6 Neck Dissection

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Miriam N. Lango,M.D., Bert W. OMalley, Jr.,M.D.,F.A.C.S., and Ara A. Chalian,M.D.

6 NECK DISSECTION

Preoperative Evaluation

In the majority of cases, cancer in the neck is a metastasis from

a primary lesion in the upper aerodigestive tract, though me-

tastases from skin, thyroid, and salivary gland neoplasms are

also encountered. Lymphomas often present as cervical

lymphadenopathy.

When a patient presents with a suspicious lesion in the neck, a

careful history and physical examination should be performed,

along with a thorough evaluation of the aerodigestive tract aimed

at locating the source of possible metastatic disease. Fine-needle

aspiration (FNA) of the neck mass should then be done to deter-

mine whether the mass is malignant. FNA can often differentiate

between epithelial and lymphoid malignancies, and this differen-

tiation will guide subsequent workup.The reported sensitivity of

FNA ranges from 92% to 98%; the reported specificity, from

94% to 100%.1,2

If FNA reveals the presence of atypical lymphoid cells,an exci-

sional lymph node biopsy should be performed to supply the

pathologist with a large enough sample to allow full typing of the

tissue.An excisional biopsy may also be performed if the FNA is

negative or indeterminate, the surgeon suspects a malignancy,

and the rest of the physical examination yields negative results.

Routine excisional biopsy of neck masses for diagnostic purposes

is not recommended, however, because it may result in tumor

spillage into the wound and complicate subsequent definitive

resection.Once the presence of an epithelial malignancy is established,

the primary site of the lesion must be determined if it is not

apparent on initial physical examination. Imaging studies (e.g.,

computed tomography and magnetic resonance imaging) may be

helpful in locating the source of a cervical metastasis. Positron

emission tomography (PET) detects lesions with increased meta-

bolic activity but has the limitation of being unable to detect

lesions smaller than 1 cm in diameter. Primary lesions greater

than 1 cm in diameter usually are easily identified on physical

examination and other imaging studies; thus, PET scans are of

limited value in this setting. In any patient with metastatic cervi-

cal adenopathy thought to originate in the upper aerodigestive

tract, panendoscopy and biopsy with general anesthesia are

mandatory for locating and characterizing the primary source ofthe tumor and ruling out the presence of synchronous lesions.

The most common occult primary sites are the base of the

tongue, the tonsils, and the nasopharynx. In 5% to 10% of

patients who present with a metastatic node, the primary lesion is

never found despite extensive workup.

INCIDENCE AND IMPACT OF NECK METASTASES

Cutaneous Squamous Cell Carcinoma

The incidence of cervical metastases is governed by many fac-

tors. Cervical metastases from cutaneous squamous cell carcino-

mas are rare, occurring in 2% to 10% of cases. However, certain

lesionsthose that are greater than 2 cm in diameter; are recur-

rent; are deeper than 6 mm; involve the ear, the temple, or

classic H zone; occur in an immunocompromised patient; or

poorly differentiatedhave a significant occult metastatic r

ranging from 20% to 60%.The presence of cervical metast

reduces 5-year survival to about 32%,3 which suggests that e

intervention for high-risk cutaneous lesions, involving regi

lymphadenectomy, sentinel lymph node (SLN) biopsy, or irr

ation of at-risk lymph node basins, may be warranted.

Salivary Gland Neoplasms

With salivary gland neoplasms [see 2:2Oral Cavity Lesion

the incidence of cervical metastases is related to the histopatogy as well as the size of the tumor.The most aggressive sali

gland lesions are squamous cell carcinoma, carcinoma ex p

morphic adenoma, adenocarcinoma, and salivary ductal carc

ma. Patients with these lesions often have cervical metastase

presentation that warrant a therapeutic neck dissection [see T

1]. How best to manage occult cervical salivary gland metas

disease is controversial.The occult metastatic rate for aggres

lesions ranges from 25% to 45%. For such lesions, a sele

neck dissection is typically incorporated into the surg

approach.4

Metastatic Well-Differentiated Thyroid Cancer

Cervical lymph node metastases are present in 10% to 15%

patients with well-differentiated thyroid carcinoma. The imof nodal metastases on local recurrence and survival has not b

established. Other factors (e.g., age, sex, tumor extent, and

tant metastases) appear to have a greater effect on progn

Nevertheless, in the presence of clinically apparent nodal dise

a formal neck dissection is advised:so-called cherry-picking o

ations or limited lymph node excisions result in higher rate

recurrence.5

Squamous Cell Carcinoma of the Upper Aerodigestive Tract

With upper aerodigestive tract squamous cell carcinomas

incidence of cervical metastases is related to the site of the

mary lesion, the size of the tumor, the degree of differentiat

the depth of invasion, and a number of other factors. A sig

cant proportion of head and neck cancer patients who harclinically silent primary tumors of the base of the tongue,

tonsils, or the nasopharynx initially present with cerv

adenopathy [see Table 1]. These sites lack anatomic barriers

limit tumor spread and are supplied by rich lymphatic netw

that facilitate metastasis. In contrast,patients with glottic and

cancers are more likely to present early, without clin

adenopathy.

