Neuro -- Congenital Malformations/syndromes

Front 1

1. What are the imaging findings in agenesis of the corpus callosum (CC)?
2. What syndromes are associated with agenesis of CC?
3. What is the order of formation of the CC?

Back 1

1.
- Radiation of medial hemispheric sulci to the level of the third ventricle
- Parallel orientation of the lateral ventricles
- Colpocephaly - bilateral expansion of the trigones and occipital horns
- High riding 3rd ventricle that communicates with the interhemispheric fissure.
- Longhorn appearance of the ventricles on coronal images.
- Probst bundles: lie medial to the lateral ventricles. They represent the axons that would have normally crossed the corpus callosum.
- Congenital lipoma may be associated with a hypogenetic corpus callosum.
2.
- Posterior fossa malformations: Dandy-Walker malformation, and Chiari II malformation
- D/O of cleavage: septo-optic dysplasia and holoprosencephaly
- Anomalies of neural migration
- Aicardi syndrome (females, seizures, mental retardation, coloboma)
- Fetal alcohol syndrome
3. Genu, body, splenium, and rostrum.

Front 2

1. What is the DDX of absence of septum pellucidum?
2. What are the imaging findings in septo-optic dysplasia (SOD)?

Back 2

1. Septo-optic dysplasia and holoprosencephaly.
2. SOD is characterized by:
- Absence of septum pellucidum
- Bilateral small globes and optic nerves
- Pituitary dysfunction (most commonly defiency of growth hormone resulting in DWARFISM). The posterior pituitary gland may also be in an ectopic location.
- Schizencephaly
- Gray matter heterotopia and polymicrogyria

Front 3

What are the imaging findings of Chiari II malformation?

Back 3

- Small posterior fossa
- Herniation of cerebellar vermis
- 4th ventricle displaced caudally and elongated
- Tectal beaking with fusion of the colliculi
- Hydrocephalus, present in 90%
- Varying degrees of cerebellar dysplasia
- Kinking of cervicomedullary junction
- Interdigitation of gyri due to a hypoplastic falx or fenestrated falx
- Agenesis/Hypogenesis of the corpus callosum
- Myelomeningocele
- Enlarged massa intermedia
- Towering of the vermis through the tentorium cerebelli.
- Luckenschadel skull
- Large foramen magnum
- Less commonly associated with syringohydromyelia.

Front 4

1. What is the differential diagnosis of large supratentorial cyst in a fetus?
2. What are the imaging features of hydrocephalus?
3. What are the imaging features of hydrancephaly?
4. What are the imaging features of holoprosencephaly?
5. What are the imaging features of porencephaly?

Back 4

1. Hydrocephalus, hydrancephaly, holoprosencephaly, and porencephaly.
2. HYDROCEPHALUS:
- preserved mantle of soft tissue surrounding the "cystic mass" which represents the dilated lateral ventricles.
- FALX cerebri is PRESENT.
3. HYDRANCEPHALY:
- no mantle of soft tissues.
- 2/2 in-utero infarction of the brain supplied by the ICA.
- preservation of structures supplied by the posterior circulation (thalamus, brainstem, cerebellum, choroid plexus). The choroid plexus continues to produce CSF which expands the lateral ventricles resulting in ex-vacuo dilatation.
- FALX cerebri is PRESENT.
4. HOLOPROSENCEPHALY:
- monoventricle (no septum pellucidum)
- ABSENCE OF FALX cerebri
- fusion of the thalami across the midline
- facial abnormalities
- associated with a dorsal cyst
5. Porencephaly = limited hydrancephaly.
- 2/2 cerebral infarction resulting in encephalomalacia of a part of the brain extending from lateral ventricle to the surface of the brain.
- Lined by gliotic white matter (differentiates from schizencephaly).

Front 5

1. What are the different types of holoprosencephaly?
2. What are the imaging findings in holoprosencephaly?
3. What is unique about the corpus callosal abnormalities seen with HP?

