0397 Autonomic Reflex Testing Confirms Autonomic Disturbances in a Cohort of Patients with Idiopathic Hypersomnia

Abstract

Abstract Introduction Symptoms suggestive of autonomic nervous system (ANS) dysfunction have been previously described in patients with idiopathic hypersomnia (IH), however, objective ANS reflex testing data has not been reported. We aimed to better quantify symptoms of ANS dysfunction in a cohort of patients with IH through the use of standardized ANS reflex testing. Methods Patients diagnosed with IH based on ICSD-3 criteria using overnight video polysomnography and multiple sleep latency testing (MSLT) were consecutively enrolled in our study, regardless of ANS symptoms. All patients underwent ANS reflex testing, including measures of parasympathetic (heart rate variability with deep breathing and Valsalva ratio) and sympathetic adrenergic function (Valsalva blood pressure response and 10-minute head-up tilt at an angle of 70 degrees) with continuous blood pressure and heart rate monitoring. Eleven patients also underwent measures of sympathetic cholinergic function (quantitative sudomotor axon reflex testing). All medications that affect ANS function were held prior to ANS testing, including wake-promoting medications and sodium oxybate. Results Twenty patients with IH were enrolled. Fifty percent (10/20) were long sleepers (>11hrs). Mean sleep onset latency and number of sleep onset REM periods (SOREMs) on MSLT were 6.9 (± 3.1) mins and 0.2 (± 0.4), respectively. Mean duration of IH symptoms prior to the date of ANS testing was 6.3 (± 8.1) yrs. Eighty-five percent (17/20) of patients had abnormal ANS testing. Of these, 75% (15/20) had sympathetic adrenergic impairment, 64% (7/11) had sympathetic cholinergic impairment, and 5% (1/20) had parasympathetic impairment. Fifty-five percent (11/20) of patients were diagnosed with postural tachycardia syndrome (POTS), 45% (5/11) with small fiber neuropathy, 5% (1/20) with inappropriate sinus tachycardia and 15% (3/20) with neurally-mediated syncope. Seventy percent (14/20) of patients reported orthostatic intolerance regardless of autonomic diagnosis. Conclusion ANS dysfunction was common and severe in our cohort of IH patients, affecting all domains of ANS reflex testing, with more prominent impairment in sympathetic domains. POTS was the most common comorbid diagnosis, and most patients reported orthostatic intolerance. There was no association with IH disease duration, though our sample size was limited. Future studies will focus on ANS testing in larger cohorts of IH patients, specifically on shared pathophysiological mechanisms of hypersomnia and ANS dysfunction. Support (If Any)