in the posteriortriangle, sometimes with extension into the medias­tinum. Presentation at birth is most commonly as anasymptomatic mass, although if it is large in size itmay cause respiratory difficulty due to compressionof the airway. The morbidity or mortality attachedto lymphatic malformations, unless they are associ­ated with chromosomal abnormalities such as Turn­er's syndrome and fetal hydrops, is low.

13.3.1Embryology of the Lymphatic System

To understand the types of lymphangioma, a reviewof the theories behind the embryology is helpful. Fol­lowing arterial and venous development in the jugu­lar region there are endothelial buds which sproutfrom the veins and unite to form plexuses. Thesedevelop into paired jugular sacs. Later the jugularsacs enlarge and maintain a single communicationwith the internal jugular vein.

There is continued growth with extensions intothe soft tissues and between muscles, to the poste­rior compartment of the neck, and other extensionsbetween the structures of the neck. This sproutingcontinues, ultimately forming lymph vessels perme­ating all the tissues, following the blood vessels andtheir branchings.

There are various theories of the pathogenesis oflymphangioma. These include failure of the lym­phatics to drain into the veins results in isolated lym­phatic channels, particularly the larger and more cen­tral cystic hygromas (WEINGAST 1988). Other authorsfavour sequestration of the lymphatic tissue early inembryogenesis with a failure to join the normal centrallymphatics (PHILIPS 1981). This explains the periph-

177

eral location of capillary or cavernous lymphangio­mas. The small lymphatic channels are presumablyrelated to their primordium at which sequestrationoccurs, which results in a fine network of lymphatics.

Yet another theory postulates abnormal buddingof lymphatic structures. These aberrant buds losetheir connections with the lymphatic primordia andeventually canalise to form lymphatic cysts (LEE1980). These cysts can grow in an uncontrolled, disor­derly manner and can penetrate and destroy anatom­ical structures. This helps to explain the permeativenature of many lymphatic malformations, particu­larly of the cavernous lymphangiomas. The aberrantprimary bud may explain the formation of the moredilated cystic hygromas near the primordial lymphsac (ZADVINSKIS et al. 1992).

Athough theories of pathogenesis related to theembryologycan explain some of the appearances, someauthors feel that many of the appearances are relatedto the anatomical location which determines the histo­logical characteristics. Where there is loose fatty tissuesuch as in the neck, growth is unimpeded, leading to theformation of a macrocystic LM or cystic hygroma. Inother locations such as the cheek or tongue, expansionis curtailed, resulting in a mixed lesion.Where the tissueis much tougher, such as in the epidermis and dermis,the malformation is smaller and results in the forma­tion of a microcystic LM (BILL and SUMNER 1965).

13.3.2Types of Lymphangioma

13.3.2.1Cystic Hygroma

Cystic hygroma is the most common form of LM and isusually macrocystic. It usually occurs in isolation, butit may occur with more generalised abnormalities suchas Turner's syndrome (45 XO chromosome karyotype).These are frequently seen in aborted fetuses and arebelieved to form as a result of failure of the juguloaxil­lary lymphatic sac to drain into the internal jugularvein (SMITH 1982). The accumulation of fluid causesprogressive dilatation of the lymphatics, resulting ina cystic hygroma. There is secondary dilatation ofthe lymphatic channels that drain the extremitiesand chest, resulting in peripheral lymphoedema andhydrops. If lymphatic drainage is re-established, thecystic hygroma may regress and result in the typicalneck webbing seen in Turner's syndrome (SMITH 1982).Whatever the true embryology of these malformations,in all instances obstruction is a feature (Fig. 13.2).

178 A.W. Duncan

Fetal cystic hygroma

Generalised lymphaticdefect

Localised lymphaticdefect

Progression

Severe Mild

No hydrops

Resolution

difficulty. Extension of such lesions into the thoracicinlet may result in stridor, cyanosis or apnoea whenimpinging on the trachea, or dysphagia when imping­ing on the oesophagus or tongue.

Plain radiographs of the neck and chest may showextension into the mediastinum and displacement andcompression of the airways. Ultrasonography is theeasiest non-invasive investigation and is usually thefirst line of study; it will demonstrate multiple septatedcystic spaces filled with hypoechoic fluid (Fig. 13.3a).These may be infiltrative, making it difficult to dis­tinguish them from adjacent tissue. If complicatedby haemorrhage into the cystic structures, the fluidbecomes echogenic (Fig. 13.3b) and may result in

Fig. 13.2. Course of fetal cystic hygroma. (Reproduced withpermission from ZADVINSKIS et al. 1992)

The solitary cystic hygroma is the most commonpresentation, resulting from failure of re-anastomosisand failure ofthe lymphatic system to drain. This resultsin multilocular cystic malformations which occur inapproximately 1in 12,000 births (STRINGEL 1993). Theyhave a predilection for the left side of the neck, mostprobably because the thoracic duct enters the subcla­vian vein on that side. They are lined by endothelialcells and produce lymphatic fluid. This results in a grad­ual but sometimes rapid enlargement with compres­sion and stretching of the adjacent structures. Eightypercent of cystic hygromas occur in the neck.

Most cystic hygromas (75%-80%) are present atbirth, 90% by the age of 2 years (TELANDER andFILSTON 1992) and 3%-10% extend into the mediasti­num (Castellote et al. 1999). They are usually discrete,soft, mobile, painless, non-tender, cystic masses, usu­ally in the posterior triangle of the neck, and varyin size up to several centimetres in diameter. As theycontain fluid they transluminate. Primarily they arepainless, but one-third present with infection and mayshow clinical features of erythema or tenderness. Theymay rapidly grow in size as a result of this infectionor haemorrhage into the cyst with or without trauma.Lymphangiomas located in the floor of the mouthand tongue are especially prone to bleed, leading toenlargement and airway compression (VAZQUEZ et al.1995). Unless complicated, they are often asymptom­atic, but because of their large size they may causecompression of the airways and result in respiratory

a

b

Fig. 13.3a,b. Cystic hygroma. a Ultrasonogram of a small cystichygroma where there are multiple small cysts all of which arehypoechoic, indicating there has been no haemorrhage. Thesmaller cysts tend not to have any haemorrhage and are there­fore hypoechoic. b Ultrasound shows large cysts, which arehypoechoic, containing fluid. Others are hyperechoic, showingtheir proteinaceous nature, which is most likely due to somehaemorrhage into the cyst

Webbed neckPeripheral oedemaAbnormal

lymphangiogram

Isolated cystichygroma

a

b

Congenital Neck Masses (Non-vascular)

fluid levels. Where the haemorrhage is mixed withthe fluid uniformly, the cystic spaces may simulate asolid structure due to the echogenic nature of the fluid(Fig. 13.3b), although the movement of the echogenicmaterial under transducer pressure usually identifiesareas of haemorrhage. A larger lesion will be betterdemonstrated by CT or MRI (Fig. 13.4); MRI is theinvestigation of choice (Fig. 13.5) since it can evaluatethe extent of the lesion and, particularly, its extensioninternally into the vital structures (Fig. 13.6) and downinto the mediastinum. A low signal on II-weightingand a high signal on TZ-weighting will indicate fluidcontent. It may show fluid layering due to haemor­rhage. Intravenous contrast medium will demonstrateits relationship to the vessels, however it is usuallyunnecessary to give contrast medium. In CT and MRIcontrast-enhanced scans may show enhancement ofthe septa (Fig. 13.4). MRI, because of its multi-planarnature, can best show the structure and may showassociated venous anomalies (DALLEY 1996). Haemor­rhage into the lymphangioma may cause acute presen-

