A new study published in Seminars in Arthritis & Rheumatism indicates that in patients with fibromyalgia the density of small nerve fibers in the cornea is reduced, supporting an evolving concept that fibromyalgia is a small fiber neuropathy.
Thus, skin biopsies of fibromyalgia patients show a reduction in intra epidermal innervation and regeneration sparing myelinated nerve fibres (N Üçeyler et al., 2013).
The cornea receives an extremely dense small fiber innervation, and the corneal confocal bio-microscopy is a new non-invasive method that can assess nerve fiber morphology and pathology.
In the Seminars in Arthritis & Rheumatism study Manuel Ramírez and colleagues, from the National Institute of Cardiology, Mexico City, Mexico, studied the cornea’s small fiber innervation in 17 female patients diagnosed with fibromyalgia. The authors demonstrate that fibromyalgia patients have thinner/smoother corneal stromal nerves and decreased corneal sub-basal nerve plexus density when compared to healthy controls.
These results indicate that, in fibromyalgia, the small fiber neuropathy is not limited to the skin, but also present in the cornea. The authors suggest that fibromyalgia pain is sympathetically-driven and closely associated with an autonomic/sympathetic nervous system dysfunction.
According to them, in the future, a more refined and comprehensive corneal bio-microscopy may become a non-invasive diagnostic tool for small fiber neuropathy such as fibromyalgia.