Evaluation of hyperpolarization potentials and nerve conduction parameters in axonal neuropathic patients

ABSTRACT

Neuropathies are diagnosed on the basis of some specific parameters of compound motor unit action potential [CMAP]. The slowing of conduction velocity along with relatively, preserved amplitude considered an indication of demyelination. While, amplitude reduction and slightly slowed conduction velocity, referred to axonal degeneration. Further, CMAP shape and distal latencies are also important for the diagnosis of neuropathies. Although, hyperpolarization is one of the important phase of CMAP but, it is mentioned only in the cases of nerve conduction block and never considered to identify other neuropathies. Therefore, in the present study the hyperpolarization phase of CMAP has been compared and evaluated in terms of its amplitude and duration and its occurrence in axonal neuropathy. The CMAP records of normal subjects and axonal neuropathic patients; randomly selected from OPD cases and evaluated for the occurrence of hyperpolarization, its amplitude, duration, latencies, CMAP amplitude and NCV. The recordings were obtained from the stimulation of median and tibial nerves [both distally and proximally] with recordings of CMAP from Abductor Pollicis Brevis and Abductor Hallucis muscles, respectively. The amplitude and duration of hyperpolarization and other parameters measured from both, median and tibial nerves were significantly lesser in neuropathic patients than the normal ones. Hyperpolarization reduces significantly in axonal neuropathy and this phase of CMAP may also be considered for the evaluation in other neuropathies. Further, criteria may be formulated for the diagnosis of various neuropathies using hyperpolarization phase of CMAP