CLINICAL REPORT Guidance for the Clinician in Rendering Pediatric Care

Incidental Findings on Brain and SpineImaging in ChildrenCormac O. Maher, MD, FAAP, Joseph H. Piatt Jr, MD, FAAP, SECTION ON NEUROLOGIC SURGERY

abstract In recent years, the utilization of diagnostic imaging of the brain and spine inchildren has increased dramatically, leading to a corresponding increase inthe detection of incidental findings of the central nervous system. Patients withunexpected findings on imaging are often referred for subspecialty evaluation.Even with rational use of diagnostic imaging and subspecialty consultation,the diagnostic process will always generate unexpected findings that must beexplained and managed. Familiarity with the most common findings thatare discovered incidentally on diagnostic imaging of the brain and spine willassist the pediatrician in providing counseling to families and in makingrecommendations in conjunction with a neurosurgeon, when needed,regarding additional treatments and prognosis.

INTRODUCTION

The importance of brain imaging in contemporary medical practice canhardly be exaggerated, and technological advances have been matched byexpansion of access to this technology. When the senior author enteredmedical school, there was precisely 1 new first-generation computedtomography (CT) unit at his prestigious referral teaching hospital. Now,much more sophisticated devices are found even in small facilities. Inrecent years, the use of diagnostic imaging of the brain has expandeddramatically, and requests for consultation to assess the meaning ofunexpected findings have multiplied. Although insurance carriersscrutinize them, few population-based data have been publisheddescribing actual numbers of studies performed, particularly amongchildren. In every year from 2008 through 2012 in the state of Delaware,slightly more than 2% of all children enrolled in Medicaid underwentCT scanning or MRI of the brain (P. White, Delaware Division of Medicaidand Medical Assistance, personal communication, 2013). A recent reviewof 6 large integrated health systems in the United States found thatMRI use quadrupled between 1996 and 2010, reflecting a 10% annualgrowth rate.1 MRI use is influenced by many factors, including increasingavailability, patient-generated demand, and “defensive” practice.2

Although rates of MRI use vary substantially by geographic region within

This document is copyrighted and is property of the AmericanAcademy of Pediatrics and its Board of Directors. All authors have filedconflict of interest statements with the American Academy ofPediatrics. Any conflicts have been resolved through a processapproved by the Board of Directors. The American Academy ofPediatrics has neither solicited nor accepted any commercialinvolvement in the development of the content of this publication.

Clinical reports from the American Academy of Pediatrics benefit fromexpertise and resources of liaisons and internal (AAP) and externalreviewers. However, clinical reports from the American Academy ofPediatrics may not reflect the views of the liaisons or theorganizations or government agencies that they represent.

The guidance in this report does not indicate an exclusive course oftreatment or serve as a standard of medical care. Variations, takinginto account individual circumstances, may be appropriate.

All clinical reports from the American Academy of Pediatricsautomatically expire 5 years after publication unless reaffirmed,revised, or retired at or before that time.

www.pediatrics.org/cgi/doi/10.1542/peds.2015-0071

DOI: 10.1542/peds.2015-0071

PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275).

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the United States,3,4 overall MRI useis substantially higher in the UnitedStates than in most other industrial-ized countries. In the most recentdata from the Organization for Eco-nomic Cooperation and Development,MRI use in the United States per 1000population was 97.7, the highest ratein the survey and more than doublethe Organization for Economic Co-operation and Development average.5

As a result, the increase in incidentalbrain and spine findings is of partic-ular importance in the United States.An unintended consequence of suchwidespread diagnostic imaging is thediscovery of many incidental findingsunrelated to the original reasons forthe studies.

BENIGN ENLARGEMENT OF THESUBARACHNOID SPACES

Benign enlargement of thesubarachnoid spaces (BESS), alsoknown as “benign externalhydrocephalus,” is a transientdevelopmental phenomenon that isreally a variant of normal and iscommonly seen in neurosurgerypractice.6–8 Because the indication forthe brain imaging that discloses BESSis usually macrocephaly, it may not bean incidental finding in a strict sense,but it is incidental insomuch astreatment is seldom necessary. In theera of CT scanning, it was the focus ofsome confusion, the term “benignsubdural effusions of infancy”suggests, but contemporaryultrasonography with Doppler or MRIcan make reliable distinctionsbetween subdural fluid collectionsand prominence of the subarachnoidspaces. Likewise, the term “externalhydrocephalus” suggestsa disturbance of cerebrospinal fluid(CSF) physiology, which has neverbeen substantiated experimentally.

