Choreo-ballistic movement after thalamotomy in a patient with Lewy body dementia.

Thalamotomy is an established treatment for medically refractory tremor. Major complications of thalamotomy include cognitive disturbance, paralysis, dysphagia, sensory loss, and speech disturbance. Hemiballism is a rare complication after thalamotomy. We herein present a 74-year-old female patient who developed choreo-ballistic movement after thalamotomy. She was diagnosed with Lewy body dementia at the age of 70 years and exhibited worsening bilateral hand tremor. Her tremor was severe and pharmacoresistant. Left thalamotomy was planned with the trajectory passing through the ventralis intermedius (VIM) nucleus to the posterior subthalamic area (PSA). The right VIM nucleus and PSA were both coagulated with one trajectory, resulting in the immediate amelioration of right hand tremor. However, four days after surgery, choreo-ballistic movement appeared in the right leg and persisted for six months. Furthermore, tremor recurred after one month. Postoperative MRI showed a small coagulated lesion in the subthalamic nucleus. Although choreo-ballistic movement is a rare complication, it needs to be considered, particularly in patients in which the inferior border of the VIM nucleus is targeted.