Can be caused by developmental anomaly, haemorrhage, infection or tumour. Tx ventricular shunt, most commonly ventriculoperitoneal shunt (VPS, lateral ventricle -> peritoneal cavity). If patient with VPS has HA, vomiting, lethargy, increased intracranial pressure then image from cranium to abdomen to look for shunt disconnection, kinking, dislocation (esp between shunt tubing and shunt chamber overlying the cranium). Head CT for interval change in ventricular size with increase suggesting insufficient shunting and slitlike ventricles overshunting. Abdominal pseudocyst from static positioning of distal tubing, usually Ix with US.
- Dorsal induction (3-4/40, neurulation) – flat bed of cells transformed into round brain and spinal cord, transformation of embryonal ectoderm cells into neuro-ectoderm.
- Primary neuralisation – Notochord induces overlying ectoderm to transform into neuroectoderm (neural plate), which folds inwads and closes, forming a neural tube (and overlying neural crest). Disorders affect spinal cord. Adhesions between inner endoderm and outer ectoderm cause neurenteric cysts and diastematomyelia. Premature separation of neuroectoderm and cutaneous ectoderm lets fat fuse with neuroectoderm, causing lipomyelocele, lipomyelomeningocele, intradural lipoma. Lack of separation caues cephaloceoels, anencephaly, Chiari malformations, spinal dysraphysm, exencephaly, craniorachischisis, dermal sinus tracts.
- Secondary neurulation – Mesenchyme condensates, forms a neural rod then cavitates to form a neural tube, later forms the inferior elements. Disorders affect conus medullaris, filum terminale, cauda equina. Include lipomas, tethered cord/filum, caudal regression syndrome, sacral agenesis.
- Ventral induction (5-8/40) – Vesicles (prosencephalon, mesencephalon, rhombencephalon) form the cerebrum, midbrain, cerebellum and brainstem, dividing into hemispheres. Include holoprosencephaly, septo-optic dysplasia, callosal dysgenisis, pituitary anomalies, Dandy-Walker, rhombencephalosynapsis, Joubert syndrome. Premaxillary facial structures also in association hence may also have cyclopia, probosci.
- Neuronal proliferation, differentiation and histgenesis (8-18/40) – Neurons proliferate and differentiated within the germinal matrix. Disorders include microencephaly, macroencephaly, phakomatoses, aqueduct stenosis, lissenephaly, vascular malformations, teratomas.
- Migration (12-22/40) – Neuroblastas and glioblasts centrifugally migrate along radial glial fibres. Neuroblasts from periventricular regions migrate 1st to molecular layer of cortical zone 1 (most peripheral grey matter). Glioblasts and neuroblasts from intermediate zone then migrate in waves to periphery then double back to fill the cortex inner->outer (zone 5->2), resulting in cortical organisation. Abnormal causes lissencephaly, heterotopia, pechygyria, polymicrogyria, schizencephaly etc.
- Myelination (22/40 -> 24/12).
Normal Patterns of Myelination
Myelinated structures (lipid myelin sheath) high T1 then low T2; on FLAIR dark (water) -> bright (‘watery brain’ resolves) -> dark (myelination). Myelination generally posterior->anterior, inferior->superior, central->peripheral, motor->sensory. Parallels developmental landmarks. Needs to be corrected for prematurity. Normal myelination mapped by Barkovitch.
- Newborn – high T1 cerebellar peduncles, dorsal brainstem, ventrolateral thalamus, lentiform, posterior limbs, corticospinal tracts -> perirolandic white matter.
- 3 months – high T1 anterior limb, cerebral white matter.
- 4 months – high T1 splenium, centrum semiovale.
- 6 months – high T1 genu; low T2 splenium.
- 8 months – high T1 subcortical; low T2 genu.
- 11 months – low T2 anterior limb.
- 14 months – low T2 occipital white matter.
- 16 months – low T2 frontal white matter.
- 18 months – adult except terminal myelination zones (periatrial, frontal horns).
- 24 months – low T2 white matter except some minimal peripherally.
Delayed myelination from in utero insult (hypoxia/ischaemia, infection, toxins, coagulopathy etc), metabolic (amino and organic acidopathies), nutritional inadequacy of myelin precursors (diet, malabsorption), leukodystrophies. Correlates with developmental delay.
Cerebral palsy is a nonprogressive neurologic motor deficit (spasticity, dystonia, ataxia, paresis) from insults occured during prenatal/perinatal periods. Risk of cerebral palsy increased with premature subependymal haemorrhage and destruction, periventricular abnormalilty with irregular ventricular wall, widespread infarction, deep grey involvement, periventricular cysts. Focal parenchymal damage is less debilitating.
Hypoxic-Ischaemic Encephalopathy (HIE)
(Neonatal encephalopathy, hypoxic ischemic injury). Perinatal hypoxic/ischaemic brain damage from foetal distress in placental abruption, meconium, proloapsed umbilical cord, uterine rupture, severe placenta previa etc. Reudced Apgar scores, neonatal acidosis, hypotonia, lethargy, seizures. <26/40 unable to mount glial/scarring response (hence no high T2, causes porencephaly), >26/40 high T2 in areas of ischaemia. Theory of shifting arterial border zones which move centrifugally with development. 1st/2nd T immediate periventricular, 2nd/3rd T peripheral white and cortical grey matter. 4 patterns of injury, usually bilaterally symmetric:
- Deep grey matter
- Cotical watershed or perirolandic
- Periventricular white matter without cortical extension
- Mixed injury ± haemorrhage
In 1st few days findingsare very subtle as oedema is difficult to distinguish in a watery neonatal brain. Posterior limb of internal capsule should be myelinated in newborn, hence loss of this high T1 suggests HIE.
Partial asphyxia in premature infants causes [[#Periventricular Leukomalacia (PVL)|periventricular leukomalacia (PVL)]] and/or [[#Germinal Matrix Haemorrhage (GMH)|germinal matrix haemorrhage (GMH)]].
Profound asphyxia (cardiac arrest, hypotension) <32/40 affects deep grey matter and brainstem. High T1/echogenic thalami, basal ganglia, perirolanderic. Restricted diffusion in posterior limbs internal capsules, basal ganglia (high metabolic rate), corona radiata.
Partial asphyxia in term infants causes cortical watershed ischaemia between arterial territories; relative sparing of central brain (diving reflex redistributes blood centrally and to cerebellum). Depths of sulci in parasagittal regions are less perfused than apices of gyri -> mushroom-shaped gyri (ulegyria), selective loss of cranial nerve nuclei of pons (pontosubicular necrosis), purkinge cells of cerebellum, injury to hippocampus. Variable deep and periventricular white matter gliosis/atrophy, ex-vacuo effect, apposition of sulci to ventricular surface. Myelination delay, thinned large white matter tracts (eg corpus callosum), irregular myelination in deep nuclei causes status marmoratus (marble-like appearance).
Profound asphyxia of term infants affects corpus striatum (globus pallidus, putamen, caudate), lateral thalami, hippocampus, dentate nuclei. Relative sparing of cortex apart from perirolandic.
Severe global ischaemia causes diffuse loss of grey white differentiation, swelling. ‘White cerebellum sign’ (‘dark cerebellum’ on T2).
