Lissencephaly-MRI

6 year old boy with seizures and developmental delay shows on MRI, smooth cortical surface of the supratentorial brain parenchyma with suggestion of subtle sulcation in inferior frontal and temporal lobes. There is no cyst formation of the basal ganglia / hypoplasia of cerebellum / agenesis / hypoplasia of corpus callosum / ocular or collicular abnormalities / posterior parieto-occipital hyperintensity band sign (Attributed to accumulated CSF signal in the absence of neuronal cells. There is extensive white matter T2 / FLAIR abnormalities. The features are suggestive of lissencephaly variety of neuronal migration  with possible leukodystrophy.

Walker – Warburg Syndrome or Fukayama Disease are less likely in the absence  of cephaloceles, callosal / occular including retinal / collicular and brainstem / cerebellar abnormalities / Polymicrogyria / muscular dystrophy.

Teaching Points  by Dr MGK Murthy, Dr Sumer Sethi,  Mr Hari Om, Mr Hamid.

Cortical formation classification have undergone many changes and is presently restricted to the variety based on major stages of formation.

1. Abnormal neuronal cellular proliferation.

- Extends from ventricles to piamater.

- Could be due to too few neurons (Microlissencephaly) / too many

neurons (Hemimegalencephaly) / abnormal cells (Focal cortical dysplasia).

2. Abnormal neuronal migration.

- Located usually in the white matter and / or cortex.

- Arrest of migration (classic lissencephaly) / over migration

(Cobblestone lissencephaly) / ectopic migration (Heterotopia).

3. Abnormal neuronal organization.

- Located only in the cortex.

- Usually due to prenatal ischemia / infection.

- Injury to the superficial parts of the brain (Polymicrogyria) / injury to  the whole thickness of the brain (Schizencephaly).

Classical lissencephaly could be with smooth brain surface (complete form) or with some sulcation in the inferior frontal and the temporal lobes (incomplete form). Complete form presence with seizures or developmental delay, where as incomplete comes with hypotonia / microcephaly / facial dysmorphism.