1336 Successful Treatment of Isolated REM Behavior Disorder with Prazosin

Abstract Introduction Rapid Eye Movement (REM) Behavior Disorder (RBD) is defined by the loss of skeletal muscle atonia during REM sleep, associated with sleep vocalization and/or complex motor behaviors. While RBD may be secondary to medications and untreated sleep disorders, isolated RBD (iRBD) is likely secondary to alpha synucleinopathy. Treatment for iRBD commonly includes nightly melatonin and benzodiazepines, however one case report and neurophysiology data from animal studies suggest norepinephrine antagonism may be effective. Report of case(s) An 82-year-old male presented with a four-year history of biweekly episodes of arm swinging, leg kicking, and yelling during sleep. No significant medical/psychiatric/medication history. Frequent nightmares of violent and persecutory content prompted initiation of prazosin 1 mg by primary care with reduction in frequency of nighttime motor/vocal activity. Polysomnography demonstrated an apnea hypopnea index of 14.1 and absence of REM sleep without atonia (RSWA). He started PAP therapy and was trialed off prazosin, resulting in an immediate rebound of nighttime motor and vocal activity. Prazosin was resumed and titrated to 2 mg, with reduced frequency of nightmares and associated activity to once every three months. Subsequent CPAP titration study demonstrated RSWA. History and physical revealed: worsening paranoid ideation, decreased blink rate, L > R resting tremor of the hands, bilateral wrist and elbow rigidity, L > R upper/lower extremity dysmetria and dysdiadokinesia, and reduced left arm swing. Neurology was consulted for suspicion of alpha synucleinopathy. Conclusion Prazosin may be a reasonable consideration for treatment of nightmares and dream enactment behavior in patients with iRBD. Noradrenergic stimulation of the sublateral dorsal nucleus (SLD) via the locus coeruleus inhibits motor neuron atonia. Alpha blockers may restore atonia during REM sleep in patients with RBD by its antagonistic effect on central alpha-1 receptors thereby hindering the typical inhibitory effect of norepinephrine on the SLD. This is partly supported by one other published case report of successful treatment of RBD with prazosin, which was confounded by concurrent use of melatonin. Support (if any) The views expressed herein are those of the authors and do not reflect the official policy of the Department of War or U.S. Government.