The presence of cervical metastases negatively affects prog

sis and has been associated with increased recurrence rates

reduced disease-free and overall survival.The presence of clin

adenopathy decreases survival by 50%. Metastatic tumors

rupture the lymph node capsulea process known as extra

sular spread (ECS)are biologically more aggressive. Pati

2004 WebMD, Inc. All rights reserved.

2 HEAD AND NECK

ACS Surgery: Principles and Pract

6 NECK DISSECTION


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2 HEAD AND NECK

ACS Surgery: Principles and Practice

6 NECK DISSECTION 2

who have palpable cervical lymphadenopathy with ECS manifest

a 50% decrease in survival compared with those who have pal-

pable cervical lymphadenopathy without ECS.6 In addition,

about 50% of clinically negative, pathologically positive neck

specimens exhibit ECS. Clinically negative, pathologically posi-

tive, and ECS-positive specimens are associated with a high risk

of regional recurrence and distant metastases.7-9 The presence of

ECS in lymph node metastases may in fact be the single mostimportant prognostic factor in patients with head and neck can-

cer. Identification of this patient subset may be the most impor-

tant benefit of elective neck dissection, in that it allows these

patients to be offered adjuvant therapy. Nonrandomized studies

have found that both disease-specific and overall survival are sig-

nificantly improved when these high-risk patients are treated

with adjuvant postoperative chemoradiation.10 However, ran-

domized clinical trials are needed to confirm the clinical benefits

of adjuvant chemoradiation in this setting.

Whereas anatomic and pathologic factors (e.g., ECS) have

long been known to predict tumor behavior, it is only compara-

tively recently that the impact of comorbidity has been well char-

acterized.When patients are stratified by tumor stage, those with

comorbidities fare worse. In fact, the impact of comorbidity onoverall survival is greater than that of tumor stage or treatment

type.10,11 In addition, comorbidity is associated with both

increased frequency and increased severity of surgical complica-

tions.These factors may be important in treatment selection and

patient counseling.To date, comorbidity has not been incorpo-

rated into clinical staging of head and neck cancer patients.

STAGING OF NECK CANCER

Staging of the neck for metastatic squamous cell carcinomas of

the head and neck is based on the TNM classification formulated

by the American Joint Committee on Cancer (AJCC) [see 2:2

Oral Cavity Lesions]. The N classification applies to cervical

metastases from all upper aerodigestive tract mucosal sites except

the nasopharynx; it also applies to metastases from major salivary

gland and sinonasal malignancies but not to metastases from

cutaneous or thyroid malignancies, which use an alternate staging

system.

The purpose of staging is to characterize the tumor burden of

an individual patient. Accordingly, an effective staging system

should incorporate factors known to have prognostic and thera-

peutic significance, thereby facilitating planning of therapy andappropriate patient counseling. In addition, it should attempt to

standardize reporting so that meaningful cross-institutional com-

parisons can be obtained.A staging system ideally should also be

simple to apply while still incorporating biologically important

factors that permit accurate patient stratification in prospective

clinical trials. Precise characterization and differentiation of tu-

mors facilitate identification of those patients who are most like-

ly to benefit from treatment.

The TNM staging system does not include a number of fac-

tors that are known to have an impact on prognosis, such as the

presence or absence of ECS and the pattern of lymphatic spread.

Nonanatomic factors (e.g., comorbidity, immune status,and nu-

tritional status) have a strong impact on survival as well but are

also not incorporated in the current staging system. In general,TNM staging has been found inadequate for use in clinical

trials.12

The limitations of clinical staging of the neck are well de-

scribed.The addition of imaging to clinical examination improves

diagnostic sensitivity but not specificity. Imaging is particularly

useful after chemoradiation because of the difficulty of clinical

examination in this setting. Pathologic review of neck specimens

remains the gold standard for anatomic staging. The addition of

ultrasound-guided FNA of neck nodes yields enhanced diagnos-

tic accuracy in cases where the neck is clinically negative but the

radiologic findings are positive. This approach is employed to

select patients for neck dissection in a number of centers, partic-

ularly in Europe; whether it provides more accurate staging than

alternative methods, such as SLN biopsy, remains to be deter-mined. Results from the First International Conference on

Sentinel Node Biopsy in Mucosal Head and Neck Cancer

revealed that SLN biopsy of the clinically negative neck has a sen-

sitivity comparable to that of a staging neck dissection.13 In gen-

eral, imaging modalities appear to be neither sufficiently sensitive

nor sufficiently specific in the evaluation of the clinically negative

neck. Uptake of 2-deoxy-3 [18F] fluoro-D-glucose, as measured

by PET scans, is undetectable in small foci of cancer in the clin-

ically negative neck.14

Proper staging is important for stratification of patients into

risk categories on the basis of tumor biology, so that high-risk

patients may be appropriately selected for clinical trials or offered

adjuvant therapy and other patients may be spared unnecessary

treatment. Until accurate methods of assessing the clinically neg-ative neck are developed, selective neck dissection will be per-

formed to treat the neck when the occult metastatic rate is

expected to be higher than 20%.

