T1 sagittal pre gad SPGR coronal T2 coronal

Diagnosis: Nodular gray matter heterotopia with nonlissencephalic cortical dysplasia.

Disorganization of sulcation and migration of gray matter may result in a spectrum of disorders classified as migrational anomalies. Nonlissencephalic cortical dysplasia refers to that type which is characterized by gyri which are smaller and more numerous than normal. (aka polymicrogyria) This is in contrast to lissencephalic cortical dysplasia which means that the gyri are absent. (aka pachygyria)

Heterotopic gray matter may be seen as an isolated finding or in conjunction with other migrational anomalies as in this case. Heterotopic gray matter may be nodular, laminar, focal or diffuse. Heterotopic gray matter is seen in approximately 3% of normals and typically appears as subependymal nodules which follow gray matter on all pulse sequences. They do not calcify or enhance. Laminar gray matter heterotopia occurs if there is arrest of all neuronal migration. The appearance is that of alternating band-like layers of gray and white matter. Patients with migrational anomalies often present with seizures and or developmental delay.

In some cases subependymal heterotopic gray matter can simulate the subependymal nodules of tuberous sclerosis. If the nodules show enhancement or do not exactly follow gray matter on all pulse sequence, the diagnosis of tuberous sclerosis may be suggested rather than subependymal heterotopic gray matter. If the T1 sagittals were the only images available, the occipital lobe could be called lissencephalic. However with the addition of the high resolution SPGR coronal images it can be seen that the gyri are present and are in fact smaller and more numerous than normal. The combination of this gyral pattern with subependymal gray matter proves the diagnosis of a migrational anomaly specifically nonlissencephalic cortical dysplasia and nodular gray matter heterotopia. Related Cases

Tuberous sclerosis Migrational Anomaly