Abstract
Purpose:
In patients with small fiber neuropathy (SFN) non-invasive diagnostic tests that allow accurate monitoring of disease progression are urgently needed. Aim of this study was to assess corneal trigeminal small sensory nerves and immune cells by in vivo corneal confocal microscopy (CCM) in histologically confrimed SFN.
Methods:
This prospective single-center study analyzed 14 patients with histologically confirmed SFN. CCM parameters (corneal nerve fiber density (NFD), total number of nerves, number of main trunks, and branches, nerve tortuosity, and dendritic cell density (DCD)) were compared to 14 age-matched healthy controls and correlated with clinical symptoms, disease course and histopathological findings.
Results:
Corneal NFD (15489.3 ± 5927.6 μm/mm2 vs. 22687.1 ± 4328.7 μm/mm2; p=0.001) and total number of nerves (10.4 ± 4.6 /frame vs. 18.5 ± 4.8 /frame; p<0.0001) were significantly reduced in patients with SFN. In contrast, nerve tortuosity was significantly increased (2.2 ± 0.31 vs. 1.7 ± 0.5; p=0.02). Corneal NFD did not correlate with intraepidermal NFD (ρ -0.158; p>0.05) or clinical measures (p>0.05). Average dendritic cell density (DCD) was increased in SFN (33.5 ± 57.5 cells/mm2 vs. 16.1 ± 13.7 cells/mm2), but did not reach significance (p>0.05).
Conclusions:
CCM provides parameters that reliably indicate injury to sensory afferents of the trigeminal nerve in patients with SFN. Our data suggest that CCM may serve both as a non-invasive diagnostic test and a surrogate marker in SFN.