REM sleep behavior disorder with predominant nightmares in a patient with ischemic pontine lesions

REM sleep behavior disorder (RBD) is a parasomnia typically associated with synucleinopathy and evolving to neurodegenerative disorders. RBD is caused by impairment of brainstem nuclei controlling REM sleep muscle atonia. Rarely, focal lesions of the brainstem can cause secondary RBD. We present the case of a 74-years-old patient, previously evaluated at age 70 years for insomnia and periodic limb movements during sleep, who then rapidly developed unpleasant dreams with minor motor behavior, affecting his sleep quality. Polysomnography recorded REM sleep without atonia and motor behaviors in REM sleep. Ischemic lesions in the pons were detected by MRI. Clinical, biological, and instrumental biomarkers of neurodegeneration were repeatedly negative at two-years follow-up. Although rare, a lesional cause of RBD must be considered in cases of atypical presentation and without evidence of neurodegeneration. The complaint of unpleasant dreams suggests a possible role of brainstem nuclei controlling REM atonia in affecting oneiric content.