Tremor in a Bassoonist: Tremor in Dystonia or Essential Tremor?

JMD Dear Editor, Tremor is a common clinical feature in dystonia. It can be seen in both affected and unaffected body parts in patients with dystonia. Clinically, it may not be easily distinguishable from essential tremor, currently defined as a bilateral, largely symmetric postural or kinetic tremor involving the hands and forearms that is visible and persistent, with an associated or isolated head tremor in the absence of abnormal posturing. 1 Efforts to differentiate these types of tremor include using neurophysiological tests such as somatosensory temporal discrimination threshold (TDT) testing, electromyography, accelerometry and reciprocal inhibition. 2,3 In patients with dystonia, TDT values have been found to be prolonged, postulated to reflect abnormalities in the basal ganglia. 2,4-6 On the other hand, investigations on patients diagnosed with essential tremor have revealed TDT values to be normal in those with upper limb tremor. To illustrate the use of TDT in tremor diagnosis, we report a case of tremor in a 48-year-old right-handed man. His symptoms began 12 years prior to consult, initially task-specific, beginning in the left hand while playing the bassoon. The tremor progressed to involve both hands, the head, voice and trunk, often simultaneously. Tremor and head pulling to the right would worsen with manual activities and emotional stress. He was seen by several neurologists and was given varying diagnoses of dys-tonia and essential tremor. Sodium oxybate dampened the tremor , but had to be discontinued due to side effects. Current medications included propranolol extended-release 60 mg daily, topiramate 100 mg twice daily, clonazepam 1 mg twice daily and escitalopram 20 mg daily. The patient's past medical history was positive for depression, alcoholism (sober for the past eight years) and asthma. There was no family history of tremor, and both parents have a history of strokes. He is a smoker, works as a priest, is separated and lives alone. Exam revealed mildly depressed affect, bradyphrenia and intermittent word-finding difficulty. The Montreal Cognitive Assessment score was 23/30 with errors in the following domains; executive, attention, language, and delayed recall. A high-frequency , asymmetric postural and kinetic tremor was noted in both upper extremities and trunk, as well as a vocal tremor. Right head tilt was present, most prominent on playing the bassoon. There were no sensory tricks. Bilateral arm posturing was noted with walking, greater on the right (Supplementary Video in the online-only Data Supplement). Magnetic resonance imaging of the brain …