Investigation of small fiber neuropathy in patients with diabetes mellitus by corneal confocal microscopy

Corneal confocal microscopy (CCM) is a non-invasive technique that examines the corneal cellular structure. Its use in the detection of small fiber neuropathy is being researched. In our study, we examined the role of CCM in the detection of small fiber neuropathy in diabetic patients, as well as the differences between CCM findings in diabetic patients with and without overt polyneuropathy with neuropathic symptoms. 56 Diabetes Mellitus (DM) patients and 18 healthy controls were included in the study. The individuals included in the study were divided into three groups. Patients with diabetes who were found to have polyneuropathy according to electrophysiological diagnostic criteria were classified as Group 1, patients with diabetes and neuropathic symptoms without overt polyneuropathy according to electrophysiological diagnostic criteria were classified as Group 2, and healthy individuals were classified as Group 3. Electrophysiological examination and corneal imaging with CCM were performed in all groups. The CNFD and CNFL values of individuals in the diabetic group were discovered to be lower. CNFD values differ statistically between the groups (p = 0.047). Group 1-Group 3 differs from Group 2-Group 3 (respectively; p = 0.018, p = 0.048). Our study demonstrates that CCM can be used in patients with neuropathic symptoms and no polyneuropathy detected in EMG and thought to have small fiber neuropathy. CCM provides an opportunity for early diagnosis in small fiber neuropathy.