Diagnostic Criteria and Delay in Diagnosis of Narcolepsy

Abstract

Narcolepsy has an early onset but a long delay until diagnosis. The delay is a mean of 8–15 years, with individual cases of > 60 years, although there is a trend over time toward a shorter diagnostic delay. The lack of symptom recognition, often resulting in misdiagnosis prior to reaching the narcolepsy diagnosis, is primarily the reason for the delay. The diagnostic criteria are largely based on objective testing in a patient with sleepiness. However, sleepiness is common in the general population, and if narcolepsy is not suspected, patients may not be referred for diagnostic testing. The current objective test for narcolepsy involves an overnight polysomnographic study followed by a daytime multiple sleep latency test. Alternatively, a positive test involves measuring csf hypocretin which when low or absent indicates narcolepsy; however, the test is not widely available. The main indication of narcolepsy is the presence of the diagnostic clinical features which include not only sleepiness but also cataplexy, hypnagogic hallucinations, sleep paralysis, and disturbed nocturnal sleep. Frequent vivid and unusual dreams as well as episodes of automatic behavior are additional features that can help in the diagnosis. To close the diagnostic gap requires expanding awareness of narcolepsy and increasing awareness of the typical clinical features.