The clinical picture is fairlyconsistent. Typically, the affectedpatient exhibits accelerated headgrowth in midinfancy but otherwisethrives. Often, 1 parent has a headcircumference at or beyond the 95th

percentile. Despite the presence ofmacrocephaly, the fontanel is slackand there is no suture separation.Brain imaging may show a minordegree of ventriculomegaly that is notin proportion to the expansion of thesubarachnoid spaces. Althoughseldom documented because of itsbenign clinical course, the naturalhistory of BESS is resolution later inchildhood; and from a clinicalstandpoint, the child’s headcircumference can be expected todrift gradually back toward the top ofthe normal range over a period ofyears.9 The developmental prognosisof BESS is the topic of somediscussion in the literature andremains imprecisely defined, evenafter imaging mimickers, such asachondroplasia, Sotos syndrome, andmucopolysaccharidoses, have beenexcluded.8,10,11 Generally, after initialgross motor delays attributable to theexcessive size of the head,development is normal, but carefulobservation is warranted.

Neurosurgical referral is notnecessary in the absence ofventricular enlargement or subduralfluid collections unless parentsrequire the reassurance of thesubspecialist. Although a degree ofventricular enlargement mayaccompany BESS, a report ofventricular enlargement raisesa question of hydrocephalus thatmust be addressed bya neurosurgeon. Likewise,a description of subdural hygroma orchronic subdural hematoma indicatesreferral.6,12–14 In addition, if theinterpretation of the initial imagingstudy fails to distinguish betweenBESS and subdural hematoma orhygroma, neurosurgical referral isindicated necessarily as well. Thedisproportion between the volume ofthe cranium and the volume of thebrain that characterizes BESS iswidely believed to createsusceptibility for development ofsubdural fluid collections, but thefinding of a subdural collectioncannot be dismissed. A recent cohort

study identified subdural collectionsin 4 of 177 young children with BESS(2.3%), 1 of whom was determined tobe a victim of abuse.15 Even in thesetting of BESS, chronic subduralhematoma still constitutes anindication for investigation of thepossibility of abuse, including dilatedfunduscopic examination andradiographic skeletal survey.15

CHOROID PLEXUS CYST

Choroid plexus cysts are commonfindings on antenatalultrasonography in the secondtrimester. Prevalence rates between0.6% and 2.3% have beenreported.16–19 Choroid plexus cystsare of some significance in perinatalmedicine because of their associationwith fetal aneuploidy in the setting ofother risk factors. AlthoughShuangshoti and Netsky20 reportedsmall choroid plexus cysts in themajority of unselected autopsyspecimens, they are infrequentincidental findings on brainultrasonography in infancy and areseldom noted on brain imagingstudies in older children and adults.Thus, choroid plexus cysts in the fetusare generally believed to regressbefore or shortly after birth. Theneurosurgical literature containsmany case reports of choroid plexuscysts that were symptomatic atpresentation from obstructivehydrocephalus, but we are aware ofonly a single example in print ofa cyst detected in the secondtrimester that persisted to term andprogressed postnatally to becomea clinical problem.21 Thus, thereseems to be little cause for concernabout postnatal neurosurgicalcomplications of antenatally detectedchoroid plexus cysts. Indeed, theauthors are unable to reference anypublished guidelines for follow-upimaging in infancy. Incidentallydetected choroid plexus cystsassociated with mass effect orhydrocephalus certainly requireneurosurgical referral. There is no

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evidentiary basis forrecommendations about smallercysts, but neurosurgical consultationis likely to prove more conclusive andless expensive than sequentialimaging studies.

CHOROIDAL FISSURE CYST

The choroidal fissure can be found onthe mesial surface of the temporallobe between the hippocampus andthe diencephalon, and a choroidalfissure cyst is a loculated cavity filledwith CSF lying in the fissure. Therelationship of the cyst to the fissureis best visualized on coronal brainimaging; on axial imaging (as in mostCT scans), the location of thisstructure can be misconstrued.22

Almost without exception, choroidalfissure cysts are incidental findings.22

The natural history of choroidalfissure cysts has not beendocumented in detail, but in general,cysts without mass effect in school-aged children are static and requireno follow-up.23,24 In infancy,choroidal fissure cysts can exhibit anunstable, progressive course.25

Because the imaging diagnosis can besubtle and because other cysticlesions of the mesial temporalstructures can have very differentclinical implications, neurosurgicalreferral is indicated.

