Session Time: 1:45pm-3:15pm
Location: Exhibit Hall C
Objective: To investigate the efficacy of selective neuromodulation to overcome stimulation-induced gait ataxia in patients with essential tremor (ET) and thalamic deep brain stimulation (DBS).
Background: Thalamic DBS is a mainstay treatment for severe and drug-refractory ET, but postoperative management may be complicated in some patients by a delayed-onset progressive cerebellar syndrome. Typically, this syndrome manifests with severe gait ataxia months after an initially effective DBS therapy and it reflects an excessive current spread in the cerebellar-thalamic pathway.
Methods: We clinically evaluated seven subjects with ET and progressive gait ataxia under stable bilateral (sub)thalamic-region stimulation (2 males; median age: 73 years, range: 65-86 years). Patients were consecutively recruited and evaluated with the Fahn-Tolosa-Marin tremor rating scale (TRS) and the SARA1-3 scale for ataxia before (baseline), at 30 min and 14 days after reducing the stimulation pulse-width to 30μs. Such a short pulse width (30μs) was chosen to possibly target exclusively to the fast conducting dentate-thalamic myelinated fibers.
Results: Short pulse-width (30μs) dramatically improved gait ataxia (baseline SARA1-3 score: 6.8±2.8) in all patients already at 30 min (SARA1-3 score: 2.6±2.8; student t test, p<0.01) and at two weeks follow-up (SARA1-3 score: 3.0±2.0; student t test, p<0.01). Tremor was always well controlled by DBS (TRS score at baseline: 10.2±9.5; TRS score at 30 min 6.5±10.3; TRS score at 14 days: 4.8±4.2; student t test, p=n.s. all).
Conclusions: DBS-induced chronic progressive gait ataxia in ET patients can be effectively managed by focusing the stimulation to fast conducting dentate-thalamic myelinated fibers, which is the proper target for tremor control. This can be achieved, by reducing the stimulation pulse-width to 30μs, without losing the positive effect of DBS on tremor. Focused stimulation may prevent current spread and antidromic activation of the uncinate tract, which might be responsible for the delayed-onset of cerebellar side effects.
To cite this abstract in AMA style:M. Reich, N. Pozzi, G. Brandt, A. Leporini, C. Palmisano, R. Lehrke, J. Volkmann, I. Isaias. Focused neuromodulation by short pulse width improves gait ataxia in thalamic DBS [abstract]. Mov Disord. 2017; 32 (suppl 2). http://www.mdsabstracts.org/abstract/focused-neuromodulation-by-short-pulse-width-improves-gait-ataxia-in-thalamic-dbs/. Accessed November 22, 2017.
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MDS Abstracts - http://www.mdsabstracts.org/abstract/focused-neuromodulation-by-short-pulse-width-improves-gait-ataxia-in-thalamic-dbs/