Primidone Therapy for Essential Vocal Tremor.

IMPORTANCE: Essential vocal tremor is difficult to treat. An effective pharmacologic treatment could allow patients to avoid or decrease the frequency or dosage of botulinum neurotoxin injections.

OBJECTIVE: To evaluate the efficacy of primidone in the treatment of essential vocal tremor.

DESIGN, SETTING, AND PARTICIPANTS: Medical records of all patients with a primary or secondary diagnosis of laryngeal spasm or essential tremor treated with primidone between June 1, 2012, and March 21, 2014, at a tertiary care medical center were reviewed. Data analysis occurred in April 2014.

MAIN OUTCOMES AND MEASURES: Duration of therapy, improvement of symptoms, and whether the patient subsequently initiated botulinum neurotoxin therapy.

RESULTS: All 30 patients were female (mean [SD] age, 71.9 [11.8] years). Mean (SD) therapy duration was 5.25 (7.22) months. Nine patients (30%) had other vocal conditions (4 had coexisting spasmodic dysphonia, 4 had laryngopharyngeal reflux disease, and 1 had muscle tension dysphonia). Twelve (40%) had previously undergone treatment. Fourteen of 26 patients (54%) reported an improvement in their vocal symptoms, and 16 of 29 (55%) did not discontinue primidone therapy. Twenty-two of 30 patients (73%) experienced adverse effects. Therapy was discontinued by 11 of 21 patients (52%) who experienced adverse effects and 2 of 8 patients (25%) who did not report adverse effects (P = .24) (1 patient who had adverse effects was missing data on discontinuation of therapy). Sixteen patients (53%) subsequently initiated botulinum toxin therapy, including 5 of 14 patients (36%) who reported clinical improvement with primidone therapy and 7 of 12 patients (58%) who did not report improvement (P = .43).

CONCLUSIONS AND RELEVANCE: Primidone therapy was an effective pharmacologic treatment for essential vocal tremor in 14 of 26 patients in this case series, providing an alternative to botulinum neurotoxin therapy.