INDICATIONS FOR NECK DISSECTION

The classic indication for neck dissection is for treatment of

metastatic carcinoma in the neck, most frequently deriving from

a mucosal site in the upper aerodigestive tract. Over time, the

indications for neck dissection have changed.With wider use of

chemoradiation therapy for head and neck cancer, treatment of

metastatic disease in the neck has become increasingly nonsurgi-

cal. Currently, neck dissections are considered either therapeutic

(performed to treat palpable disease in the neck) or elective (per-

Table 1 Incidence of Cervical Metastases inSelected Head and Neck Cancers

Tumor

Cutaneous squamous cell carcinoma

Salivary gland malignancies

Mucoepidermoid carcinoma (high-grade)

Adenoid cystic carcinoma

Malignant mixed tumor

Squamous cell carcinoma

Salivary duct carcinoma

Acinic cell carcinoma

Metastatic well-differentiated thyroidcancer

Squamous cell carcinoma of upperaerodigestive tract

Alveolar ridge

Hard palate

Oral tongue

Anterior pillar/retromolar trigoneFloor of mouth

Soft palate

Tonsillar fossa

Tongue base

Bilateral

Incidence of Cervical Adenopathy

2%10%

30%70%

8%

25%

46%

50%

40%

10%15%

30%

10%

30%

45%30%

44%

76%

78%

20%


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6 NECK DISSECTION

formed when the expected incidence of occult metastases from a

lesion exceeds 20%).Technically, neck dissections are classified as

comprehensive dissections, which incorporate five levels of the

neck, or selective dissections, in which only selected lymph node

levels are removed according to predicted drainage patterns from

specific primary sites.There is also a third technical classification,

extended neck dissections, which can be combined with selectiveor comprehensive neck dissections for removal of additional

nodal basins [see Operative Planning, Choice of Procedure,

below]. Six lymph node drainage basins in the neck are recognized

[see Figure 1].

CONTRAINDICATIONS TO NECK DISSECTION

The only absolute contraindication to neck dissection is surgi-

cal unresectability. The determination of unresectability is made

by the operating surgeon either preoperatively, on the basis of

imaging studies, or in the operating room.Typically, the presence

of Horner syndrome, paralysis of the vagus nerve or the phrenic

nerve, or invasion of the brachial plexus or the prevertebral mus-

cles indicates that the tumor is unresectable. The involvement of

the carotid artery may be predicted on the basis of imaging stud-ies. Encasement of the carotid artery by tumor suggests direct

invasion of the vessel; however, studies correlating imaging char-

acteristics and pathologic invasion of the carotid have shown that

tumors surrounding 180 or more of the carotids circumference

have a higher incidence of carotid invasion than tumors sur-

rounding less than 180 (75% versus 50%). In the absence of

direct invasion of the vessel wall, tumor may be peeled off by

means of subadventitial surgical dissection. Tumors surrounding

270 of the vessel have an 83% incidence of carotid invasion,

necessitating sacrifice of the artery.15 However, sacrifice of the

carotid artery, with or without reconstruction with a vein graft,

has been associated with significant morbidity and confers no

survival benefit.16

Operative Planning

CHOICE OF PROCEDURE

Comprehensive Dissection: Radical and Modified Radical N

Dissection

The radical neck dissection was first described in 1906

George Crile, who based his approach on the Halstedian prple of en bloc resection. The procedure was subsequently s

dardized by Hayes Martin at Memorial Hospital in New Yor

the 1930s and 1940s. In this latter version of the procedure, l

phatic structures from the strap muscles anteriorly, the trape

posteriorly, the mandible superiorly,and the clavicle inferiorly

removed. Nonlymphatic structures in this space are also s

ficed, including the spinal accessory nerve, the sternocleidom

toid muscle, the internal and external jugular veins, the

mandibular gland, and sensory nerve roots.The routine sacr

of the spinal accessory nerve, the internal jugular vein, and

sternocleidomastoid muscle contributes to the significant m

bidity associated with radical neck dissection.

Since the 1970s, the necessity of en bloc resection for o

logic cure has been reexamined. Structures once routinely sficed are now routinely preserved unless they are grossly invo

with cancer.The various functional, or modified,radical neck

sections are classified according to which structures are

served. Type I dissections preserve the spinal accessory ne

type II, the spinal accessory nerve and the internal jugular v

type III, both of these structures along with the sternocleidom

toid muscle. Modified radical neck dissections have proved t

as effective in controlling metastatic disease to the neck as

classic radical neck dissection.17

Selective Neck Dissection

In a selective neck dissection, at-risk lymph node drain

basins are selectively removed on the basis of the location of

primary tumor in a patient with no clinical evidence of cervlymphadenopathy. Cancers in the oral cavity, for example, typ

ly metastasize to levels I through III and, occasionally, IV; la

geal cancers typically metastasize to levels II through IV.The ra

nale for selective neck dissection is based on retrospective pa

logic reviews of radical neck dissection specimens from pati

without palpable lymphadenopathy. These reviews revealed

lymph node micrometastases were confined to specific neck le

for a given aerodigestive tract site.18

The advantages of selective neck dissection over radical

modified radical neck dissection are both cosmetic and funct

al. A selective neck dissection involves less manipulation

thus less risk of devascularization) of the spinal accessory ne

thereby decreasing the incidence of postoperative shoulder

function. Preservation of the sternocleidomastoid muscle alates the cosmetic deformity seen with a radical neck dissec

and provides some protection for the carotid artery.

Preservation of the internal jugular vein decreases venous c

gestion of the head and neck and is necessary if the contralat

internal jugular vein is sacrificed.With primary lesions locate

the midline in the base of the tongue, the supraglottic larynx

the medial wall of the piriform sinus,bilateral regional metast

are common,and bilateral neck dissections are therefore ind

ed. Sacrifice of both internal jugular veins is associated with

nificant morbidity, including increased intracranial pressure,

drome of inappropriate antidiuretic hormone secretion, air

edema, and death. Bilateral internal jugular sacrifice is man

by staging the neck dissections or by carrying out vascular rep

I

II

III

V

IV

VI

Figure 1 Cervical lymph nodes are divided into six levels

on the basis of their location in the neck.


