title: Impaired pain processing in Parkinson's disease and its relative association with the sense of smell.
abstract: OBJECTIVE
  Many non-motor symptoms are associated with Parkinson's disease (PD). Of these, pain and olfactory disturbance tend to be common premotor symptoms. PD has been shown to exhibit abnormal central pain processing, although underlying mechanisms are not yet fully understood. In order to investigate this further, we assessed PD patients by specific Aδ stimulation with intra-epidermal needle electrode and determined olfactory function.
  
  
  METHODS
  Forty-two patients (18 males and 24 females) with PD and 17 healthy control subjects (8 males and 9 females) were studied. A thin needle electrode was used to stimulate epidermal Aδ fibers, and somatosensory evoked potentials (SEPs) recorded at the vertex. Olfactory function was evaluated using the Odor Stick Identification Test for Japanese (OSIT-J) and its relationship with pain-related SEPs was investigated.
  
  
  RESULTS
  There were no significant differences in N1 latencies or P1 latencies although N1/P1 peak-to-peak amplitudes were significantly lower (p < 0.01) in PD patients than in control subjects. In PD patients, there were significant correlations between N1/P1 amplitudes and disease duration (r = -0.35, p < 0.05), Hoehn-Yahr stage (r = -0.38, p < 0.05) and UPDRS part III (r = -0.42, p < 0.01). Furthermore, the OSIT-J scores correlated with SEP amplitude (r = 0.41, p < 0.01).
  
  
  CONCLUSIONS
  Pain processing in PD patients was impaired under specific nociceptive stimulation of Aδ fibers and significant correlation with smell dysfunction was detected. We suggest that this mechanism may involve the limbic system during PD pathology.
authors: Department of Neurology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
authors: Takashi
authors: T
authors: Hara
authors: Masaaki
authors: M
authors: Hirayama
authors: Yasuaki
authors: Y
authors: Mizutani
authors: Tetsuo
authors: T
authors: Hama
authors: Norio
authors: N
authors: Hori
authors: Tomohiko
authors: T
authors: Nakamura
authors: Shigenori
authors: S
authors: Kato
authors: Hirohisa
authors: H
authors: Watanabe
authors: Gen
authors: G
authors: Sobue
mesh_terms: D000368:Aged; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D000857:Olfaction Disorders / Q000150:complications / Q000503:physiopathology*; D010146:Pain / Q000150:complications; D010147:Pain Measurement / Q000379:methods; D010300:Parkinson Disease / Q000150:complications / Q000503:physiopathology*; D012903:Smell / Q000502:physiology*