Megalencephaly with formation of Rosenthal fibers in symmetric subependymal gliomatous proliferations: clinicopathologic report.

Clinical and neuropathologic observations are reported concerning a girl with retarded psychomotor development accompanied with a steady increase in the volume of the cranium and brain, tetraparesis, and a serious epileptic syndrome resulting in death at the age of 13 years. The neuropathologic study revealed a marked megalencephaly and the presence of two bilateral and symmetric areas of atypical glial proliferation, corresponding with the optostriatal groove, with endoventricular protrusion: in this region the histologic findings gave evidence of a tapetum of Rosenthal fibers. Discussion is focused on the observed neuropathologic aspects in relation to the various diagnostic hypotheses: Alexander's disease, primary megalencephaly associated with astrocytomas or reactive gliosis, or megalencephaly associated with subependymal hamartomas.