The implication of nigrostriatal dopaminergic degeneration in the pathogenesis of REM sleep behavior disorder.
OBJECTIVE
The pathogenesis of rapid eye movement (REM) sleep behavior disorder (RBD) is not clear despite its frequent association with Parkinson's disease (PD). We investigated whether the nigrostriatal dopaminergic system is involved in the development of idiopathic RBD.


METHODS
Fourteen patients with RBD, 14 patients with PD and 12 normal controls were included in the study. The diagnosis of RBD was confirmed on polysomnography. All the participants performed single-photon emission computed tomography imaging 3 h after injection of [(123)I]FP-CIT. During REM sleep of the RBD patients, each 30-s epoch was rated as 'tonic' when there was at least 50% of tonically maintained chin electromyography (EMG) activity in the epoch. Phasic EMG activities were calculated as the percentage of 3-s mini-epoch containing phasic EMG events (leg and chin, separately).


RESULTS
The RBD patients showed a trend of lower binding in the striatum than the normal controls (P = 0.07), and the significance was revealed in the putamen (P = 0.02). However, in 11 individual cases of the 14 RBD patients, the dopamine transporter (DAT) densities in the putamen still remained within the normal range. In the RBD patients, there was no correlation between EMG activities and DAT densities.


CONCLUSIONS
Nigrostriatal dopaminergic degeneration could be a part of the pathogenesis of RBD, but not essential for the development of RBD. The lack of correlation between RBD severity and DAT densities suggests that another pathogenic process not related to nigrostriatal dopaminergic transmission may be implicated in RBD.
Kim
Y K
YK
Department of Nuclear Medicine, Seoul National University Bundang Hospital, Bundang-gu, Seongnam, Korea.
Yoon
I-Y
IY
Kim
J-M
JM
Jeong
S-H
SH
Kim
K W
KW
Shin
Y-K
YK
Kim
B S
BS
Kim
S E
SE
D000368:Aged; D001205:Ascorbic Acid; D002421:Caudate Nucleus / Q000000981:diagnostic imaging / Q000378:metabolism; D002680:Chin / Q000503:physiopathology; D002762:Cholecalciferol; D003342:Corpus Striatum / Q000000981:diagnostic imaging / Q000378:metabolism*; D003687:Dehydroepiandrosterone / Q000031:analogs & derivatives; D004298:Dopamine / Q000378:metabolism; D050483:Dopamine Plasma Membrane Transport Proteins / Q000378:metabolism*; D004576:Electromyography; D005152:Facial Muscles / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009410:Nerve Degeneration / Q000000981:diagnostic imaging / Q000378:metabolism; D009539:Nicotinic Acids; D010936:Plant Extracts; D017286:Polysomnography; D011699:Putamen / Q000000981:diagnostic imaging / Q000378:metabolism; D020187:REM Sleep Behavior Disorder / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000503:physiopathology*; D015899:Tomography, Emission-Computed, Single-Photon; D014326:Tropanes
D050483:Dopamine Plasma Membrane Transport Proteins; C524255:HUM 5007; D009539:Nicotinic Acids; D010936:Plant Extracts; D014326:Tropanes; C087552:2-carbomethoxy-8-(3-fluoropropyl)-3-(4-iodophenyl)tropane; D002762:Cholecalciferol; D003687:Dehydroepiandrosterone; D001205:Ascorbic Acid; D004298:Dopamine