Basilar arterio-venous pseudoparallelism due to persistence of embryonal venous pattern.

A vascular malformation, consisting of a venous vessel bridgeing the right inferior petrosal sinus and the anterior spinal veins, was found in the posterior fossa. The vessel presented a ring-like course around the right trigeminal root, and it was parallel and dorsal to the basilar artery. The malformation was associated with cutaneous and hepatic angiomas and peri-osteal lipomas. It had been clinically silent for 52 years, when it thrombosed causing death. The authors think that, within a general mesenchymopatic state, this is a result of the persistence of an embryonal cerebral venous pattern.