DDx Nonhypoxic ischaemic encephalopathy, with metabolic/toxic insult to sensitive basal ganglia. Cx cerebral palsy, cognitive disabilities (common).
Very common (25-50%) in asymptomatic term infants, more common in vaginal and assisted deliveries. Usually posterior parafalcine, <4mm, posterior fossa. Resolves within 1/12.
Periventricular Leukomalacia (PVL)
(White matter injury of prematurity, WMIP). Watershed infarcts of perforator aa, causing spastic diplegia, visual field deficits. P>A esp trigone. Not initially seen on US unless haemorrhage. In 1st 2 days periventricular white matter echogenicity (as echogenic as choroid plexus). If severe -> necrosis -> cyst formation (2-4/52) which coalesce (multicystic encephalopathy) -> porencephalic cysts -> resolve or cause ventriculomegaly with irregular contours from atrophy, thin corpus callosum, reduced white matter volume. Gliosis (best seen on PD) causes reduced white matter thickness, enlarged ventricles extending close to cortex, deep diving sulci. On US grade I evanescent echogenicity lasting <1/52; grade II lasts >1/52; III evolves into small cysts; IV evolves into extensive cysts; V involves subcortical white matter with extensive periventricular and subcortical cysts. On MR there may be extensive periventricular and subcortical haemorrhagic foci despite more mild US findings.
Germinal Matrix Haemorrhage (GMH)
(Subependymal/intraventricular haemorrahge). Form of ischaemic brain injury. Germinal matrix is a zone of proliferating, highly vascular neuroectodermal cells between ependyma of ventricles and caudate nucleus (caudothalamic groove), source of neuroblasts and spongioblasts (migrate to brain forming cortical glial cells), usually involutes at 32/40 (hence GMH not usually seen after this). Sensitive to injury -> haemorrhage of fragile vessels. From apnea, hypoxia, acidosis, bradycardia, unstable BP, impaired cerebral blood flow autoregulation. Incidence 30-55% of infants born at 24-32/40, most in 1st 1/52. At term, germinal matrix involutes as border zones move peripherally. Grade III-IV poor prognosis.
- Grade I – Small isolated subependymal haemorrhage, echogenic anterior to caudothalamic groove, may resolve or -> subependymal cyst. Asymmetric enlargement of choroid plexus is suspicious.
- Grade II – Intraventricular haemorrhage without dilatation. Any echogenic foci in frontal or occipital horns represents haemorrhage (no choroid plexus here).
- Grade III – IVH with dilatation. Ventriculomegaly 1st 2/52 after haemorrhage, persisting for 3-6/12.
- Grade IV – Intraparenchymal haemorrhage, ?from venous infarction (rather than primary bleed) from obstruction of thalamostriate veins draining periventricular white matter. Residual porencephaly.
Haematoma initially echogenic -> echolucent centrally -> shrinks. Hydrocephalus from obstructing clot, organised ependymitis or arachnoid granulation obstruction. Spastic paralysis from injury to corticospinal tracts. Cognitive defects.
Maternal Cocaine Abuse
Higher risk of focal infarctions to basal ganglia, neural tube defects. ?Vasospasm from cocaine.
Glucose level <3mg/mL from hyperinsulinaemia, may cause seizures, altered mental state. From maternal diabetes, hypoxic-ischaemic injury, sepsis, gestational immaturity/malnutrition, glucose dysmetabolism (Beckwith-Wiedemann syndrome, endocrinopathies). May cause high T2 and T1 in parieto-occipital region from haemorrahge, calc, demyelination.
(Bilirubin encephalopathy). High signal in globus pallidus, resolving with normalisation of bilirubin.
Retinopathy of Prematurity
(Retrolental fibroplasia). From chronic high concentrations of oxygen, esp for treatment of SDD. In the initial hyperoxic phase I vascular endothelial growth factor (VEGF) is reduced, causing endothelial apoptosis. In phase II there is relative hypoxia on return to room air ventilation, increasing VEGF and inducing retinal neovascularisation and fibrous scar ± retinal detachment. Increased risk of strabismus, glaucoma, cataracts and myopia in later life.
Congenital and Developmental Abnormalities
From failed embryologic event or destruction of already formed structure. Type of lesion reflects timing of disturbance, multiple distinct abnormalies may be present.
No brain, should be detected prenatally with raised AFP. Cranial vault small with only face and posterior fossa well seen given ‘frog-eye’ or ‘Mickey Mouse’ appearance. Malformation of anterior end of neural tube. Area cerebrovasculosa – flattened remnant of disorganised brain tissue, ependyma, choroid plexus and meningothelial cells. Posterior fossa structures may be spared. Associated with spinal dysraphism.
Infarction of both hemispheres from ?early compromise to both carotids but preserved posterior circulation (hypercoagulation, placental issues, severe in-utero infection). Little or no supratentoral brain tissue, no ‘rind’, thin-walled cystic structures in place of parenchyma. Typically preserved thalami, occipital lobes, inferior temporal lobes, brainstem and cerebellum (vertebral aa), thin rim of leptomeningeal connective tissue (including falx, cf holoprosencephaly). May be impossibe to be differentiate from severe/maximal hydrocephalus.
Parenchymal injury prior to end of 2nd trimester (<26/40) with no glial scar formation. Porencephalic cyst = thin-walled fluid-filled spaces communicating with ventricles, no septations.
Spectrum from failed cleavage of cerebral hemispheres. Orbital hypotelorism or cyclopia, variable facial dysmorphism. Always has absent septum pellucidum. May have solitary central maxillary incisor. Olfactory tracts usually absent. Associated with caudal agenesis, DiGeorge syndrome, fetal alcohol syndrome, Kallmann syndrome, maternal diabetes, trisomy 13/15/18.
- Alobar holoprosencephaly – Severe, stillborn or die soon after birth. Anterior rind of brain tissue with posterior tips = hippocampal ridges, large horseshoe-shaped monoventricle communicating with dorsal cyst/sac, fused thalami, absent septum pellucidum, corpus callosum and falx, single ACA, absent 3rd ventricle.
- Semilobar holoprosencephaly – Partial fusion of hemispheres with part of the interhemispheric fissure, falx and temporal horns usually formed, partial separation of thalami. Absent or dysgenic corpus callosum (interhemispheric fissure required for this to form). Absent septum pellucidum with single ventricle anteriorly. Associated with migration anomalies.
- Lobar holoprosencephaly – Partial absence frontal interhemispheric fissure and falx. Absent septum pelluidum. May have dysgenic corpus callosum (genu and rostrum absent).
Septo-Optic Dysplasia (SOD)
(De Morsier syndrome). Can be consided to be mildest form of spectrum of holoprosencephaly. Variable hypoplasic optic nerves (may be limited to opitic disks). Complete/partial absence of septum pellucidum -> squared-off frontal horns pointing inferiorly. May have agenesis/dysgensis of corpus callosum. Associated with hypothalamic and pituitary dysfuctions (esp reduced GH), migration anomalies, periventricular cysts common, heterotopia, schizencephaly, cleft lip/palate, flat nasal bridge, hypotenorism.
