Evoked potentials in the diagnostics of central nervous system disorders in diabetic patients

Background. Patients with diabetes suffer central nervous system (CNS) damage which is difficult to diagnose. Examination of evoked potentials (EP) — bioelectric responses of the nervous system to external sensory (SEP), acoustic (BAEP) or visual (VEP) stimuli — may be used to assess CNS dysfunction. Material and methods. We performed VEP and SEP studies in the median (SEPm) and the tibial (SEPt) nerves in 90 patients with type 1 and 2 diabetes using the four-channel device Premiere. EP were estimated according to the presence of peripheral polyneuropathy, glycemic control, sex and diabetes type. The diagnosis of peripheral polyneuropathy was established by clinical examination according to the Neuropathy Disability Scale (NDS). Results. Abnormal SEP were found in 25% of patients without the clinical symptoms of neuropathy. Abnormal SEPt were found in 64.4% of patients and abnormal SEPm and VEP in 31.1% of patients. Abnormal VEP were more common in patients with clinical signs of peripheral polyneuropathy (P = 0.004), insufficient glycaemic control (P < 0.02), type 2 diabetes (P = 0.004, right eye; P = 0.001, left eye) and in the elderly patients (P < 0.001). Abnormal SEPt (P < 0.05) and SEPm (P < 0.01) correlated with age and SEPt additionally correlated with the presence of peripheral polyneuropathy (P 0.0053). Conclusions. Examination of evoked potential in patients with diabetes allows to diagnose subclinical CNS damage. The more frequent occurrence of abnormal tibial verus median nerve bioelectric response probably results from the difference in length between the two nerves. Examination of VEP seems to be more useful for the evaluation of the effects glycaemic control on CNS function than examination of evoked potentials from the peripheral nerves. key words: evoked potentials, diabetes mellitus, central nervous system