Researchers found more severe neuropathy — specifically, small fiber damage to the skin and cornea — in patients with type 1 diabetes who experienced painful diabetic neuropathy as opposed to those with painless diabetic neuropathy, according to their study, published in European Journal of Neurology.
The cross-sectional study compared large and small nerve fiber measurements and looked at skin biopsies and corneal confocal microscopy (CCM) in 41 patients with type 1 diabetes and painful diabetic neuropathy, as well as 50 patients with type 1 diabetes with painless diabetic neuropathy, and 50 controls. To reach their findings, investigators used the McGill pain questionnaire, neuropathy disability score (NDS), vibration perception threshold (VPT), warm and cold sensation thresholds (WST, CST), electrophysiology, corneal confocal microscopy (CCM), and skin biopsy in participants.
They found that the duration of diabetes, body mass index, glycated hemoglobin (HbA1c), blood pressure, and lipid profile had no differences in those with painful and painless neuropathy. While neuropathy disability score and vibration perception threshold were higher, sural nerve conduction velocity was lower, and sural nerve amplitude, peroneal nerve amplitude, and conduction velocity, and cold and warm sensation had no differences between the painful and painless diabetic neuropathy groups.
However, the study shows that intra-epidermal nerve fiber density, corneal nerve fiber density, corneal nerve branch density, and corneal nerve fiber length are all significantly lower in participants with painful diabetic neuropathy than in those with painless diabetic neuropathy.
Corneal confocal microscopy “represents a rapid noninvasive ophthalmic imaging technique to objectively quantify small fiber pathology and differentiate patients with painful from painless diabetic neuropathy,” the study says.
The study’s limitations include its design, which didn’t allow researchers to determine “a causal relationship between small fiber damage in the skin and cornea in patients with painful diabetic neuropathy.” In addition, the study was only performed in patients with type 1 diabetes, so results might not apply to those with type 2 diabetes.
Ferdousi M, Azmi S, Kalteniece A, et al. Greater small nerve fibre damage in the skin and cornea of type 1 diabetic patients with painful compared to painless diabetic neuropathy. Eur J Neurol. Published online January 31, 2021. doi:10.1111/ene.14757.