Pallidotomy for tremor

We studied tremor-related activity in globus pallidus internus (GPi) neurons and the effects of pallidotomy on tremor in patients with Parkinson's disease. By using microelectrode recording, we identified GPi neurons with rhythmic firing at the frequency of contralateral tremor. There was a strong correlation between the tremor-related neuronal activity and limb tremor (r = 0.73). The majority of tremor-related neurons were located in the ventral one half of the caudal GPi, the area that is the target for pallidotomy. We found that pallidotomy produced striking improvements in off-period contralateral tremor. These effects were immediate and were maintained for > or = 2 years. This benefit is obtained despite the progressive nature of the illness and the often reduced dose of medications after surgery.