Pattern of paresis in amyotrophic lateral sclerosis: A cohort study

Objective: To explored the dynamic changes of split phenomenon in multiple antagonistic muscle groups among amyotrophic lateral sclerosis (ALS) patients. Methods: One hundred and twenty limb-onset ALS patients were followed up regularly with an interval of 3 months. Two clinicians collected the muscle strength of elbow extensor-flexor, wrist flexor-extensor, knee extensor-flexor and ankle flexor-extensor individually. Results: Significant differences in muscles strength were observed between flexors and extensors of elbow, wrist, knee, and ankle (p < 0.05). The frequency of split phenomenon of elbow extensor-flexor was 15.1%, 13.8%, 19.1%, 17.8%, and 12.5% at the baseline, 3-, 6-, 9-, and 12-month follow-up points, respectively. For wrist flexor-extensor, the frequency was 20.8%, 18.2%, 18.6%, 19.9%, and 20.4%, respectively. For knee extensor-flexor, the frequency was 3.0%, 8.0%, 7.6%, 8.4%, and 8.9%, respectively. For ankle flexor-extensor, the frequency was 8.8%, 9.2%, 10.9%, 15.4%, and 15.7%, respectively. For muscles with 3-4 levels of muscle strength, significant dissociation of muscle strength was common, especially among patients with a slow progression rate. Conclusion: Split phenomenon of muscle strength between antagonistic muscles was common in limb-onset ALS patients. Muscle strength and progression rate were influence factors of the split phenomenon. As disease progressed, the split phenomenon gradually became obvious, and might then slowly disappeared due to the loss of LMNs.