Gamma Knife Thalamotomy for a Medically Refractory Tremors: Longitudinal Evaluation of Clinical Effects and MRI Response Patterns.

Abstract

The present longitudinal study evaluated the results of Gamma Knife surgery (GKS) for medically refractory tremors. The outcome after Gamma Knife thalamotomy targeting the ventral intermediate nucleus (VIM) was analyzed in 17 patients (9 men and 8 women; mean age 72years) with either Parkinson's disease or an essential tremor, who were followed up for at least 2years after treatment. Clinical and magnetic resonance imaging (MRI) examinations were done before and every 3months after GKS. The mean rates of symptom improvement (a decrease in the tremor frequency) were 6%, 39%, 63%, and 64% at 3, 6, 12, and 24monthsafter treatment, respectively. The defined MRI response patterns included a minimum reaction (in 3 patients), a normal reaction (in 11 patients), and a hyperreaction (in 3 patients). They were not associated with any evaluated pretreatment, radiosurgical, or outcome parameter, although 2 patients with a hyperreaction exhibited mild-to-moderate motor weakness in the contralateral limbs. Linear contrasting of the border between the thalamus and the internal capsule adjacent to the lesion site was noted on follow-up MRI in 13 cases and was associated with a higher symptom improvement rate. GKS allows effective and safe management of medically refractory tremors. The treatment is characterized by variable MRI response patterns. Some imaging findings during follow-up may be associated with clinical effects.