Dysgenesis of the Corpus Callosum
(Callosal dysgenesis). Normally forms from anterior body -> posterior splenium -> rostrum; but myelinates posterior -> anterior; hence partial agenesis has absent posterior body and splenium. Complete (agenesis) or partial. Absent septum pellucidum is occasionally associated with absent corpus callosum; callosal dysgenesis is always associated with absent septum pellucidum; ie septum pellucidum requires the corpus callosum to form. Concomitant failed eversion of cingulate gyrus -> absent cingulate gyrus. Separated lateral ventricles with 3rd ventricle exending more superiorly between lateral ventricles. Medial hemispheric sulci extend to 3rd ventricle (spoke-wheel gyri). Redirection of callosal fibers (bundles of Probst) along medial ventricular walls -> coronal ‘steer-horn’, transverse ‘racing car’/’parallel ventricle’ appearances to frontal horns. Absent splenium means decreased posterior white matter, dilatation of ocipital horns -> colpocephaly. Associated with midline masses (lipoma and arachnoid cyst), interhemispheric cysts that may communicate with the 3rd ventricle, agyria, pachygyria, heterotopias, Dandy-Walker, holoprosencephaly, septo-optic dysplasia, cephalocoeles, Chiari I/II, trisomey 13/15/18, fetal alcohol syndrome, Meckel syndrome (occipital encephalocoele, microcephaly, polycystic kidneys, polydactyly), Aicardi syndrome in females (triad of callosal agenesis, epilepsy, choroid abnormality). DDx prominent hippocampal commissure (may mimic splenium), secondary destruction or holoprosencephaly (disorganised callosal development).
Congenital Optic Nerve Hypoplasia
Commonly associated with isolated hormone deficiencies, absent anterior pituitary, truncated pituitary stalk, ectopic/absent posterior pituitary bright spot.
Congenital hindbrain abnormality. Foramen magnum obstruction may increase systolic spinal cord motion, impaired recoil, impaired diastolic CSF motion at anterior C2-3 and in posterior fossa.
- Chiari I – Cerebellar tonsillar ectopia, foramen magnum appears full. Normal cerebellar tonsils are lowest at 5-15yo (up to <6mm), otherwise should be <5mm below foramen magnum. May have suboccipital HA, retroorbital pressure, clumsiness, vertigo, tinnitus, lower cranial nerve Sx (dysphagia, dysarthria, sleep apnoea, tremors), usually presents 30s-40s, F>M. Best seen on T1 sag. Elongated rather than round cerebellar tonsils. Medulla and 4th ventricle in normal position. Altered CSF dynamics may -> cervical cord syrinx (in 25%), hydrocephalus. Associated with Klippel-Feil syndrome (C2-3 fusion), short clivus, odontoid/C1 anomaly, compression of CSF spaces posterior and lateral to cerebellum, reduced height of supra-occiput.
- Chiari II (Arnold-Chiari malformation) – F>M. Severe neural tube disorder. Diminutive posterior fossa with cerebellum forced superior (through widened incisura), inferior (tonsillar herniation) and anterior (around brainstem), small vertical slit 4th ventricle, aqueduct stretched inferiorly with stenosis (in 70%), cervicomedullary kink as medulla buckles inferiorly. Obstructive hydrocephlus with squared off frontal horns (50-90%), inferior pointing lateral ventricles, tectal beaking (tectum pointed posteriorly), fenestrated falx cerebri (herniation of gyri), enlarged massa intermedia, partial/complete agenesis/dysgenesis of corpus callosum (80-90%), dysplastic posterior cingulate gyrus, syringohydromyelia (50-90%). Almost always associated with tethered cord and myelomeningocoele (almost all of these also have Chiari II), occasionally associated with closed spinal dysraphism. Tonsils may necrose causing fragments of cerebellar tissue in cervical CSF.
- Chiari III – rare, herniated posterior fossa contents through occipital or high cervical encephalocoele (cervicooccipital cephalocele).
- Chiari IV – rare, agenesis of the cerebellum.
Posterior Fossa Cystic Malformations
- Dandy-Walker malformation – Large posterior fossa with torcular-lambdoid inversion (high tentorial and torcular insertion above the lambda, cf Chiari malformations). Dilated 4th ventricle communicating with posterior fossa cyst causing mass effect, hypoplastic/absent inferior cerebellar vermis, absent falx cerebelli, hydrocephalus. ?Due to obstruction of foramina of Magendie and Luschka. High association with holoprosencephaly, callosal dysgenesis, polymicrogyria, heterotopias, schizencephaly, meningoencephalocoeles, lipomas, infundibular hamartomas, malformed olives, hydromyelia, cerebral hterotopia. May be associated with PHACES syndrome (posterior fossa malformation, haemangiomas, arterial anomalies, cardiac defects, eye abnormalities, sternal defects).
- Dandy-Walker variant – Some but not all criteria from classic malformation present. Usually posterior fossa cyst but normal-sized posterior fossa, hypoplastic vermis and cerebellar hemispheres, but no significant mass effect, no torcular-lambdoid inversion. Variable hydrocephalus. One or more of the 4th ventricle outlet foramina thought to be open.
- Mega/giant cisterna magna – Posterior fossa CSF cyst, fully developed vermis, prominent cisterna magna without mass effect (cf retrocerebellar arachnoid cyst). May see vessels coursing through the subarachnoid space.
- Arachnoid cyst – Posterior fossa CSF cyst, fully developed vermis, mass effect on the cerebellum and 4th ventricle, doesn’t communicate with 4th ventricle, no vermian hypoplasia.
- Inferior vermian dysgenesis/hypoplasia – may occur in isolation or associated with Dandy-Walker, Walker-Warburg syndrome, metabolic and toxic lesions, Chiari malformations, Down syndrome, Joubert syndrome.
AR, ataxia, sleep apnoea, abnormal eye/tongue movments, hypotonia. Parallel enlarged horizontal cerebellar peduncles and elongated pontine-midbrain junction (molar tooth sign), hypoplasia of vermis with virtual contact of cerebrellar hemispheres, 4th ventricle in bat wing appearance (maldeveloped middle cerebellar peduncle, superior cerebellar peduncle, pyramidal decussation). Associated with callosal dysgenesis, retinal dysplaisa, cystic renal disease.
Rare fusion of cerebellum across midline with absent anterior vermis, fusion of dentate nuclei and middle cerebellar peduncles, deficient posterior vermis. Associated with agenesis of septum pellucidum.
From chromosomal abnormalities, fetal alcohol syndrome, infection etc. Reduction in neurons reaching neocortex, with simplification of gyral folding. Migratory neurons leave the pool of periventricular proliferation precursor cell pool too early.
Arrested migration of neurons travelling from subependymal regions/germinal matrix to cortex along radial-glial fibres. May become foci of seizure activity.
Sulcation abnormality at 12-24/40 due to migration not proceding completely to superficial layers of cortex. Prematurity can mimic appearances. Associated with heterotopic grey matter, schizencephaly, callosal hypogenesis. Lissencephaly is smooth brain with litte/no sulcation.
