Neuroimaging of rapid eye movement sleep behavior disorder: transcranial ultrasound, single-photon emission computed tomography, and positron emission tomography scan data

Idiopathic rapid eye movement sleep behavior disorder (iRBD), which typically develops in middle-aged individuals or later and progresses chronically, is a common clinical manifestation of Lewy body–related syndrome. It is important that combinations of neuroimaging markers in iRBD are considered for the purpose of diagnosing neurodegenerative diseases such as Parkinson disease (PD), dementia with Lewy body disease (DLB), or multiple system atrophy (MSA) at an early stage. Important advances have been made in the diagnosis of PD or DLB using imaging methods such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) scans or transcranial B-mode ultrasonography (TCS). These methods are important in clinical research, in which the identification of biomarkers for iRBD offers diagnostic opportunities and points the way to new therapeutic strategies. This review focuses on neuroimaging studies of rapid eye movement sleep behavior disorder (RBD) patients using techniques such as TCS, SPECT, and PET scans.