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.