- Pachygyria/agyria complex (complete lissencephaly) – Smooth hourglass/figure-of-eight brain with absent gyri (agria) and broad thick (8mm) multilayered cortex (pachygria). Incomplete migration to 6-layered cortex, ?cortical laminar necrosis of cell-sparse 3rd layer causing high T2. Absent interdigitating subcortical white matter. High risk in congenital CMV. White matter volume is reduced.
- Classical lissencephaly (LIS1 gene on chromosome 17) – 4 cortical layers with band heterotopias, affecting posterior > anterior.
- X-linked lissencephaly (DXC doublecortin gene) – affects anterior > posterior.
- Cobblestone lissencephaly (type II) – associated with Fukuyama muscular dystrophy, Walker-Warburg syndrome. Nodular surface irregularities, ocular anomalies, muscular disorders. Neuroblasts migrate beyond expected confines of superficial cortex, protruding into subarachnoid space. Thickened meninges adherent to cortex. In Fukuyama muscular dystrophy (Japanese patients) there may be cerebellar polymicrogyria, lissencephaly and clusters of intraparenchymal cerebellar cysts.
- Pachygyria (incomplete lissencephaly) – short broad fat gyri from abnormal sulcation and gyration of cortex.
- Polymicrogyria – ?Ischaemic laminar necrosis of 5th cortical layers ?CMV or vascular insult at end of neuronal migration, with reduced number layers left. Entrapment of meningeal tissue. Cortical thickening (5-7mm) of grey matter with multiple small disorganised cortical convolutions. White matter thickeness normal. Absent interdigitating subcortical white matter. May have deeper white matter high T2 ?gliosis, may be associated with DVA. When focal = cortical dysplasia. Frequently associated with Chiari, schizencephaly.
- Congnital bilateral perisylvian/opercular syndrome – polymicrogyria involving operculum, abnormal sylvian fissure sulcation. May be associated with schizencephaly, DVA.
- Type 1 focal cortical dysplasia (without balloon cells) – 11-23% of patients with epilepsy. Subtle findings with mild focal volume loss, cortical thickening, abnormal sulcation or blurring of cortical margins. CSF cleft overlying a cortical dimple reflects cortical dysgenesis. Homogeneous high T2 in subcortical white matter, tapering as it extends to the ventricle (from hypomyelination or Wallerian degeneraion). Microdysgenesis – too many cells in cortex, ectopic neurons in white matter, altered cortical lamination, no balloon cells; ? from hypoglycaemia.
- Balloon cell focal cortical dysplasia of Taylor – Increased number of neurons which are malorientated. Cortical thickening, high subcortical white matter T2, indistinct grey-white interface, radial bands from ventricle to cortex, usually frontal lobe (cf tumours in temporal lobe). Similar to cortical tuber. Focal grey transmantle dysplasia – grey matter extends from subependymal zone to cortex with pachygyria, heterotopia, polymicrogyria and schezencephaly. May have anomalous venous drainage.
- Megalencephaly – enlargement (including white matter), usually assocated with pachygria/agyria/polymicrogyria/heterotopias, ipsilateral ventriculomegaly. May be bilateral or unilateral (hemimegalencephaly). Associated with syndromes eg NF1, Soto syndrome, proteus syndrome, epidermal nevus syndrome, TS, Kippel-Trenaeunay-Weber syndrome. In later life may cause hemimicroceophaly due to retarded growth.
Islands of heterotopic grey matter in arrested migration anywhere between ependymal surface and cortex (between 7th-16th/40) ?due to damage to radial glial fibres. Isointense and parallel normal grey matter on all sequences, occasionally high T2 or hyperdense due to dystrophic microcalcifications. Associated with seizures and developmental delay. May be associated with encephalocoeles, holoprosencephaly, schizencephaly, Chiari, callosal agenesis.
- Nodular type (most)
- Subependymal/periventricular (most) – esp trigone, occipital horns, frequently bilateral. May be defective protein filamin-A on long arm of X chromosome, lethal in males. DDx tuberous sclerosis nodules which have intensity more similar to white matter, may grossly calcify.
- Subcortical – often abnormal sulcation superficially. Nodular or diffuse/laminar/curvilinear, usually closer to cortex.
- Band type – associated with severe developmental delay, earlier onset seizures. Isointense to grey, well-defined smooth margin. Thin interface of white matter between the band/laminar heterotopia and cortex creating double cortex sign. May have mass effect. May have overlying abnormal sulcation/gyration/migration.
Grey-matter lined clefts invaginating brain. In-utero insult (?ischemic watershed) or genetic 4th-7th/40 damage to germinal matrix and radial glial fibres near ventricles, impeding neuronal migration. Pial-ependymal seam communicates with ventricle. Uni- or bi-lateral, at frontal, frontoparietal, or occipital. Polymicrogyric clefts are focal cortical dysplasis not extending to ventricle. Open- or closed-lipped (may be missed) depending of apposition of cleft walls. Usually nodular heterotopia at ventricular junction. Associated with other migrational anomalies, heterotopic grey matter, anomalous venous drainage, focal cortical dysplasia (polymicrogyria), pachygyria. Most associated with dysgenesis of corpus callosum, agenesis of the septum pellucidum. DDx porencephaly – zone of encephalomalacia communiting with ventricle, but lined with white and grey matter (ie extends through both).
Vein of Galen Malformation
(Vein of Galen aneurysm). Arteriovenous fistula connecting cerebral artery(ies) with vein of Galen, usually presenting with CHF, cardiomegaly, widened superior mediastinum (vascular enlargement). Large vascular mass in region of posterior 3rd ventricle with feeding aa and v. Associated cortical loss, cortical oedema, hydrocephalus. Tx embolisation, untreated may -> death.
(Phakomatoses). Disorders of ectodermal origin, primarily skin and nervous systems.
Other syndromes with CNS disease include:
- Li-Fraumeni syndrome – medulloblastomas
- Turcot syndrome – medulloblastoma, glioblastoma
Neurofibromatosis Type 1 (NF-1)
(von Recklinghausen disease). Most common inherited CNS disorder (1:4,000), presents in childhood, AD, NF1 gene on chromosome 17 (encodes neurofibromin; 17 = number of letters in von Recklinghausen).
Diagnostic criteria include two or more of:
- >/=6 cafe-au-lait macules
- >/=2 neurofibromas or one plexiform neurofibroma
- axillary or inguinal freckles
- optic nerve glioma
- >/=2 Lisch nodules
- bone dysplasia (esp sphenoid wing absence) or pseudoarthrosis of long bone
- 1st degree relative with NF-1.
- CNS ‘NF-1 spots’ (foci of abnormal signal intensity FASI lesions) – nonenhancing high T2 foci in the globus pallidus, cerebellar peduncles and grey matter, brainstem (esp pons), internal capsule, splenium and thalami. Typically arise 3yo, increase in number and size until 12yo then regress. Wax and wane on serial imaging. No mass effect. ?Benign myelin vacuolisation, hamartomas, focal gliosis, Wallerian degeneration, dysplastic white matter or preneoplastic lesions.
- Optic tract and other gliomas (pilocytic astrocytoma) – typically fusiform enlargement of optic nerve (also optic chiasm, tracts and radiations, cerebellum, brainstem and cerebrum), enhancing high T2. Consider when an NF-1 spot enlarges.
