title: Evidence for small fiber neuropathy in early Parkinson's disease.
abstract: Parkinson's disease (PD) is neurodegenerative movement disorder affecting primarily the central nervous system with several recognized non-motor symptoms that can occur at various stages of the disease. Recently it has been shown that patients with PD may be prone to peripheral nervous system pathology in the form of a peripheral neuropathy (PN). It is unclear if PN is an inherent feature of PD or if it is an iatrogenic effect of the mainstay PD treatment Levodopa.
  
  
  
  To determine if peripheral neuropathy occurs in early untreated PD we employed a case-control study design using gold standard tests for PN, including neurological examination according to the Utah Early Neuropathy Scale (UENS) and nerve conduction studies, as well as new, more sensitive and informative tests for PN including the skin biopsy and corneal confocal microscopy (CCM).
  
  
  
  We studied 26 patients with PD and 22 controls using the neurological examination and nerve conduction studies (NCS) and found no significant difference between groups except for some reduced vibration sense in the PD group. Epidermal nerve densities in the skin biopsies were similar between our cohorts. However, using CCM - a more sensitive test and a surrogate marker of small fiber damage in PN, we found that patients with PD had significantly reduced corneal nerve fiber densities and lengths as compared to controls.
  
  
  
  We conclude that our positive CCM results provide evidence of preclinical PN in newly diagnosed PD patients.
authors.affiliation: Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Podgorny
authors.affiliation: Department of Medicine (Neurology), University of Alberta, Edmonton, Alberta, Canada; Department of Medical Genetics, University of Alberta, Edmonton, Alberta, Canada; Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada. Electronic address: Oksana.Suchowersky@albertahealthservices.ca.
authors.forename: Oksana
authors.initials: O
authors.lastname: Suchowersky
authors.affiliation: Department of Surgery, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Kenneth G
authors.initials: KG
authors.lastname: Romanchuk
authors.affiliation: Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Feasby
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003315:Cornea / Q000000981:diagnostic imaging / Q000294:innervation; D004817:Epidermis / Q000000981:diagnostic imaging / Q000294:innervation; D005260:Female; D006801:Humans; D008297:Male; D018613:Microscopy, Confocal; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology*; D010300:Parkinson Disease / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D000071075:Small Fiber Neuropathy / Q000000981:diagnostic imaging / Q000209:etiology / Q000473:pathology / Q000503:physiopathology
keywords: Iatrogenic; Levodopa; Parkinson's disease; Peripheral neuropathy