Brainstem proton magnetic resonance spectroscopy in idopathic REM sleep behavior disorder

Abstract

Study Objectives: Rapid-eye-movement (REM) sleep behavior disorder (RBD) is thought to result from a dysfunction of the brainstem structures that regulate physiologic REM sleep muscle atonia. Proton magnetic resonance spectroscopy (1H-MRS) is a noninvasive method that allows detection of in vivo neuronal dysfunction in localized brain areas. The aim of our study was to investigate whether 1H-MRS can detect brainstem abnormalities in patients with idiopathic RBD. Design: 1H-MRS centered on the midbrain and the pontine tegmentum was acquired in 15 patients with idiopathic RBD and 15 control subjects matched for age and sex. Setting: University hospital sleep laboratory center. Participants: Fifteen untreated patients with chronic RBD diagnosed by history and video-polysomnography, normal neurologic examination, and normal cranial MRI. Fifteen healthy controls with no sleep complaints and normal polysomnography and brain MRI. Interventions: N/A. Measurements and Results: The metabolic peaks detectable with 1H-MRS, N-acetylaspartate (NAA), creatine-phosphocreatine (Cr), choline-containing compounds (Cho) and myoinositol (ml), and the ratios of NAA, Cho and ml to Cr were evaluated both in the midbrain and pontine tegmentum. No significant differences in N- acetylaspartate/creatine, choline/creatine and myoinositol/creatine ratios were found between patients and controls. Conclusions: The results do not suggest that marked mesopontine neuronal loss or 1H-MRS detectable metabolic disturbances occur in idiopathic RBD.