Botulinum Toxin Therapy: A Series of Clinical Studies on Patients with Spasmodic Dysphonia in Japan

Spasmodic dysphonia (SD) is a rare voice disorder caused by involuntary and intermittent spasms of the laryngeal muscles. Both diagnosis and treatment have been controversial. Therefore, a series of clinical studies has recently been conducted in Japan. A nationwide epidemiological survey revealed that adductor SD predominated (90–95% of all cases; 3.5–7.0/100,000), principally among young women in their 20s and 30s. To facilitate early diagnosis, we created diagnostic criteria for SD and a severity grading system. The diagnostic criteria include the principal and accompanying symptoms, clinical findings during phonation, the treatment response, and the differential diagnoses. The severity grade is determined using a combination of subjective and objective assessments. Botulinum toxin (BT) injection is the treatment of choice; however, there have been few high-quality clinical studies and BT has been used off-label. We conducted a placebo-controlled, randomized, double-blinded clinical trial of BT therapy; this was effective and safe. BT treatment is now funded by the Japanese medical insurance scheme. Studies thus far have facilitated early diagnosis and appropriate therapy; they have fostered patient awareness of SD.

Botulinum toxin treatment for adductor spasmodic dysphonia with EMG and endoscopic guidance

Background & Objective: Spasmodic dysphonia is idiopathic focal dystonia characterized by irregular contractions or postural disorders of the laryngeal muscles, resulting in abnormal speech. Progress in laryngoscopy has resulted in development of a precise technique of botulinum toxin (BTX) injection into the thyroarytenoid muscle under visual control. Methods: We used EMG and endoscopic guidance for BTX injection in adductor spasmodic dysphonia (AdSD). Results: Thirty eight patients with AdSD were injected with BTX in 84 treatment sessions. The voice handicap index (VHI) level of the patients were: severe (73.8%), moderate (26.2%) and mild (none). The average VHI score was 74.6 points. After 8 weeks of BTX treatment, the VHI level was: Severe (3.6%), moderate (10.8%), and mild (85.7%). The average VHI score was 27.7 points. The average values of jitter, shimmer and harmonic to noice ratio (HNR) improved statistically (p < 0.05). The incidence of side effects were: breathiness (17.9%), choking (15.5%); hoarseness (8.5%), and dysphagia (4.7%). Conclusions: Injection of BTX under both EMG and laryngoscopy guidance for treatment of adductor spasmodic dysphonia is an effective and safe treatment.

Neurogenic Laryngeal Disorders

The larynx is critical to performing complex tasks of airway protection, phonation, respiration, and deglutition. Various focal and systemic neurologic disorders impact the larynx, causing deficits that lead to dysfunction in voice, speech, breathing, and swallowing function. The most common hyperfunctional neurolaryngeal disorders include spasmodic dysphonia (laryngeal dystonia), essential vocal tremor, and muscle tension dysphonia. Some hypofunctional neurolaryngeal disorders include parkinsonian disorders, neuromuscular junction diseases, and myopathies. A multidisciplinary approach involving evaluation by neurologists, voice-trained otolaryngologists and speech-language pathologists is often key to diagnosis and treatment of these challenging and sometimes lifelong disorders. Botulinum toxin injection into the laryngeal musculature is currently the gold-standard treatment for both spasmodic dysphonia and vocal tremor. However, much research is being conducted to advance less invasive and more definitive medical and surgical treatment interventions. This review contains 3 figures, 11 videos, 6 tables and 29 references Keywords: laryngeal neurophysiology, laryngeal dystonia, adductor spasmodic dysphonia, abductor spasmodic dysphonia, essential vocal tremor, hyperfunctional voice disorders, hypofunctional voice disorders, botulinum toxin injection

Thalamic Deep Brain Stimulation Ameliorates Mixed and Abductor Spasmodic Dysphonia: Case Reports and Proof of Concept

BACKGROUND AND IMPORTANCE Spasmodic dysphonia (SD) is a dystonia of the vocal folds causing difficulty with speech. A recent randomized controlled trial showed that thalamic deep brain stimulation (DBS) was safe and could improve this condition in the most common subtype—adductor SD. We investigated if thalamic DBS could also improve the other subtypes of abductor SD and mixed SD. These prospective blinded trials of 1 were designed to assess the safety of thalamic DBS in mixed and abductor SD and to quantify the magnitude of any benefit from unilateral or bilateral thalamic stimulation. CLINICAL PRESENTATION One patient with mixed SD and one patient with abductor SD received bilateral thalamic DBS. After optimizing their DBS settings for vocal improvement, they were blinded and prospectively randomized to receive 1 mo of left, right, both, or neither hemisphere stimulation. Outcome was assessed by a speech language pathologist, blinded to the settings, rating voice recordings with the Unified Spasmodic Dysphonia Rating Scale, and by patient self-reported quality-of-life questionnaires. Additional outcomes included scores of mood and cognition. There were no complications. Both patients reported a subjective improvement of their voice and quality of life with blinded left thalamic DBS. The quality of their voice was also objectively rated as improved with blinded left thalamic DBS. CONCLUSION This small proof-of-concept study suggests that left thalamic DBS can improve the quality of voice and quality of life of patients with mixed SD and abductor SD.