0972 The Utility of CSF Orexin Testing in Investigating for Narcolepsy Type-1 in a Patient with Diencephalic Mass

Abstract

Abstract Introduction Narcolepsy type 1 (NT1) is characterized by pathologic hypersomnolence, REM intrusion phenomena, including cataplexy, and orexin deficiency. The diagnosis of NT1 is established based on the presence of bone fide cataplexy and supportive PSG and MSLT testing which requires patients to achieve sufficient sleep duration and regularity and discontinue centrally acting medications that might alter REM sleep. In cases where there is a high index of suspicion for NT1, CSF orexin deficiency is helpful to support the diagnosis of NT1. This is particularly true when PSG-MSLT are not feasible, CNS medication cannot be discontinued, or cataplexy cannot be validated. Report of case(s) A 16 year old girl presented for evaluation of excessive daytime sleepiness in the setting of suprasellar germinoma which was resected and treated with chemoradiation at age 11. She subsequently developed panhypopituitarism and severe hypersomnolence in the setting of sleep-wake schedule irregularities, variability of sleep duration, refractory delayed sleep phase disorder, and snoring. She reported episodic weakness in the setting of negative triggers, which was atypical for cataplexy. Her medications included modafinil, amphetamine-dextroamphetamine, and the SSRI fluoxetine. Physical examination depicted normal airways. Epworth Sleepiness Scale score was 18. Screening polysomnography showed a sleep efficiency of 78%, sleep latency of 46.5 minutes, REM latency 2 hours, AHI of 0/hr, and periodic limb movements of 35/hr without arousals. While the REM latency on polysomnography was inconsistent with NT1, the clinical history of a diencephalic mass and chemoradiation was suggestive of secondary NT1. She was unable to proceed with PSG-MSLT due to her psychiatrist's advice against discontinuing her SSRI and her difficulty in maintaining sleep-wake regularity. An evaluation for CSF orexin was performed establishing a normal level of 337 pg/mL (reference level of 200 pg/mL in healthy individuals), ruling out orexin deficiency /narcolepsy type 1. The patient was subsequently improved with wake-promoting antidepressants and light therapy in the AM. Conclusion This case illustrates the value of CSF orexin testing in the setting of diencephalic lesions in patients unable to undergo formal narcolepsy testing. Support (if any)