Interictal, potentially misleading, epileptiform EEG abnormalities in REM sleep behavior disorder

Study Objectives: To examine the implications of interictal epileptiform abnormalities (IEA) in idiopathic REM-sleep behavior disorder (RBD), particularly the risk of misdiagnosing RBD episodes as epileptic nocturnal seizures. Design: Observational analysis and review. Setting: Tertiary sleep center. Patients: Thirty patients (28 men; mean age 66.3 +/- 7.5 years) referred to our sleep unit for a definite diagnosis of nocturnal sleep-related motor and behavioral paroxysmal episodes. Interventions: N/A. Measurements and Results: All the patients were found to be affected by idiopathic RBD according to standard clinical and videopolysomnographic criteria. IEA(sporadic, fronto-temporal sharp-waves) were detected in 8 subjects (26.6%) during routine electroencephalogram and/or nocturnal in-lab videopolysomnography with extended EEG montages. In 2 of these 8 patients, IEA occurred during REM sleep. Conclusions: When only the clinical history is considered, RBD episodes may be confused with nocturnal epileptic focal seizures. The presence of IEA either on routine awake electroencephalograms, or during sleep electroencephalograms, may add support for a diagnosis of epileptic nocturnal seizures. Our data show that IEA may occur in wake and sleep (non rapid eye movement and rapid eye movement sleep) tracings of subjects with episodes of idiopathic RBD. However full-night extended electroencephalogram montages and polysomnography recording of an episode proved useful in establishing a definite diagnosis of RBD in these potentially misleading cases. Comparison of the patients' demographic data and RBD features revealed no differences between RBD with IEA and without IEA. On this basis-and given that these abnormalities have also been described in elderly people with wakefulness-related nonepileptic disorders-IEA in RBD could simply be interpreted as a nonspecific phenomenon, probably related to brain aging.