Establishing a quantitative evaluation method for the strength of cranial muscle groups and its application in amyotrophic lateral sclerosis (ALS)

Abstract

Objective: To establish a quantitative method for strength evaluation targeting cranial muscle groups and applied it in amyotrophic lateral sclerosis (ALS) patients.

Methods: Detailed physical examination were conducted on patients with neuromuscular disorders or healthy population for the selection of the actions innervated by cranial nerves. The six-level strength by manual assessment was designed according to the Medical Research Council (MRC) score. ALS patients were consecutively recruited to explore the clinical significance of the quantitative method.

Results: A total of fourteen actions regarding cranial muscle groups were finally involved in our quantitative evaluation method which was named the MRC cranial score, all of which showed satisfied inter-observer and intra-observer consistency. Among 58 ALS patients, 40 (68.97%) showed decrease in the MRC cranial score at baseline, mainly presenting dysfunction in cheek bulging, swallowing, speech and tongue extension. During the 3-month follow up, there was a significantly negative correlation between the baseline MRC cranial score and ALS progression rate (p<0.001). Low MRC cranial score was significantly related to the need of invasive respiratory support (p=0.005) and gastric catheterization (p=0.003).

Conclusion: In the study, we designed the MRC cranial score, which was a easily operating evaluation method of the strength involving 14 actions innervated by cranial nerves. The MRC cranial score could quantify the involvement of cranial nerves in neuromuscular diseases comprehensively, which was negatively related to the progression rate and might be a predictor of the need of gastric tube or respiratory support in ALS patients.