179

b

Fig.l3.5a,b. Cystic hygroma. a CT scan shows a massive lymph­angioma involving both sides of the neck. The hypodenseareas are due to fluid-filled cystic spaces. The more solidelements could be residual normal tissue or microcysticlymphangiomatous component of the lymphangioma. b Samepatient. Sagittal section II-weighted MRI shows the lymph­angioma much better, demonstrating extension to the floor ofthe mouth. The brighter signal in the lower portion may wellrepresent small areas of haemorrhage

..Fig. l3Aa, b. Cystic hygroma. a CT with contrast shows a cystichygroma in the neck displacing the oropharynx. It has mul­tiple enhancing septa. It is of uniform low attenuation, indicat­ing fluid. b Coronal T2-weighted MRI shows the septa wellwithout contrast medium

a

180

Fig. 13.6. Cystic hygroma. T2-weighted MRI shows the moreinfiltrative nature of some cystic hygromas, with medial exten­sion into the posterior pharyngeal space

Fig. 13.7a, b. Cystic hygroma with recent haemorrhage. a Plainfilm shows the massive prevertebral soft tissue opacity dis­placing the airway forwards. b Same patient. CT scan showsthe massive cystic hygroma displacing the airway forwardsand to the left side. The central area of increased density prob­ably represents haemorrhage, with some fluid levels of bloodand clear fluid of the cystic hygroma

tation due to its sudden increase in size with associ­ated respiratory difficulties (Fig. 13.7).

Although spontaneous regression can occur, itonly occurs in 6% of cases (CASTELLOTE et a1. 1999).Aspiration alone is often unproductive as re-accu­mulation of fluid occurs, but there has been somesuccess with various sclerosing agents with complexcystic hygromas that cannot be completely surgicallyexcised.

A full account of the imaging and treatment ofLM's is given in Chap. 20.

13.3.2.2 Cavernous Lymphangioma

Cavernous lymphangioma is composed of mildlydilated cavernous lymphatic spaces that are muchsmaller than the cystic hygroma and are usually sub­cutaneous in location. They occur in the tongue andsalivary glands. They penetrate between structuresrather than destroying them. They therefore haveless clear-cut margins than cystic hygroma. As theyarise in more solid structures which give resistanceto growth, they tend to be permeative and smaller.

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They have a low signal on Tl-weighted MRI and ahigh signal on T2-weighted scans.

13.3.2.3 Capillary Lymphangioma

Capillary lymphangioma is not only the leastcommon form of lymphangioma and not commonlyseen in the neck, but it is also uncommon in children.Up to 25% of these lesions are first seen in patientsover 45 years old.

13.3.2.4 Lymphangiohaemangiomas

Lymphangiohaemangiomas are part of a vascularlymphatic malformation, probably form from anembryologically abnormal bud and retain their origi­nal venous communication.

Ultrasound may show multiple high echoes fromthe walls of these small cysts. There may be largervessels passing through the mass on its periphery,which on Doppler imaging can often show bloodflow. This, however, depends on the amount of thehaemangioma component and the degree of flow. The

a

b

Congenital Neck Masses (Non-vascular)

investigation of choice is MRI, which can demon­strate the mass - usually high signal on T2-weightedscans - but without the large cystic spaces. If MRI isnot available then CT scans will show a low-attenua­tion mass between vessels, and the vascular areas willenhance with contrast medium.

13.4Thyroglossal Duct Cyst

These occur most commonly in the region of the hyoidbone and are the most common midline lesion of theneck in children, accounting for 70% of all congenitalneck lesions (SANTIAGO et al. 1985). They are rarelynoted at birth, but usually present in the first 5 yearsof life, often with infection at between 2 and 10 years.A third of patients present at over 20 years of age(BROWN and AZIZKHAN 1998). Infection is commondue to communication with the base of tongue andconsequent exposure to oral bacteria. Embryologicallythey form from a persistence of the thyroglossal duct,a remnant of which is seen in 7% of the population(EWING et al. 1999). The thyroid gland forms as adiverticulum from the anterior wall of the pharynx,later identified by the foramen caecum in the poste­rior tongue. This diverticulum descends, reaching itsnormal position anterior to the trachea. During itsdescent there is a connection by the thyroglossal ductto the tongue, which ultimately disappears.

The hyoid bone develops simultaneously from thesecond branchial arch and thus this duct, after passingthrough the tongue, maintains an intimate relation­ship with the central portion of the hyoid bone to con­nect with the thyroid gland (ELLIS and VAN NOSTRAND1977). This probably explains the common occurrenceof the thyroglossal duct cyst at the hyoid bone.

Persistence of the thyroglossal duct may occurand, if segments of this duct fail to regress, maydifferentiate into epithelial blind cysts (NOUJAIM etal. 1997). When the epithelial cells cease to remaininactive, secretions are produced and form enlargingcysts (TODD 1993). More than 50% contain normalthyroid tissue in their walls, which may be func­tional (OKSTAD et al. 1986). A thyroglossal cyst canlie anywhere from the foramen caecum to the normalthyroid position suprasternally (WADSWORTH andSIEGEL 1994). The cysts lie in the midline, 80% at orjust below the hyoid bone. Some reports suggest over95% split equally at or below the hyoid bone (AHUJAet al. 2000a). Occasionally they may be slightly lat­eral to the midline. There is usually no external open-

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ing unless there is infection resulting in spontaneousdrainage, which helps to differentiate it from bran­chial cleft cyst (MICKEL and CALCETERRA 1983). Ifthe tongue is protruded, the cyst moves cephaladbecause of its connection with the base of the tongue.The cyst itself is lined by epithelium and containscolourless, viscous secretion.

Occasionally thyroglossal cysts lie in unusual sit­uations, 3% being sublingual and 10% suprasternal(ROWE 1995). They are usually soft, smooth and non­tender although they will become warm, tender, pain­ful and oedematous if infected, and may well have afistula draining externally.

The typical ultrasonographic appearance was orig­inally described as an anechoic,well-defined cyst withincreased acoustic through-transmission, between 5mm and 25 mm in diameter, sometimes with a smallbeak at the attachment to the thyroglossal duct (Fig.13.8). Most lesions have thin walls, they are usuallyunilocular. The cyst fluid is usually described asanechoic, but more recent studies suggest that fre­quently it is hyperechoic, probably due to protein­aceous material secreted by the wall lining (WAD­SWORTH and SIEGEL 1994). In a more recent studyanechoic lesions were uncommon (13%), complexheterogeneous echo patterns were more frequent(30%), and a uniform homogeneous pseudo-solidappearance was the most common (AHUJA et al.2000a). The last appearance, however, can be clarifiedby applying pressure to the transducer, which willdisturb the proteinaceous contents of the fluid, pro­ducing echoes which move, showing the true cysticnature of the structure (AHUJA et al. 2000A). Thecomplex heterogeneous internal echogenic appear­ance is caused by debris and septa. Posterior enhance­ment, which occurs in cystic lesions, only occurs in

Fig. 13.8. Thyroglossal duct cyst. Ultrasound shows the typi­cal hypoechoic fluid in the cyst, with a small beak (arrows)representing the thyroglossal duct pointing cephalad

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approximately half of the cases, and is less likely tobe seen in the pseudo-solid type. Most lesions areunilocular with thin walls, but some are thick-walledwith internal debris due to inflammation. Although itis uncommon, about 1% of duct cysts may be malig­nant (WEISS and ORLICH 1991), and therefore thepresence of a true solid component in the cyst sug­gests the possibility of malignant degeneration intocarcinoma, usually a papillary carcinoma (HAYES andMARLOW 1968) - although this is very rare in chil­dren (DAVIES and CYCOES 1977).

