Corneal Confocal Microscopy: A Non-Invasive Surrogate Marker of Small Nerve Fibre Damage and Repair in Patients with Small Fibre Neuropathy

Abstract

Aim: ‘Painful neuropathy’ is presumed to be secondary to small fibre damage from a variety of causes. Methods to detect, characterize and quantify small fibre damage are time consuming and highly variable (QST’s), or invasive (skin or nerve biopsy). We have recently shown that corneal nerve damage assessed using corneal confocal microscopy is an accurate surrogate marker for somatic nerve damage in patients with diabetic neuropathy. We have now assessed corneal nerve morphology in patients with painful neuropathy who had been labelled as having ‘small fibre neuropathy’. Methods: 30 patients aged 60 + 13 with ‘small fibre neuropathy’ and 12 age-matched control subjects underwent assessment of the Neuropathy Deficit Score in the lower limb (NDS), Neuropathy Symptom Profile (NSP), Electrophysiology, QST for thermal perception and corneal confocal microscopy (CCM). CCM quantified corneal nerve morphology: nerve fibre density (NFD), nerve branch density (NBD), nerve fibre length (NFL), nerve fibre tortuosity (NFT). Results: According to the results obtained for “neuropathy severity assessment” including NDS, NSP, electrophysiology and QST data , a significance reduction in corneal nerve NFD (P< 0.0001), NBD (P< 0.0001), NFL (P< 0.0001) and no statistical significant changes in tortuosity was shown. Discussion: Corneal confocal microscopy offers a rapid, non-invasive, and reiterative technique to accurately detect, and quantify nerve damage in patients with ‘small fibre neuropathy’.