LIPOMA OF THE FILUM TERMINALE

Filum terminale lipomas are a type oflumbosacral lipoma in which fat isentirely within the filum terminaleand separate from the conusmedullaris. Filum lipoma issometimes detected as a genuinelyincidental finding but more often isa finding of uncertain significancethat comes to light in the course of aninvestigation of intractable urinaryincontinence, chronic constipation,pes cavus, gait abnormalities, oranomalies of the intergluteal crease.The prevalence of filum lipoma atautopsy has been reported to be6%.26 Its prevalence among childrenand adults undergoing MRI for

unrelated reasons is 1.5% to 4%.27–31

The concern is that filum lipoma maybe a cause of or marker for spinalcord tethering.32 Symptoms oftethered cord syndrome include backand lower extremity pain, urologicabnormalities, lower extremityweakness, gait disturbance, and footand ankle deformities such as pescavus.33–35 With the increasing use ofMRI, filum lipomas have beenidentified more frequently inasymptomatic individuals.28,36,37 Theclinical significance of a filum lipomain an asymptomatic child is a subjectof debate.27,36,37 Division ofa lipomatous filum for relief oftethering (a relatively simpleneurosurgical procedure) isundertaken commonly in selectedpatients with pain, progressiveneurologic deficits, scoliosis, ordisturbances of bowel and bladderfunction.34,38,39 Unfortunately,symptoms such as back pain andurologic complaints are common inchildren without neurologicabnormalities, and many of thesesymptoms resolve with time, medicalmanagement, and behavioraltherapy.40,41 Therefore, themanagement of children withsubjective symptoms of tethered cordsyndrome is controversial, especiallyfor those patients without lower thannormal position of the spinal cord onimaging. The untreated naturalhistory of asymptomatic filum lipomais probably benign for mostpatients.29 For this reason,prophylactic untethering is notindicated for most patients, althoughsome authorities in the past havepromoted aggressive prophylactictreatment.38 Neurosurgicalevaluation is appropriate, but surgicalintervention will seldom provenecessary for incidentally discoveredlesions.

PERINEURAL (TARLOV) CYSTS

Perineural cysts arise from the spinalnerve root or dorsal root ganglion.They have a meningeal lining and

contain CSF that is in variablecommunication with CSF of the thecalsac, and nerve rootlets and ganglioncells lie in the cyst or within the cystwall. The eponym “Tarlov” is appliedto cysts arising in the sacral region,which is by far the most commonsite.42 Among adults, the imagingprevalence of Tarlov cysts has beenreported to be between 1.5% and4.6%.31,43–45 The prevalence amongchildren is much lower, consistentwith gradual acquisition andexpansion of the lesions based onupright posture and hydrostatic CSFpressure. Incidental cysts greatlyoutnumber symptomatic ones.Clinical assessment must focus oncorrelating anatomy with symptomsand with the segmental neurologicexamination. Perineural cysts area doubtful explanation for nonspecificlow back pain, but they can causeradicular pain and neurologic signs.In the sacral region, perineal pain,bladder symptoms, and sexualdysfunction are relevant.Characteristic features areexacerbation by Valsalva-type eventsand relief with recumbency.Anatomically consistentradiculopathy indicates neurosurgicalreferral, and when the nature of thepresenting symptoms is obscure,neurosurgical consultation isnecessary as well. No imagingsurveillance is required in most cases.

INCIDENTAL BRAIN TUMORS

There is no alternative toneurosurgical referral andmanagement of a child with animaging study interpreted to show anincidental brain tumor. Nevertheless,the primary care physician canaddress family anxiety and adjustexpectations more effectively withsome understanding of managementissues.

The great majority of incidentallydiscovered brain tumors in childhoodare benign. This fact is readilyexplained by the overall slightpredominance of benign over

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malignant tumors in childhood andthe much longer time intervalbetween the threshold of imagingdetection and production ofsymptoms for benign tumors.46

Examples of benign childhood braintumors include astrocytoma (WorldHealth Organization grades 1 and 2),ganglioglioma, and dysembryoplasticneuroepithelial tumor.

