Background: Narcolepsy is a chronic hypersomnia of central origin, linked with dysfunction of hypocretin-containing neurons, localized in the lateral hypothalamus. Main symptoms of narcolepsy include excessive daytime sleepiness, cataplexy, hypnagogic hallucinations and sleep paralysis. Establishing the proper diagnosis is very important, because of the negative impact of narcolepsy on patients' functioning in social-life and the possibility of improvement of quality of life with adequate treatment.
Aim of the study: Present review describes clinical characteristics of narcolepsy, usefulness of neurophysiological tests in differential diagnosis of narcolepsy and assessing the efficacy of the treatment, as well as the application of novel biological methods in diagnosis of narcolepsy.
Methods and results: According to diagnostic criteria of ICSD-2 the diagnosis of narcolepsy is based on the clinical features and diagnostic examinations and tests. Among them neurophysiological procedures, such as polysomnography (PSG) and Multiple Sleep Latency Test (MSLT) are still recommended as most useful in differential diagnosis of narcolepsy and other hypersomnias. In recent decades novel biochemical and genetic tools have been developed as diagnostic measures in narcolepsy, including the levels of hypocretin in cerebral spinal fluid and HLA DQB1*0602 typing. These both biological markers are strongly associated with the occurrence of cataplexy, therefore do not present considerable diagnostic value in narcolepsy without cataplexy.
Conclusions: Neurophysiological procedures (MSLT) and biological markers are necessary in the diagnosis of narcolepsy with cataplexy and hypersomnia without cataplexy. Neurophysiological procedures are useful in monitoring of the treatment of hypersomnia also.