Comparative study of electrophysiological changes in snake bites.

AIMS: To study and compare the electrophysiological changes in neuroparalytic or vasculotoxic snakebites. MATERIALS AND METHODS: 40 patients who had a definite history of snakebite, either vasculotoxic or neuroparalytic, were selected. They were grouped as Group A, 20 patients having a neuroparalytic snakebite with definite envenomation at the time of admission, and Group B, 20 patients having a vasculotoxic snakebite with definite envenomation at the time of admission. All patients underwent a detailed clinical examination, all relevant investigations and nerve conduction studies according to protocol. RESULTS: In this study, we noticed that the motor nerve conduction amplitude, conduction velocity and distal latency were within normal limits in both the groups. On RNS (repetitive nerve stimulation study) of facial and median nerves, a decremental response was seen in 13 (65%) patients in facial nerve and in 7 (35%) patients in median nerve in Group A; while, the same response was seen in 8 (40%) patients in facial nerve and 3 (15%) patients in median nerve in Group B. A post exercise decremental response was seen in 13 (65%) patients in median nerve and 16 (80%) patients in facial nerve in Group A; and, in 3 (15%) patients in median nerve and 8 (40%) patients in facial nerve in Group B. CONCLUSIONS: In our study, we noticed that the decremental response on RNS was not only present in neuroparalytic snake bite (post-synaptic neuromuscular blockade) but also in vasculotoxic snakebite [pre-synaptic neuromuscular blockade] (seen in Russel's viper).