Blink reflex abnormalities in diabetes mellitus

Background Damage of the peripheral nervous system is particularly frequent in diabetes mellitus (DM), but somatic cranial neuropathies usually presen ting as mononeuropathies are rare. Oculomotor and facial nerves are among t he most commonly affected, whereas the Vth, IXth and Xth cranial nerves are less often affected. While existing neurophysiological tests in the subcli nical diagnosis of damage to the peripheral nerve in diabetic patients have advanced, the same does not hold true for the subclinical diagnosis of the central nervous system (CNS). Electrophysiological studies such as the bli nk reflex was shown to be an effective method for revealing subclinical inv olvement of cranial nerves in generalised neuropathies. The aim of the pres ent study was to evaluate the efficacy of blink reflex as a method for obta ining early diagnosis of cranial nerve involvement in diabetic patients fre quently affected with peripheral neuropathy. Methods, Twenty diabetic patients with electrophysiologically confirmed neu ropathy were included in the present study for the evaluation of blink refl ex. Patients with earlier cranial nerve involvement were excluded. Results Abnormal blink reflex responses were found in 55% of patients studi ed. R2Y and R2C latencies in diabetic patients were prolonged relative to c ontrols (p<0.001 and p<0.001, respectively). However R1 values in diabetic patients did not differ significantly from those of normal controls (p < 0. 5). R2Y, and R2C prolongation showed a positive correlation with the durati on of disease (p=0.015 and p=0.009, respectively). However the same correla tion could not be found with RI values. No correlations were found between R1, R2Y, R2C values and HbA(1c) nor between R1, R2Y, R2C values and patient s' age. Conclusion We suggest that blink reflex testing is a useful method for obta ining early diagnosis of cranial nerve compromise in diabetic patients, who do not show any clinical symptoms or signs of CNS involvement. Copyright ( C) 2001 John Wiley & Sons, Ltd.