13. CephalocelesCephaloceles
Cephalocoele refers to the outward herniation of
CNS contents through a defect in the cranium.
The vast majority are midline.
There are two main subtypes:
• encephalocoele: herniation of meninges and CSF
and brain parenchyma
• cranial meningocoele: herniation of meninges
and CSF only
14.
15. Location
• occipital cephalocoele: most common, up to 75%
• parietal cephalocoele: up to 37%
• frontal cephalocoele/
fronto-ethmoidal cephalocoele: ~10%, this type is
most common in Asia
• petrous apex cephalocoele : rare
• intra sphenoidal cephalocoele: rare
32. Two selected images from an MRI of the brain demonstrate
fusion of the frontal horns of the lateral ventricles with
abnormal genu and rostrum of the corpus callosum and partial
fusion of the cingulate gyrus anteriorly. The anterior cerebral
artery is azygous and displaced anteriorly.
33. Axial non-contrast CT of the brain (with thick slice sagittal
reformat) demonstrates fused frontal lobes with absent anterior
part of the falx cerebri. There is also absence of the septum
pellucidum with fusion of the lateral ventricles with rudimentary
occipital and temporal horns, with a prominent dorsal cyst.
34. Non-contrast CT demonstrates a thin rim of cerebral tissue
anteriorly, without midline cleft. There is a large CSF density
space posteriorly. There is no evidence of falx cerebri. The
cerebellum is malformed with abnormal appearance of the
fourth ventricle. Brainstem is visualized.
36. Syntelencephaly
MRI of this child demonstrates dysmorphic lateral ventricles with absent
septum pellucidum. Abnormal bridging grey matter is shown between the
hemispheres along the level of the body of the corpus callosum with
resultant thinning and irregular shape of the body of corpus callosum. The
genu and splenium of the corpus callosum are relatively enlarged.
37. Septo-optic dysplasia
Selected images from the MRI of a child demonstrates absence
of the septum pellucidum and an optic chiasm that is markedly
reduced in size. Also note the azygous anterior cerebral artery.
38.
39. DWM DWV Persistent
Blake’s pouch
Mega cisterna
magna
Anterior membranous area anomaly Posterior membranous area anomaly
Retro-cerebellar cyst
Vermis Hypo-plastic
Rotated upwards
Hypo-plastic No or mild
hypoplasia
No or mild
hypoplasia
4th
ventricle Markedly dilated Dilated Dilated Normal
Posterior fossa Expanded Normal size Normal size Normal size
hydrocephalus 75 % of cases 25% of cases Present No
57. Focal cortical dysplasias (FCD) represent a heterogeneous group
of disorders of cortical formation, which may demonstrate both
architectural and proliferative features. They are one of the
most common causes of epilepsy and can be associated with
hippocampal sclerosis and cortical glioneuronal neoplasms.
MRI findings:
•cortical thickening
•blurring of white matter–grey matter junction with abnormal
architecture of subcortical layer
•T2/FLAIR signal hyperintensity of white matter with or without the
transmantle sign
•T2/FLAIR signal hyperintensity of grey matter
•abnormal sulcal or gyral pattern
•segmental and/or lobar hypoplasia/atrophy
58. Also, each type of focal cortical dysplasia can exhibit more or less of
these features. The types below refer to the Blumcke classification
of focal cortical dysplasia (2011).
Type I
•location
o type Ia: usually confined to temporal lobes
if associated with hippocampal atrophy (as is common), it is
now classified as type IIIa in the Blumcke classification
o type Ib: more frequently seen outside of the temporal lobes
•structure
o blurring of grey/white matter junction (less marked than
with Type II FCD)
o prominent segmental or lobar atrophy/hypoplasia with loss
of regional white matter volume
•signal
o white matter
moderately increased T2/FLAIR signal
decreased T1 signal
59. Type II
•location
– commonly found in frontal lobes
– less likely to be in the temporal lobes compared to
Type I FCD
•structure
– abnormal gyri and sulci
– marked blurring of grey/white matter junction
– cortical thickening
60. • signal
– white matter
• moderately increased T2/FLAIR signal, typically brighter
than adjacent cortex
• decreased T1 signal
• focal signal abnormality may extend from cortex to
ventricle (transmantle sign): not seen in type I
– grey matter
• some increase in T2 signal
– despite increase in T2 signal, cortex remains hypointense to
much brighter adjacent white matter 4
– more evident than in type I
61. Type III
•Type III focal cortical dysplasia (according to the
Blumcke classification) as associated with
adjacent other abnormalities (e.g. IIIa
- hippocampal atrophy; IIIb - glioneural tumour
(e.g. DNET or ganglioneuroma); IIIc - vascular
malformation; IIId - early childhood insult (e.g.
gliosis)) and as such imaging appearances will be
dominated by the associated abnormality rather
than the dysplasia itself.
66. Neurological
•cortical/subcortical tubers: 50% are in the frontal lobe; high T2
and low T1 with only 10% of tubers showing enhancement;
frequently calcify after two years of age
•subependymal hamartomas
– 88% are associated with calcification, although
calcification absent in early childhood
– visible within the first six months of age
Also known as tuberous sclerosis complex or Bourneville
disease, is a neurocutaneous disorder (phakomatosis)
characterised by the development of multiple benign tumours of
the embryonic ectoderm (e.g. skin, eyes, and nervous system).
