Clinical characteristics of essential voice tremor: a study of 34 cases.

OBJECTIVES/HYPOTHESIS: To describe and characterize essential voice tremor, including signs, symptoms, and severity, and its relation to other manifestations of essential tremor. Description of aspects of treatment is a secondary goal.

STUDY DESIGN

Descriptive clinical cohort study.

METHODS

Thirty-four patients with essential voice tremor were identified over 40 months. Historical information regarding duration, family history, ethanol effect, arm tremor, and prior diagnosis was collected and examination was performed. Laryngeal and pharyngeal signs were graded using the Vocal Tremor Scoring System (VTSS); arm tremor was scored using the Washington Heights Inwood Genetic Study of Essential Tremor Rating Scale (WHIGET). Patients rated vocal disability using the Voice Handicap Index (VHI). Information regarding treatment was collected both historically and prospectively.

RESULTS

Ninety-three percent of patients were female. Voice tremor typically began in the seventh decade (62.9 +/- 15.0 years), and had been present for a mean of 6.7 +/- 13.4 years at the time of presentation. Tremor was present in a first-degree relative in 13 patients (38.2%); nine (26.5%) reported a beneficial effect of ethanol. Only 11 (32.3%) were aware of an arm tremor. Seven patients (20.6%) had been correctly diagnosed prior to evaluation; 16 (47.1%) were undiagnosed, and 10 (29.4%) had been misdiagnosed as spasmodic dysphonia. Clinical features were scored as follows: VTSS = 7.7 +/- 3.3, range 1 to 14; WHIGET = 8.5 +/- 7.5, range 0 to 31; VHI = 71 +/- 28, range 2 to 115. VTSS did not correlate with WHIGET, but did correlate with VHI. Only 56% of treated patients found botulinum toxin helpful.

CONCLUSIONS

Essential voice tremor appears to affect more women than men. One third to one half of affected individuals have a family history of tremor. About one half of cases occur with upper extremity tremor no more severe than that seen in similarly aged normal individuals, contrary to what has been thought to date. Essential voice tremor is probably more common than is generally suspected, and many cases appear to be undiagnosed many years after onset or are misdiagnosed, most often as spasmodic dysphonia. The key feature is kinetic laryngeal tremor which usually extends beyond the larynx to involve the phonatory apparatus globally. Botulinum toxin may be helpful, but benefit is typically incomplete and not universal. Prolonged postinjection breathiness is the most common barrier to useful treatment.