Factors involved in long-term efficacy of deep brain stimulation of the thalamus for essential tremor

Abstract

Object Although nucleus ventralis intermedius stimulation has been shown to be safe and efficacious in the treatment of essential tremor, there is a subset of patients who eventually lose benefit from their stimulation. Proposed causes for this phenomenon include tolerance, disease progression, and suboptimal location. The goal of this study was to assess the factors that may lead to both stimulation failure, defined as loss of meaningful tremor relief, and less satisfactory outcomes, defined as leads requiring voltages > 3.6 V for effective tremor control. Methods The authors present their clinical outcomes from 31 leads in 27 patients who had effective tremor control for > 1 year following nucleus ventralis intermedius stimulation. All patients postoperatively had a mean decrease in both the writing and drawing subscales of the Fahn-Tolosa-Marin Tremor Rating Scale (p < 0.001). Results After a mean follow-up of 40 months, 22 patients continued to have tremor control with stimulation. Four patients eventually lost efficacy of their stimulation at a mean of 39 months. There was no difference in age, duration of disease, or disease severity between the groups. Examination of perioperative factors revealed that suboptimal anteroposterior positioning as evidenced on intraoperative fluoroscopy occurred significantly more frequently in patients with stimulation failure (p = 0.018). In patients with less satisfactory outcomes, no difference was seen between group demographics. Fluoroscopy again revealed suboptimal positioning more frequently in these patients (p = 0.005). Conclusions This study provides further evidence that suboptimal lead position in combination with disease progression or tolerance may result in less satisfactory long-term outcomes.

The Treatment of Tremor

“…While botulinum toxin may be likely efficacious, side effects are often limiting and, in our experience, efficacy is modest, at best. Stereotactic Surgery, Gamma Knife Thalamotomy and Experimental Approaches for ET Thalamotomy and thalamic [ventralis intermedius (Vim)] deep brain stimulation (DBS) have large treatment effects for upper limb tremor in ET with gradual loss of control of tremor over months or years and a mean 0-10 satisfaction rating of more than 8 (10 = extremely satisfied; 0 = not satisfied) [77][78][79][80][81][82][83]. Vim, the zona incerta, and the radiation praelemniscalis are all in close proximity and are probably the best targets for ET [9].…”

Factors Affecting Stereotactic Accuracy in Image-Guided Deep Brain Stimulator Electrode Placement

“…Studies have linked clinical efficacy and durability of treatment to the accuracy of electrode placement [4,5,6,7,8]. The degree of accuracy necessary to ensure good clinical outcomes has been traditionally achieved using a combination of frame-based stereotaxy, microelectrode recording, and test stimulation with macroelectrodes.…”

Long-Term Effects of Deep Brain Stimulation for Essential Tremor with Subjective and Objective Quantification via Mailed-In Questionnaires

“…However, after an average follow-up of 13 months, 4 of 16 patients did not sustain improvement and would not have the procedure repeated, pointing out the fact that patient satisfaction was directly proportional to improvement in daily activities and tremor control and that loss of efficacy could occur in ET patients after VIM DBS. Patients who initially responded well to DBS with good tremor control and later lost efficacy have been reported [13,14] and can be challenging to manage. Options include reprogramming the DBS device as well as revising the lead or adding additional leads in novel targets [27,28,29].…”

“…The short- and middle-term outcomes of DBS for ET are well established and have been thoroughly published [7,8,9,10,11,12]. Studies aimed at evaluating long-term effects of DBS have also been conducted, indicating a concern for loss of efficacy in a subset of patients over time [13,14]. The total number of patients reported with long-term follow-up is still limited, and additional case series are needed to further evaluate the stability of the effects of DBS for tremor control.…”