Case report
Failed DBS for palliation of visual problems in a case of oculopalatal tremor

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Abstract

Objective

To report the results of attempted bilateral red nucleus (RN) deep brain stimulation (DBS) for the palliative treatment of visual problems associated with oculopalatal tremor (OPT).

Background

It is hypothesized that OPT results from a defect in the Guillain–Mollaret triangle, a circuit that includes connections with the dentate nucleus, the contralateral red nucleus, and the inferior olive. We present a high functioning patient (an accountant) who underwent a palliative trial of RN region DBS in an approach targeted through the subthalamic nucleus region. The aim was to reduce eye tremor and improve vision through interruption of the pathologically oscillating circuit in the Guillain–Mollaret triangle.

Methods

Following informed consent, a patient with OPT (and failure of multiple classes of medication and botulinum toxin therapy) underwent placement of bilateral DBS electrodes within the region of the RN. He underwent preoperative testing and testing after 12 months of continuous stimulation with the device in monopolar, bipolar, low frequency, and high frequency settings.

Results

The patient did not demonstrate significant changes in the neurological examination following the procedure and postoperative programming sessions. Eye tremor was monitored pre- and postoperatively by ocular EMG and did not change in frequency. Following the one-year trial, stimulation was discontinued as there were no improvements in vision.

Conclusion

DBS for OPT was not clinically effective. There were many potential reasons for failed efficacy including a failure to implant the electrodes deep and medial enough into the target region because of stimulation induced side effects. Other targets within the Guillain–Mollaret circuit (and outside of the circuit) may be more useful, though they may prove to be less safe and even more difficult to access. Better custom designed DBS leads may be needed for such small targets in critical brain regions.

Introduction

Oculopalatal tremor (OPT), first described over 100 years ago as oculopalatal myoclonus [1], often presents as pendular nystagmus associated with a palatal tremor. Secondary cases of OPT typically follow acute brainstem lesions or vascular events [2]. Most reported cases involve continuous palatal tremor in association with vertical pendular nystagmus, though notable variations may include monocular, horizontal or torsional nystagmus, as well as involvement of other branchial-derived muscles [2]. The palliative treatment of visual problems associated with OPT by targeting red nucleus (RN) with DBS has not been previously explored. We present the case of a patient with OPT who had bilateral RN region DBS through an approach similar to STN DBS for Parkinson disease. The indication for therapy was the palliative treatment of visual difficulties.

Section snippets

Case report

A 44-year-old man with a history of a pontine cavernous malformation, which was previously surgically resected, presented after awakening with numbness in his hands, diplopia, and a feeling of generalized weakness. Magnetic resonance imaging (MRI) of his head revealed a new pontine hemorrhage. Followup MRI scans showed a persistent cavernous malformation in the pons, and this malformation was extracted by a vascular neurosurgeon.

Following this second surgical resection of the pontine cavernous

Discussion

Our attempt to regularize red nucleus firing through DBS failed to produce successful results in attenuating the OPT. This negative result may have been due to several factors, the most important being the side effects encountered when attempting to place the electrode into the RN region. The final measured coordinates of lead placement were discrepant from the planned coordinates mainly because of intraoperative adjustments due to patient discomfort. The dorsal and lateral placement and

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