Abstract
Dopaminergic deficiency, shown by many studies using functional neuroimaging with Single Photon Emission Computerized Tomography (SPECT) and Positron Emission Tomography (PET), is the most consistent neurochemical feature of rapid eye movement (REM) sleep behaviour disorder (RBD) and, together with transcranial ultrasonography, and determination of alpha-synuclein in certain tissues, should be considered as a reliable marker for the phenoconversion of idiopathic RBD (iRBD) to a synucleopathy (Parkinson’s disease –PD- or Lewy body dementia -LBD). The possible role in the pathogenesis of RBD of other neurotransmitters such as noradrenaline, acetylcholine, and excitatory and inhibitory neurotransmitters; hormones such as melatonin, and proinflammatory factors have also been suggested by recent reports. In general, brain perfusion and brain glucose metabolism studies have shown patterns resembling partially those of PD and LBD. Finally, the results of structural and functional MRI suggest the presence of structural changes in deep gray matter nuclei, cortical gray matter atrophy, and alterations in the functional connectivity within the basal ganglia, the cortico-striatal, and the cortico-cortical networks, but they should be considered as preliminary.
Highlights
In 1986, Schenk et al [1,2] described a new type of parasomnia in patients with several neurological diseases, resembling previous findings in studies in cats with pontine tegmental lesions, that consisted in abnormal behaviors during rapid eye movement (REM) sleep such as “stereotypical hand motions, reaching and searching gestures, punches, kicks, and verified dream movements”
While one study showed significant microstructural changes in the white matter at several areas including the brainstem, the right substantia nigra, the left temporal lobe, the olfactory region the fornix, the corona radiata, the internal capsule and the right visual stream of idiopathic REM sleep behaviour disorder” (RBD) (iRBD) patients compared with controls [163], other failed to find any microstructural difference between iRBD patients, prodromal PD patients, and controls, described a significant increase in mean diffusivity (MD) in prodromal PD relative to iRBD in widespread, but mostly right-lateralized regions [179]
There are enough data suggesting the role of dopaminergic dysfunction in iRBD
Summary
In 1986, Schenk et al [1,2] described a new type of parasomnia in patients (most of them men) with several neurological diseases, resembling previous findings in studies in cats with pontine tegmental lesions, that consisted in abnormal behaviors during rapid eye movement (REM) sleep such as “stereotypical hand motions, reaching and searching gestures, punches, kicks, and verified dream movements”. A study involving 347 RBD patients and 347 matched controls showed that, compared with controls, RBD patients were more likely to smoke, to report a previous head injury, and to have worked as farmers, with a borderline increase in welding, to have previously occupational exposure to pesticides, and to have few years of formal schooling, while there were no significant differences in coffee consumption [18].
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