Ultrasound should also show the presence of anormal thyroid gland.

MRI is usually unnecessary but clearly shows thelesion with low signal on Tl-weighted scans (Fig.13.9a) and high signal with T2 weighting due to thefluid within the cyst, with the sagittal sections show­ing the superior extent of the thyroglossal duct (Fig.13.9b). If MRI is not available, CT shows the lesion,which occasionally can be very large (Fig. 13.10).

The clinical differential diagnosis includes ecto­pic thyroid tissue, dermoid cyst, sebaceous cyst, sub­mentallymphoiditis, cystic hygroma, haemangioma,lipoma and, exceedingly rarely, neoplasm. Lingualand sublingual thyroid may simulate thyroglossalduct cyst, and inadvertent removal of the only thy­roid tissue will produce hypothyroidism.

Ultrasound will differentiate solid from cysticstructures and therefore exclude ectopic thyroidtissue, dermoid cyst and sebaceous cyst. Lipomashave a feathery pattern with multiple bright echoesat right angles to the transducer surface (AHUJA et al.1998). Cystic hygromas have multiple cystic spaces.They also tend to lie more laterally. Off-midline thy­roglossal duct cysts may clinically be mistaken forbranchial cleft cysts, and may be a problem as thesetwo entities show similar sonographic appearances

A. W.Duncan

(AHUJA et al. 2000b). Lymphadenopathy is usuallyeasy to differentiate, being hypoechoic with echo­genic hila and vascular malformations show flowwith Doppler ultrasonography. There may be phlebo­liths in some cases.

The treatment for non-infected cases is completeexcision by the Sistrunk technique (SISTRUNK 1928).This involves excision of the thyroglossal duct with acentral portion of the hyoid bone and the thyroglos­sal tract that will ultimately open into the oral cavityand foramen caecum.

Some authorities suggest that thyroid functiontests and isotope scanning should be carried outprior to surgery to ascertain that there is normalfunction. A euthyroid patient with midline and infra­hyoid thyroglossal cyst should be tested for thyroidstimulating hormone (TSH) (RADKOWSKI et a1.1991).If TSH is normal, radioisotope scintigraphy is unnec­essary. TSH, radioisotope scintigraphy and MRIshould be carried out in suprahyoid lesions includingthe lingual site (TODD 1993). Routine preoperativeradioisotope scanning to ensure that the thyroglos­sal duct does not contain thyroid tissue is generallynot recommended because the surgery would haveto take place irrespective of the findings. If thereis significant thyroid tissue on a pathological speci­men, postoperative thyroid function tests will iden­tify patients requiring replacement therapy (FILSTON1989). In view of the attendant risk of removing ecto­pic thyroid tissue which has been mistaken for thy­roglossal duct cysts, ultrasonography is imperative inall cases prior to surgical removal of the mass, to con­firm the presence of a normal thyroid gland (BREWISet al. 2000). Thyroid function tests and radioisotopescans are recommended if the patient is hypothy­roid or when no gland is seen on ultrasound (LIMDUNHAM et al. 1995).

a

Fig. 13.9a, b. Thyroglossalduct cyst. a Axial Tl­weighted image of thyro­glossal duct cyst whichappears isodense to muscleand splits the anteriorstrap muscles with ananterior left paramedialcomponent. b Sagittal T2­weighted image. The highsignal in the thyroglossalduct cyst extends in anarrow tract from the levelof the hyoid bone downto the thyroid. (Repro­duced with permissionfrom HARDING HAM and

b GOLDING 2000)

Congenital Neck Masses (Non-vascular)

Fig.B.10. CT. Large thyroglossal cyst from base of tongue dis­tending the suprahyoid portion of the neck. (Reproduced withpermission from TODD 1993)

13.5Thornwaldt's Cyst

This cyst of Thornwaldt's bursa forms as a bulge onthe posterior-superior wall of the nasopharynx dueto closure of the sac's drainage duct. The pharyn­geal bursa is an embryonic remnant occurring in 3%of healthy adults (BIURRuN et al. 1992) due to anadhesion between the notochord and the pharyngealectoderm. It is usually small, although it may reachseveral centimetres in diameter. It is usually of noclinical significance unless it becomes infected. If itdoes become symptomatic it presents between theages of 15 and 30 years. It is usually found as anincidental finding on an MRI scan (BOUCHER et al.1990), with the typical appearance of fluid-filled cyst,low-signal on Tl- and high-signal on T2-weightedsequences (EDWARDS 1993), and in one series hasbeen reported in as many as 20% of cases on MRI,although without histological proof (BATTINO andKHANGURE 1990).

13.6Branchial Cleft Anomalies

Branchial cleft anomalies include cysts, sinuses, fis­tulae and cartilaginous remnants with skin tags. They

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are a third as common as thyroglossal duct cysts(TODD 1993). Internal cysts and fistulae of the phar­ynx are rare. The nomenclature of branchial deriva­tives is as follows: a fistula is a patent, duct-like struc­ture, having both external cutaneous and internalpharyngeal orifices. An external sinus is blind-end­ing space extending inwards from the skin. An inter­nal sinus is a blind-ending space extending outwardsfrom the orifice in the pharynx. Both these sinusesare thought to be non-obliterated branchial pouches.Cysts are spherical or ovoid spaces with no com­munication to the pharynx or skin, lying along thetract of the branchial pouch or cleft (SKANDALAKISand TODD 1993). Ninety-five percent ofbranchial cleftderivatives arise from the second cleft and occur atthe anterior border of the sternomastoid and near theangle of the mandible (HARNSBERGER 1995). Firstbranchial cleft anomalies usually give rise to lesionsin the submandibular and preauricular regions, e.g.cyst near the lower pole of the parotid, and are rare.Third and fourth cleft anomalies are even rarer andare potential tracts that may give rise to fistulae (Har­dingham and Golding 2000). Occasional deep cystshave been attributed to third and fourth pouch rem­nants (Gray and Skandalakis 1972).

Branchial cleft tracts or sinuses are most com­monly seen in the first decade; branchial cleft cystusually presents in the second decade. The sinusesand fistulae are seen along the lower third of the ante­rior border of the sternomastoid muscle. The open­ing is usually of pin-point size and exudes mucoidmaterial. They may appear bilaterally. Second bran­chial cleft cysts can occur along the same tract as fis­tulae from the supraclavicular region, from behindthe mandible to the tonsillar fossa. The most commonsite is above the level of the hyoid bone in a higherlocation than fistulae, most commonly near the bifur­cation of the carotid artery just below the angle ofthe jaw. Branchial cleft cysts may arise if the sinustract orifice becomes occluded (BRowN and AZIZ­KHAN 1998). Clinically they appear, unless infectionintervenes, as painless swellings along the upper thirdof the anterior border of the sternomastoid behindthe angle of the mandible. They range in diameterfrom 1 to 10 em and usually do not have any connec­tion to the exterior (TELANDER and FILSTON 1992),although a sinus tract or fistula may open anteriorlyabove the clavicle or in the tonsillar fossa (HARDING­HAM and GOLDING 2000). They present in infancy or,more often, later, in the young adult, because of infec­tion or trauma. Branchial vestiges may occur whenthere is failure of disappearance of branchial carti­lages, apart from those which form ligaments and

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bones. Cartilaginous or bone remnants may veryrarely present in infancy, embedded in the anteriorborder of the lower third of the sternomastoidmuscle.

Diagnosis in many cases can be made by inspec­tion. Sinus tracts usually do not require any investi­gation, and the use of water-soluble contrast is usu­ally considered inappropriate because of the risk ofinfection (TAPPER 1993).

