Differential Diagnosis between Neurogenic and Functional Dysphonia

ABSTRACT

Voice disorder is classified into three categories, structural, neurogenic and functional dysphonia. Neurogenic dysphonia refers to a disruption in the nerves controlling the larynx. Common examples of this include complete or partial vocal cord paralysis, spasmodic dysphonia. Also it occurs as part of an underlying neurologic condition such as Parkinson's disease, myasthenia gravis, Lou Gehrig's disease or disorder of the central nervous system that causes involuntary movement of the vocal folds during voice production. Functional dysphonia is a voice disorder in the absence of structual or neurogenic laryngeal characteristics. A near consensus exist that Muscle tension dysphonia (MTD) is functional voice disorder wherein hyperfunctional laryngeal muscle activity whereas Spasmodic dysphonia (SD) is neurogenic, action-induced focal laryngeal dystonia including several subtype. Both Adductor type spasmodic dysphonia (AdSD) and MTD may be associated with excessive supraglottic contraction and compensation, resulting in a strained voice quality with spastic voice breaks. It makes these two disorders extremely difficult to differentiate based on clinical interpretation alone. Because treatment for AdSD and MTD are quite different, correct diagnosis is important. Clinician should be aware of the specific vocal characteristics of each disease to improve therapeutic outcome.