- Retinal hamartoma
- Lisch nodule – pigmented nodule of the iris
- Hydrocephalus from aqueduct stenosis
- Pachygyria, polymicrogyria, syringomyelia, other heterotopias
- Cutaneous and plexiform neurofibromas – prone to malignant degeneration higher than comparable tumours in others
- Cafe au lait spots – cutaneous hyperpigmented macules
- Vascular dysplasia – aneurysms, FMD-type stenoses (esp ICA with moyamoya pattern)
- Hypoplastic/absent cranial bones – sphenoid wing, post-sup orbital wall, mastoid, macrocranium, enlarged cranial neural foramina (neurofibromas)
- Spinal: posterior vertebral body scalloping and enlarged neural foramina from dural ectasia or neurofibromas, kyphoscoliosis (T3-7, prone to rapid progression and instability -> paralysis), lateral thoracic meningogoeles.
- Bony overgrowth, anterior distal tibial bowing with pseudoarthrosis and tapered margins, areas of sclerosis, numerous NOFs, twisted-appearing/ribbon ribs (mesodermal dysplasia)
- Parenchymal lung disease in 20% with diffuse symmetric lower zone fibrosis, upper zone assymetric bullae. Symptoms usually minimal/absent.
Neurofibromatosis Type 2 (NF-2)
1:50,000, presents as young adult, AD, NF2 gene on chromosome 22 (encoding merlin). Diagnostic criteria include bilateral acoustic schwannomas or 1st degree relative and single acoustic schwannoma or any two of: schwanoma, neurofibroma, meningioma, glioma.
- Bilateral vestibular schwannomas and other schwannomas involving cranial nerves (esp CNV).
- Optic and other glial tumours including ependymomas
- Non-neoplastic schwanosis (Schwann cells growing into spinal cord), meningioangiomatosis (meningeal cells and blood vessels into brain and glial hamartoma (microscopic collections of glial cells in abnormal locations)
- Sublenticular capsular cataract.
- Rarely Cafe au lait spots.
Tuberous Sclerosis (TS)
(Bourneville disease). Most spontaneous, others AD as TSC1 on chromosome 9 (encodes hamartin) or TSC2 on chromosome 16 (encodes tuberin, more common). Triad of seizures, mental retardation, adenoma sebaceum. Most common cause of infantile spasm is TS; 50% of TS have infantile spasms. Affects skin, CNS, skeletal system, abdominal organs. Brain lesions are ?abnormal migration of dysgenetic giant cells capable of astrocytic or neuronal differentiation.
- Subependymal nodules/hamartomas – parallel grey matter signal before calc (80%), when calc iso-/hyper-T1, occasionally enhance. Droplike masses bulging into the ventricles like candle-guttering. Interval growth and development of enhancement suggest malignant degeneration (rare). In infants nodules are high T1, low T2 (opposite of adults).
- Cortical tubers/hamartomas – White matter hamartomas are linear radiating from ventricle or triangular with apex towards ventricles. Low T1, high T2, 50% calcify, occasionally enhance. Frontal>parietal>occipital>temporal>cerebellar. Often epileptogenic.
- Subependymal giant cell astrocytomas (SGCA/SEGA) – usually near foramen of Monro, may causes hydrocephalus. Usually enhance (cf occasionally mild in subependymal nodule). ?Arise from subependymal nodules. Don’t usually have malignant transformation.
- Cerebral atrophy
- Retinal astrocytic/glial hamartoma – focal calcification in retina, more extensive than drusen. Slow growing, don’t metastasise.
- Skin: Adenoma sebaceum (facial angiofibromas of the skin, red papules), ash-leaf spots, Shagreen patches (areas of leathery skin with orange-peel dimpling), subungual fibromas (tumours around/under toenails/fingernails).
- Cardiac rhabdomyoma
- Renal angiomyolipomas, RCC
- Cysts in liver, kidneys, pancreas
- Pulmonary TS is rare, indistinguishable from LAM. Smooth muscle proliferation in peribronchovascular and parenchymal interstitium involving entire lung symmetrically, scattered adenomatoid nodules, reticular/reticulonodular opacities, small thin walled cysts (uniform <10mm), normal to increased lung volume from small airways obstruction. Pneumothorax from ruptured subpleural cyst common. Often leads to PAH, cor pulmonale.
(Encephalotrigeminal angiomatosis). Low flow vascular malformations/angiomatous lesions of intra- and extra-cranial CNV distribution involving skin (port wine naevus V1 distribution) and meninges (pial angiomatosis). Seizures, mental retardation and hemiparesis. Usually sporadic, M=F. Pial angiomas cause gyral/serpigninous/tram-track cortical/subcortical calcifications within 4th layer of cortex esp occipital, parietal or temporal lobes; not seen until 2yo. Chronic ischaemia of underlying grey matter -> gyral atrophy and gliosis, hemiatrophy. Altered superficial cortical venous drainange -> enlarged deep and subependymal veins (resembling AVMs) with reduced cortical veins. Small ipsilateral cerebral aa with slow blood flow. Initially subtle underlying white matter low T2 without calc. Ipsilateral choroid plexus hypertrophy. Contrast reveals full extent with marked enhancement of pia; occasionally cortical enhancement by ischaemic injury. Overlying cranial thickening. 50% have ocular enhancment from choroid haemangioma or inflammation from glaucoma. May be bilateral. DDx Wyburn-Mason syndrome (less severe form with facial CNV naevus, retinal angioma, midbrain AVM), Klippel-Trenaunay-Weber syndrome (hemihypertrophy, cutaneous angiomas, varices, anomalous venous drainage).
Von Hippel-Lindau Syndrome (VHL)
Inherited AD, VHL tumour suppressor gene on chromosome 3 (encodes pVHL). May be associated with MENS, NF.
- Retinal angiomas.
- Haemangiomas/haemangioblastomas – highly vascular, mural nodule with large cyst. In cerebellum (most common), medulla, spinal cord, supratentorial (uncommon), retrobulbar optic nerve and orbit, kidneys, pancreas, liver.
- Cerebellar HB are benign (but 25% recurence) near pia-arachnoid surface. Well-circumscribed cyst with enhancing mural nodule, or solid mass ± central cysts, or cyst alone. Highly vascular, prone to sudden haemorrhage.
- Spinal HB (1/3 associated with VHL) are mostly intramedullary, some intra- and extra-medullary, occasionally extramedullary or extradural. Thoracic > cervical cord, most </= 10mm, rarely see flow voids if <15mm. Commonly associated with syrinx.
- Cysts in kidneys, pancreas, liver, adrenal, lung, epididymis
- Renal RCC
- Pancreatic islet cell tumour, adenocarcinoma
- Hepatic and splenic adenomas
- Bone haemangioma
- Endolymphatic sac tumour
- Cardiac rhabdomyoma
Basal Cell Naevus Syndrome
(Gorlin syndrome). Basal cell carcinomas, palmar skin pits, mandible cysts, patchy and enostosis-like bone sclerosis, scoliosis, medulloblastoma.
AD, colonic polyps, cutaneous tumours, meningiomas, dysplastic gangliocytoma of the cerebellum (Lhermitte-Duclos disease), thyroid/breast neoplasms.
