Reduced striatal dopamine transporters in idiopathic rapid eye movement sleep behaviour disorder - Comparison with Parkinson's disease and controls

Rapid eye movement (REM) sleep behaviour disorder (RBD) is characterized by complex behaviour during REM sleep. The aetiology of this disorder is stil l unknown, but a recent study showed an association between RED and Parkins on's disease. We therefore studied striatal postsynaptic dopamine D-2 recep tor density with [I-123] (S)-2-hydroxy-3-iodo-6-methoxy-(1-ethyl-2-pyrrolid inylmethyl) benzamide ([I-123]IBZM) and the striatal presynaptic dopamine t ransporter with (N)-(3-iodopropene-2-yl)-2 beta-carbomethoxy-3 beta-(4-chlo rophenyl)tropane ([I-123]IPT) using single-photon emission computed tomogra phy (SPECT) in patients with idiopathic RED. We compared the [I-123]IPT-SPE CT results of five patients with polysomnographically confirmed idiopathic RED with the [I-123]IPT-SPECTs of seven age- and sex-matched controls witho ut a history of sleep disorders, and of 14 patients with Parkinson's diseas e (Hoehn and Yahr stage I). All RED patients had significantly reduced stri atal [I-123]IPT binding compared with the controls (RBD: right, 2.94 +/- 0. 32, left, 3.03 +/- 0.41; controls: right, 4.41 +/- 0.17, left, 4.34 +/- 0.2 1; P = 0.003), but significantly higher striatal [I-123]IPT binding compare d with the striatum contralateral to the symptomatic body side of the Parki nson's disease patients (Parkinson's disease: ipsilateral, 3.17 +/- 0.36, P = 0.298; contralateral, 2.51 +/- 0.31, P = 0.019). Uptake of [I-123]IBZM w as not significantly different in the RED group compared with the controls. This study demonstrates that [I-123]IPT-SPECT is a useful diagnostic tool in RED and that reduced striatal dopamine transporters may be a pathophysio logical mechanism of idiopathic RED. (Results are given as mean +/- standar d deviation.)