Subependymal grey matter heterotopia is a malformation of cortical development, where there is an abnormal neural migration of cells to the subependymal region, this is not a neoplastic proliferation of cells. The majority of cases are sporadic, some are X-linked and these females tend to develop epilepsy.

These types of malformations can be bilateral diffuse, unilateral diffuse or unilateral focal.

Typically these lesions follow the grey matter density and intensity with no calcifications; associated with anomalous ventricle; no mass effect and frequently seen in the trigones and occipital horns.

Differential diagnoses are:

• subependymal tubers in the context of tuberous sclerosis
  • usually higher signal in T2
• subependymal giant cell astrocytoma
  • in tuberous sclerosis context and near the foramen of Monro

The head of the caudate nucleus is the only grey matter that lines the ventricles.