Corneal confocal microscopy : a novel means to detect nerve fibre damage in idiopathic small fibre neuropathy

Abstract

Patients with idiopathic small fibre neuropathy (ISFN) have been shown to have significant intraepidermal
nerve fibre loss and an increased prevalence of impaired glucose tolerance (IGT). It has been suggested that
the dysglycemia of IGT and additional metabolic risk factors may contribute to small nerve fibre damage in
these patients.
Twenty-five patients with ISFN and 12 aged-matched control subjects underwent a detailed evaluation of
neuropathic symptoms, neurological deficits (Neuropathy deficit score (NDS); Nerve Conduction Studies
(NCS); Quantitative Sensory Testing (QST) and Corneal Confocal Microscopy (CCM)) to quantify small nerve
fibre pathology.
Eight (32%) patients had IGT. Whilst all patients with ISFN had significant neuropathic symptoms, NDS, NCS
and QST except for warm thresholds were normal. Corneal sensitivity was reduced and CCM demonstrated a
significant reduction in corneal nerve fibre density (NFD) (Pb0.0001), nerve branch density (NBD)
(Pb0.0001), nerve fibre length (NFL) (Pb0.0001) and an increase in nerve fibre tortuosity (NFT) (Pb0.0001).
However these parameters did not differ between ISFN patients with and without IGT, nor did they correlate
with BMI, lipids and blood pressure.
Corneal confocal microscopy provides a sensitive non-invasive means to detect small nerve fibre damage in
patients with ISFN and metabolic abnormalities do not relate to nerve damage.