Clinical Neurology · Child Neurology
Congenital Brain Malformations
Congenital malformations of the brain.
| Malformation | Description |
|---|---|
| Lissencephaly | Absence of sulci — "smooth brain" |
| Pachygyria | Few broad, thick gyri — "incomplete lissencephaly" (pachy = thick) |
| Polymicrogyria | Numerous small gyri |
| Schizencephaly | Cleft lined with grey matter connecting ventricle to pial surface; open-lip or closed-lip |
| Porencephaly | Cleft or cyst in the hemisphere, not lined with grey matter — "encephalomalacia" |
| Hydranencephaly | Cerebral hemispheres absent, replaced by CSF |
| Holoprosencephaly | Forebrain fails to divide into two hemispheres.
|
| Anencephaly | Absence of the brain, skull, and scalp |
| Encephalocele | Sac-like protrusion of brain and meninges |
| Septo-optic dysplasia (De Morsier) | 2 of the following: absence of septum pellucidum, pituitary gland, and optic nerves. Can be caused by in-utero valproate exposure |
| Dandy-Walker Syndrome | |
| DW malformation | Most severe form, consists of:
|
| DW variant | Mild form with hypoplastic vermis, mildly enlarged 4th ventricle |
| Chiari Syndrome | |
| Chiari I | Displacement of peg-like cerebellar tonsils through foramen magnum >5 mm |
| Chiari II (Arnold-Chiari) | Displacement of medulla, 4th ventricle, and vermis through foramen magnum; usually associated with peaked tectum and lumbar myelomeningocele |
| Chiari III | Similar to Chiari II with occipital encephalocele |
| Chiari IV (obsolete) | Cerebellar hypoplasia (now called primary cerebellar agenesis) |
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