1204 Importance of Arm Electromyography for REM Without Atonia Detection

Abstract Introduction Dream enactment raises concern for rapid-eye movement (REM) sleep behavior disorder (RBD). RBD is a parasomnia during which the patient has loss of normal atonia during REM sleep. RBD is highly associated with α-synucleinopathies (i.e., Parkinson disease, dementia with Lewy bodies, and multiple system atrophy) and can precede additional neurodegenerative signs and symptoms. REM sleep without atonia (RWA) is demonstrated through electromyography (EMG) during polysomnography. RWA requires the presence of tonic/sustained activity with ≥50% of the epoch containing excessive chin activity or phasic/transient muscle activity in ≥5 mini-epochs of 3-second duration in a 30-second epoch. We present a case that highlights the necessity of ordering polysomnography with arm EMG when evaluating for RBD. Report of case(s) A 73-year-old man presented to the clinic for concern of obstructive sleep apnea. He was also evaluated by neurology and given a diagnosis of essential tremor. During the initial visit, he also reported frequent “night terrors,” which he later described as dream enactment. His medications included metoprolol but no antidepressants; however, the dream enactment started prior to beta-blocker use. His physical exam was notable for right cogwheel rigidity, mild decrease in right serial finger tapping and rapid alternating movements, and mild dysphonia. A polysomnogram with arm EMG was ordered. On polysomnography, RWA was present in multiple epochs that was seen predominantly with arm (flexor digitorum superficialis) EMG. The RWA index (% of REM sleep meeting criteria for RWA) using the leg (anterior tibialis) and chin EMG was only 5%; however, the RWA index with the addition of arm EMG increased the RWA index to 64%. Conclusion The presence of RWA on PSG with dream enactment behavior gives this patient the diagnosis of RBD. While leg EMG is a part of routine PSG, arm EMG is not and needs to be specifically requested. Although research supports the use of arm EMG leads, we commonly find the addition of arm EMG leads is not ordered by providers when assessing for RBD. Arm EMG increases the chance of observing RWA and can be of strong importance to solidify an RBD diagnosis. Support (if any)