Adductor Spasmodic Dysphonia (AD-SD)

A variant of spasmodic dysphonia in which the spasms push the vocal cords together, choking off or straining the voice. Adductor spasmodic dysphonia (AD-SD), also called strain-strangle phonation, is the most common variant of spasmodic dysphonia, comprising about 90% of the cases. It is to be distinguished from abductor spasmodic dysphonia (AB-SD), a variant in which the spasms pull the vocal cords apart.

In its classic variant, the adductory spasms of adductor spasmodic dysphonia are intermittent, each time clamping the vocal cords together momentarily, so that words or syllables in a person’s speech are intermittently choked out. In its tonic variant, the adductory spasms are more constant and sustained than intermittent, so that instead of interrupting the person’s speech, the spasms cause a constant strained or “tight” vocal quality.

Occasionally, a person has both abductory and adductory spasms; this is called mixed AB-AD spasmodic dysphonia.

Pure AD-SD tonic only, moderate severity

Adductory spasm

TA-only Paresis after Botox Injection for Spasmodic Dysphonia

This man with adductory spasmodic dysphonia, has had consistent results during 15 years of botulinum toxin injections, administered several times per year. After his most recent (routine, and unremarkable) injection with his longstanding dose, his initial weakness was exaggerated and is only beginning to subside after six weeks. This dramatic “outlier” result that cannot be attributed to botox targeting.  As seen in the photos below, the explanation is instead a right TA-only paresis.

The only reasonable interpretation is that the needle tip has “sheared” the branch of the recurrent laryngeal nerve supplying the thyroarytenoid muscle (leaving branches to the posterior cricoarytenoid and lateral cricoarytenoid muscles (PCA + LCA) undisturbed.

In a practice that supplies treatment to approximately 100 patients per month and ~1200 injections per year, this phenomenon occurs perhaps twice per year. The voice “always” recovers back to baseline SD symptomatology, but excessive breathiness starts to resolve only 6 weeks after the injection.