Downbeat nystagmus with compression of the medulla oblongata by the dolichoectatic vertebral arteries.

A case is reported of downbeat nystagmus associated with compression of the caudal brain stem by the dolichoectatic vertebral arteries, which was revealed by magnetic resonance imaging. Before surgery, the patient complained of oscillopsia at rest. Downbeat nystagmus was observed in the primary eye position and was increased in lateral gaze, especially to the left. Surgical repositioning of the left vertebral artery succeeded in resolving the downbeat nystagmus in the primary position within 1 month, and the nystagmus in all the other gaze positions almost completely disappeared over the subsequent months. Other ocular abnormalities also were improved after surgery. Thus, this case shows clear evidence of downbeat nystagmus arising from compression of dolichoectatic vertebral arteries to the medulla oblongata. Surgical neurovascular decompression of the dolichoectasia reverses the progression of symptoms if permanent neurologic damage has not already occurred.