1176 Extended Polysomnography Confirms Idiopathic Hypersomnia Diagnoses: A Case Series

Abstract Introduction Idiopathic hypersomnia (IH) is often underdiagnosed since at least 30-40% have normal mean sleep latency tests (MSLT) and test-retest reproducibility is poor. We report two cases of IH with multiple normal sleep evaluations diagnosed at Cleveland Clinic through extended polysomnography (PSG) using a 32-hr bed rest protocol as published by Evangelista et al., 2018. Report of case(s) Case 1: A 28-year-old female reported daytime sleepiness (Epworth Sleepiness Scale (ESS) 15), fatigue, sleep inertia, habitual sleep duration of 10-14 hr, brain fog and rare sleep-related hallucinations with symptom onset of 10 yr of age. PSG/MSLT evaluations at ages 13, 22 and 26 yr were normal, with MSLT mean sleep latencies (MSL) of 12.9, 15 and 16.8 minutes and 0 SOREMPs after normal PSG with adequate sleep. On extended PSG, total sleep time (TST) was 19.3 hr (1155 min) on the 32-hr recording and 13.1 hr (785 min) on the 24-hr recording. Case 2: A 42-year-old female reported excessive sleepiness (ESS 22), sleep inertia, memory and attention complaints, and rare sleep paralysis associated with sleep-related hallucinations beginning in the 2nd decade of life. Habitual sleep duration was 9.5 hr. PSG/MSLT evaluations at 40 and 41 yr were normal, with MLST MSL of 14.2 and 12.8 min and 0 SOREMPs and negative urine toxicology following normal PSG with adequate sleep and nocturnal sleep of 8-8.5 hr on actigraphy. On extended PSG, TST was 19.1 hr (1147 min) on the 32-hr recording and 11.7 hr (704 min) on the 24-hr recording. Conclusion We report two cases with IH phenotypes, multiple normal PSG/MSLT evaluations, and debilitating symptoms for over two decades. Both met the 19-hr cutoff for the diagnosis of IH using the 32-hr bed rest protocol based on published criteria and one met the 12-hr cut-off using the 24-hr protocol. This work illustrates the limitations of current IH diagnostic criteria and underscores the need to establish more accurate diagnostic test modalities for IH given the lack of biomarkers. Support (if any)