(Progressive facial hemiatrophy). ?From chronic vasomotor/ischaemia to sympathetic nervous system. Unilateral focal infarction of corpus callosum, diffuse deep and subcortical white matter change, mild cortical thickening, leptomeningeal enhancement with mineralisation.
(Meningioangiomatosis). Hamartomatous proliferation of meningeal cells into cortex via intraparenchymal vessels. Leptomeningeal thickening, may be calcified. Cortical proliferation along Virchow-Robin spaces, psammomatous calcification (tram-track). No vascular abnormalily (cf Sturge-Weber).
Usually sporadic. Melanoblasts in globes, skin, inner ear, sinonasal cavity, leptomeninges causing cutaneous naevi and meningeal thickening. Diffuse enhancement of meninges (brain and spine), may be high T1 and hyperdense (similar to SAH). May cause hydrocephalus (obstructed arachnoid villi), neuropathies, syrinx. Malignant transofrmation of CNS melanosis in 50% with parenchymal or intramedullary infiltration.
Hereditary Haemorrhagic Telangiectasia (HHT)
(Osler-Weber-Rendu syndrome). Mucocutaneous telangiectasias and visceral AVMs. 5% have cerebral AVMs (2% of these associated with HHT). AVMs may have nidus (esp adults) or fistula (esp children).
Benign Macrocrania of Infancy
(Increased subarachnoid fluid space of infancy). Head circumference >97% for age, usually normalising after 2yo. Usually present 6/12-2yo. Prominent lateral ventricles and extraxial spaces, otherwise imaging normal. Diagnosis of exclusion. Imaging unable to differentiate with communicating hydrocephalus.
From direct viral infection, autoimmune response to virus/immunisation or extension of meningeal infection. Seizures, lethargy, focal neurologic defects.
- Herpes simplex type 1 – may -> necrotising meningoencephalitis. If from reactivation from CNV nerve, typically affects one/both temporal lobes. High signal in cortex, areas of haemorhage.
- Subacute sclerosing panencephalitis – disease of childhood ?reactiviation of latent measles. Nonspecific atrophy and increased T2 throughout cerebral white matter. Volume loss and dilatation of ventricles.
- Acute disseminated encephalomyelitis (ADEM) – response to recent viral infection/immunisation days to weeks later. Increased T2 in white matter (esp post), brainstem, cerebellum. Tx steroids.
Meningitis from haematogenous spread (respiratory infections) or direct (ear or sinus infection). H.influenze, E.Coli, group B strep. Inflammation of pia and arachnoid. Echogenic sulci, echogenic debris in ventricles, enlarged ventricules (obstruction from exudate), echogenic and shaggy thickening of ependyma, transient extra-axial collections. Cx persistent hydrocephalus, infarction or cerebritis (abnormal parenchymal enchogenicity), brain abscess.
Most common abnormality of paediatric orbit. Usually bacterial infection extending from sinusitis including staphylococcus, streptococcus and pneumococcus. Preseptal or postseptal (when inflammation extends posterior to septum, typically extraconal and subperiosteal). Septum defined as line through anterior bony confines of the orbit. Almost all associated with ethmoid sinus disease. Abscess has rim enhancement around fluid or gas, typically treated sugically. Cellulits treated with antibiotics alone.
Retropharyngeal cellulitis following URTI/pharyngitis. Fever, stiff neck, dysphagia, occasionally stridor. Thickened retropharyngeal tissues (soft tisse between aerated pharynx and anterior vertebra > AP verterbal body diameter) with anterior convexity. Pseudothickening esp patients with short necks improve with full extension. CT for ?drainable abscess.
Skull XR provide little useful information, a visualised fracture doesn’t necessarily indicate intracranial injury, absence doesn’t exclude it, fracture doesn’t usually affect management. Intracranial injuries include subdural, epidural and subarachnoid haematomas, parenchymal contusion. Generally NAI findings similar to accidental injury. Shaking may cause interhemispheric subdural haematoma. Suffocation/strangulation causes combination of traumatic subdural/subarachnoid haematoma with anoxic-ischaemic injury. Subdural haematomas of varying ages is also suggestive.
Neoplasm and Hamartomas
CNS tumours most common solid malignancies of childhood.
Posterior Fossa Tumours
More common than adults. Often present with obstructive hydrocephalus.
Most common posterior fossa tumour. Low grade pilocytic subtype, best prognosis of any CNS malignancy, most requiring only resection. Vermis or cerebellar hemispheres. Variable appearances, predominantly cystic ± enhancing mural nodule or completely solid. Well-defined margins (particularly with 4th ventricle). 4th ventricle displaced anteriorly. Heterogeneous enhancement. Calcification and haemorrhage is uncommon (cf medulloblastoma, ependymoma).
Primitive neuroectodermal tumour (PNET) arising from granular layer of superior medullary velum of the vermis (roof of 4th ventricle), occupying the 4th ventricle. Poorly defined margins, especially with the vermis. Hyperdense, diffuse homogeneous enhancement. MR signal more homogeneous than astrocytoma or ependymoma, tend to be low/mildy high T2. Propensity for intracranial and intraspinal CSF seeding. Hypercellular -> hyperdense and restricted diffusion on DWI.
Common moderately aggressive astrocytomas in the pons, WHO II or I. Tend to present with cranial nerve abnormalities, pyramidal tract signs, cerebellar dysfunction; rather than hydrocephalus (cf others). Circumferential enlargement of brainstem or exophytic. Homogeneous high T2. Enhancement prior to treatment is rare, except exophytic lesions. 10% have cystic components. 4th ventricle displaced posteriorly. Complete surgical resection usually not possible, radiation primary Tx.
Relatively slow-growing, benign tumour from ciliated ependymal cells lining ventricles. 2/3 arise from 4th ventricle, broad connection with floor (cf medulloblastoma roof). May fill and extend out of 4th ventricle via foramina -> cisterna magna, spinal canal. Heterogeneous, enhances. Well-defined lobulated margins (except poorly defined with floor 4th ventricle). Calcifications in 70%.
Much less likely than posterior fossa tumours. Most are glial (astrocytoma, oliogodendroglioma, glioblastoma), ranging from circumscribed to infiltrative. Appearances do not always correlated with grade. Less commonly PNETs, ependymoma, choroid plexus tumours. Choroid plexus tumours esp lateral ventricles, benign, slow growing; uncommonly malignant choroid plexus sarcomas which are markedly vascular with enhancement.
Tumours in the Region of Suprasellar and Third Ventricle
Include suprasellar, pineal and intraventricular tumours. Multiple differentials in this region.
Most common suprasellar tumour in childhood. Typically astrocytic involving any/all of visual pathway (optic nerve, chiasm, hypothalami). Range from benign hamartomas to aggresive malignancies. Higher risk in NF-1. Fusiform or exophytic enlargement of optic nerve. Optic chiasm lesion difficult to distinguish from hypothalamic gliomas as they tend to extend to each other, both high T2 with diffuse enhancement.
Germ Cell Tumours
Commonly in regions of pineal gland, hypothalamus or 3rd ventricle. Most common germinoma (identical histology to ovarian dysgerminoma and testicular seminoma), others teratoma (w fatty tissue or calc), embryonal carcinoma, choriocarcinoma. May have haemorrhage.