67. – variable signal, frequently high T1 and iso to high T2
– enhancement is variable and is not a useful feature in
distinguishing them from subependymal giant cell
astrocytomas (SGCA); only serial growth is reliable
•subependymal giant cell astrocytomas (SGCA)
– peak occurrence 8-18 years
– tend to be large and demonstrate growth 9-10
– tend to have intense enhancement
•white matter abnormalities
– variable appearance, with nodular, ill-defined, cystic and
band-like lesions seen
– radial bands are thought to be relatively specific for TS 12
•retinal phakomas
72. Heterotopias
• Normal neurons at abnormal sites
• Result from arrested neuronal migration from
periventricular germinal zone to the cortex.
• Heterotopias are isointense to normal gray
matter in all pulse sequences and do not
enhance on administration of IV contrast.
73. Hetertopia
• Isointense to grey matter on all pulse
sequences
No enhancement.
No associated mass effect.
Internet picture. Potter’s pg. 1960: The neural tube enlarges in its cranial part (at the cranial neuropore) in three primary vesicles: prosencephalon (forebrain or rostral vesicle); mesencephalon (midbrain or intermediate); rhombencephalon (caudal or hindbrain). Prosencephalon - telencephalon - evaginates into two lateral vesicles (future hemispheres) and diencephalon. Mesencephalon gives rise to peduncles and lamina quadrigemina. Rostral portion of rhombencephalon gives rise to the pons and cerebellum while the caudal portion develops into the medulla oblongata. Basal structures develop in this stage also: optic vesicles and olfactory bulbs evaginate and the basal ganglia and hypothalamus are formed. Anomalies such as holoprosencephaly group and arrhinencephaly originate during this time.
. Occipital cephalocele. Sagittal T1W (a) image shows herniation of severely dysplastic cerebellar tissue and the occipital lobe into a large CSF containing sac through an osseous defect in the occipital bone(thin white arrow). Thin strand of dysplastic brain tissue or septa can be seen traversing the CSF within the sac. Also note small posterior fossa, and deformed brain stem. 2D Time-of- flight venogram (b) demonstrates no herniation of dural venous sinuses in the cephalocele sac. This is important information for the surgeons.
Parietal cephalocele. Sagittal T1W(a) image of brain shows a small parietal
cephalocele containing CSF and dysplastic brain tissue(thin white arrow). 2D TOF
venogram(b) shows non visualization of small segment of superior sagittal sinus in the region of osseous defect consistent with sinus thrombosis(thin white arrow).
Atretic occipital cephalocele. Sagittal T2W(a), axial T1W(b) image shows a small
subcutaneous mass (thin white arrow) in high occipital region just external to a small defect in the calvarium. Note that the brain is not entering the cephalocele; instead, a thin strand of fibrous tissue is seen extending across the osseous defect, from the surface of the brain to the subcutaneous mass. Small posterior fossa arachnoid cyst is also seen. 2D TOF venogram (c) shows presence of median procencephalic vein within embryonic falcine sinus(thin white arrow) and absence of sagittal sinus.
Dandy Walker Malformation: A, Axial CT image. Fourth ventricle (Arrow) dorsally opens into a large CSF filled cyst. Subtle remodeling of occipital bone is noted. Gross hydrocephalus is present (White dots).
Axial T2 weighted MR image shows a large posterior fossa CSF intensity cyst with hypoplastic vermis and cerebellar hemispheres.
Dandy Walker Variant. A, Axial CT image. B, Axial T1 weighted MR image (Different cases). There is communication (Arrows) between posteroinferior fourth ventricle and cisterna magna through enlarged vallecula, with a posterior fossa cyst. Severe hydrocephalus is present in Figure 7A
Mega Cisterna Magna. Sagittal T1W(a) and axial T2W(b) image demonstrates an
intact vermis with enlarged posterior fossa CSF space(asterix) that extends superiorly above the vermis and communicates with adjacent CSF space. Prominent scalloping of the occipital squamae is also seen (arrow). No hydeocephalus present.
Posterior fossa arachnoid cyst. Sagittal T1W(a) and axial T2W(b) image shows a
classical posterior fossa arachnoid cyst(asterix). Note normally formed but displaced fourth ventricle (arrow) and vermis.
Corpus callosal agenesis(complete). Sagittal T1W(a) and coronal T2W (b) image
shows complete absence of the corpus callosum and cingulate sulcus (thin white arrow), high riding third ventricle communicating with the interhemispheric fissure(thin black arrow), and crescent shaped frontal horns indented medially by white matter tracts of Probst’s bundles(thick white arrow). Widely separated and parallel lateral ventricles with colpocephaly are also seen (double thin white arrow) on axial T2W image(c).
Corpus callosal agenesis (partial). Sagittal T1W(a) and axial T2W (b,c) image shows
presence of only the genu of the corpus callosum (thin white arrow), high riding third ventricle(thin black arrow),widely separated and parallel lateral entricles(double thin white arrow).
Corpus callosal agenesis(partial) with dorsal interhemispheric cyst. Sagittal T1W(a)
and axial T2W(b) image shows presence of the genu and anterior part of body of the corpus callosum while, the posterior body, splenium and rostrum is absent (thin white arrow). The lateral ventricles are widely separated and a moderately large dorsal interhemispheric cyst (asterix) is present which is seen communicating with the overlying subarachnoid space via a narrow schizencephalic cleft (thin black arrow). Solitary nodular heterotopia can be seen within the body of left lateral ventricle which is mildly dilated (thin white arrow).
Band or laminar type
A layer of neurons interposed between the ventricle and cortex, seen as alternating
layer of gray and white matter band
- The cortex overlying the heterotopia is nearly always abnormal with pachygyria or
polymicrogyria.
- Nodular type:
Multiple masses of gray matter which are of variable size
Common location: subependymal or subcortical
Focal or diffuse
Subependymal focal nodules indent the ventricular wall, whereas diffuse
heterotopias border the walls of the lateral ventricle