Background and Aims

Diabetic neuropathy (DN) is the most common complication of diabetes mellitus (DM). Corneal confocal microscopy (CCM) is a new noninvasive method that can help to study small nerve fibers in patients with DN.

To evaluate corneal small nerve fibers in patients with type 1 DM and DN, and dynamics of the nerve fibers by CCM during of the DM treatment.

Methods

20 patients with type 1 DM and DN were included. Median age 29 years [18.0; 45.0], the median HbA1c 8.5% [7.0; 10]. Neuropathy was assessed by Neuropathy Total Symptom Score (NTSS-9), Neuropathy Disability Score (NDS), CCM, lower limb electroneuromyography. After adjustment of glycaemia to HbA1c<7%, all tests were repeated.

Results

After reaching HbA1c<7%, there was a clinically significant improvement in NTSS-9 scores by 66.3% (p <0.001). There were increase in the number of nerve fibers (+16%), their thickness (+25.6%), the number of nerve branches (+32.4%) and nerve branch density – by 23.6% (p<0.001 for all parameters). The nerve fiber tortuosity decreased by 14.5%. Also, there was an increase of nerve conduction velocity of n. tibialis by 8.3% and n. suralis by 4.05% (p<0.05). Amplitudes of stimulation responses of these nerves increased by 9.9% and 8.5%, respectively (p<0.05).

Conclusions

The results allow us to propose the use CCM for diagnosis of DN. Improved glycemic control has a positive effect on the structural characteristics of corneal nerves.