title: Pathophysiology of Small-Fiber Sensory System in Parkinson's Disease: Skin Innervation and Contact Heat Evoked Potential.
abstract: Sensory symptoms are frequent nonmotor complaints in patients with Parkinson's disease (PD). However, few investigations integrally explored the physiology and pathology of the thermonociceptive pathway in PD. We aim to investigate the involvement of the thermonociceptive pathway in PD.Twenty-eight PD patients (16 men, with a mean age and standard deviation of 65.6 ± 10.7 years) free of neuropathic symptoms and systemic disorders were recruited for the study and compared to 23 age- and gender-matched control subjects (12 men, with a mean age and standard deviation of 65.1 ± 9.9 years). We performed skin biopsy, contact heat-evoked potential (CHEP), and quantitative sensory tests (QST) to study the involvement of the thermonociceptive pathway in PD.The duration of PD was 7.1 ± 3.2 (range 2-17 years) years and the UPDRS part III score was 25.6 ± 9.7 (range 10-48) during the off period. Compared to control subjects, PD patients had reduced intra-epidermal nerve fiber (IENF) density (2.48 ± 1.65 vs 6.36 ± 3.19 fibers/mm, P < 0.001) and CHEP amplitude (18.02 ± 10.23 vs 33.28 ± 10.48 μV, P < 0.001). Twenty-three patients (82.1%) had abnormal IENF densities and 18 (64.3%) had abnormal CHEP. Nine patients (32.1%) had abnormal thermal thresholds in the feet. In total 27 patients (96.4%) had at least 1 abnormality in IENF, CHEP, or thermal thresholds of the foot, indicating dysfunctions in the small-fiber nerve system. In control subjects, CHEP amplitude linearly correlated with IENF density (P < 0.001). In contrast, this relationship disappeared in PD (P = 0.312) and CHEP amplitude was negatively correlated with motor severity of PD independent of age, gender, and anti-PD medication dose (P = 0.036), suggesting the influences of central components on thermonociceptive systems in addition to peripheral small-fiber nerves in PD.The present study suggested impairment of small-fiber sensory system at both peripheral and central levels is an intrinsic feature of PD, and skin biopsy, CHEP, and QST provided an integral approach for assessing such dysfunctions.
authors.affiliation: From the Department of Neurology (C-HL, C-CC, S-WW, F-PF, Y-HL, S-TH), National Taiwan University Hospital; the Department of Pathology (P-CH), Far Eastern Memorial Hospital; Institute of Health Policy and Management (Y-MC), National Taiwan University, Taipei, Taiwan; and Department of Anatomy and Cell Biology (S-TH), Graduate Institute of Brain and Mind Sciences, and Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Chin-Hsien
authors.initials: CH
authors.lastname: Lin
authors.forename: Chi-Chao
authors.initials: CC
authors.lastname: Chao
authors.forename: Shao-Wei
authors.initials: SW
authors.lastname: Wu
authors.forename: Paul-Chen
authors.initials: PC
authors.lastname: Hsieh
authors.forename: Fang-Ping
authors.initials: FP
authors.lastname: Feng
authors.forename: Yea-Huey
authors.initials: YH
authors.lastname: Lin
authors.forename: Ya-Mei
authors.initials: YM
authors.lastname: Chen
authors.forename: Ruey-Meei
authors.initials: RM
authors.lastname: Wu
authors.forename: Sung-Tsang
authors.initials: ST
authors.lastname: Hsieh
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000502:physiology*; D010300:Parkinson Disease / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D010525:Peripheral Nerves / Q000503:physiopathology*; D010523:Peripheral Nervous System Diseases / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D012677:Sensation / Q000502:physiology*; D011984:Sensory Receptor Cells / Q000502:physiology; D012720:Severity of Illness Index; D012867:Skin / Q000294:innervation* / Q000473:pathology