[Paroxysmal bilateral ballism induced by hypoglycemia].

Ballism is a kind of involuntary movement presenting as irregular but stereotyped jerking and writhing movements of the limbs with proximal dominance. The most common type is hemiballism, and bilateral ballism is extremely rare. In contrast to hemiballism with preferential involvement of the contralateral subthalamic nucleus, bilateral ballism results from diffuse lesions on both sides of the basal ganglia. Here, we present a patient in whom bilateral ballism occurred as a result of hypoglycemia. A 75-year-old man with long-standing insulin-dependent diabetes mellitus had suffered recurrent episodes of paroxysmal and transient involuntary movements of all 4 limbs over a 6-week period. When he visited our hospital first, he was alert and well-oriented. Neurological examination revealed no deficits except right hemianopsia. Violent involuntary movements suddenly manifested 10 days later during MRI scans. Involuntary movements occurred in all 4 limbs, more prominently on the left side, lasted over 15 min in total, and ceased spontaneously. These movements were considered as bilateral ballism. The patient was awake, but rather confused. Serum glucose level during this attack was 25 mg/dl. Intravenous glucose was administered, and he became aware. Brain CT and MRI showed no evilence of ischemic or other basal ganglia pathology and no significant vascular lesions were detected by MR angiograhy. EEG revealed no epileptic discharges. He was admitted to our hospital and insulin dosage was adjusted. No further episodes occurred during a 6-month follow up. Our patient experienced an episode of bilateral ballism associated with documented hypoglycemia. In addition, good control of serum glucose with an appropriate insulin treatment has abolished the involuntary movement episodes described above. Conversely, the basal ganglia is known to be vulnerable to hypoglycemia, due to large metabolic demand and poor vascularization. Recurrent episodes of bilateral ballism in this case may thus have been caused by transient dysfunction of the basal ganglia due to hypoglycemia. We proposed a hypothesis to explain why the involuntary movements disappeared spontaneously.