Branchial cleft cysts can be identified by ultra­sound, which shows the location of the cyst anteriorto the upper portion of the sternomastoid musclesand lateral to the carotid sheath. It may have highechogenicity due to cholesterol crystals,keratin,cellu­lar debris or secondary infection, and have a pseudo­solid appearance (REYNOLDS and WOLINSKI 1993). If

A. W.Duncan

further evaluation is needed, contrast-enhanced CTdemonstrates a uni- Olr multilocular cyst with a thinuniform wall. The contents are of water density ormay be of higher attenuation if there is infection. Awall does not generally enhance unless infection hasoccurred.

MRI demonstrates the anatomy to much greateradvantage. The lesion is usually seen as a roundedcyst posterior to the mandible and anterolateral tothe major vessels, often displacing the sternomastoidmuscle posteriorly. A beak extending between theinternal and external carotid arteries (Fig. 13.11)ispathognomonic for second branchial cleft cyst (HAR­DING HAM and GOLDING 2000). On MRI the cyst con­tents, like any fluid, show as low signal on Tl- andhigh signal on T2-weighted images. If there are blood,

a

c

b

Fig. B.lla-c. Second branchial cleft cyst. a Axial andb coronal T2-weighted images show a cyst in the rightposterior submandibular region with a beak pointingtowards the pharynx. c Axial STIR image. A large leftsecond branchial cleft cyst lies between the subman­dibular gland anteriorly and the sternomastoid mnscleposteriorly with the carotid artery displaced medially.(Reproduced with permission from HARDING HAM andGOLDING 2000)

Congenital Neck Masses (Non-vascular) 185

a b

Fig. B.12a, b. Infected second branchial cleft cyst. a Axial CT. The cyst has a thick enhancing wall due toinfection which makes it indistinguishable from a simple abscess or from a cystic neoplasm on imaging. b MRISTIR image. This infected cyst has extensive surrounding oedema and may well be mistaken for a neoplasm.It would therefore require biopsy in addition to drainage. (Reproduced with permission from HARDING HAM

and GOLDING 2000)

protein or cholesterol crystals in the cyst, the Tl­weighted images may have a higher signal. A septummay be identified within the cyst and the cyst isdemonstrated within the carotid sheath. If there isinfection, the walls become irregular and thick (Fig.13.12a) with internal debris and lymphadenopathy.This, with surrounding oedema, may well have theappearance of a malignant process (Fig.13.12b).

The differential diagnosis includes necrotic neuraltumour, cervical abscess, submandibular gland cyst,cystic lymphangioma, necrotic malignant tumourand inflammatory lymphadenopathy (HARDING HAMand GOLDING 2000). Early surgical excision is advisedbecause of the high risk that the cysts may becomeinfected.

13.7Piriform Sinus Fistula (Abscess)

The piriform sinus is a rare branchial pouch anomaly(Choi and Zalzal 1995). Most piriform sinus fistulaeare located on the left side of the neck, sometimes witha sinus tract through the left lobe of the thyroid gland.The sinus tract extends from the apex of the piriformsinus to the thyroid region. It is rarely detected unlessinfected, when it presents as a neck abscess, draining

sinus, acute suppurative thyroiditis or even medias­tinal abscess (LEE 1999). The fistulae may presentin childhood or adulthood. They commonly presentas painful neck swellings, with patients experiencingfever and painful dysphagia over a period of yearsfrom childhood. Often the patients have undergonemultiple surgical procedures with only temporary res­olution of the abscess. There is no gender preferenceand patients have been reported from as early 2 daysto as late as 67 years of life (BURGE and MIDDLETON1983; PARK and PARK 1993). 93% of the fistulaeare left-sided (GODIN et al. 1990), although bilateraland right-sided presentations have been recorded.Although there may be recurrent episodes, the firstsymptoms start before 14 years of age (LEE 1999).Contrast studies usually demonstrate the fistula witha tract running from the left piriform fossa to theexterior in the lower neck (Fig. 13.13). It is advisableto perform the contrast study 2 months after acuteinfection since the oedematous tract may not permitpassage of contrast into the tract (LEE 1999). Thefistula can also be demonstrated by endoscopy, butfalse negative results may occur (COTE and GIANOLI1996). In the acutely infected stage, CT or MRI willdelineate the extent of the infection. Treatment is bycomplete excision of the fistulous tract, performedsoon after the contrast study when the patient hasbeen free of infection for a period of time.

186

Fig. 13.13. Piriform sinus fistula. Barium swallow demon­strates a fistula tract extending from the apex of the left piri­form sinus to the lower neck near the clavicle. (Reprinted withpermission from LEE 1999)

13.8Thymic Cyst

Thymic cysts originate from the persistence ordegeneration of the thymopharyngeal ducts. They areknown as one of the rarest congenital neck masses,but are probably under-recognised since many areasymptomatic and may well be discovered inciden­tally (SPIGLAND et al. 1990). They are usually on theleft side of the neck and in about 50% of cases arecontinuous with the mediastinum, due to the fact thatthe thymus embryologically develops in the neck andmigrates to the superior mediastinum. This medias­tinal extension requires different management fromother congenital neck masses (KELLEY et al. 1997).The thymus develops as an outgrowth from the ven­tral aspect of the third pharyngeal pouch, whichdivides into a dorsal wing, to become the inferiorthyroid gland, and a ventral wing, which becomes thethymus gland (SPIGLAND et al. 1990). The thymusdescends into the mediastinum. It is therefore notuncommon for thymic tissue to remain in the neck:prevalence has been reported to be as high as 21 %

A. W.Duncan

(LAU et al. 1984). These thymic anomalies may besolid or cystic. The solid thymic tissue is most likelydue to arrest of thymic tissue during the descent ofthe gland; these entities are usually small and donot present clinically. Cystic thymic tissue usuallypresents clinically, similar to other congenital neckanomalies. There are several theories as to the originof the thymic cyst, but the most plausible are cysticdegeneration of the Hassall's corpuscles, and cysticchange to the remnants of the thymopharyngeal duct(SPEER 1938; SPIGLAND et al. 1990). This duct formsas a tubeless structure by elongation of the dorsalwing of the third pharyngeal pouch. It usually atro­phies and disappears, but may remain and becomecystic (KELLEY et al. 1997). Most cysts are multilocu­lar with clear or straw-coloured fluid. Occasionallythey may be semi-solid with necrotic debris and oldblood. Cholesterol crystals have been found withinthe lumen, suggesting previous haemorrhage. Ulcer­ation of the epithelial wall occurs, and there may beinfection resulting in fibrous tissue development. Thecyst wall can vary in thickness from a few millimetresto a centimetre (KELLEY et al. 1997).

