Fact-sheet: Polymicrogyria
Updated on 04/23/2018 at 9:28 AM
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Definition
Excessive secondary folding of the cortical ribbon resulting in multiple gyri separated by shallow sulci.
Clinical features
- Motor deficit (hemiparesis, hemiplegia)
- Epilepsy
- Intellectual disability
Perisylvian polymicrogyria: characteristic clinical picture:
- Pseudobulbar palsy
- Dysarthria
- Developmental delay
- Epilepsy: 50-80% of cases, manifesting as absence seizures, tonic-atonic attacks, and generalized tonic-clonic seizures. Perioral seizures.
MRI
- Multiple fused gyri separated by shallow sulci.
- Irregularity of the gray-white matter junction.
- Cortical thickening
- Gliosis frequently present at the corticosubcortical junction.
- Abnormalities often bilateral
T2-weighted spin-echo sequences allow detection of gliotic changes and white matter lesions.
Volumetric T1-weighted gradient-echo or T1 inversion-recovery sequences must be performed, as they allow better analysis of the cortical mantle.
Classification
Simplified Barkovich et al. 2011 classification:
1) Disorders of neuronal and glial proliferation or apoptosis:
- Non-tumoral: Focal cortical dysplasia with balloon cells
- Hemimegalencephaly
- Tumoral: DNET
- Ganglioglioma
- Gangliocytoma
2) Neuronal migration disorders:
- Agyria/pachygyria or lissencephaly
- Gray matter heterotopia
3) Disorders of cortical organization:
- Polymicrogyria
- Schizencephaly
- Cortical dysplasia without balloon cells
4) Other congenital brain malformations:
- Agenesis of corpus callosum
Differential diagnosis
Other cortical malformations (see classification)