Reliable statistics describing theprevalence of asymptomatic braintumors in childhood do not exist.Imaging case series of children withheadache are uninformative fora variety of reasons. Such seriesfeature only highly selected patients.Brain tumors reported in these seriesare seldom explicitly stated to beincidental, and no accounting is madefor possible indolent tumors amongwhat are called “white matter lesions”or “parenchymal tissueabnormalities.”47–51 The recruitmentof normal adults for MRI research isgenerating a growing volume ofliterature on the prevalence ofincidental findings among genuinelyasymptomatic individuals, butthere is very little information onnormal pediatric research subjects.Kim et al52 found 1 likely cerebellartumor among 225 children (0.4%)enrolled in MRI research. Jordanet al53 found 4 asymptomatic braintumors among 953 children (0.4%)with sickle cell disease recruited to animaging study of silent cerebralinfarction. Seki et al54 noted no braintumors among the MRI studies in 150normal Japanese children between5 and 8 years of age. No brain tumorswere recognized among 96 normalchildren from Malawi studied via MRIby Potchen et al.55 Because theneoplastic nature of an isolatedincidental finding can often beconfirmed only by growth revealedon sequential studies, cross-sectionalsurveys of normal subjectsnecessarily produces low estimates.

Whatever their true prevalence maybe, incidental brain tumors area regular feature of pediatric

neurosurgery and neurooncologypractice.56–58 As expected, benignlesions predominate. In 1 relativelylarge series, only 3 of 47 tumors weremalignant.58 Management isindividualized on the basis of theappearance and location of the lesion.Lesions recognized to be malignant,such as medulloblastoma, areinvestigated and treated aggressively.Lesions for which even a small degreeof expansion may magnify thedifficulty of surgical treatment, suchas craniopharyngioma, are alsoinvestigated and treated expediently.On the other hand, the neurosurgeonmay choose to observe lesions thatappear to be benign glial tumors.56–58

Benign glial tumors in childhood havea favorable natural history comparedwith histologically similar lesionsamong adults, for whom eventual andlethal malignant degeneration is therule. Benign childhood gliomas growslowly, and incidental lesions can betreated surgically for cure before theycause symptoms. Malignantdegeneration is rare among children,so withholding of treatment untilimaging surveillance reveals growthis often a safe and attractive strategy.The emotional stress of periodicimaging is burdensome for somefamilies, so patient and familypreferences must be weighed.

INCIDENTAL VASCULAR LESIONS

Four types of vascular malformationsare recognized in the central nervoussystem: arteriovenous malformation(AVM), cavernous hemangioma,developmental venous malformation(DVM), and telangiectasia. The last ofthese lesions, telangiectasia, is almostinvisible on CT scan. It requiresselected MRI sequences, contrastadministration, and ideally, highmagnet strengths for clearidentification.59 It is believed to poseno risk of hemorrhage and is nota common incidental finding inchildhood.60

AVMs vary greatly in size andcomplexity, but the defining feature is

the direct connection between thearterial and venous systems withoutan intervening capillary bed. AVMspose a lifelong risk of hemorrhage atarterial pressures, leading to highrates of neurologic disability andpossible mortality. Incidentaldiscovery of a cerebral AVM is anindication for neurosurgical referral,and families may be counseled thata recommendation for proactivetreatment may be forthcoming.

Cavernous hemangioma, or“cavernoma,” is a less-threateninglesion composed of thin-walledvessels of varying luminal sizewithout any intercalated normalbrain tissue. Constituent vessels thatare not thrombotic convey blood atcapillary or venous pressures and atvery low flow rates. Cavernomas areinvisible on catheter angiography, butthey have a vivid and distinctive MRIappearance. Multiple lesions are notuncommon, and follow-up may revealenlargement of existing lesions andde novo appearance of new ones. Theclassic autopsy prevalence is 0.4%.61

The imaging prevalence of incidentalcavernomas in childhood has beenestimated at 0.3%, and prevalenceseems to increase with age.62

Cavernomas become symptomaticeither with seizures or fromhemorrhage. They are distinct fromAVMs in that hemorrhages aresmaller, are less likely to causedisability depending on anatomiclocation, and are infrequently fatal.The annual risk of hemorrhage islower as well; a recent report ofa pediatric series estimated a 0.2%per lesion per year rate for incidentalcavernomas.62 Finally, in comparisonwith AVMs, the surgical managementof cavernomas is relativelystraightforward. Neurosurgeons aregenerally reluctant to operate onasymptomatic cavernomas, butexceptions may be made on the basisof such factors as intervalenlargement, anatomic location, orfamily preference. The referringphysician may reassure the familythat an incidental cavernoma poses

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no immediate threat to the life andwell-being of the child, but allowancemust be made for exercise of theconsultant’s judgment in treatmentrecommendations.