Cervical thymic cysts usually present in the firstdecade of life and 75% at less than 20 years. There is2:1 male-to-female dominance. The cysts are usuallysolitary but may be multiple (HYDE et al. 1944). Mostpatients have an antecedent history of the presenceof mass for 6-9 months, sometimes presenting orincreasing in size due to infection or haemorrhage(KELLEY et al. 1997). Fluctuation in size with recentupper respiratory infection is a relatively commonfinding (WAGNER et al. 1998). The cysts are foundin the lower third of the neck anterior to and extend­ing beneath the sternomastoid muscle, but they mayoccur in the trachea, posterior pharynx and piriformsinus. Dysphagia, dyspnoea, hoarseness or cervicalpain occurs in up to 10% of patients due to com­pression and displacement of the adjacent structures.With large congenital thymic cysts, severe respiratorycompromise may occur, especially in neonates, dueto extrinsic compression or intrinsic obstruction bythe mass within the trachea. This is particularly thecase if there is mediastinal extension. The mass mayextend into the mediastinum as a solid or cystic massor a fibrous cord. Occasionally there may be vocalcord paralysis due to traction on the recurrent laryn­geal nerve. Pericardial tamponade has been reported(McLEOD and KARANDY 1981). Valsalva manoeuvremay produce transient increase in size due to vascu­lar engorgement or transmitted intrathoracic pres­sure (KELLEY et al. 1997). This does not occur witha branchial cyst, which helps differentiate the two

Congenital Neck Masses (Non-vascular)

lesions. Most thymic cysts are congenital in origin,but infection, neoplasm, radiation therapy, traumaand thoracotomy may all be aetiological agents(MURAYAMA et al.1995). The clinical differential diag­nosis includes cystic hygroma, cystic thymic tumouror teratoma with cystic change, abscess, lymphade­nopathy, thyroid adenoma, parathyroid cyst, bran­chial cleft cyst, dermoid and epidermoid cyst, or, ifmidline in location, thyroglossal duct cyst (KELLEY etal. 1997; CASTELLOTE et al. 1999).

The first imaging modality for differentiating theselesions is ultrasound. A thymic cyst may appear asa homogeneous, non-homogeneous or cystic mass(KELLEY et al. 1997). It may show mediastinal exten­sion, and if this is suspected then a chest X-ray isrequired. This may be more difficult to evaluate inyounger children under 2 years of age when thethymus is normally present. If the cyst is large, MRIis the investigation of choice as it shows the detailedanatomy in multiple planes as well as better tissuecharacterisation. The cyst is well defined, often withthin septa, and lies partially within the carotid sheath.The fluid contents have a low signal on Tl-weightedimages, but this may be higher if there is blood orprotein in the cyst. High signal will occur in fluid­filled lesions on T2-weighted scans. MRI or, whenthis is not available, CT will show the thymic originof tissue by demonstrating mass within the carotidsheath and connection to the thymus and medi­astinum (LAu et al. 1984). On CT the thymic cystappears as a large, homogeneous mass of water den­sity (Fig. 13.14). Fine-needle aspiration has not beenuseful as an aid to diagnosis (LYONS et al. 1981).Complete surgical excision of the cyst is the recom­mended treatment, and the possibility of mediastinalextension should always be considered even if thishas not been definitely demonstrated prior to sur-

Fig. 13.14. Thymic cyst. CT scan shows a large left cysticmass with deviation of the airway to the contralateral side.(Reprinted with permission from KELLEY et al. 1997)

187

gery. Partial excision of the cyst may be necessaryto relieve symptoms in the neonate unless separatemediastinal thymic tissue has been identified byimaging (GILMORE 1941; SPIGLAND et al. 1990).

13.9Cervical Extension of the MediastinalThymus

When there is incomplete descent of the thymus, itmay remain as a solid midline structure at the tho­racic inlet. Although up to 40% of infants may havethymic tissue in the neck, it is only rarely that itpresents as a small midline mass (ZARBO et al. 1983;BENSON et al. 1992). It may lie laterally, more com­monly on the left side. Most are asymptomatic, apartfrom the neck swelling, but hypertrophied tissue mayrarely cause dyspnoea or dysphagia due to compres­sion (LEWIS 1962). Malignancy has been reported(GRAY and SKANDALAKIS 1972). Ultrasonography,CT and MRI will show the imaging features of anormal thymus, and may demonstrate the connec­tion with the mediastinal thymus (Fig. 13.15).

Fig. 13.15. Cervical thymus. Oblique sagittal Tl-weightedimages. MRI shows extension of the thymus from the anteriormediastinum to the lower neck (arrows). (Reprinted with per­mission from CASTELLOTE et al. 1999)

13.10Dermoid/Epidermoid Cyst

Dermoid and epidermoid cysts develop due to ecto­dermal elements being buried beneath the skin(BROWN and AZIZKHAN 1998). Dermoid cysts containglandular elements, which differentiates them from

188

epidermoid cysts. They both contain sebaceous mate­rial (McAvoy and ZUCKERBRAUN 1976). Althoughdermoid cysts are common lesions in the head andneck of young children, they usually present in thehead rather than the neck. When they occur in theneck they usually lie in the mid superior cervicalregion, overlying or above the hyoid bone. In thislocation they may be confused with a thyroglossalduct cyst. However ,because they lie subcutaneouslyand are mobile, the clinical examination differenti­ates a dermoid cyst from a thyroglossal duct cyst.This is of clinical importance as a simple excision of adermoid cyst can be done intact and requires no dis­section to find any extension internally (TELANDERand FILSTON 1992). An enlarged lymph node overly­ing the hyoid bone should be included in the diagno­sis of a thyroglossal duct cyst or dermoid. Investiga­tion is rarely necessary, but ultrasound can easilydifferentiate the solid-looking mass due to fat andkeratin of the dermoid from a cystic structure orcharacteristic lymph node (TEELE and SHARE 1991).Although rare, malignant transformation has beenreported in dermoid cysts (McAvoY and ZUCKER­BRAUN 1976).

13.11"Plunging" Ranula

Ranulas are not true congenital lesions, but areacquired inflammatory retention cysts of the sublin­gual salivary gland due to duct stenosis or occlusion(QUICK and LOWELL 1977) which may be congeni­tal. This sublingual salivary cyst usually presentsbeneath the tongue as a glistening mass in the floorof the mouth. It was given its name by Hippocratesbecause of its likeness to the belly of a little frog. The"plunging" ranula is an uncommon lesion resultingfrom rupture of the duct and extravasation of thisfluid containing amylase into the submental region,where it presents as a pseudocyst without an epithe­liallining (BROWN and AZIZKHAN 1998). If midline,it may sometimes be confused with the thyroglos­sal duct cyst (KHAFIF et al. 1975). Other differen­tial diagnoses include a midline cervical dermoidand lymph node (TELANDER and FILSTON 1992).Ultrasound will demonstrate the cystic nature ofthe lesion. MRI demonstrates the thin-walled cysticcollection with an intermediate signal on Tl- anda high signal on T2-weighted scans consistent withfluid, the bulk of the lesion being in the subman­dibular space with a characteristic connection to the

A. W.Duncan

floor of the mouth (Fig. 13.16) (HARDINGHAM andGOLDING 2000). It can be seen on CT, but this hasthe disadvantage of involving radiation and doesnot give the same spatial relationship or tissuecharacterisation.

13.12Ectopic Thyroid Gland

The thyroid gland appears embryologically as a mid­line diverticulum of the pharyngeal floor between thefirst and second branchial arches (SADLER 1990). Theregion of the tongue where the thyroid develops isthe site of the foramen caecum. The thyroid diver­ticulum becomes bilobed and descends into the neck.As the thyroid descends it remains connected tothe pharyngeal pouch by the thyroglossal duct. Thethyroid diverticulum descends anterior to the hyoidbone and larynx and arrests just inferior to the thy­roid cartilage and upper tracheal rings. Any abnor­mality in this descent may result in an ectopic loca­tion of the thyroid gland. This is usually at the baseof the tongue, below the tongue, or in a pre-laryngealand substernal position. The ectopic thyroid glanditself is usually of no consequence. However, if it lieshigh in the neck and is mistaken for a thyroglossalcyst, there may be a problem if it is inadvertentlyremoved, as this will result in profound hypothyroid­ism (LEUNG et al. 1995).