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6 NECK DISSECTION 4

In the presence of multiple pathologically positive lymph nodes

or evidence of ECS, adjuvant therapy is indicated.19 Accordingly,

selective neck dissection may be viewed as a diagnostic as well as

a therapeutic procedure.To date, however, no randomized clini-

cal trials have demonstrated that selective neck dissection with

adjuvant treatment as needed is better than so-called watchful

waiting with regard to prolonging survival in patients who present

without evidence of cervical metastatic disease. Therefore, itis not yet possible to justify the added cost and morbidity of elec-

tive neck dissection in patients without evidence of metastatic dis-

ease. SLN mapping may facilitate pathologic staging in this set-

ting and spare low-risk patients from unnecessary interventions;

however, its sensitivity and specificity for this purpose are still

under investigation.

The growing focus on preservation of function and limitation

of morbidity has led some surgeons to promote the use of selec-

tive neck dissection to treat node-positive neck tumors.

Although retrospective studies have suggested that a selective

neck dissection may be adequate in carefully selected node-pos-

itive patients,20 the effectiveness of this approach is still

unproven, and its application remains subject to individual sur-

gical judgment.

Extended Neck Dissection

Extended neck dissections can be combined with selective

or comprehensive neck dissections to remove additional nodal

basins, such as the suboccipital and retroauricular nodes. These

groups of nodes, which are located in the upper posterior neck,

are the first-echelon nodal basins for posterior scalp skin can-

cers. The retroauricular nodes lie just posterior to the mastoid

process, and the suboccipital nodes lie near the insertion of the

trapezius muscle into the inferior nuchal line. Cancers of the

anterior scalp,the temple,and the preauricular skin drain to peri-

parotid lymph nodes; these lymph nodes are removed in con-

junction with a parotidectomy [see 2:5 Parotidectomy]. Retro-

pharyngeal nodes may be removed in the treatment of selectedcancers originating in the posterior pharynx, the soft palate, or

the nasopharynx. A mediastinal lymph node dissection may be

combined with a neck dissection in the treatment of metastatic

thyroid carcinomas.

NECK DISSECTION AFTER CHEMORADIATION

The indications for neck dissection have been significantly

affected by the increasing use of organ preservation protocols for

the treatment of head and neck cancer. Nasopharyngeal carcino-

mas, which are uniquely radiosensitive, are generally treated with

irradiation, with or without chemotherapy; neck dissection is

reserved for patients who experience an incomplete response and

for patients with bulky cervical lesions. Similarly, patients with

early nodal disease (N0 or N1) treated according to organ preser-vation protocols may undergo nonsurgical therapy. For patients

who have advanced neck disease (N2 or N3) or who respond

incompletely to therapy, a planned posttreatment neck dissection

is recommended because surgical salvage of so-called neck fail-

ures is rarely successful.21 As a rule, the planned neck dissection

should be done within 6 weeks of the completion of chemoradi-

ation therapy: if it is delayed past the 6-week point, progressive

soft tissue fibrosis may develop, resulting in difficult surgical dis-

section, increased postoperative morbidity, and, potentially,

tumor progression.

A 2003 study highlighted the need for planned neck dissection

after definitive chemoradiation for N2 or N3 nodal disease.22 In

this study, 76 patients presenting with N2 or N3 disease under-

went a planned neck dissection.Tumor cells were present in the

neck specimens of 25% of patients with complete and 39% of

patients with incomplete clinical responses. No patients with

complete pathologic responses experienced regional recurrence,

whereas 20% of patients with pathologically positive neck dis-

section specimens experienced nonsalvageable regional recur-

rences. In addition,planned neck dissection led to reduced rates

of regional recurrence in patients treated with chemoradiation.The authors suggested that all patients presenting with N2 or

N3 cervical lymphadenopathy should undergo planned neck

dissection, regardless of clinical response to chemoradiation

therapy.

The required extent of planned neck dissection after chemora-

diation is still under investigation. Neck dissection after chemora-

diation carries significant morbidity in the form of severe soft tis-

sue fibrosis and increased spinal accessory nerve injury. Pathologic

review of comprehensive neck specimens after chemoradiation

reveals that in patients with oropharyngeal cancer, levels I and V

are rarely involved in the absence of radiographic abnormalities,23

which suggests that a planned selective dissection involving levels

II through IV may be sufficient for cases of oropharyngeal cancer

treated with chemoradiation. This more limited approach un-doubtedly causes less morbidity, but additional data are required

to assess its oncologic efficacy.

Typically, management of the neck is determined in part by

management of the primary tumor. Early neck dissection for

bulky nodal disease before nonsurgical treatment of the primary

lesion is a controversial practice. Bulky cervical adenopathy is

unlikely to exhibit a complete pathologic response to nonsurgical

treatment. A patient who requires dental extractions before radi-

ation therapy may undergo a neck dissection at the same time,

proceeding to radiation therapy 7 to 10 days after operation.

Early neck dissection decreases the tumor burden, thereby allow-

ing lower adjunctive doses of radiation to be delivered to the neck.