What were formerly called “venousangiomas” are now denominated“developmental venousmalformations” (DVMs), because theyhave come to be recognized asnothing more than anomalouspatterns of venous drainage ofnormal brain parenchyma. DVMs arecommon incidental imaging findingswith an autopsy prevalence of2.5%.61 They can be seen at any levelof the neuraxis, but in the cerebralhemispheres they have a typicalmorphology: a dominant, radiallyoriented vein drains superficially ordeeply and converging on the originof this vein are a number of smallertributaries. This typical morphology,the “caput medusae,” recalls theappearance of snakes emanating fromthe head of Medusa in Greekmythology. DVMs can be seen inassociation with other vascularmalformations, most commonlycavernomas, in which case clinicalmanagement is dictated by thecharacter of the associatedlesion.63–65 In isolation, DVMs haveno recognized causal relationshipwith hemorrhage, seizures, or anyother clinical phenomena.64 Childrenwith incidentally discovered DVMsdeserve neurosurgical review, but inthe absence of any associatedvascular pathology, isolated DVMs donot require treatment or follow-up.60,65

PITUITARY ABNORMALITIES

Unanticipated imaging findingsinvolving the pituitary gland are socommon that the term “pituitaryincidentaloma” has established itselfin the literature.66 The autopsyprevalence of pituitary tumors hasbeen estimated at 14%,67 but the mixof incidental findings also includescysts of various kinds, physiologicand pathophysiologic hypertrophy of

the gland, the so-called empty sellasyndrome, and morphologicanomalies of the sella itself that candistort the appearance of thegland.68–71

As is true of incidentally discoveredbrain tumors, there is no alternativeto neurosurgical referral forincidentally discovered pituitarylesions, but the general pediatriciancan set expectations and initiate theinvestigation. A sensible first step isto obtain a menstrual history, ifappropriate, and screening endocrinedata: cortisol, thyroxine (T4),triiodothyronine (T3), thyroid-stimulating hormone, insulin-likegrowth factor 1 or somatomedin,prolactin, and, in postmenarchialgirls, b-human chorionicgonadotropin. In this context, notemust be made of the naturalhypertrophy of the pituitary glandassociated with pregnancy70 and theunnatural but secondary hypertrophyof the pituitary gland associated withprimary hypothyroidism.71 Unlike inadults, the most common secretorytumor of the pituitary gland inchildhood is the corticotrophadenoma, followed by prolactinomaand somatotroph adenoma, butmanagement proceeds according tothe same principles as in adulthood.72

Visual field testing is indicated forexpansive lesions large enough todistort the optic chiasm, and as foradults, surgical intervention is usuallyindicated.

Normal developmental expansion ofthe pituitary gland in peripubertalgirls continues to be an occasion forconfusion.73 Normative values for thedimensions of the gland have beenanalyzed.74 The gland may take ona spherical shape, the diaphragm ofthe sella may assume a convexcontour, and the gland may abut theoptic chiasm. Uniform signal intensity,prompt homogeneous contrastenhancement, and normal endocrinelaboratory data confirm thephysiologic nature of these changes.Similar but less pronounced features

may be seen in boys.74 Neurosurgicalreferral may be considered indoubtful cases, but experiencedneurosurgeons are very reluctant tocall an enlarged pituitary abnormal inthis clinical setting.73

Patients with other incidentalfindings and normal endocrinelaboratory values will be referred forneurosurgical consultation as well,but families may be reassured thatimaging surveillance will likely be therecommendation. The frequency andduration of imaging surveillanceremain a matter for neurosurgicaljudgment.75

ARACHNOID CYSTS

Arachnoid cysts are very common.Most recent large studies haveestimated arachnoid cyst prevalenceon imaging at ∼2%.76–79 Theprevalence of arachnoid cysts doesnot change significantly withadvancing age. Boys are nearly twiceas likely to harbor arachnoid cystsas girls.77,80–83 Most arachnoid cystsare found in the anterior middlefossa and retrocerebellarlocations.76,77,80–83 Middle fossaarachnoid cysts have a left-sidedpredominance.76,77,79,80,83 Arachnoidcysts may be very large or very small,but size does not correlate preciselywith symptoms or the need fortreatment.

