New neurological findings in trisomy 13.

The patient in this report had many of the classic neuropathologic stigmata of trisomy 13, including retinal dysplasia, arrhinencephaly, holoprosencephaly, single external nare and granular cell heterotopias in the cerebellum and microthalmia. In addition, several new findings apparently were present in this case. The neuropathologic entities were as follows: (1) herniation of the cochlear nuclei into the eighth cranial nerve bilaterally to the transition of central to peripheral myelin; (2) gray matter present in eleventh cranial nerve bilaterally; (3) arteriovenous malformations of letpomeningeal and intracerebral vessels; (4) arachnoid cyst at the cauda equina; and (5) retinal pigment epithelium within the optic nerve.