Correlation between neuropathy score and electroneurographic parameters values in patients with painful diabetic polyneuropathy before and after the low intensity laser therapy

Introduction: Low intensity laser therapy (LILT) is one of methods used in physical medicine for pain reduction in different medical conditions. There are only a few studies about LILT treatment of painful DPN with different results, because pain reduction was not significant in all studies. Some other effects of LILT in painful DPN, as on Neuropathy score and electroneurographic (ENG) parameters values, was not precisely defined yet. Aims of research: To define the effect of LILT on Neuropathy score and ENG parameters values in patients with painful DPN and also to consider correlation between those parameters before and after LILT. Patients and methods: We analysed 31 patients with clinical and ENG signs of painful DPN, average age 54.77 years (54.77+/-11.39). All analysed patients received 30 LILT treatments during the period of 12 weeks. Prior to and after the 12 weeks period of LILT treatment, Diabetic Neuropathy Examination (DNE) score and Michigan Neuropathy Screening Instrument (MNSI) total score were determined. For ENG examination we used surface electrodes, and we registered motor (MCV) and sensory conduction velocities (SCV) values (in m/s) of peroneal (PN) and ulnar nerves (UN) and their minimal F-wave (PNFL and UNFL) latencies (in ms) after 40 repetitive stimulations of those nerves. SCV (in m/s) of PN an UN was determined by antidromic technique. Control group consisted 31 patients with painful DPN, corresponding ages, who received only vasoactive therapy. For statistical analysis we used t-test and Pearson bivariate correlation (sig. 2-tailed). Results: We registered statistical significant difference (p<0.001) between MNSI values before (5.61+/-1.76) and after LILT (4.23+/-1.67), and also (p<0.001) between DNE values before (7.68+/-2.27) and after LILT (5.61+/-1.89), but those differences were not significant (p>0.05) in control group. We didn't register significant difference (p>0.05) between analysed ENG parameters values before and after LILT (applied during the period of 12 weeks) in patients with painful DNP. We didn't register significant correlation (p>0.05) between MNSI total score and analysed ENG parameters values before and after LILT. We registered statistical significant negative correlation (p<0.05) between DNE score and PN MCV before LILT and also in control group. We registered statistical significant positive correlation (p<0.05) between DNE score and PN FL values and statistical significant negative correlation (p<0.01) between DNE score and UN SCV values after LILT. We didn't register any adverse and/or side effect of LILT treatment in patients with painful DPN. Conclusion: In our study LILT had a significant effect (p<0.001) on MNSI total score and DNE score values reduction, but we didn't register significant effect (p>0.05) of LILT on analysed ENG parameters values in patients with painful DPN. We didn't register significant correlation (p>0.05) between MNSI total score and analysed ENG parameters values before and after LILT. There was statistical significant negative correlation (p<0.05) between DNE score and PN MCV values before LILT and also in control group. It indicates that registration of PN MCV values and it's following is important for diagnosis and evaluation of neuropathy severity in patients with painful DPN. There was statistical significant positive correlation (p<0.05) between DNE score and PN FL values after LILT and it indicates that registration of this electrophysiologic parameter value might be useful for evaluation of possible direct effect of LILT on impulse conduction along the whole length of PN motor axons, particulary their proximal parts, including corresponding roots and spinal segments. There was statistical significant negative correlation (p<0.01) between DNE score and NU SCV values after LILT and it indicates that registration of this electrophysiologic parameter value might be useful for evaluation of possible indirect ("remote") effect of LILT on impulse conduction along ulnar nerve sensory axons. Further clinical double-blind randomized controlled studies of LILT treatment in patients with painful DPN is necessary.