Arachnoid cysts occasionally presentwith neurologic signs or symptoms;however, in most cases they areasymptomatic and foundincidentally.77,84,85 Becausearachnoid cysts are commonincidental findings, individualsfrequently present with both anarachnoid cyst and an unrelatedcondition or symptom. Cliniciansshould exercise caution whenascribing any nonspecific symptom,such as headache, behaviordisturbance, or epilepsy, to thepresence of an arachnoid cyst.85,86

Furthermore, such symptoms oftenpersist after surgical treatment of an

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arachnoid cyst.81,86 Althougharachnoid cysts may occasionallyenlarge or decrease in size, most donot change substantially overtime.76,77

Although most arachnoid cysts shouldnot be treated, there are certain clearexceptions that will benefit fromtreatment. Cysts should be treated inmost cases if they are causingclear and specific neurologicsymptoms.87–90 Even small cysts mayrequire treatment if they blocknormal CSF pathways and causesymptomatic hydrocephalus.Arachnoid cysts in the suprasellarlocation are especially likely to causesymptoms and require treatment. Aswith any surgical procedure, theseoperations are associated withpotential morbidity,81,91–93 and thedecision to treat surgically should bemade very carefully and only aftertaking the prevalence and naturalhistory of these cysts into account.Most middle fossa and retrocerebellararachnoid cysts should not betreated. A minority of neurosurgeonscontinue to make an argument thatarachnoid cysts may alter cognitionand have used this argument asa justification for surgery in somecases.94,95 Evidence of mass effect onimaging is not, by itself, a sufficientindication for surgical treatment of anarachnoid cyst. Any large intracranialcyst can have the appearance of masseffect on imaging. This criterion,therefore, is too inclusive to be usedas a reliable indicator for selectingpatients for surgical treatment.Because arachnoid cysts are commonand the untreated natural history ofmost arachnoid cysts is benign, mostbelieve that surgical treatment shouldbe avoided except in the unusualinstance in which a cyst is clearlyresponsible for specific symptoms.

Arachnoid cysts may occasionallydevelop associated subduralhygromas resulting froma spontaneous or traumatic tear inthe outer cyst lining.86,96,97 Thesehygromas are rare, and although they

are often symptomatic, they do notalways require surgical treatment.Furthermore, surgical treatment ofarachnoid cysts can cause iatrogenichygromas.86,87,93 For these reasons,prophylaxis against future hygromarisk should not be regarded as anadequate indication for surgicaltreatment. Hemorrhage mayoccasionally occur into an arachnoidcyst after trauma.97–100 Because thisis also a very rare event, prophylaxisagainst future hemorrhage riskshould not be used to justify surgicaltreatment in an asymptomatic child.Furthermore, hemorrhagesassociated with arachnoid cysts areassociated with generally goodoutcomes, even when surgicalevacuation of the hemorrhage isdeemed necessary.97

PINEAL CYSTS

Pineal cysts are also frequentlydiscovered on brain MRIs inchildren.101–106 Pineal cystprevalence changes with age, butthese cysts are found more frequentlyin girls than in boys in all agegroups.101–103,105–109 They arerelatively unusual in infants,becoming more common in childhoodand adolescence, and peak in youngadulthood when they are seen in asmany as 2% to 4% of brain MRIs.They become increasingly uncommonwith advancing age inadulthood.101,103,105,110 Becausemost pineal cysts are too small to bedetected on MRI, the prevalence ofmicrocysts on autopsy studies is evenhigher.111,112 Despite the frequentoccurrence of this finding on imaging,the discovery of a pineal cyst oftenresults in a neurosurgicalconsultation.105,107,113

Pineal cysts have a typical appearanceon MRI. Cyst contents may be eitherisointense or slightly hyperintenseto CSF on T1-weighted andhyperintense on T2-weightedimaging.104,108,114–116 The cyst rimappears smooth and thin in mostcases, but multiple septations within

the cyst itself is a commonfinding.111,112,117 Many benign pinealcysts show evidence of irregularnodular enhancement or ringenhancement on MRI118,119 becauseof surrounding venous structures orthe displaced pinealtissue.101,103,120,121

Several groups have reported on thenatural history of untreated pinealcysts over time.101–103,105,107,120

Although some cysts enlarge andothers involute, most cysts remainthe same size over several yearsof follow-up. Importantly, the vastmajority of asymptomatic cystsremain asymptomatic. Some growthover time is more often seen inchildren, and involution is more oftenseen in adults. Taken together withthe cyst prevalence data, the naturalhistory data suggest that pineal cystsfrequently arise and change duringchildhood and then involute duringadulthood. For this reason, cystgrowth alone in an asymptomaticchild should be regarded as thenatural course of these cysts andshould almost never, by itself, be usedas a justification for surgery.101–103

Pineal cysts are almost alwaysasymptomatic. Rarely, hydrocephalusmay result from cerebral aqueductalobstruction due to a large pinealcyst.106 Some reports have suggestedthat cysts larger than 1 cm inmaximal dimension are more likely tobe symptomatic.106,112,119,122 Mostcysts that cause hydrocephalus aregreater than 2 cm in maximaldimension.123 Rarely, large pinealcysts have also been associated withgaze palsy and Parinaudsyndrome.106,108,118,122,124,125

Although large cysts may besymptomatic, this occurrence is rare.The vast majority of even large cystsmay be expected to presentincidentally and remainasymptomatic.101–103,107,115,120 Giventheir common incidence on imaging,pineal cysts have a frequentcoincidental association withcommon symptoms such as headache.

