Gamma knife thalamotomy for treatment of tremor: long-term results

Object. The purpose of this study was to investigate the long-term effects of gamma knife thalamotomy for treatment of disabling tremor. Methods. One hundred fifty-eight patients underwent magnetic resonance imag ing-guided radiosurgical nucleus ventralis intermedius (VIM) thalamotomy fo r the treatment of parkinsonian tremor (102 patients), essential tremor (52 patients), or tremor due to stroke, encephalitis, or cerebral trauma (four patients). Preoperative and postoperative blinded assessments were perform ed by a team of independent examiners skilled in the evolution of movement disorders. A single isocenter exposure with the 4-mm collimator helmet of t he Leksell gamma knife unit was used to make the lesions. In patients with Parkinson's disease 88.3% became fully or nearly tremor fr ee, with a mean follow up of 52.5 months. Statistically significant improve ments were seen in Unified Parkinson's Disease Rating Scale tremor scores a nd rigidity scores, and these improvements were maintained in 74 patients f ollowed 4 years or longer. In patients with essential tremor, 92.1% were fully or nearly tremor free p ostoperatively, but only 88.2% remained tremor free by 4 years or more post -GKS. Statistically significant improvements were seen in the Clinical Rati ng Scale for tremor in essential tremor patients and these improvements wer e well maintained in the 17 patients, followed 4 years or longer. Only 50% of patients with tremor of other origins improved significantly. One patien t sustained a transient complication and two patients sustained mild perman ent side effects from the treatments. Conclusions. Gamma knife VIM thalamotomy provides relief from tremor equiva lent to that provided by radiofrequency thalamotomy or deep brain stimulati on, but it is safer than either of these alternatives. Long-term follow up indicates that relief of tremor is well maintained. No long-term radiation- induced complications have been observed.