1143 Nuclear Narcolepsy

Abstract Introduction The sleep -wake mechanism is a complex network of structures of the brain and numerous neurotransmitters. Notably, the hypothalamus produces a powerful wake promoting peptide, orexin, which lack thereof results in narcolepsy. Moreover, studies have demonstrated that the thalamus,although not fully elucidated, plays a dichotomous role in the sleep -wake cycle. This case highlights an interesting iatrogenic cause of hypersomnia. Report of case(s) Patient is a 49 year old male who presents for evaluation of hypersomnia. He had some sleepiness throughout his adult life but worsened significantly in the recent years prior to presentation. His Epworth Sleepiness Scale is 21. No hypnagogic/hypnopompic hallucinations, cataplexy, sleep attacks, sleep paralysis reported. Mild snoring is present. His BMI is 24kg/m2. His PMH is notable for essential tremor treated with stereotactic radiosurgery thalamotomy four years prior to presentation. He underwent polysomnography that was overall unremarkable with no evidence of sleep disordered breathing or periodic limb movements, but the study had sleep onset REM of 13 minutes. The following day, an MSLT was performed and demonstrated sleep latency of 3 minutes and 26 seconds and one sleep onset REM. He was diagnosed with secondary narcolepsy and started on pharmacotherapy with modafinil. Conclusion The patient in this case underwent stereotactic radiosurgery to the thalamus for treatment of essential tremor. Given the proximity of the thalamus to the hypothalamus, it is thought that damage to this structure resulted in loss of orexin causing secondary narcolepsy. Furthermore, excessive daytime sleepiness is a consequence of thalamic lesions such as thalamic stroke further demonstrating the role of the thalamus in the sleep -wake mechanism. Support (if any) Cai H, Wang XP, Yang GY. Sleep Disorders in Stroke: An Update on Management. Aging Dis. 2021 Apr 1;12(2):570-585. doi: 10.14336/AD.2020.0707. PMID: 33815883; PMCID: PMC7990374. Cheng P, Roehrs T, Roth T. Daytime Sleepiness and Alertness. Principles and Practice of Sleep Medicine. 7th Edition. Elsevier. 2022. Chapter 4, 35-45.e5.