1360 Actigraphy-Supported Diagnosis of Kleine–Levin Syndrome in an Adolescent with Recurrent Hypersomnia

Introduction Kleine–Levin syndrome (KLS) is a rare, relapsing–remitting neurologic sleep disorder characterized by recurrent episodes of severe hypersomnia accompanied by cognitive, behavioral, and autonomic disturbances, with complete inter-episode recovery. It predominantly affects adolescent males. Diagnosis is frequently delayed because of its episodic nature, nonspecific symptoms, and lack of definitive biomarkers. Objective documentation of hypersomnia during symptomatic periods is challenging. Actigraphy offers a practical, noninvasive approach to capturing sleep–wake patterns during active episodes. Report of case(s) A 16-year-old male presented with a nearly two-year history of recurrent hypersomnia episodes occurring every 2–3 months and lasting several days to weeks. During episodes, he slept 15–20 hours per day and exhibited hyperphagia and mild irritability as prodromal symptoms. Initial symptom onset followed multiple upper respiratory infections. Between episodes, he returned fully to baseline with normal sleep patterns and daytime functioning. Extensive medical evaluation was unrevealing. Epstein–Barr virus serology showed elevated IgG titers with negative PCR and low IgM levels, not felt to explain his presentation. Evaluation for Marfan syndrome, primary immunodeficiency, autoinflammatory and autoimmune disorders, and immunologic abnormalities was normal. Neurologic workup, including head CT, brain MRI, and EEG, was unremarkable. Wrist actigraphy performed during a symptomatic episode demonstrated markedly prolonged total sleep time, reduced daytime wakefulness, and disrupted circadian organization. Subsequent polysomnography revealed mild obstructive sleep apnea. A multiple sleep latency test was not consistent with narcolepsy (mean sleep latency 9 minutes, two sleep-onset REM periods). These objective findings, in conjunction with the characteristic clinical course and exclusion of secondary causes, supported a diagnosis of Kleine–Levin syndrome. Conclusion This case highlights the clinical utility of actigraphy as an accessible and objective tool for documenting hypersomnia during acute KLS episodes. While polysomnography may be logistically difficult during symptomatic periods, actigraphy allows longitudinal assessment of sleep–wake patterns and can aid in distinguishing KLS from other hypersomnia disorders, mood disorders, and behavioral sleep disturbances. Support (if any)