Spasmodic dysphonia: treatment options and challenges

Abstract

Functional voice disorders (FVD) are caused by insufficient or improper use of the phonation apparatus without either anatomical or neurological abnormalities. Neurologic voice disorders occur as part of an underlying neurologic condition such as Parkinson's disease, multiple sclerosis, myasthenia gravis, or ALS. They can also happen as the result of a stroke. These disorders can affect the strength of the muscles of the voice box, and impact the control of the voice. Many of these neurological disorders affect the body systemically, but patients will often complain of dysphonia before other symptoms develop. The otolaryngologist can therefore be the first physician to diagnose such neurological conditions. This impacts speech to varying degrees and results in strained and strangled voice quality. While there is currently no cure for such disorders, voice therapy and chemodenervation with botulinum toxin (BT) injections remain the base of management. Surgery also may be performed in some cases. However BT injections are used to treat spasmodic dysphonia and essential tremor. While BT injections may show vocal improvement, results can depend on several factors such as the general health of the patient, onset and severity of the condition, dosage, interval between injections and experience of the practitioner. While many studies have documented the efficacy of botulinum toxin for improving vocal symptoms, this review aims to discuss some of those studies.