Unilateral thalamic deep brain stimulation in essential tremor demonstrates long-term ipsilateral effects
Section snippets
Background
Essential tremor (ET) is one of the most common movement disorders [1] and is clinically characterized by bilateral postural and action tremors affecting the arms in 94% cases and less frequently it affects the head, voice, trunk and legs [1]. Approximately 50% of the ET patients are reported to be refractory to oral medications [2], and for these patients deep brain stimulation (DBS) of the thalamus has become a well-established FDA approved treatment modality [4].
ET is a bilateral disease,
Patients
ET patients who underwent unilateral thalamic DBS at University of Florida Center for Movement Disorders & Neurorestoration (from July 2002 to July 2011) and who were followed for at least three years were enrolled. These patients signed informed consent to deposit their results from clinical testing into an Institutional Review Board approved database for research. Data was analyzed retrospectively. Patients originally implanted at outside institutions were excluded from the analysis.
According
Demographics
Over a period of 9 years, (2002–2011), we found 67 patients with refractory ET had undergone thalamic DBS surgery at our center. Fifty-four of these patients had unilateral DBS and 22 patients presented for follow-up more than 3 years after surgery. A retrospective analysis was performed on these twenty-two patients (12 males, 10 females). The mean age was 71 (±2.6) years and 17 patients were right handed (Table 1). Ten patients reported social drinking and one reported regular alcohol
Discussion
Many DBS centers advocate bilateral placement of DBS leads in the Vim nucleus of the thalamus [5], [8], [9], [10]. The implantation of the second sided lead is typically aimed at treating and controlling disabling tremors on the contralateral side. Recently, there have been increasing reports of side effects and complications related to bilateral surgeries including dysarthria, dysphagia and gait/balance impairment. Therefore, the risks and benefits of bilateral DBS implantation should be
Conclusions
Unilateral thalamic DBS for medication refractory ET demonstrates significant improvements in the ipsilateral arm tremors. The benefits are milder on the ipsilateral side compared to the contralateral side but sustained at long-term follow-up. The selection of unilateral vs. bilateral thalamic DBS should be tailored to an individual patient's risk and benefit analysis. The underlying mechanisms that can explain ipsilateral effects of unilateral DBS will require further study.
Acknowledgments
This work was support by Grant-in Aid for Clinical Research from St. Luke's Life Science Institute of Japan, Japan Society for Promotion of Science, University of Florida CTSI, and the UF INFORM database.
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