Peripheral neuropathy i̇n patients with vi̇tami̇n D defi̇ci̇ency

Introductıon: Vitamin D is a vitamin acting in the body as a hormone through its metabolites. Receptors of vitamin D are present in many organs in the body including the nerves. It has been shown to be related to some diseases and to have impacts on other systems in addition to its classical effects on the calcium homeostasis and bone metabolism. Recently, experimental and clinical data have been reported on neuroprotective and neurotrophic effects of vitamin D. There are several studies reporting that deficiency of vitamin D is a risk factor for development and attacks of multiple sclerosis, Alzheimer's disease, and cerebrovascular conditions. Studies on involvement of peripheral nerves are scarce. Some of them are experimental. Clinical studies suggest that deficiency of vitamin D is a risk factor for polyneuropathy independent of diabetes in the diabetic patients and supplementation of vitamin D improves polyneuropathy. No study has been found in the literature directly exploring relationship between level of vitamin D and involvement of the peripheral nerves. Methods: Forty subjects with low serum level of vitamin D on their routine investigations without history of any disease or use of medication that might cause PNP were included in the present study as study group, and 40 age- and gender-matched subjects with normal serum level of vitamin D as control group. All subjects in the study and control groups underwent neurological examination and ENMG. ENMG evaluated bilateral median and ulnar nerves in the upper limbs and unilateral posterotibial, fibular, sural nerves in the lower limb for sensory and motor response and additionally, sympathetic skin responses were obtained from the lower and upper limbs. Findings: No PNP was found in any subject in both groups, and distal latency, nerve conduction velocity, mean amplitude values were all found to be within normal limits. When compared statistically, although some differences were found in favor of the group with low level of vitamin D especially for nerve conduction velocities, this was not considered to be significant because the values were within normal limits. When the groups were compared in number of subjects with abnormal electrophysiological findings in only one nerve, no difference was found between them. Furthermore, correlation was examined between level of vitamin D and electrophysiological values in the group with low level of vitamin D but no correlation was found. Conclusion: In the present study, although no significant pathology was found for electrophysiological values in the group with low level of vitamin D compared to that with normal level of vitamin D, further studies with more subjects are needed to discuss impacts of vitamin D on the peripheral nerves.