DOWN-BEAT NYSTAGMUS WITH COMPRESSION OF THE MEDULLA-OBLONGATA BY THE DOLICHOECTATIC VERTEBRAL ARTERIES

A case is reported of downbeat nystagmus associated with compression o f the caudal brain stem by the dolichoectatic vertebral arteries, whic h was revealed by magnetic resonance imaging. Before surgery, the pati ent complained of oscillopsia at rest. Downbeat nystagmus was observed in the primary eye position and was increased in lateral gaze, especi ally 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 almo st completely disappeared over the subsequent months. Other ocular abn ormalities also were improved after surgery. Thus, this case shows cle ar evidence of downbeat nystagmus arising from compression of dolichoe ctatic vertebral arteries to the medulla oblongata. Surgical neurovasc ular decompression of the dolichoectasia reverses the progression of s ymptoms if permanent neurologic damage has not already occurred.