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A substantial number of childrenpresent to their pediatrician withheadaches and a pineal cyst that iscoincidentally rather than causallyassociated. Although there are reportsof pineal cyst surgery performed forthe treatment of chronicheadaches,119,122,126,127 mostsurgeons do not regard a history ofchronic headache in the absence ofhydrocephalus as an indication forsurgical treatment of a pineal cyst.Not surprisingly, headaches can beexpected to have reliablepostoperative symptomatic relief onlyif the headaches were caused byhydrocephalus.123

Pineal cysts are usually incidentallyidentified and, once identified, do notresult in clinical symptoms in mostcases. Specialty consultation andfollow-up imaging should beconsidered merely optional for mostasymptomatic children witha conclusive imaging diagnosis ofa pineal cyst. In almost every case,cysts smaller than 1 cm will notrequire neurosurgical evaluation.Larger cysts may also be managedwithout surgery in many cases butmay benefit from an evaluation bya neurosurgeon.

CHIARI AND SYRINGOMYELIA

Chiari malformation type I (CM) isa condition found frequently inchildren as well as in younger andmiddle-aged adults. CM isoccasionally associated withneurologic symptoms. The classicpresentation of CM is headacheprecipitated by Valsalva-type events,such as sneezing, coughing, orstraining. Typically, these headachesare short-lived and locatedposteriorly. Other symptoms arelegion but often nonspecific. Theseinclude visual disturbances,dysphonia, dysphagia, sleep apnea,clumsiness and incoordination, andsensory disturbances.128,129 CM mayalso lead to the development ofsyringomyelia, which, in turn, maylead to other symptoms including

motor and sensory difficulties, pain,and scoliosis.130–134 Surgical caseseries tend to overestimate thefrequency of syringomyelia inpatients with CM.135–137 Theprevalence of syringomyelia in thesetting of CM estimated from imagingdatabases has been reported to bebetween 12% and 23%.138,139

Syringes are less likely to be foundassociated with CM in childrenyounger than 5 years but maydevelop later in childhood.139 Lowerposition of the cerebellar tonsils inCM is associated with a greaterlikelihood of syringomyelia.139–141

It is probable that Chiari symptomsand the formation of spinal syringesare the result of crowding at theforamen magnum that leads toabnormal movement of CSF at thecraniocervical junction.134 Childrenwith CM often have a smaller thannormal posterior fossa volume,resulting in crowding of the posteriorfossa and foramen magnumcontents.142–144 This crowding at theforamen magnum may be appreciatedon sagittal MRI by the typical “peg-shaped” appearance of the cerebellartonsils. Because “crowding” isdifficult to quantify or objectivelydetermine, the diagnosis of CM onimaging is usually made bya determination of cerebellar tonsilposition on MRI. Most often, childrenare assigned a diagnosis of CM if thecerebellar tonsils are found to be5 mm or more below the foramenmagnum, usually defined as a linebetween the basion and opisthion inthe midsagittal plane.78,139,145–148

This definition of CM resulted fromthe publication of several clinicalstudies involving small numbers ofpatients at the dawn of the MRIera.145,146 Although cerebellar tonsilmeasurements that define CM on MRImay be a convenient marker forcrowding at the foramen magnum,the correlation is not exact. Patientswith less than 5 mm of descent canoccasionally present with typical CMsymptoms or even syringomyeliaattributable to crowding at the

foramen magnum.149 Conversely,many patients with cerebellar tonsilsthat are more than 5 mm below theforamen magnum are completelyasymptomatic.139,150,151 Although CMdoes present with symptoms in manycases, it is also a very commonincidental finding in asymptomaticindividuals. Unfortunately, thecurrent clinical tendency appears tobe unreservedly admitting suchpatients to a patho-anatomic groupwe call CM on the basis of tonsilposition alone.

