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Case 2

Seizures

Diagnosis

Gray Matter Heterotopia, Subependymal

Gray Matter Heterotopia (GMH)

Abnormality of neuronal migration

Collections of nerve cells are in abnormal locations secondary to arrest of radial migration of neurons.

GMH are due to premature arrest of neuronal migration from the germinal matrix to the cerebral cortex at the 7th – 16th week of gestation

GMH

Types

Nodular

Subependymal

Subcortical

Band

GMH, types

Nodular

1) Subependymal (most common)

Few, asymmetrical, primarily confined to the trigones, temporal horns, occipital horns

Rarely familial

May be assoc. with

Chiari II malformation

Agenesis of the Corpus Callosum

Cephalocele

Large number of lesions that nearly completely line the ventricles

May be familial with mutation of Xq28

DDx: Subependymal GMH vs. Tuberous Sclerosis with Subependymal Nodules:

GMH

Nodular

2) Focal Subcortical

Patterns

Multinodular

Swirling, curvilinear bands

Isointense to GM

Thin overlying cortex

Small ipsilateral cerebral hemisphere

Associated anomalies

70% with Callosal agenesis or hypogenesis

>70% with dysplastic basal ganglia

DDx: Subcortical GMH vs. tumor

GMH

Band

“Double cortex”

> 90% Female

Xq22.3-q23 (XLIS/doublecortin gene)

Presentation

Most in childhood

Developmental delay (variable severity)

Seizures

Generally, earlier onset

GMH is in a spectrum with Lissencephaly

Lissencephaly, type 1

Smooth brain surface

Hourglass configuration of brain

Part of agyria/pachygyria spectrum

Thicker inner band of GM

Cell sparse WM zone

Thin outer layer of GM

Lissencephaly, type 2 (“cobblestone”)

Usually occurs with congenital muscular dystrophies

Neurons “overmigrate” through gaps in external layer of cortex…pebbled surface of brain

Assoc. ocular, cerebellar anomalies

Very poor prognosis

GMH, Prognosis

Nodular, Subependymal

Isolated: Seizures in 2nd decade; otherwise, normal development of motor function

May have other congenital anomalies

Nodular, Subcortical (1st or 2nd decade: seizures)

Bilateral, large, thick heterotopia

Severe developmental delay and motor dysfunction

Unilateral, large

Hemiplegia; less severe (if any) mental retardation

Unilateral, thin

May have normal motor function and development

GMH, Prognosis

Band

Related to thickness of band heterotopia

Thicker heterotopia…Thinner overlying cortex with shallow sulci

Thinner cortex…worse clinical prognosis.