Towards a more objective diagnosis of REM Sleep Behavior Disorder

Abstract

The prevalence of REM sleep behavior disorder (RBD) has been estimated to be around 0.5 % in the general population, while in patients with Parkinson’s disease the frequency ranges between 40 and 46 %. Current criteria for the diagnosis of RBD do not specify a clear quantitative cut-off for muscle activity, that is, how much EMG activity during REM sleep is normal, and at what point does it become abnormal? It is important that RBD be correctly diagnosed as (1) RBD can be the first manifestation of a neurodegenerative disease, (2) it can involve serious injury to the patient and/or bed partner, and (3) because it is a treatable disorder. In this review we seek to improve this situation and to move toward a more objective diagnosis of RBD. The time has come to move from a qualitative diagnosis of RBD to a quantitative diagnosis. Increased tonic and phasic muscle activity can and should be quantified. Cut-offs have now been established: the combination of “any” EMG activity in the mentalis muscle with both phasic flexor digitorum superficialis muscles yielded a cut-off of 32 % (AUC 0.998) for patients with idiopathic RBD and with Parkinson RBD. Such cut-offs help make the diagnosis of RBD more objective and avoid false positive diagnosis.