Deep brain stimulation therapy for rare tremor syndromes

Deep brain stimulation targeting both the ventral intermediate nucleus and the posterior subthalamic area effectively treats rare tremor syndromes, offering flexible electrode placement and improved outcomes.

Assessing the safety and efficacy of simultaneously targeting both the ventral intermediate nucleus (VIM) and the posterior subthalamic area (PSA) to treat tremors, especially in rare tremor syndromes. 

Twenty-two patients diagnosed with rare tremor syndromes underwent bilateral DBS targeting VIM and PSA. The study compared patients' tremor scores before and 12 months after surgery, while also investigating the optimal stimulation areas within the VIM and PSA regions.

The cases under consideration included 7 patients with isolated head tremor, 1 patient with altered level of consciousness as a result of liver failure due to Abernethy malformation, 2 patients with voice tremor, 4 patients with dystonic tremor, and 8 patients with Holmes low-frequency tremor (2 with multiple sclerosis, 2 with cerebellar insult and 4 post-traumatic cases).

After 12 months post-surgery, there was a significant decrease in the mean tremor rating scale (TRS) score from 3.70 to 0.45. Specific outcomes varied by tremor type: 6 out of 7 patients experienced a reduction in TRS scores to zero for head tremor; vocal tremor patients showed improvement but were insignificant due to small sample size; dystonic tremor patients experienced complete tremor relief or reduced TRS scores; Holmes tremor cases saw an 80% decrease in TRS scores; hepatic encephalopathy tremor and Abernethy syndrome cases displayed a 75% improvement in the TRS scores.

Complications, such as electrode repositioning, electrode removal and re-implantation due to infections, slurred speech, re-implantation, and stimulation-induced impaired coordination, were managed by adjusting stimulation parameters.

Targeting both the VIM and PSA in DBS holds promise for improving outcomes in treating rare tremor syndromes. However, additional research and electrophysiological studies are required to validate these findings.