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Long‐term Thalamic Deep Brain Stimulation for Essential Tremor: Clinical Outcome and Stimulation Parameters
Author(s) -
Rodríguez Cruz Pedro M.,
Vargas Antonio,
FernándezCarballal Carlos,
Garbizu Jose,
De La CasaFages Beatriz,
Grandas Francisco
Publication year - 2016
Publication title -
movement disorders clinical practice
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.754
H-Index - 18
ISSN - 2330-1619
DOI - 10.1002/mdc3.12337
Subject(s) - deep brain stimulation , essential tremor , stimulation , medicine , surgery , psychology , anesthesia , parkinson's disease , physical medicine and rehabilitation , disease
Background The reasons underlying the loss of efficacy of deep brain stimulation ( DBS ) of the thalamic nucleus ventralis intermedius ( VIM ‐ DBS ) over time in patients with essential tremor are not well understood. Methods Long‐term clinical outcome and stimulation parameters were evaluated in 14 patients with essential tremor who underwent VIM ‐ DBS . The mean ± standard deviation postoperative follow‐up was 7.7 ± 3.8 years. At each visit (every 3–6 months), tremor was assessed using the Fahn‐Tolosa‐Marin tremor rating scale ( FTM ‐ TRS ) and stimulation parameters were recorded (contacts, voltage, frequency, pulse width, and total electrical energy delivered by the internal generator [ TEED 1sec ]). Results The mean reduction in FTM ‐ TRS score was 73.4% at 6 months after VIM ‐ DBS surgery ( P < 0.001) and 50.1% at the last visit ( P < 0.001). The gradual worsening of FTM ‐ TRS scores over time fit a linear regression model (coefficient of determination [R 2 ] = 0.887; P < 0.001). Stimulation adjustments to optimize tremor control required a statistically significant increase in voltage ( P = 0.01), pulse width ( P = 0.01), frequency ( P = 0.02), and TEED 1sec ( P = 0.008). TEED 1sec fit a third‐order polynomial curve model throughout the follow‐up period (R 2 = 0.966; P < 0.001). The initial exponential increase (first 4 years of VIM ‐ DBS ) was followed by a plateau and a further increase from the seventh year onward. Conclusions The current findings suggest that the waning effect of VIM ‐ DBS over time in patients with essential tremor may be the consequence of a combination of factors. Superimposed on the progression of the disease, tolerance can occur during the early years of stimulation.