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Introduction: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by motor neuron damage, with high comorbidities and in most cases fatal. We carried out a review of our Mexican hospital center on the performance of a neurophysiological index using the Abductor Pollicis Brevis / Abductor Digiti Minimi (APB/ADM) with cut-off values of less than 0.6, which is reproducible, sensitive and easy to perform in patients with suspected ALS, and at the same time, analyzes the correlation that this index has with the clinical scale of ALSFRS (Amyotrophic Lateral Sclerosis Functional Rating Scale).

Method: A retrospective cross-sectional study was carried out where a total of 26 patients who were admitted to the neurology department of a reference hospital in Mexico City were included, these patients met the inclusion criteria for a diagnosis of ALS according to El Escorial criteria, from January 2018 to June 2023.

Results: Of the total number of patients, 14 were women and 12 were men, the mean age was 57.4 with 95% CI (51-63), at the time of diagnosis the mean ALSFRS scale 31.4 with 95% CI (27.35-35.5). Indices were obtained in the APB/ ADM nerve conduction study as less than 0.6, which was positive in 22 patients and negative in 4 patients. In the statistical analysis, where neurophysiological and biochemical variables were tested using the Chi-square test, the only variables that demonstrated a significant difference were the APB/ADM index less than 0.6 with ALSFRS greater than 25, where a P=0.028 was obtained.

Conclusions: The split-hand index was found positive at the time of diagnosis in 84%, and showed a statistically significant relationship for both  the APB / ADM index ratio less than 0.6 along with an ALSFRS scale score (>25) in our population, which could be a potential marker correlated with the functional rating scale of patients with ALS.