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Patients with FM have smaller stromal nerve thickness, lower corneal sub-basal plexus nerve density
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Women with fibromyalgia (FM) had a thinner average stromal nerve thickness and decreased corneal sub-basal plexus nerve density per square millimeter compared with healthy control participants, and corneal confocal microscopy could be a useful tool to identify patients with FM, according to the results of recently published research.
Researchers enrolled 17 women with fibromyalgia (FM) who met both American College of Rheumatology 1990 and 2010 criteria for FM and 17 healthy women matched for age. Participants were between 18 and 50 years of age with no concurrent diseases.
All participants completed Spanish language questionnaires to assess FM symptoms, including autonomic dysfunction, sleep quality, anxiety, depression, fatigue, neuropathic pain and general well-being. The questionnaires included the Fibromyalgia Impact Questionnaire (FIQ), the Medical Outcome Sleep Scale (MOS), the Composite Autonomic Symptoms and Signs (COMPASS) assessment, the Hospital Anxiety and Depression Scale (HADS), the Multidimensional Assessment of Fatigue Scale (MAF), SF-36, and the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) assessment.
One ophthalmologist expert in corneal pathology blinded to diagnosis evaluated central corneal scans of both eyes of each participant. A coronal section of 340 µm by 255 µm was represented across four full-thickness corneal sequences of 350 images.
Corneal nerve thickness was defined as the average corneal nerve thickness between the widest and most narrow portion of each stromal nerve that was analyzed. The difference between the widest and most narrow areas of each nerve was defined as nerve smoothness. NAVIS software (Nidek) was used to calculate nerve thickness and smoothness, and the corneal sub-basal plexus nerve density was calculated based on the number of sub-basal plexus nerves and branches manually counted by the ophthalmologist and calculated by the NAVIS software.
Although healthy participants frequently responded affirmatively to some questions regarding fatigue, problems with sleep and anxiety or depression, patients with FM had mean FIQ scores of 69, and all but one patient with FM had a LANSS score above 12, which suggested a neuropathic component of pain, according to the researchers. High COMPASS scores were also seen in patients with FM, suggesting prominent dysfunction in the autonomic (sympathetic) nervous system.
Patients with FM had an average nerve thickness of 5 µm, which was significantly different from healthy women, who had an average thickness of 6.1 µm. Nerve smoothness was 1.8 in patients with FM compared with 2.4 in healthy participants. Sub-basal plexus small nerve fiber density was also lower in patients with FM at 85 per square millimeter compared with 107 per square millimeter in healthy participants, according to the researchers.
Among all participants, the LANSS neuropathic pain symptoms questionnaire scores correlated with more slender nerves.
No correlation between the corneal measurements and age, disease duration or number of symptoms was found among patients, according to the researchers. - by Shirley Pulawski
Disclosure: No financial disclosure information was available at the time of publication.
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