Voice Response to Injection of Succinylcholine in the Thyroarytenoid Muscle of Normal Subjects

Botulinum toxin (Botox) is commonly used in the treatment of spasmodic dysphonia. Succinylcholine is a neuromuscular blocking agent that mimics the biological activity of Botox yet takes effect within minutes. Four subjects with normal voice underwent bilateral vocal fold injection of succinylcholine to determine whether the drug would alter voice in a way comparable to previously reported analyses of voice response with Botox. Acoustic analyses confirmed that succinylcholine induced an increase in fundamental frequency, jitter, and shimmer, and a decrease in harmonic-to-noise ratio. Glottal flow rates were elevated after drug injection. Succinylcholine induced perceptual changes in pitch and quality. These findings suggest that succinylcholine alters vocal parameters that are also influenced by Botox. This drug may prove useful as a screening agent in patients for whom the benefit of Botox is questionable, or as an agent injected coincidentally with Botox to predict an optimal voice result and avoid the side effects associated with treatment.