Botulinum toxin for essential tremor of the voice with multiple anatomical sites of tremor: a crossover design study of unilateral versus bilateral injection

Laryngoscope. 2000 Aug;110(8):1366-74. doi: 10.1097/00005537-200008000-00028.


Objectives/hypothesis: To evaluate the relative efficacy of unilateral and bilateral injections of botulinum toxin injection (BOTOX) in the treatment of essential tremor of the voice (ETV).

Study design: Prospective open-label crossover study.

Methods: Patients referred to the Neurolaryngology Clinic at Toronto General Hospital with a diagnosis of ETV were eligible for the study. Patients were sequentially assigned to receive BOTOX as either a bilateral 2.5-U or a unilateral 15-U electromyography-guided injection, followed by the alternative injection 16 to 18 weeks later. Acoustic, aerodynamic, and nasopharyngoscopic data were collected approximately 2, 6, 10, and 16 weeks after each injection. Patients were asked to provide a perceptual evaluation of BOTOX effects at the conclusion of the study.

Results: Three of 10 patients demonstrated an objective reduction in tremor severity with bilateral injection, and 2 of 9 with unilateral injection. However, 8 of 10 patients wished to be re-injected at the conclusion of the study. A reduction in vocal effort appeared to be coincident with reduction in laryngeal airway resistance after BOTOX injection.

Conclusions: Using objective acoustic measures, only a small proportion of patients achieved benefit from BOTOX injection for ETV. However, a majority of patients in our study benefited from a subjective reduction in vocal effort that may have been attributable to reduced laryngeal airway resistance.

Publication types

  • Clinical Trial
  • Controlled Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Botulinum Toxins, Type A / administration & dosage*
  • Cross-Over Studies
  • Electromyography
  • Essential Tremor / drug therapy*
  • Female
  • Humans
  • Injections
  • Male
  • Middle Aged
  • Neuromuscular Agents / administration & dosage*
  • Patient Satisfaction
  • Voice Disorders / drug therapy*


  • Neuromuscular Agents
  • Botulinum Toxins, Type A