Thus, it is possible that early neck dissection for bulky resectable

cervical adenopathy can reduce the expected morbidity ofplanned postchemoradiation neck dissection.There is limited evi-

dence in the literature that such an approach is feasible in certain

circumstances24; however, it is recommended that significant

delays in initiating treatment to the primary site be avoided

because such delays may ultimately have a negative impact on

survival.

RECONSTRUCTION AND RECURRENCE AFTER NECK

DISSECTION

The use of microvascular free tissue transfer to reconstruct

surgical defects in the head has allowed surgeons to resect large

tumors with large margins while simultaneously achieving

improved functional results. Preservation of vascularand,

occasionally, neuralstructures during neck dissection mayfacilitate the reconstructive process. Typically, several vessels,

including an artery and one or two veins, are required for inflow

and outflow into a free flap. The facial artery, the retro-

mandibular vein, and the external jugular vein, which are pre-

served during level I and level II dissection, are the vessels that

are most frequently used for flap revascularization. If these ves-

sels are unavailable as a consequence of high-volume neck dis-

ease, the superior thyroid artery and the transverse artery, with

companion veins, are suitable substitutes. To date, there is no

evidence in the literature that preservation of vascular structures

in the neck predisposes patients to regional recurrence. Cau-

tion must, however, be exercised in the setting of pathologic

lymphadenopathy.


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6 NECK DISSECTION

Operative Technique

RADICAL NECK DISSECTION

Step 1: Incision and Flap Elevation

When a radical or modified radical neck dissection is indicated,

appropriate neck incisions must be designed so as to facilitate expo-

sure while preserving blood flow to the skin flaps [see Figure 2].The

incision provides access to the relevant levels of the neck, affects

cosmesis, and determines the extent of lymphedema and postoper-

ative fibrosis (woody neck), especially in previously irradiated

areas. If a biopsy was previously performed, the tract should be

excised and incorporated into the new incision.When a total laryn-

gectomy is done, the stoma is fashioned separately from the neck

incision; in the event of a pharyngocutaneous fistula, the salivary

flow will be diverted away from the stoma.

Once the incision is made, subplatysmal flaps are raised. If

there is extensive lymphadenopathy or extension of tumor intothe soft tissues of the neck, skin flaps may be raised in a

supraplatysmal plane to ensure negative surgical margins. Such

flaps, however, are not as reliably vascularized as subplatysmal

flaps.Clinical judgment must be exercised in these situations.The

flaps are raised to the mandible superiorly, the clavicle inferiorly,

the omohyoid muscle and the submental region anteriorly, and

the trapezius posteriorly. Typically, radical neck dissections are

performed in patients with clinically positive lymphadenopathy,

and adequate exposure of levels I through V is required. If a ver-

tical limb is used, it must not be centered over the carotid artery,

because of the risk of potentially catastrophic dehiscence. Deep

utility-type incisions yield more limited exposure of level I but

provide reliable vascular inflow to skin flaps.

Step 2: Dissection of Anterior Compartment

Embedded within the fascia overlying the submandib

gland is the marginal mandibular branch of the facial ne

which must be elevated and retracted to prevent lower-lip w

ness.The submental fat pad is then grasped, retracted poste

ly and laterally, and mobilized away from the floor of the

mental triangle.The omohyoid muscle is identified inferior to

digastric tendon and skeletonized to its intersection with the s

nocleidomastoid muscle posteriorly.The omohyoid muscle fo

the anteroinferior limit of the dissection.

Fat and lymphatic structures are dissected away from

digastric muscle and the mylohyoid muscle.The hypoglossal

lingual nerves lie just deep to the mylohyoid muscle and are

tected by it [see Figure 3]. In this region, the distal end of the f

artery can be identified and preserved as needed for reconst

tive purposes. Once the posterior edge of the mylohyoid mu

is visualized, an Army-Navy retractor is inserted beneathmuscle to expose the submandibular duct, the lingual nerve

its attachment to the submandibular gland, and the hypoglo

nerve.The submandibular duct and the submandibular gangl

with its contributions to the gland, are ligated, and the

mandibular gland is retracted out of the submandibular trian

The posterior belly of the digastric muscle is then identi

inferior to the submandibular gland and skeletonized to the s

nocleidomastoid muscle posteriorly, where it inserts on the m

toid tip.The specimen must be mobilized off structures just i

rior to the digastric muscle. To prevent inadvertent injury,

essential to understand the relationships among these struct

[see Figure 3]. The hypoglossal nerve emerges from beneath

mylohyoid muscle and passes into the neck under the diga

a b c

d e f

Figure 2 Illustrated are incisions used for neck dissections. Incision design is a critical element of operative plan-

ning. Incisions are chosen with the aims of optimizing exposure of relevant neck levels and minimizing morbidity. The

incisions depicted in (a) and (b) are useful for selective neck dissections. For the more extensive exposure required in

a radical or modified radical neck dissection, a deeper half-apron style incision (c) may be used, or a vertical limb

may be dropped from a mastoid-submental incision (d); the latter incision is less reliable and may break down, expos-

ing vital structures such as the carotid.The incision depicted in (e) is also useful for selective neck dissections.The

Macfee incision (f) provides limited exposure and results in persisent lymphedema in the bipedicled skin flap.