The ectopic thyroid gland is extremely rare, witha prevalence of 1 per 100,000-300,000 persons, and isreported to occur in 1 per 4,000-8,000 patients withthyroid disease (YEUNG et al. 1987). Although a con­genital lesion, it usually presents later in life with adifferential diagnosis of epidermoid cyst, lymphade­nopathy, lipoma, lymphangioma, sebaceous cyst and,rarely, midline branchial cyst. Any midline neck massmerits clinical examination of the thyroid gland inaddition to the mass, to ensure that the normal thyroidgland is detected. If a normal gland is not detected, orif ectopic thymus tissue is suspected, ultrasonographyshould be performed (NOYEK and FRIEDBERG 1981).An ectopic thyroid gland presenting as a mass will, onultrasound, have the same characteristics as a normalthyroid gland, and ultrasound will also show its rela­tionship to other structures. MRI or CT will confirmthis, although this is rarely necessary. If there is stilldoubt, radionuclide scanning should show the loca­tion, size and activity of the functioning thyroid tissue(Fig. 13.17). There is a full discussion of radionuclidescanning of the thyroid gland in Chap. 23.

a

a

Congenital Neck Masses (Non-vascular)

Fig. 13.16a, b. Plunging ranula. a Axial and b coro­nal T2-weighted images of the left-sided plungingranula extending into the sublingual and subman­dibular spaces. (Reproduced with permission fromHARDING HAM and GOLDING 2000) b

b

189

Fig.13.17a, b. Ectopic thyroid gland. Scintigraphy demonstrates a the anterior and b the lateral projection of the lingual thyroid

An ectopic thyroid gland is usually associatedwith normal thyroid function in children (GRANT

et al. 1978). However, it may be associated withhypothyroidism in 33% of patients (NEINAS et al.1973). The gland secretes thyroxine but in insuffi­cient amounts (LEUNG 1986). It is therefore impor­tant to estimate T4, T3 and TSH in all patients withectopic thyroid. Hypothyroidism may become man­ifest in periods of physiological stress and goitremay develop within the ectopic thyroid gland. If a

child is asymptomatic and euthyroid with ectopicthyroid gland, no treatment is necessary apart fromcontinued observation. Where there is deficiency ofthe thyroid hormone, elevated TSH levels or phys­iological impairment due to obstruction, or glandenlargement producing disfigurement, then thy­roid supplements are advocated. Some authorities(KANSAL et al. 1987) suggest that there should belifelong thyroxine suppression to prevent enlarge­ment of the gland.

190

13.13Sternomastoid "Tumour"

Congenital sternomastoid "tumour" is part of a spec­trum of abnormality causing congenital torticollis.Torticollis varies from a palpable sternomastoid mass,through thickening of the sternomastoid muscle, tothe final group due to postural head tilt or oculartorticollis. The last group shows no detectable organicabnormality of the sternomastoid muscle and may bedue to some localised muscular dysfunction resultingin an imbalance in the action of the muscles, leadingto torticollis (GOLDEN et al. 1999). It may present asa sign of ocular torticollis due to a squint or, in theolder age group, cerebellar tumour, or cervical rotarysubluxation. Congenital neck anomalies can occur inassociation with vertebral anomalies, particularly ofthe cervical vertebrae. Torticollis is the most commonmuscular presentation of craniovertebral junctionanomalies in older children (MANALIGOD et al.1999).There is another disorder, benign paroxysmal tor­ticollis, which is an episodic functional disorder ofunknown aetiology occurring in the first few monthsof life, with the child's head tilted to one side for afew hours or days without any associated signs. Thedisorder is self-limiting. It is important to recognisethe difference in order to avoid carrying out numer­ous investigations (DRIGO et al. 2000).

Congenital muscular torticollis or sternomastoidtumour, or "fibromatosis colli" as it is also known, isof debatable aetiology but the high rates of obstetri­cal complications leads some authorities to the con­clusion that birth trauma is probably the main aeti­ological factor (Ho et al. 1999). However, there areother theories that suggest that the presence of maturefibrous tissue in the neonate would indicate that thecondition occurs prior to birth and is more likely tobe the cause rather than the effect of obstetrical prob­lems. There is further support for this view - that thecondition is caused by intrauterine position - sincethere is an association of congenital dislocation ofthe hip and tibial torsion with torticollis (BROWN andAZIZKHAN 1998). Fibrosis and shortening of the ster­nomastoid muscle pulls the head and neck toward theaffected side (ARMSTRONG et al. 1965). Pathologicallythere is fibrous tissue between bundles of normalmuscle (MIDDLETON 1930). Clinically there is no pre­dilection for the side or sex of the patient. The mass isusually noted between 2 and 8 weeks of age, and themajority before 6 months (Ho et al. 1999). The childpresents with a characteristic posture with face andchin tilted away from the affected side and the headtilted toward the ipsilateral shoulder.

A.W. Duncan

Ultrasonography shows increased echogenicity dueto the fibrous tissue (Fig. 13.18). The normal sterno­mastoid muscle is hypoechoic with the facial planesinterspersed with the muscle producing thin, linear,echogenic lines. The presence of a "tumour" is dem­onstrated by the increased echogenicity and alsoincreased size. In classical cases there is a fusiformmuscle enlargement, but at times there may be gen­eralised muscle enlargement only. Although generallyhyperechoic, the "tumour" is occasionally hypoechoicand sometimes has mixed echogenicity (BEDI et al.1998). The ultrasonographic appearances correlatewith the pathology and Hsu (Hsu et al.1999) classifiedthem into four types: (1) fibrotic mass in the involvedmuscle; (2) diffuse fibrosis mixed with normal muscle- the most common, accounting for over three-quar­ters of cases; (3) diffuse involvement of the musclewithout any normal muscle (uncommon type); (4)fibrotic cord in the involved muscle, the rarest type.Types 1 and 4 are more likely to undergo surgicaltreatment, type 3 much less so. The lower third of themuscle is most commonly involved, but with increas­ing severity the whole of the muscle becomes involved.In severe cases, without appropriate treatment, facialand cranial asymmetry will develop within 6 months.

The majority of cases of neonatal torticollisrespond to physiotherapy and postural changes, forc­ing the infant to look to the contralateral side. Mildcases need observation only. Development of facialhemihyperplasia is the main reason for surgical inter­vention. However, the ultimate decision of whethersurgical intervention is necessary is clinical andit may necessitate serial ultrasound examinations(Fig. 13.19) to aid clinical judgement.

Fig. 13.18. Sternomastoid tumour. This shows a typical hyper­echoic thickened sternomastoid tumour compared with thenormal muscle

a

c

Congenital Neck Masses (Non-vascular)

13.14Congenital Teratoma

Teratomas are a rare cause of neck masses; although10% of childhood teratomas occur above the level ofthe clavicles (BERRY et al.1969),only 3% occur in thecervical region (JORDAN and GAUDERER 1988) andmost of these present in the newborn period. Theymay obstruct the airway and be life-threatening, andmay be associated with maternal polyhydramnios(HAJDU et al. 1966). When found in the neck theyhave an intimate relationship to the thyroid gland,although there is no evidence to suggest that they arisefrom the gland. Almost all are congenital in origin.The cells of a teratoma arise from pluripotential pri­mordial germ cells and may give rise to many tis­sues foreign to the organ in which they originate.

191

Brain tissue is the most frequent component,but othertissues such as bronchoepithelium, thyroid elements,cartilage and ependymal cysts are also found.

Congenital teratomas are invariably benign com­pared with those presenting later in life (FILSTON1994). Serum a-fetoprotein and ~-HCG levels areoften elevated.

