Band heterotopia: continuous, bilateral band of grey matter interposed between the ventricles and the cortex. The laminar-shaped heterotopic grey matter parallels the signal of the normal cortex in all imaging sequences and seems a \"double cortex\".
Grey Matter Heterotopia is a neurological disorder caused by clumps of grey matter being located in the wrong part of the brain due to arrested migration of neurons to the cerebral cortex. It is characterized as a type ofcortical dysplasia. The neurons in heterotopia appear to be normal, except for their mislocation.
Types:
Band heterotopia: MR reveals a bilateral band of heterotopic grey matter between the lateral ventricles and cortex, separated by normal-appearing white matter. The band is isointense with the cortex in all MR pulse sequences and does not show contrast enhancement.
Electrical seizure activity seems to originate from the band. Band heterotopia is considered the mildest expression of disorders that include type I lissencephaly. Inheritance: autosomal dominant or X-linked with female predominance.
Subependymal heterotopia: most common location for heterotopia. Clinical features: symptomatic women with subependymal heterotopia typically present with partial epilepsy during the second decade of life.
Focal subcortical: Subcortical heterotopia form as distinct nodes in the white matter. Clinical features: fixed neurologic deficits, partial epilepsy between the ages of 6 and 10.