Availability of Neurophysiological Index in Amyotrophic Lateral Sclerosis: Application of Neurophysiological Index to Median Nerve /Abductor Digiti Minimi and Posterior Tibial Nerve/Abductor Hallucis

ABSTRACT

BACKGROUND: Neurophysiological Index (NI) is derived from compound muscle action potentials, distal motor latency and F-wave frequency in the ulnar nerve/abductor digiti minimi. Recent studies suggested that NI could be used as a sensitive measure of change during the course of ALS. However, the NI has several limitations which include being derived only from the ulnar nerve territory and is less valuable when atrophic change of the abductor digiti minimi is severe. Thus, this study aimed to evaluate the correlation of NI with the functional status of ALS patients and the availability of NI obtained from median and posterior tibial nerve territory. METHODS: The subjects of the study were 25 patients with ALS. The NI, Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised (ALSFRS-R) and grip power were obtained during the same period and NI values were compared with ALSFRS-R and grip power. RESULTS: A significant correlation was observed between ALSFRS-R and various NI values. Moreover, NI values derived from the ulnar nerve/abductor digiti minimi and the median nerve/abductor pollicis brevis on the dominant hand were statistically correlated with fine motor function scores in ALSFRS-R, and NI values from posterior tibial nerve/abductor hallucis were significantly correlated with lower limb function scores. CONCLUSIONS: Our results support the previous findings that NI is a useful neurophysiological measurement in ALS patients. Moreover, we might suggest NI values from the median nerve/abductor pollicis brevis and the posterior tibial nerve/abductor hallucis also could be used in measuring the functional status of ALS patients.