Congenital lesions give rise to problems duringpregnancy and delivery because of the size of thetumour. Polyhydramnios occurs in up to 19% ofcases due to impairment of swallowing, which ismore common with the larger lesions (WELCH 1986;FILSTON 1994). The large size also results in obstructedlabour, premature labour and sometimes stillbirth(WELCH 1986). Even after delivery mortality may ariseas a result of respiratory compromise, and even withsurgery it occurs in 10% of cases. Without treatment

b

d

e

Fig.13.19a-e. Ultrasonograms of the evolution of the sternomastoidtumour. a Longitudinal section shows the slightly hypoechoic centralportion of the sternomastoid, which is increased in bulk comparedwith the narrow normal lower end of the sternomastoid muscle.b The transverse section shows the prominent bulk of the sterno­mastoid tumour. c A week later, the longitudinal section shows thetumour becoming more hypoechoic in relation to the muscle. dTransverse sections comparing the two sides of the neck show theincreased bulk on the left compared with the normal muscle on theright. e Two months later the longitudinal section shows the massreducing and becoming more uniform in thickness rather than afocal tumour. The echogenicity is returning to more normal muscle

192

the mortality can be between 80% and 100% (WELCH1986). Congenital teratomas are frequently recog­nised in utero by ultrasonography, which gives a greatadvantage in preparing for delivery and subsequentimmediate postnatal care, particularly in relation torespiratory compromise by the effect of the mass onthe airways. The teratoma presents as a large, usuallyunilateral mass with a differential diagnosis of cystichygroma. It may be difficult to distinguish teratomasfrom cystic hygromas when they are extremely largeand cystic, but calcification, which is seen in 50%of teratomas on plain films, will help to distinguishbetween the two conditions (WELCH 1986). Ultra­sound will demonstrate thin-walled cysts and calci­fication, if present, by increased echogenicity withacoustic shadowing. CT will show calcification andcystic lesions. If calcification is not present, distinc­tion from cystic hygroma may be difficult. MRI showsthe extent of the tumour and its spatial relationshipsto much better advantage than CT. It also gives bettertissue characterisation and involves no radiation. Itusually shows a multi-loculated cystic structure witha high signal on T2-weighted scans due to fluid withinthe cyst. The presence of fat, giving a high signal onTl-weighted images, a low or absent signal on STIRsequences, and a signal void from calcification willhelp to distinguish it from cystic hygroma (GREEN etal. 1998) (Fig. 13.20). Formed structures resemblingfingers or limbs have been described, and there maybe intradural extension (FULMER et al.1997).

Even after surgical removal there may be problemsrelated to pulmonary insufficiency and chondroma­lacia due to the mass effect in utero (LARSEN et al.1999), and hypothyroidism has been reported follow­ing excision of a large cervical teratoma. If identifi­able thyroid tissue is not seen at the conclusion ofsurgical removal, a thyroid function test should beperformed postoperatively (CHOWDHARY et al.1998).Follow-up with determination ofserum a-fetoproteinand B-HCG levels is usually used to detect tumourrecurrence in those cases that are malignant.

13.15Cervical Neuroblastoma

Neuroblastomas are probably all congenital in origin,originating from the neural crest, and therefore willoccur anywhere there is sympathetic neural tissue.They are a common malignant tumour in infancy,although rare in the cervical region. Most neuroblas­tomas occur below 5 years of age, and cervical neuro-

A. W.Duncan

Fig. 13.20a, b. Congenital teratoma. a Axial T2-weighted MRIdemonstrates the large tumour with cystic components withseveral fluid levels. b Oblique sagittal inversion recovery sec­tion shows the high signal due to fluid. The dense signal voidprobably represents some calcification, with a slightly highsignal around representing haemorrhage

blastoma under 1year of age; sometimes they presentsoon after birth, with stridor, dyspnoea and swallow­ing difficulties in addition to the visible mass (TAlet al. 1997). The tumour has a favourable prognosiscompared with neuroblastoma at other sites, prob­ably in part due to its early visible presentation. Whenpresenting other than in the newborn period, themasses are commonly mistaken for infectious ade­nitis (ABRAMSON et al. 1993). Serum and urinarycatecholamine concentrations are usually elevated.The first examination to be carried out is most likelyultrasonography, which will show a solid mass withvascular displacement and possibly narrowing of thevessels. If there is calcification, this will show as echo­genic areas with acoustic shadowing (Fig. 13.21a).Plain chest X-ray will show any calcifications and anyintrathoracic extension, which may also be seen on

a

b

Congenital Neck Masses (Non-vascular) 193

Fig. 13.21a-c. Congenital neuroblastoma. a Longitudinal ultra­sound shows a large cervical mass with areas of hyperecho­genicity probably representing calcification. b Axial CT scanshows a large tumour on the right with slightly lower attenua­tion than adjacent muscle, with small areas of increased atten­uation probably representing calcification. There is displace­ment of the airway to the left side with some narrowing. cMIBG 1231 scan, anterior projection, shows high uptake of theisotope in the neuroblastoma

ultrasound. Destructive bone changes may be seen,although since the lesion is usually detected earlythese are rare. MRI is the investigation of choice toshow the extent of the lesion and also any intraspi­nal extension. CT (Fig. 13.21b) will show calcificationto better advantage than MRI. Cervical neuroblas­toma may present as Horner's syndrome. However,Horner's syndrome with no evidence of a mass onclinical examination or ultrasound, and with normalvanillylmandelic acid levels and no other clinicalsigns such as heterochromia, requires no furtherinvestigation (GEORGE et a1. 1998). There is highuptake of MIBG (metaiodobenzylguanidine) in neu­roblastoma in most cases (Fig. 13.21c). The well­differentiated form of neuroblastoma, ganglioneu­roblastoma, may also occur but is extremely rare(AL-JASSIM 1987).

13.16Laryngocele

Laryngoceles are not truly congenital lesions unlessone considers that the weakness in the laryngeal ven­tricle is of congenital origin and responsible for dila­tation. They usually occur as a result of increasedintraglottic pressure. An internal laryngocele is morecommon and presents as stridor. The rarer externallaryngocele presents as a lateral neck mass, oftenincreasing in size with a Valsalva manoeuvre. Ultra­sound is of little value in uncomplicated casesbecause the air-filled sac produces artefact. Plainfilms will show an air-filled lateral structure (Fig.13.22). Laryngoceles may be imaged by CT or MRI,which demonstrates a unilocular air- or fluid-filledcyst (Fig. 13.23). Fluid levels may be seen. Externallaryngoceles lie mainly within the submandibularspace and may communicate through the thyrohyoidmembrane to the internal component, although thismay have collapsed and not be visible (HARDING HAMand GOLDING 2000).

13.17Lung Herniation

Lung herniation is protrusion of the lung beyond theconfines of the thorax. The herniation may be cervi­cal, intercostal or diaphragmatic. Most lung hernia­tions are acquired due to trauma or surgery or sec­ondary to a neoplastic or inflammatory process, or

c

a

b

194

else spontaneous, although 20% are considered to becongenital (BHALLA et al. 1990; MONCADA et al. 1996).Congenital cervical herniation is due to agenesis ofSibson's fascia. Most are asymptomatic or present witha few infrequent or vague symptoms. Clinically theyappear as a painless, rhythmic bulge of the supracla­vicular region that increases with respiratory effort(MONCADA et al. 1996). Congenital cervical lung her­niation has been described with multiple hernia, lead­ing to the theory that it may be a defect in the coelomicmesoderm (ZAGLUL and ODITA 1995). The diagnosiscan be established with a plain radiograph showingherniation at the apex into the neck. This is accen­tuated by a Valsalva manoeuvre. In most cases notreatment is required but just reassurance, althoughif the herniation is large, clinically progressive orcauses respiratory distress, surgical intervention maybe necessary (GONZALES-DEL-REY and CUNHA 1990).In addition to the symptoms a cosmetic problem maywell also arise, requiring repair of the fascial defect(BRONSTHER et al. 1968). One should also be awareof the possibility of a pneumothorax in this group ofpatients (DEVGAN and BRODEUR 1976).

