The authors report the case of a 43-year-old woman with a venous malfo
rmation of the mesencephalon occluding the sylvian aqueduct. Neuroradi
ological investigations suggested aqueductal stenosis, while the prese
nce of a venous malformation was diagnosed by both magnetic resonance
imaging and an angiogram, and was visualized using a neuroendoscope. T
his is the first reported instance of a venous malformation being obse
rved in situ and the subependymal course taken.