Range from benign pineocytomas to highly malignant pineoblastomas (histology similar to PNET). Almost exclusively in childhood. Enhancing pineal mass, almost always associated with hydrocephalus.
From persistence and proliferation of squamous epithelial cells of cranioparyhngeal duct. Benign, slow growing. Typically intrasella and suprasella. Calcify in 80%. Cystic and solid enhancing portions. Cystic components contain proteinaceous and cholesterol-laden fluid (high signal on all sequences).
Now thought to be congenital rather than neoplasm, from meninx primitiva (neural crest tissue which forms neural tube). High T1 suppressing with FS. Chemical shift artifact along frequency encoding direction. No mass effect, vessels pass unpertubed. Corpus callosal lipomas associated with callosal anomalies. Other locations include pericallosal interhemispheric fissure (50%), quadrigeminal plate, pineal region, suprasellar cistern, cerebellopontine angle, sylvian fissure, cerebellar vermis, lamina terminalis. Vessels often course through the lipoma making resection difficult.
Typically <5yo, bilateral in 25%, rarely also invovles pineal region with pineoblastoma (trilateral retinoblastoma, hereditary). Typically calcified intraocular mass, MR heterogeneous, variable enhancement. Predisposed to secondary osteosarcoma after radiotherapy. DDx orbital pseudotumour, haemangioma, lymphatic/venous malformation, optic nerve glioma, rhabdomyosarcoma, lymphoma/leukaemia, LCH, metastatic nerublastoma, haematoma.
(Craniostenosis). Premature closure of skull sutures which may be primary idiopathic or secondary to genetic/metabolic disorder. Typically present at birth, M>F. Perisutural sclerosis, lipping, bony bridging, narrowing of suture. May cause microcephaly, elevated ICP (chronic venous hypertension from jugular stenosis) with reduced brain perfusion, communicating hydrocephalus, tonsillar herniation. May be associated with Crouzon syndrome, Apert syndrome, Carpenter syndrome, endocrine abnormalities (rickets – usually caues widened delayed closure, hyperthyroidism, hypophosphatasia).
- Sagittal suture (most common) – long and narrow boat-shaped head (dolichocephaly/scaphocephaly).
- Coronal suture – wide L-R (brachycephaly). Unilateral coronal causes flattened forehead and orbital rim giving harlequen/winking eye appearance with elevated superolateral corner of the oval orbit and oblique lateral margin.
- Portion of a suture – asymmetric flattening/distortion (plagiocephaly)
- Metopic suture – pointed/triangular forehead (trigonocephaly) like triceritops.
- Synostosis of all sutures – clover-leaf skull (Kleeblattschadel) with bulging in squamosal areas and bregma; associated with thanatophoric dwarfism and Crouzon syndrome.
(Luckenschadel). Defect in mesenchymal formation of skull, almost all associated with myelomeningocoele/Chiari II. Multiple oval lucencies (thining of inner table) more prominent in occipital and parietal regions. Present in all patients with myelomeningocoele <3/12, typically resovles by 6/12.
DDx skull changes with increased intracranial presure where there is marked accentuation of normal convolutional markings (like hammer-beaten silver, less severe than lacunar skull), sutural diastasis, sellar enlargement and demineralisation.
(Cephalocoele). Failure of skull and dura to cover brain -> herniation. Meningocoele = herniated leptomeninges alone (less common). Encephalocoele = herniated brain and leptomeninges. Most occipital (associated with Chiari III, may be associated with holoprosencephaly, aqueduct stenosis), others parietal, frontoethmoidal (associated with craniofacial anomalies incl hypertelorism and callosal abnormalities, nasal dermoids), sphenoidal (occult, nasopharyngeal mass containing 3rd ventricle, hypothalamus, optic chiasm), Meckel’s cave (marked CSF enlargement). Intracranial brain stretched and distorted towards defect. Anterior cephalocoeles may be associated with agenesis of corpus callosum, coloboma (defect in eye), cleft lips.
Calvarium invovled in AD and AR types. Thickening with stenosis of skull base foramina causing CN palsies, optic atrophy, carotid and jugular stenosis. Diffuse bone thickening and increased density.
Small foramen magnum, macrocephaly may be due to hydrocephalus (venous outflow obstruction reducing arachnoid villi absorption), short clivus, platybasia, J-shaped sella, congenital spinal stenosis (short pedicles).
Congenital/deveplomental lesions most common paediatric intraspinal mass.
Congenital Vertebral Anomalies
- Transitional segmentation – variation from 7C, 12T, 5L and 5S vertebrae. May have lumbarisation of T/S, sacralisation of L, 11 or 13 rib pairs. Line between iliac crests usually passes through L4-5, widest transverse process usually L3, left renal vein usually anterior to L1-2.
- Failure of formation – incarcerated/free/multiple hemivertebra (failed lateral cartilagnious centre), wedge vertebra (failed ant/post), butterfly vertebra (central sagittal defect from lack of fusion of the two cartilaginous centres)
- Failure of segmentation – bilateral failed segmentation -> block vertebra with short spine, unilateral unsegmented bar -> progressive curve (incomplete disc)
Failure of cevical segmentation at multiple levels usually with short AP diameter and short webbed neck, low hairline, limited motion. Most commonly fused vertebral bodies C2-3 and C5-6. May be associated with Chiari malformation, syrinx, renal, spinal cord, inner/middle/outer-ear abnormalities, congenital heart disease. 1/3 also have Sprengel’s deformity with tethering of scapular to C-spine by fibrous band or anomalous omovertebral bone causing high-riding scapula and reduced shoulder mobility.
Most common congenital CNS abnormal. Failed fusion of posterior bony and neuronal tissues (neural tube) with skin remaining lateral to the neural ectoderm. Most common lower lumbar spine, but may be at any level. Absent posterior spinal elements, widening of spinal canal and interpediculate distances, may have associated congenital vertebral anomalies. May be asymptomatic or sacral dimple, patch of hair, subcutaneous mass/dermal tract, bladder dysfunction, lower extremity neurologic abnormality or bony deformities of feet/legs. May be associated with tethered cord. Suspicious findings on US -> MRI for definitive evaluation. Myelo/meningo- abnormality from absent separation between cutaneous and neural ectoderm (associated with Chiari malformations); lipo- abnormality from premature separation with abnormal migration of primitive mesenchyma cells into neural placode introducing fat (not associated with Chiari).
Closed/occult spinal defect (spina bifida occulta) without mass:
- Spinal lipoma – intradural lipoma between lips of unfused placode. Thoracic > lumbosacral.
- Tight filum syndrome – thickened filum (>2mm) ± fatty infiltration, tethering with inferior conus. Adult tethered cord syndrome causes kyphoscloiosis, midline bony defects, conus ischaemia, sphincteric dysfunction, foot deformities, abnormal gait.
- Lipoma of filum terminale – may cause tethering. Small amounts common (fibrolipoma/filar lipoma), asymptomatic unless tethered.
