Heterotopic neuroglial tissue in the cerebral dura mater.

The presence of heterotopic neuroglial tissue in the cerebral dura mater has not been documented. This report describes three cases of heterotopic neuroglial tissue in the parasalgittal cerebral dura mater found in a study of 257 adult brains, with an incidence of 1.2%. None were associated with developmental abnormalities of the CNS. The heterotopias were isolated and completely encased within the dura mater with no attachment to the leptomeninges. Their number varied from one to nine. They were composed primarily of astrocytes in a glial network and often stained strongly for glial fibrillary acidic protein and S-100 protein. Oligodendrocyte-like cells were noted but nerve cells, ependyma-lined canals and choroid plexus were absent. Dural neuroglial heterotopias are likely developmental malformations and may represent formes frustes of encephalocele.