Small fiber neuropathy in Parkinson's disease: A clinical, pathological and corneal confocal microscopy study

Lewis Kass-Iliyya, Saad Javed, David Gosal, Christopher Kobylecki, Andrew Marshall, Ioannis N. Petropoulos, Georgios Ponirakis, Mitra Tavakoli, Maryam Ferdousi, Kallol Ray Chaudhuri, Maria Jeziorska, Rayaz Malik, Monty A. Silverdale

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Autonomic and somatic denervation is well established in Parkinson's disease (PD). Objectives: (1) To determine whether corneal confocal microscopy (CCM) can non-invasively demonstrate small nerve fiber damage in PD. (2) To identify relationships between corneal nerve parameters, intraepidermal nerve fiber density (IENFD) and clinical features of PD. Methods: Twenty-six PD patients and 26 controls underwent CCM of both eyes. 24/26 PD patients and 10/26 controls underwent skin biopsies from the dorsa of both feet. PD patients underwent assessment of parasympathetic function [deep breathing heart rate variability (DB-HRV)], autonomic symptoms [scale for outcomes in Parkinson's disease - autonomic symptoms (SCOPA-AUT)], motor symptoms [UPDRS-III "ON"] and cumulative Levodopa dose. Results: PD patients had significantly reduced corneal nerve fiber density (CNFD) with increased corneal nerve branch density (CNBD) and corneal nerve fiber length (CNFL) compared to controls. CNBD and CNFL but not CNFD correlated inversely with UPDRS-III and SCOPA-AUT. All CCM parameters correlated strongly with DB-HRV. There was no correlation between CCM parameters and disease duration, cumulative Levodopa dose or pain. IENFD was significantly reduced in PD compared to controls and correlated with CNFD and UPDRS-III. However, unlike CCM measures, IENFD correlated with disease duration and cumulative Levodopa dose but not with autonomic dysfunction. Conclusion: CCM identifies corneal nerve fiber pathology, which correlates with autonomic symptoms, parasympathetic deficits and motor scores in patients with PD. IENFD is also reduced and correlates with CNFD and motor symptoms but not parasympathetic deficits, indicating it detects different aspects of peripheral nerve pathology in PD.

Original languageEnglish
Pages (from-to)1454-1460
Number of pages7
JournalParkinsonism and Related Disorders
Issue number12
Publication statusPublished - 1 Dec 2015



  • Confocal microscopy
  • Cornea
  • Intraepidermal nerve fiber density
  • Parkinson's disease
  • Small fiber neuropathy

ASJC Scopus subject areas

  • Neurology
  • Geriatrics and Gerontology
  • Clinical Neurology

Cite this

Kass-Iliyya, L., Javed, S., Gosal, D., Kobylecki, C., Marshall, A., Petropoulos, I. N., Ponirakis, G., Tavakoli, M., Ferdousi, M., Chaudhuri, K. R., Jeziorska, M., Malik, R., & Silverdale, M. A. (2015). Small fiber neuropathy in Parkinson's disease: A clinical, pathological and corneal confocal microscopy study. Parkinsonism and Related Disorders, 21(12), 1454-1460.