Closed/occult spinal defect with mass extending through bony defect:
- Lipomyelocoele – dorsal dura incomplete (pia and arachnoid anterior to placode), with SC fat contiguous with the lipoma extending inferior and posterior through defect in dura and bone, adherent to dorsal surface of placode.
- Lipomyelomeningocoele – similar to lipomyelocoele but protrudes beyond spinal boundaries and expands CSF space. Lipoma may be assymmetric, rotating the placode and discrepant lengths of nerve roots.
- Meningocoele – contains meninges but no neural tissue. Uncommon. May progressively increase in size causing posterior scalloping or enlarged foramina. Anterior sacral meningocele (rare) protrudes into pelvis, may be associated with Currarino’s triade (anorectal malformation, bony sacral defect, presacral mass). More common in NF1 (esp lateral thoracic), Marfan.
- Myelocystocele – dura, arachnoid and hydromyelic spinal cord encysted under skin. Associated with cloacal exstrophy.
Spina bifida aperta (open) if neural tissue exposed through bone and skin defect. Detected prenatally with elevated αFP. Requires surgery to prevent infection.
- Myelomeningocoele/meningomyelocoele (99%) – herniation of meninges and portion of spinal cord or nerve roots with dilatation of subarachnoid space. Associated with Chiari II in 90%, hydrosyringomyelia (dilatation of central canal).
- Myelocele – herniation of neural placode (plaque of unneuralated neural tissue) representing lower spinal cord is flush with skin. Very little CSF present with only a layer of arachnoid over the myelocele.
Tethered cord – low conus (newborn is usually above L2-3, may be difficult to see due to tethered cauda equina), nerve roots are not free moving during real-time US and are postioned antidependent posteriorly forming a taut mass, filum terminale may be short and thick (>2mm). May be primary or associated with lipomyelomeningocoele, haemangioma or dermal tract. Not all lumbar intradural fatty deposits are tethered; small fibrolipomas of filum terminale common. If untreated may cause inferior displacement of brain/cerebellum. Postop the conus may remain low (expected).
Dermal sinus tract – epithelium lined tract extending from skin to deep soft tissues, may connect to spinal canal or end in dermoid, epidermoid or lipoma. If communicates with thecal sac is nidus of infection, should be removed. Lumbosacral > occipital > thoracic > cervical. Should never be injected, avoid LP prior to imaging. 50% have associated spinal dermoid/epidermoid (30% of these have an associated sinus).
Pilonidal cysts – most benign spinal dysraphism with normal cord, thecal sac and vertebral column. Tuft of hair with small subcutaneous cyst at coccyx. May have associated dermal sinus tract at a higher level.
Caudal Regression Syndrome
(Caudal dysplasia sequence). ?Insult to mesoderm and ectoderm during 4/40, may be associated with maternal diabetes but most sporadic. Hypoplastic/absent distal spine and sacrum. Fusion of caudal vertebrae with dysplastic lowermost segments. Spina bifida, spinal stenosis, angular wedge-shaped/truncated conus terminating early (~T12) which may be tethered, thickened filum, presacral meningocoele, syrinx. May be associated with cardiac and renal anomalies, sirenomelia (congenital fusion of lower extremities).
Most injuries involve superior cervical spine (cf lower C-spine in adults), particularly atlas and axis ?due to large relative head size.
- Flexion injury -> fracture base of dens at C2 dens-body synchondrosis, anterior displaced C1, soft tissue swelling.
- Extension injury -> fracture posterior arch C1, dens or ‘hangman fracture’ (post arch C2)
- Atlantooccipital dislocation – severe, usually -> death. Increased occiput-C1 distance, marked soft tissue swelling.
- Lap belt inuries -> Chance fracture (anterior compression L-spine with disrupted posterior processes), commonly associated with intraabdominal/bowel injury, usually no neurological injury.
Normal Variants and Congenital Anomalies of the Cervical Spine
- Cervical pseudosubluxation – slight anterior position of C2 on C3 (or C3/4), but posterior longitudinal line maintained.
- Atlas ossifies in 3 ossifications centres, fusing posteriorly by 1yo and laterally by 3yo. May have a contenital defect in posterior C1.
- Axis has multiple ossification centres with dens-body synchondrosis fusing 3-6yo. Ossiculum terminale (tip of dens) fuses by 12yo. Dens may also be tilted slightly post.
- Occipitalisation of C1, may be associated with atlantoaxial instability.
Transverse ligament injury -> increased predental space (anterior arch C1 to dens) >5mm with reduced spinal canal diameter ± cord compression. Causes include trauma, inflammation (JIA, retropharyngeal abscess), congenital predisposition (Down syndrome, hypoplasia of the dens, absence of anterior arch C1). Children with Down syndrome are typically screened for atlantoaxial instability prior to physical activity participation.
Spondylolysis and Spondylolisthesis
Spinal cord split into hemicords by sagittal bony/cartilaginous spur or fibrous band with cord reuniting below the cleft. Most lower thoracic/upper lumbar. Each hemicord has 1 dorsal and 1 ventral horn and central canal. Type I one enlarged dural sac (more common), type II 2 dural sacs. Most associated with vertebral segmentation abnormality, spina bifida, widened interpedicular distances, tethered cord, scloiosis, hairy skin patches, syrinx.
Diplomyelia (very rare) – duplication of spinal cord with full cet of motor and sensory roots from each cord.
(Syrinx). Hydromyelia is central canal dilatation, syringomyelia cavity eccentric to canal (syrinobulbia if extends into brainstem), may be both; synonomyous with syringohydromyelia. Hydromyelia associated with congenital spinal/hindbran anomalies eg Chiari (?obstruction at foramen magnum rather than inferior transmitted CSF pressure), myelomeningocoele. Most syringomyelia is congenital, may also be from trauma, ischaemia, adhesions, neoplasms. Destruction of adjacent grey and white matter with surrounding reactive gliosis. 10s-20s with loss of pain and temperature sensation in upper limbs. DDx ventriculus terminalis (‘5th ventricle) in neonatal conus.
Most common paediatric neck masses are suppurative lymphadenitis from systemic viral of focal bacterial infection. Nodes >10-15mm are abnormal. May lead to drainable abscess.
- Congenital – thyroglossal duct cyst (midline), branchial cleft cyst (persistence of branchial arches, most common 2nd cleft at angle of mandible), lingual thyroid, laryngocoele, dermoid/epidermoid.
- Inflammatory – suppurative lymphadenitis, abscess, inflammed salivary gland, ranula (mucocoele floor of mouth)
- Neoplastic – most present as painless mass. Rhabdomyosarcoma (preschool), lymphoma (older child), mets
- Vascular – venous and lymphatic malformations
Head and neck dystonia with phasic movements resulting in fixed or dynamic posturing. From spasm of SCM, trapezius and/or other neck muscles. Congenital torticolis is rare, from perinatal trauma to SCM (-> fibrosis, haematoma), SCM cysts, vertebral anomalies, Chiari II, spina bifida, clavicle fractures. Aquired torticollis is from trauma, infection/inflammation, atlantoaxial rotatory subluxation, idiopathic (chronic progressive) or benign proxysmal (self-limited). Imaging may be useful for cord impingement, radiculopathies, evaluation of associated swallowing disorders, planning of botulinum toxin injections, other neurologic causes.