Rapid eye movement sleep behaviour disorder symptomatic of a brain stem cavernoma

Summary A 75‐year‐old man complained of excessive daytime sleepiness ( EDS ), difficulty falling asleep and nocturnal agitation during sleep. Restless legs syndrome ( RLS ) was diagnosed and treated. Because of persistent EDS , snoring and nycturia, a nocturnal polysomnography ( PSG ) was performed. PSG showed high sleep fragmentation related to a moderate to severe obstructive sleep apnea syndrome. Continuous positive airway pressure treatment ( CPAP ) was proposed. Because of the persistence of abnormal nocturnal behaviours, characterized by screaming, punching and falling out of bed, a video‐ PSG with CPAP treatment was performed. The recording showed typical chin electromyography ( EMG ) activity increase associated with violent movements during rapid eye movement ( REM ) sleep, suggesting REM sleep behaviour disorders ( RBD ). Clinical neurological examination found no parkinsonian syndrome, no dysautonomic sign and no neurological focal sign. Dopamine transporter imaging [123I‐ FP ‐ CIT single photon emission computed tomography ( SPECT )] did not find any presynaptic dopaminergic pathways degeneration. Brain magnetic resonance imaging showed a vascular lesion suggestive of cavernoma located in the pons. The present case illustrates the complexity of sleep disturbance diagnosis with a possible entanglement of aetiologies responsible for nocturnal agitation, and confirms that an isolated pons cavernoma should be considered among the rare causes of RBD .