The superior laryngeal nerve: function and dysfunction.

Despite long-standing clinical interest in SLN dysfunction, most aspects of this entity continue to require clarification. The replacement of the laryngeal mirror by flexible fiberoptic and rigid rod-lens laryngoscopy (including stroboscopy) and the resulting improvement in laryngeal visualization and documentation of examination has not resulted in a better definition of characteristic signs. Symptoms are often vague, and most are shared with other voice disorders. Under the circumstances, there is good reason to suppose that SLN dysfunction yields a clinical picture at least as heterogeneous as recurrent laryngeal nerve injury and a good deal more subtle. Faced with significant inconsistencies in clinical presentation, the clinician is hard-pressed to draw conclusions regarding prevalence, patterns of dysfunction, natural history, treatment, and even about its overall significance. EMG. used judiciously and complemented by frequency range testing, seems to hold more promise as a means of reliable diagnosis than laryngoscopic examination and may serve to resolve some of the confusion surrounding SLN dysfunction. It is equally important that the otolaryngologist guard against falling into the easy habit of attributing vocal disturbance that cannot be otherwise explained to SLN dysfunction in the absence of EMG evidence. If ambiguities surrounding SLN paralysis and paresis are to be clarified, diagnostic rigor is essential.