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muscle. It then loops around the external carotid artery at the ori-

gin of the occipital artery and ascends to the skull base between

the external carotid artery and the internal jugular vein. Often,the hypoglossal nerve is surrounded by a plexus of small veins,

branching off the common facial vein. Bleeding in this region

places the hypoglossal nerve at risk.The jugular vein, located just

posterior to the external carotid artery and the hypoglossal nerve,

may be isolated and doubly suture-ligated at this point.

Frequently, the spinal accessory nerve is identified just lateral and

posterior to the internal jugular vein, proceeding posteriorly into

the sternocleidomastoid muscle.

In a radical neck dissection, the sternocleidomastoid muscle

and the spinal accessory nerve are transected at this point and ele-

vated off the splenius capitis and the levator scapulae to the

trapezius posteriorly. The anterior edge of the trapezius is skele-

tonized from the occiput to the clavicle. The accessory nerve is

again transected where it penetrates the trapezius.

Step 3: Control of Internal Jugular Vein Inferiorly; Ligation of

Lymphatic Pedicle

The sternal and clavicular heads of the sternocleidomastoid

muscle are transected and elevated to expose the anterior belly of

the omohyoid muscle.The soft tissue overlying the posterior belly

of the omohyoid muscle is dissected, clamped,and ligated as nec-

essary.The omohyoid muscle is then transected, and the jugular

vein, the carotid artery, and the vagus nerve are exposed. The

jugular vein is isolated and doubly suture-ligated. Care is taken

not to transect the adjacent vagus nerve and carotid artery. The

lymphatic tissues in the base of the neck adjacent to the internal

jugular vein are clamped and suture-ligated 1 cm superior to the

clavicle. If a chyle leak is encountered, a figure-eight stitch is

placed along the lymphatic pedicle until there is no evidence of

clear or turbid fluid on the Valsalva maneuver. Care is taken to

avoid inadvertent injury to the vagus nerve or the phrenic nerve,which course through this region.

Step 4: Mobilization of Supraclavicular Fat Pad (Bloody

Gulch)

The fascia overlying the supraclavicular fat pad is incised, and

the supraclavicular fat pad is bluntly retracted superiorly so as to

free the tissues from the supraclavicular fossa. If transverse cervi-

cal vessels are encountered, they are clamped and ligated as nec-

essary. Fascia is left on the deep muscles of the neck, which also

envelop the brachial plexus and the phrenic nerve.

Step 5: Dissection and Removal of Specimen

Attention is then turned to the posterior aspect of the neck. Fat

and lymphatic tissues are retracted anteriorly with Allis clamps,and the specimen is dissected off the deep muscles of the neck

with a blade. Again, a layer of fascia is left on the deep cervical

musculature: stripping fascia off the deep cervical musculature

results in denervation of these muscles, which adds to the mor-

bidity associated with accessory nerve sacrifice. Once the speci-

men is mobilized beyond the phrenic nerve, the cervical nerves

(C1C4) may be divided.The specimen is peeled off the carotid

artery and removed.

Step 6: Closure

The neck incision is closed in layers over suction drains.

MODIFIED RADICAL NECK DISSECTION

The incision is made and flaps elevated as in a radical neck dis-


2 HEAD AND NECK


6 NECK DISSECTION 6

Internal CarotidArtery

Common CarotidArtery

ExternalCarotidArtery

LingualArtery

SuperiorThyroidArtery

Facial

ArteryDigastricMuscle

HyoglossalMuscle

MylohyoidMuscle

Occipital Artery

Internal JugularVein

SpinalAccessoryNerve

Ansa Hypoglossi

HypoglossalNerve

Vagus Nerve

Hyoid Bone

Carotid Sheath

Figure 3 Depicted are the key anatomic relationships in levels I and II that must be kept in

mind in performing a neck dissection.View is of the right neck.


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2 HEAD AND NECK


6 NECK DISSECTION

section. Care must be exercised in elevating the posterior skin

flap.Typically, the platysma is deficient in this area, and often, no

natural plane exists. Dissection deep in the posterior triangle may

result in inadvertent injury to the spinal accessory nerve, which

travels inferiorly and posteriorly across the posterior triangle in a

relatively superficial plane to innervate the trapezius.

A type I modified radical neck dissection begins with dissec-

tions of levels I and II, as described for a radical neck dissection(see above).The spinal accessory nerve is identified just superfi-

cial or posterior to the internal jugular vein and preserved; the

distal spinal accessory nerve is then identified in the posterior tri-

angle.Typically, the spinal accessory nerve can be identified 1 cm

superior to the cervical plexus along the posterior border of the

sternocleidomastoid muscle. Provided that the patient is not fully

paralyzed, the surgeon can distinguish this nerve from adjacent

sensory branches by using a nerve stimulator.

Once the spinal accessory nerve is identified, it is dissected and

mobilized distally to the point at which it penetrates the trapez-

ius. Proximally, the nerve is dissected through the sternocleido-

mastoid muscle, which is transected over the nerve.The branch

to the sternocleidomastoid muscle is divided with Metz scissors,

and the nerve is fully mobilized from the trapezius posteroinferi-orly to the posterior belly of the digastric muscle anterosuperior-

ly, then gently retracted out of the way.