Like most morphometricmeasurements, cerebellar tonsilposition with respect to the foramenmagnum follows an essentiallynormal distribution in all agegroups.152 Those on the lower end ofthis population distribution fallwithin the range that may bediagnosed as CM on MRI. The averageposition of the cerebellar tonsilstrends inferiorly during childhoodand young adulthood, but the trendreverses with advancing age inadulthood.147,152 Females have, onaverage, a lower tonsil position thanmales, and CM is more frequentlydiagnosed in females.139,140,151

If the current imaging definition oftonsils 5 mm below the foramenmagnum is used, CM is notrare.78,138–140,153,154 CM is found inapproximately 0.8% to 1% of allpatients undergoing MRI when age isnot considered.78,138,153 Whenprevalence is stratified by age, it isclear that the prevalence in childrenand young adults is greater.152 Asmany as 3.6% of children undergoingMRI of the brain or cervical spinehave CM by imaging criteria; mostchildren who meet the definition ofCM by imaging criteria areasymptomatic.139,154

There are no universally acceptedsurgical indications for CM.Asymptomatic individuals withouta spinal syrinx are only exceptionallyconsidered for surgical treatment.Those with clear symptoms who alsohave syringomyelia are generally

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considered excellent candidates forChiari decompression surgery.155

Treatment of those with nonspecificsymptoms such as headache (withoutthe usual characteristic features ofChiari-associated headache) iscontroversial. Because headaches area common symptom in the generalpopulation and CM is a commonincidental finding on imaging,surgeons must exercise restraintwhen selecting these patients fortreatment. The natural history of anincidentally discovered Chiari may beexpected to follow a benign course inmost cases.150,151,156 Symptoms andMRI findings are stable over time formost patients, with no symptoms orminimal symptoms that are followedwithout surgical treatment, althoughspontaneous improvement orworsening of both the CM as well assyringomyelia does occasionallyoccur.150,151,156

Although most cases of clinicallyrelevant syringomyelia are associatedwith CM, it may also be seen inpatients with spinal cord tumor,tethered cord, or arachnoiditis.157,158

In general, the management ofsyringomyelia should be directed atthe primary disorder. When noprimary disorder is identified, thesyrinx is considered idiopathic. Theuntreated natural history ofidiopathic syringomyelia isexcellent,158,159 and the majority ofsuch cases should not be consideredfor surgical treatment. Small spinalsyringes may be difficult todistinguish from minimal dilations ofthe central canal of the spinal cord.Central spinal cord fluid collections ofless than 2 or 3 mm in maximaldiameter on axial imaging generallyrepresent only a dilated central canaland are not associated withsymptoms.

Children with imaging diagnoses ofCM or syringomyelia generallyrequire neurosurgical consultation,but the pediatrician can reassureparents that incidental, asymptomatic

findings are unlikely to requiresurgical treatment.

CONCLUSIONS

Unexpected findings on imagingstudies now account for a largefraction of new patients referred topediatric neurosurgical practices.They are the cause of a great deal ofparental distress, and they putpatients at risk of unnecessaryadditional testing and unnecessarysurgery. Rational use of diagnostictechnology and subspecialtyconsultation can minimize theseconfusing family experiences, but thediagnostic process will alwaysgenerate an irreducible minimum ofunexpected findings that must beaccepted and managed for thepatient’s welfare. Familiarity with themost common entities allows thepediatrician to allay parentalanxieties with informed preliminarycounseling and to set appropriatepriorities for subsequent referralsand investigations. By improving theirknowledge base about incidentalfindings on neuroimaging,pediatricians can provide guidance tofamilies, with neurosurgicalconsultation when needed regardingclinical relevance, need for additionaltesting, and need for follow-up.

LEAD AUTHORS

Cormac O. Maher, MD, FAAPJoseph H. Piatt, Jr, MD, FAAP

SECTION ON NEUROLOGIC SURGERYEXECUTIVE COMMITTEE, 2013–2014

John Ragheb, MD, FAAPPhillip R. Aldana, MD, FAAPDavid P. Gruber, MD, FAAPAndrew H. Jea, MD, FAAPDouglas Brockmeyer, MD, FAAPAnn Ritter, MD, FAAP

IMMEDIATE PAST CHAIR

Mark S. Dias, MD, FAANS, FAAP

STAFF

Vivian ThorneLynn Colegrove, MBA

ACKNOWLEDGMENT

We thank Ms Holly Wagner forproviding editorial assistance.

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DOI: 10.1542/peds.2015-0071 originally published online March 30, 2015; 2015;135;e1084Pediatrics 

Cormac O. Maher, Joseph H. Piatt Jr and SECTION ON NEUROLOGIC SURGERYIncidental Findings on Brain and Spine Imaging in Children

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