Fig. 13.22. Laryngocele. The appearance is of an air-filledcavity on the lateral projection, which would be compatiblewith a laryngocele or oesophageal diverticulum. Oral contrast,however, does not fill it and suggests that this is not related tothe oesophagus. In fact, it actually represented duplication ofthe larynx, which has a similar appearance

A.W.Duncan

Fig. 13.23. Axial CT shows bilateral externallaryngoceles. Theleft laryngocele contains only air. On the right there are air­fluid attenuation contents together with a soft tissue attenua­tion component which would suggest infection or malignancy.(Reproduced with permission from HARDING HAM and GOLD­

ING 2000)

13.18Thyroid Gland Hemiagenesis

Hemiagenesis of the thyroid gland presents as anuncommon mass due to hypertrophy of a single thy­roid lobe or due to thyroid dysfunction. It is morefrequently seen on the left side and may be an inci­dental finding (DE REMIGIS et al. 1985. Functionalhemiagenesis, identified scintigraphically, can be dif­ferentiated from anatomical hemiagenesis by ultra­sonography, which on the transverse section showsabsence of one side of the gland with a normalappearing contralateral side and isthmus, produc­ing the so-called hockey stick sign (Vazquez et al.1995). Scintigraphy identifies functioning tissue. Ifthe gland is non-functioning, it will be seen on ultra­sound. If it is true hemiagenesis, it will not be seenon either modality.

13.19Midline Cervical Cleft

This unusual anomaly appears as a long, linear skindefect but can occasionally be associated with scar­ring contracture, which can produce a small masseffect.

Congenital Neck Masses (Non-vascular)

13.20Bronchogenic Cyst

These are rare congenital lesions that usually arisenear the hilar region, presenting due to infectionor compression of vital structures. They have beendescribed as an unusual cause of a lump in the neck(RAPADO et al. 1998).

13.21Lingual Thyroid Gland

Thyroid rests may occur anywhere along the thy­roglossal duct. The majority lie near the foramencaecum of the tongue. Occasionally a goitre may resultin airway obstruction. Ectopic tissue in 77% of casesis the only functioning thyroid tissue (VAZQUEZ et al.1995). In congenital hypothyroidism ultrasonographyis usually performed when a normally located glandis not felt (MILLER 1985). Thyroid scintigraphy willconfirm this (Fig. 13.17). However, if the tissue is non­functioning it will yield false negative results.

13.22Congenital Vascular Lesions

These may present as masses. The reader is referredto Chap. 20 for a full discussion of vascular lesions.

13.22.1 Haemangioma

Haemangiomas are the most common congenitallesions of the head and neck in childhood, occur­ring in about 2.5% of all newborn infants ( MacCol­lum and Martin 1956). They are uncommon in theneck apart from the back of the neck. They occurpredominantly in the skin and mucosa but can beinvasive. Cutaneous haemangiomas present primar­ily in infants and young children. The capillary typeusually involutes spontaneously while the cavernoustype regresses only when it has been present frombirth (Edwards 1993). The capillary types tend tothe appearance of a flattened strawberry and haveno mass effect. Cavernous types have large vascularspaces and are compressible, being raised above theskin with a warty granular surface (Potter 1976).Mixed capillary and cavernous types produce theraised vascular strawberry naevi. Haemangiomaswith cavernous components may grow massively.

195

Although present at birth, most do not becomenoticeable until after the first month of life. Most willinvolute spontaneously, but a small proportion maybecome quite large and present a difficult manage­ment problem due to airway obstruction, involve­ment of vital organs, cardiac failure or coagulationproblems due to platelet trapping.

The first investigation of a mass suspected to bea haemangioma is ultrasonography, which will showhypoechoic areas with echogenic septations. The cap­illary areas, due to echoes from the walls of the ves­sels, may show as an echogenic region. The echo­genicity can also be due to thrombosis. For the moreextensive lesions, MRI or, if that is not possible,CT demonstrates the extent of the lesion. Contrast­enhanced CT will show the vascular nature of thelesion.

Most haemangiomas require no more than obser­vation unless they become a clinical managementproblem, when more aggressive therapy may beneeded. A full account of the imaging and manage­ment is given in Chap. 20.

13.22.2Varix of the Jugular Vein

Localised swelling in the neck during strammg,coughing or crying may be due to fusiform dilata­tion of the jugular vein. This is readily shown byultrasound demonstration of its expansion on theValsalva manoeuvre, and also by the presence of flowon Doppler imaging (KOVANLIKAYA et al. 1990).

13.22.3Carotid Artery Aneurysm

Carotid artery aneurysms are extremely rare in chil­dren, trauma and infection being the usual causeswhen they do occur. Congenital carotid artery aneu­rysms due to a defect in the arterial wall areeven rarer and may be a manifestation of a gener­alised connective tissue disorder, such as Ehlers-Dan­los, Marfan's, Kawasaki's or Maffucci's syndromes(VAZQUEZ et al. 1995). They can readily be evaluatedby ultrasound.

13.22.4Cervical Aortic Arch

The high position of the aortic arch may manifestitself due to compression of the airways or oesopha-

196

gus producing respiratory difficulties or dysphagia.It is usually a right-sided aortic arch and may beassociated with other cardiac or vascular anomalies(DOORENBOS et al. 1991). It may be asymptomatic.Very occasionally this congenital extension of theaortic arch into the neck may produce a pulsatileneck swelling (MURRAY and NEGRETTE 1989). Asa mass in the neck it can be identified by ultra­sound and its nature determined with flow identifiedby Doppler ultrasonography. Plain films may showindentation of the trachea. Tl-weighted MRI willshow the high position of the arch passing throughthe thoracic inlet (CASTELLOTE et al. 1999).

13.23Rare Congenital Tumours, Cystsand Infections

Very rare congenital tumours such as rhabdoid tumour(COSTES et al. 1997), neurofibroma (KOKANDKAR et al.1994), fibrosarcoma (Fig. 13.24) (BooN et al. 1995) andforegut cysts (COHEN et al. 1985) may present as neckmasses. Congenital infections such as tuberculosis canpresent with neck masses but rarely do (THORA et al.1985). Parathyroid cysts are rare and of questionableembryonic origin. They usually present in the adult asa painless neck mass that is occasionally symptomatic(GRAY and SKANDALAKIS 1972).

Fig. 13.24. Fibrosarcoma. Axial CT scan of the neck withintravenous contrast shows a large mass in the right side ofthe neck displacing the airway anteriorly and laterally. It haspatchy enhancement, particularly of the rim

A.W. Duncan

13.24Summary

Congenital neck lesions are a common finding in thepaediatric age group and must be differentiated fromlesions from other causes. Clinical examination willindicate the nature of most lesions. Ultrasonogra­phy is the first line of investigation; it can differenti­ate between cystic and solid lesions, and in manyinstances will reveal the nature and extent of thelesion. When the lesion has a solid component it isalways important to identify a normal thyroid glandto ensure that the only functioning thyroid tissue isnot removed at surgery. Larger lesions are evaluatedby MRI, particularly Tl-weighted sequences, for thespatial relationships, or, if MRI is not available, CT.Occasionally isotope studies are needed to identifyfunctioning thyroid tissue, and a contrast swallowmay in rare instances aid diagnosis.

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