The rest of the neck dissection proceeds as described for a rad-

ical neck dissection. If the tumor does not involve the internal

jugular vein, it may also be preserved; this constitutes a type II

modified radical neck dissection. If the spinal accessory nerve, the

internal jugular vein, and the sternocleidomastoid muscle are all

preserved, the procedure is a type III modified radical neck dis-

section. In a type III dissection, the sternocleidomastoid muscle

is fully mobilized and retracted with two broad Penrose drains,

and the contents of the neck are exposed. The spinal accessory

nerve is preserved thoughout its entire course, including the

branch to the sternocleidomastoid muscle.The remainder of the

neck dissection proceeds as previously described (see above).

SELECTIVE NECK DISSECTION

Levels I to IV

In a selective neck dissection, the posterior triangle is not

removed; thus, there is no need to elevate skin flaps posterior to

the sternocleidomastoid muscle. Limited elevation of skin flaps is

beneficial, particularly for patients who have previously under-

gone chemoradiation therapy, in whom extensive flap elevation

may contribute to significant persistent lymphedema after opera-

tion. Subplatysmal skin flaps are raised sufficiently to expose the

neck levels to be dissected, with the central compartment left

undisturbed. If level I dissection is planned, the fascia overlying

the submandibular gland is raised and retracted so as to preservethe marginal nerve.The submental fat pad is grasped and mobi-

lized away from the floor of the submental triangle (composed of

the anterior belly of the digastric muscle and the mylohyoid mus-

cle). Inferiorly, the lymphatic tissues are mobilized off the poste-

rior aspect of the omohyoid muscle, which forms the anteroinfe-

rior limit of the neck dissection.

Once the digastric tendon and the posterior edge of the mylo-

hyoid muscle are visualized, the mylohyoid is retracted with an

Army-Navy retractor so that the submandibular duct, the lingual

nerve with its attachment to the submandibular gland, and the

hypoglossal nerve are visualized. The submandibular duct and

ganglion are ligated, and the submandibular gland is retracted out

of the submandibular triangle.

At this point, the facial artery is encountered and suture-ligat-

ed. Because the artery curves around the submandibular gl

the facial artery, if not preserved, must be ligated twice (pr

mally and distally). If the neck dissection is part of a large epative procedure involving free-flap reconstruction, the f

artery is preserved for use in microvascular anastomosis.

The posterior belly of the digastric muscle is then ident

inferior to the submandibular gland. This muscle has b

referred to as one of several residents friends in the n

because it serves to protect several critical structures that lie

deep to it, including the hypoglossal nerve, the external car

artery, the internal jugular vein, and the spinal accessory n

[see Figure 4].The posterior belly of the digastric muscle is sk

tonized to the sternocleidomastoid muscle,where it inserts on

mastoid tip.The specimen is then mobilized away from struct

just inferior to the digastric muscle. The hypoglossal n

emerges from beneath the mylohyoid muscle and passes into

neck just below the digastric muscle, looping around the extecarotid artery at the origin of the occipital artery and ascend

to the skull base between the external carotid artery and the in

nal jugular vein. Bleeding from small branches of the comm

facial vein that envelop the hypoglossal nerve place this struc

at risk for injury. The spinal accessory nerve is often visual

just superficial or posterior to the internal jugular vein, exten

posteriorly to innervate the sternocleidomastoid muscle.

Next, the fascia overlying the sternocleidomastoid musc

grasped and unrolled medially throughout its length, startin

the anterior edge of the muscle.The fascia is removed unti

spinal accessory nerve is identified at the point where it p

trates the muscle.This nerve is dissected and mobilized supe

ly through fat and lymphatic tissues to the digastric muscle. C

must be taken not to inadvertently injure the internal jug

MylohyoidMuscle

ExternalCarotidArtery

OccipitalArtery12th Nerve

11th NervInternalJugularVein

OmohyoidMuscle

Sternocleido-mastoidMuscle

CommonCarotidArtery

Digastric Muscle(Posterior Belly)

Figure 4 Selective neck dissection.The posterior belly of the

digastric muscle is identified inferior to the submandibular gla

This muscle protects several critical structures just deep to it (

hypoglossal nerve, the carotid artery, the internal jugular vein,

and the spinal accessory nerve). View is of a left neck dissectio


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2 HEAD AND NECK


6 NECK DISSECTION 8

vein, which lies in close proximity to the nerve superiorly.Tissue

posterior to the accessory nerve is grasped and freed from the

deep muscles of the neck, the digastric muscle superiorly, and the

sternocleidomastoid muscle posteriorly.The tissue included in so-

called level IIb is passed beneath the spinal accessory nerve and

incorporated into the main specimen.

The sternocleidomastoid muscle is retracted, and the fascia

posterior to the internal jugular vein is incised. Dissection is car-ried down to the deep cervical musculature and cervical nerves,

which form the floor of the dissection.The specimen is retracted

anteriorly. A layer of fascia is left on the deep cervical musculature

and the cervical nerves to preserve innervation of the deep mus-

cles of the neck and protect the phrenic nerve as it courses over

the anterior scalene muscle.

The specimen is peeled off the internal jugular vein and

removed. Dissection too far posteriorly behind the vein may result

in injury to the vagus nerve or the sympathetic trunk and predis-

poses to postoperative thrombosis of the vein. Ligation of internal

jugular vein branches should be done without affecting the caliber

of the vein or giving the vessel a sausage link appearance, which

would create turbulent flow patterns predisposing to thrombosis.

