Multiple system atrophy with macro square wave jerks and pendular nystagmus

A 51-year-old woman was admitted to our hospital because of gait disturbance and dysuria. Neurological examination revealed limb and truncal ataxia, orthostatic hypotension, cogwheel rigidity in all limbs, generalized hyperreflexia without pathological reflex, and horizontal gaze nystagmus. She became progressively worse and bedridden at age 52. Then she developed abnormal eye movements. Electrooculogram revealed vertical, horizontal or oblique macro square wave jerks and pendular nystagmus. Macro square wave jerks appeared during fixation and disappeared with eye closure or in the dark room. Macro square wave jerks were characterized by a duration of about 200 msec and an amplitude of 10 to 15 degrees. Pendular nystagmus with a duration of several seconds and amplitude of 5 to 15 degrees appeared when she changed her fixation or the point of fixation disappeared. Macro square wave jerks and pendular nystagmus were mildly suppressed after the intramuscular injection of 100 mg of phenobarbital, the oral intake of sodium valproate of 600 mg/day or baclofen of 60 mg/day. They were almost completely depressed after the intravenous injection of 3 mg of diazepam or the oral intake of clonazepam of 1.5 mg/day. We suggested that both macro square wave jerks and pendular nystagmus in this patient might be caused by the dysfunction of GABAergic system in the saccadic eye movement system.