Duane's syndrome with giant aneurysm of the vertebral basilar arterial junction.

A 36-year-old man who had signs of Duane's syndrome since birth developed symptoms of a posterior fossa mass. Angiography revealed a giant aneurysm in the area of the vertebral basilar junction. The association of these two anomalies provides support for the vascular origin of some cases of Duane's syndrome due to vascular hypofunction during the 4th and 5th weeks of embryogenesis.