Overall, gentle dissection around all vessels, with care taken toavoid pulling-related trauma, minimizes the risk of endothelial

injury. Dissection behind the internal jugular vein may result in

injury to the vagus nerve or the sympathetic trunk.

A level IV dissection may be facilitated by retracting the omo-

hyoid muscle inferiorly or by dividing it for additional exposure.

The tissue inferior to the omohyoid is mobilized and delivered

with the main specimen.The lymphatic pedicle is clamped and

ligated. Care is taken to look for leakage of chyle, particularly

when a level IV dissection is performed on the left.

Levels II to IV

When level I is spared, a smaller incision suffices for exposure.

Subplatysmal flaps are raised superiorly to the level of the sub-

mandibular gland.The inferior flap is raised, exposing the anteri-or edge of the sternocleidomastoid muscle. Dissection proceeds

just inferior to the submandibular gland until the posterior belly of

the digastric muscle is identified. The digastric muscle is skele-

tonized posteriorly to the sternocleidomastoid muscle and anteri-

orly to the omohyoid muscle, which forms the anterior limit of the

dissection. The rest of the neck dissection proceeds as described

for a selective neck dissection involving levels I through IV.

Complications

INTRAOPERATIVE

Most intraoperative complications may be prevented by means

of careful surgical technique, coupled with a thorough under-

standing of head and neck anatomy. Injury to the internal jugular

vein may occur either proximally or distally. Uncontrolled proxi-

mal bleeding endangers adjacent critical structures, such as the

carotid artery and the hypoglossal nerve.The bleeding may be ini-

tially controlled with pressure, followed by a methodical search for

the bleeding source. Internal jugular vein lacerations can often be

repaired with 5-0 nylon sutures; if a laceration cannot be repaired,

the vein must be ligated. Occasionally, a laceration extends up to

the skull base, and the vessel cannot be controlled with clamping

and ligation. In these cases, it is acceptable to pack the jugular

foramen for hemostasis.

It is important to gain distal control of the internal jugular vein

before repair to prevent air embolism.Harbingers of air embolism

include the presence of a sucking sound in the neck, a mill-wheel

murmur over the precordium, ECG changes, and hypotension.

Predisposing factors include elevation of the head of the bed and

spontaneous breathing, which increase negative intrathoracic

pressure and thus promote entry of air into the venous system.

Injury to the internal jugular vein is more difficult to control when

it occurs distally in the neck or chest at the junction with the sub-

clavian vein. For this reason, ligation of the internal jugular vein inradical and modified radical neck dissections is typically per-

formed 1 cm superior to the clavicle.

Opalescent or clear fluid in the inferior neck suggests the pres-

ence of a chyle fistula. Chyle fistulas generally can be prevented

by clamping and ligating the lymphatic pedicle at the base of the

neck.Those fistulas that occur are repaired at the time of the neck

dissection.There is no benefit in isolating individual lymphatic ves-

sels, because these structures are fragile, do not hold stitches, and

are prone to tearing. A figure-eight stitch is placed along the lym-

phatic pedicle until there is no evidence of clear or turbid fluid

on the Valsalva maneuver.Care must be taken not to inadvertently

injure the vagus nerve or the phrenic nerve during repair of a chyle

leak.

POSTOPERATIVE

The best treatment of postoperative complications such as

hematoma and chyle leak is prevention. Hematomas, once pre-

sent, are best managed by promptly returning the patient to the

OR for evacuation.Management of postoperative leakage of chyle

depends on the volume of the leak. Low-volume leaks may be

managed with packing, wound care, and nutritional supplemen-

tation with medium-chain triglycerides.

Wound complications (e.g., infection,flap necrosis, and carotid

artery exposure or rupture) share certain interrelated causative

factors. Poor nutritional status, advanced tumor stage at presen-

tation, hypothyroidism, and preoperative radiation therapy have

all been associated with wound complications. After chemoradia-

tion therapy, the use of smaller incisions and more limited dissec-tion of soft tissues may lower the incidence of postoperative

wound problems, including persistent lymphedema and soft tis-

sue fibrosis. Conversely, poor planning of skin incisions may

increase the likelihood of wound complications such as wound

breakdown, skin flap loss, and exposure of vital structures.Wound

complications predispose to carotid artery rupture, the most cat-

astrophic complication of neck dissection.

In some case, severe edema after planned neck dissections in

patients previously treated with chemoradiation may cause respi-

ratory decompensation that necessitates tracheotomy. Postopera-

tive internal jugular vein thrombosis is not uncommon despite

preservation at the time of surgery,25 and it may exacerbate

edema. Impaired venous outflow predisposes to increased

intracranial pressure.26 This may be a greater concern in patients

who require bilateral neck dissections. If a radical neck dissection

is performed on one side, the internal jugular vein must be pre-

served on the other, or else the neck dissections must be staged.

These problems are further exacerbated when the patient has

undergone chemoradiation therapy before operation.

Most neck dissections result in some degree of temporary

shoulder dysfunction. Patients in whom nerve-sparing procedures

are performed can expect function to return within 3 weeks to 1

year, depending on the procedure performed. Shoulder dysfunc-

tion and pain are exacerbated when nerves supplying the deep

muscles of the neck are also sacrificed. All patients benefit from

physical therapy, which preserves full range of motion in the

shoulder while function returns.


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Acknowledgment

Figures 1 through 3 Tom Moore.

References

Documents

6 Neck Dissection