title: Olfactory dysfunction in early Parkinson's disease is associated with short latency afferent inhibition reflecting central cholinergic dysfunction.
abstract: Our study aimed to determine whether the short latency afferent inhibition (SAI) response could be associated with the severity of olfactory dysfunction in PD patients.
  
  
  
  A total of 71 PD patients and 20 controls were enrolled. All PD patients were classified into 3 groups by the severity of the olfactory deficit. Single-pulse transmagnetic stimulation (TMS) parameters and SAI were assessed.
  
  
  
  The integrated SAI in the PD with anosmia and PD with hyposomia groups was significantly less inhibited than that in the PD with normosmia and control groups [64.79 {Interquartile range (IQR): 59.96, 71.33}, 84.79 {IQR: 75.03, 90.63} versus 36.72 {IQR: 32.28, 48.33}, 42.15 {IQR: 34.60, 44.96}, respectively]. In PD subjects, the severity of olfactory dysfunction also showed a significant negative correlation with the SAI response (r=-0.829, p<0.001).
  
  
  
  Considering that the SAI response partly reflects central cholinergic dysfunction and that our study shows a relationship between the SAI response and the severity of olfactory dysfunction in PD, our findings indicate that cholinergic dysfunction could possibly contribute to the pathogenesis of olfactory dysfunction in early PD.
  
  
  
  SAI could be a useful marker to detect severe olfactory dysfunction in PD.
authors.affiliation: Department of Neurology, Chungnam National University College of Medicine, Chungnam National University Hospital, Daejeon, Republic of Korea.
authors.forename: Eungseok
authors.initials: E
authors.lastname: Oh
authors.affiliation: Department of Neurology, Inje University, Haeundae Paik Hospital, Busan, Republic of Korea.
authors.forename: Jinse
authors.initials: J
authors.lastname: Park
authors.affiliation: Department of Neurology, Samsung Medical Center, Seoul, Republic of Korea.
authors.forename: Jinyoung
authors.initials: J
authors.lastname: Youn
authors.affiliation: Department of Neurology, Soonchunhyang University Hospital, Seoul, Republic of Korea.
authors.forename: Ji Sun
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Department of Biostatistics, Soonchunhyang University Hospital, Seoul, Republic of Korea.
authors.forename: Suyeon
authors.initials: S
authors.lastname: Park
authors.affiliation: Department of Neurology, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Republic of Korea. Electronic address: neveu@gnah.co.kr.
authors.forename: Wooyoung
authors.initials: W
authors.lastname: Jang
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D059329:Cholinergic Neurons / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009433:Neural Inhibition; D009833:Olfactory Pathways / Q000503:physiopathology*; D055696:Olfactory Perception; D010300:Parkinson Disease / Q000503:physiopathology*; D011930:Reaction Time
keywords: Cholinergic system; Korean version of the Sniffin' stick test (KVSS); Olfaction; Parkinson’s disease; Short latency afferent inhibition (SAI)