Treatment of the interarytenoid muscle with botulinum toxin for laryngeal dystonia.

The treatment of laryngeal dystonia with botulinum toxin has provided various degrees of relief to the majority of patients with adductor dysphonia; however, a significant number of patients have limited or no improvement with this type of therapy. It remains unclear why some patients respond to the routine administration of toxin to the thyroarytenoid muscles whereas others do not. Injections into the lateral cricoarytenoid muscles have provided an improved voice in some patients who were unresponsive to injections into the thyroarytenoid muscles. Fine-wire electromyography can demonstrate the particular dystonic activity of these muscles to help determine which muscle is predominantly involved. It can also demonstrate dramatic dystonic activity in the interarytenoid (IA) muscle in many patients. We present the results of 23 patients treated with injections to the IA muscle after demonstration of dystonic IA activity. Ten have benefited from IA therapy. Five of these 10 patients did not have a good result from botulinum toxin until IA injections were added to the treatment plan. In 8 patients, IA therapy provided no improvement, and 5 patients were lost to adequate follow-up. According to fine-wire electromyography and clinical response, the IA muscle is an active dystonic muscle in some patients with laryngeal dystonia and should be treated with botulinum toxin in selected patients.