Surgical treatment of movement disorders

The renaissance of surgery for Parkinson's disease (PD) is presently being extended to other movement disorders. Different targets are used depending on the signs and symptoms to be treated. Bilateral high frequency stimulation of the subthalamic nucleus is the most promising therapy of advanced PD whether the predominant problem consists of motor fluctuations, levodopa-induced dyskinesias, painful off-period dystonia or severe tremor. A good levodopa response is a prerequisite for a good outcome. Alternatives in patients with asymmetric symptoms and severe levodopa-induced dyskinesias are a unilateral pallidotomy or a uni- or bilateral pallidal stimulation. Thalamic surgery in tremor-dominant patients is rarely indicated as tremor usually is not an isolated sign. In the light of the excellent effect of pallidotomy on levodopa-induced dyskinesias, posteroventral pallidotomy has recently been explored in dystonia, hemichorea and hemiballism. Given the dramatic results obtained in single patients, the smaller lesion volume and the lower incidence of speech problems, pallidotomy compares favorably to ventrolateral thalamotomy which was preferred in the past. The results appear to be more consistent in primary than in secondary dystonia. Pallidal stimulation has also shown dramatic results in dystonia, however, there is only limited experience so far. The ventrointermediate nucleus of the thalamus (Vim) remains the target of choice for essential tremor. Bilateral Vim stimulation is relatively safe and highly successful. Intention tremor has a much lower rate of good functional outcome in the long term follow up. Compared to ablative surgery the stimulation technique has a lower incidence of permanent morbidity, especially in bilateral surgery.