THE CLINICAL SPECTRUM OF EXCESSIVE SLEEPINESS: NEUROBIOLOGICAL MECHANISMS, ASSESSMENT, AND TREATMENT- A NARRATIVE REVIEW
Abstract
Hypersomnolence disorders constitute a heterogeneous group of conditions characterized by excessive daytime sleepiness (EDS), impaired alertness, and reduced quality of life. These disorders represent a significant medical and social challenge due to their impact on cognitive functioning, occupational performance, interpersonal relationships, and the increased risk of accidents. The regulation of sleep and wakefulness is a complex process involving interactions between circadian and homeostatic mechanisms, as well as numerous neurotransmitter systems, including orexin, dopamine, serotonin, histamine, acetylcholine, and gamma-aminobutyric acid (GABA). Advances in polysomnography, neuroimaging, and neurophysiology have improved understanding of the mechanisms underlying sleep regulation and central disorders of hypersomnolence. This review summarizes the physiological basis of sleep, current methods used in the assessment of excessive sleepiness, and the clinical characteristics of the major hypersomnolence disorders. Particular attention is given to narcolepsy type 1 and type 2, idiopathic hypersomnia, Kleine–Levin syndrome, and hypersomnia associated with neurological, psychiatric, metabolic, endocrine, inflammatory, vascular, genetic, and traumatic conditions. Diagnostic approaches, including sleep questionnaires, actigraphy, polysomnography, and the Multiple Sleep Latency Test, are discussed in the context of differential diagnosis. The article also reviews current therapeutic strategies, emphasizing both non-pharmacological interventions, such as sleep hygiene, scheduled naps, and behavioral modifications, and pharmacological treatments including modafinil, armodafinil, stimulants, sodium oxybate, pitolisant, and emerging therapeutic approaches targeting the orexin system. Early recognition of hypersomnolence disorders and appropriate management are essential for improving patient outcomes, reducing disease burden, and enhancing overall quality of life.