Neurological Disorders

Independency of Selective Neuropsychological Dysfunctions from Subjective Daytime Sleepiness in Drug-Naive Patients with Narcolepsy

Abstract

Vincent Marcel Eric Lothar Nin*, Ulf Kallweit, Markus Ramm and Martina Piefke

Besides key symptoms of narcolepsy such as excessive daytime sleepiness, cataplexy, and disturbed nighttime sleep, patients affected by the disease also suffer from cognitive deficits, particularly impairments in attention, concentration, and various memory skills. However, it is still not fully understood to what extent cognitive impairments are independent of daytime sleepiness. In this study we aimed at identifying the taxonomy of neuropsychological dysfunctions in patients with narcolepsy without any stimulant or specific narcolepsy medication and the degree of independency of specific cognitive impairments of subjective daytime sleepiness. We expected that memory impairments, prefrontal dysfunctions, and disturbed emotion processing are independent of subjective daytime sleepiness and age. 22 patients with narcolepsy and 89 healthy controls were assessed by a comprehensive neuropsychological testing battery, psychological questionnaires on depression, alexithymia, as well a questionnaire on general daytime sleepiness. We found that narcolepsy patients exhibited independent of daytime sleepiness and age, significant deficits in tonic attention, set-shifting and in the conscious experience of arousal associated with emotions. Our results show for the first time that narcolepsy itself may lead to neuropsychological deficits that cannot be explained by subjective daytime sleepiness or aging-related cognitive decline. We propose that these novel insights are of considerable scientific and clinical relevance.