Back 5

1. Alobar, semilobar, lobar
2.
- Absence of the septum pellucidum
- Absent (alobar) to nearly complete interhemispheric fissure (lobar).
- Absent (alobar) to nearly normal (lobar) falx cerebri.
- Fusion of thalami and basal ganglia
- Continuity of gray and white matter across the midline.
- Variable ventricular differentiation (ranges from a horse-shoe shaped monoventricle to nearly normal morphology.
- Callosal anomalies.
- Large dorsal cyst in continuity with a monoventricle.
- Absence of olfactory bulbs and tracts.
- Facial anomalies (hypoplasia of the central face).
3. Typically, the posterior portion of the corpus callosum is formed and the anterior portion is absent.
NOTE: In contrast, the anterior CC is normal and posterior portion is malformed in callosal anomalies outside of the HP spectrum.

Front 6

1. What are the imaging findings in cephaloceles?
2. What are the common locations for cephaloceles?

Back 6

1.
- Focal defect in the calvarium.
- Herniation of portions of cerebral hemispheres through the defect.
- Herniating tissue may show evidence of ischemia/infarction/encephalomalacia with increased signal intensity on T2WI.
- Corpus callosal abnormalities
- Hydrocephalus

2.
- Occipital cephaloceles are the most common.
- Ethmoidal cephaloceles can also occur and may be misdiagnosed as a nasal polyp on sinus CT scans.
NOTE: Look for associated bony defect in the floor of the intracranial fossa to rule-out cephalocele.

Front 7

1. What is tonsillar ectopia?
2. What are the imaging findings of Chiari 1 malformation?
3. With sequence may be helpful in determining the severity of Chiari 1 malformation?

Back 7

1. Tonsillar ectopia is defined as inferior descent of the cerebellar tonsils below the level of the foramen magnum.
- Tonsillar ectopia of < 5 mm = clinically INsignificant
- Tonsillar ectopia of > 5 mm = clinically significant. Note: In children under 15 years of age, the tonsils may normally extend 6 mm below the foramen magnum.
2.
- Cerebellar tonsillar tissue surrounds the medulla and upper cervical spinal cord extending below the foramen magnum.
- Tonsils are pointed (peg-like)
- Syringohydromyelia may be present in 20 to 40% of cases.
3. Cine phase contrast MR study is directly assess the flow of CSF at the level of the foramen magnum and may help predict which patient will benefit from posterior fossa decompression.

Front 8

1. What are the imaging findings in Dandy-Walker malformation?
2. What is the etiology of Dandy-Walker?
3. What is D-W malformation associated with?
4. What other processes can result in a cystic mass in the posterior fossa?

Back 8

1.
- Cystic dilatation of the 4th ventricle.
- Complete or parital agenesis of the cerebellar vermis.
- Enlargement of the posterior fossa with upward displacement of the transverse sinus (torcular-lambdoid inversion). Normally, the lambdoid suture confluence is higher than the torcular. However in D-W malformation the relationship is inverted with the torcular residing more superiorly.
- Hydrocephalus
2. Ischemic event to the 4th ventricle prevents proper development of foramina of Luschka and Magendie resulting in partial or total CSF outflow obstruction. A large 4th ventricle cyst splays the developing cerebellum, preventing fusion and vermis formation.
3.
- Agenensis of the CC
- Gray matter heterotopia, polymicrogyria, agyria
- Schizencephaly
4.
- Mega cisterna magna: midline location, cerebellum is normally formed, posterior fossa is not enlarged, normal vessels traverse the mega cisterna magna.
- Posterior fossa arachnoid cyst.

Front 9

What is Joubert Syndrome?

Back 9

- AD d/o
- Vermian hypoplasia but no cystic component as seen in Dandy-Walker malformation.
- Axial images through the midbrain reveal a molar tooth appearance of the midbrain and superior cerebellar peduncles (elongation of the superior cerebellar peduncles)
- 4th ventricle has a bat wing appearance