Objective: To report a case series of thalamic-subthalamic deep brain stimulation for the treatment of refractory orthostatic tremor.

Background: Orthostatic tremor (OT) is a rare, disabling movement disorder characterised by the development of a high frequency tremor of the lower limbs and feelings of unsteadiness upon standing compelling the patient to sit down or walk. Medical therapy is often unsatisfactory.Previous reports suggest deep brain stimulation of the ventral intermediate (Vim) nucleus of the thalamus may improve clinical outcomes.

Methods: We report 3 patients with severe OT refractory to medical therapy, with a mean duration of symptoms of 17 years. Bilateral DBS of the Vim-caudal zona incerta in a single centre and clinical assessments, EMG recording and gait analysis were performed pre and post surgery and ON and OFF stimulation. Additonally in one patient thalamic local field potentials (LFPs) were recorded from the bilateral deep brain stimulation electrodes simultaneously with tibialis anterior surface EMG activity in the post-operative period.

Results: Following surgery, all 3 patients demonstrated increased latency to symptom onset, complete withdrawal of medication and improved activities of daily living, with sustained benefits noted 18 months post surgery in 2 patients. Gait analysis and EMG evaluation of the tibialis anterior, gastronimius, rectus femoris, biceps femoris, and paraspinal muscles revealed no change in tremor frequency or time of initiation of tremor ON or OFF stimulation. One patient developed cerebritis following surgery and the DBS hardware was removed.

Conclusions: Our cases provide further evidence to support the efficacy of bilateral thalamic-subthalamic Vim DBS for OT and are consistent with previous findings of clear improvements in latency of clinical symptoms and reduced unsteadiness despite no alteration in peripheral tremor rhythm. The efficacy of thalamic-subthalamic DBS despite absence of any change in leg tremor, together with the evidence of coupled oscillatory activity in the ViM suggests that the cerebellar input to thalamus (ViM) may be part of this feedback loop. Based on these and previous cases, further long term data from controlled clinical trials examining the efficacy of this approach in OT are needed.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/thalamic-subthalamic-deep-brain-stimulation-for-refractory-orthostatic-tremor-a-report-of-3-cases/