Objective: We report an elderly patient with jaw opening dystonia and blepharospasm post-bilateral thalamic DBS performed for atypical dystonic tremor.

Background: Ventral intermediate nucleus (VIM) deep brain stimulation (DBS) is an effective treatment for essential tremor (ET) and dystonic tremor (DT). Dysarthria and ataxia are known complications following bilateral DBS. Jaw opening dystonia and blepharospasm post-bilateral VIM-DBS has not been reported.

Methods: Case: A 76-year old man had an 8-year history of alcohol-responsive kinetic and postural tremor in left more than right upper limb. He had a null point on pronation-supination of upper limb tremor and subtle slowing of right foot rapid alternating movements. Long-acting propranolol and primidone resulted in a transient improvement. MRI brain showed microvascular ischemic changes. Tremor recording showed single peak of 4.7 Hz tremor. An initial diagnosis of ET was made, but prior to DBS left leg dystonia was noted. To treat the disabling tremor bilateral VIM-DBS was performed at age 79. Tremor responded very well to DBS initially, but over several weeks settings had to be increased due to kinetic tremor breakthrough. Stimulation settings were limited by dysarthria, but still sufficient to provide effective symptom control. However, over a 6-12 month period he reported increasing posturing in his right foot impairing gait followed by increasing difficulty in talking and eating. On re-examination, he had developed blepharospasm and jaw opening dystonia in addition to worsening of right foot dystonia. These features did not resolve to adjustment of settings or switching off the stimulation.

Results: Our patient initially presented with ET-like tremor with minor dystonic features and developed prominent more generalized dystonia post thalamic DBS. A diagnosis of late onset dystonia usually affects the face or neck and limbs less frequently. Spread to jaw from arms and leg is exceptional. The evolution of disabling dystonic features after VIM DBS is notable, having been minor and stable for many years prior to DBS.

Conclusions: Distinguishing ET from dystonic tremor is difficult. Dystonia can evolve over time and long follow up is required. The development of jaw opening dystonia and blepharospasm post VIM-DBS for dystonic tremor is unusual and it remains unclear why this occurred.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/jaw-opening-dystonia-and-blepharospasm-following-bilateral-vim-dbs-for-postural-and-action-dystonic-tremor/