[Hyperkinésie volitionnelle following head injury]

A 13-year-old girl was struck by a car while riding her bicycle. She was comatose on her arrival at the hospital. Neurological examination revealed no focal sign except for right oculo-motor palsy. She became alert 15 days after the head injury when she first experienced a coarse tremor-like movement on the right arm. Neurological examination showed persistent oculo-motor palsy on the right side, decreased sensation of pain and touch on the left. There was no pyramidal deficit. Her gait and speech were normal and joint sensation was intact. A coarse tremor of the right arm was induced by volitional movements especially such as maintaining the arm in certain posture. It was not present at rest. Trajectory of finger-to-nose test was fairly well. However, the tremor became worse when the patient kept her finger near the target. Occasionally myoclonic-jerk and movement oppositionniste were mixed. Superficial EMG recordings of the tremor revealed 4 c/s rhythmic reciprocal grouping discharges, alternating flexor and extensor muscles. From these features, the abnormal movement should better be called tremor type of hyperkinésie volitionnelle (HV). The HV subsided spontaneously 4 months later. MRI of T2-weighted image showed high-intensity areas corresponding anatomically to the caudal part of right red nucleus and the right superior cerebellar peduncle just before its decussation. It is widely believed that lesions in cerebellar outflow pathway (i.e. dentate, red nucleus and thalamus) can cause HV.(ABSTRACT TRUNCATED AT 250 WORDS)