Long-term efficacy and cognitive effects of voltage-based deep brain stimulation for drug-resistant essential tremor

Objectives: To analyze the long-term efficacy and cognitive effects of voltage-based deep brain stimulation (DBS) for drug-resistant essential tremor (ET).

Patients and methods: Patients with drug-resistant ET and treated by voltage-based DBS of the ventral intermediate nucleus (VIM-DBS) were continuously enrolled. Seizure outcomes were assessed by blinded observers using the Tremor Rating Scale (TRS). The full-scale intelligence quotient, full-scale memory quotient, Hamilton Depression Scale, Hamilton Anxiety Scale, and Quality of Life in Essential Tremor Questionnaire were assessed as measures of cognitive function.

Results: Eleven patients met the inclusion criteria, and two of them were excluded because of loss to follow-up. The patient follow-up times ranged from 48 to 66 months (median 51 months). TRS scores decreased by 60.4% and 46.0% at the 12- and 48-month follow-ups, respectively. Both changes were highly significant. During the follow-up period, the patients' intelligence and memory had not significantly changed; depression, anxiety, and quality of life significantly improved. After long-term follow-up, the stimulation efficacy and quality of life gradually decreased, and the depression and anxiety levels increased.

Conclusion: For patients with drug-resistant ET, voltage-based DBS can provide acceptable benefits on tremor, cognitive function, and quality of life. However, the efficacy of VIM-DBS decreased over time.

Keywords: Cognitive functions; Deep brain stimulation; Efficacy; Essential tremor; Voltage.