Assessment of cervical skeletal muscle index in early and late phases of amyotrophic lateral sclerosis.

OBJECTIVES

The diagnosis of Amyotrophic Lateral Sclerosis (ALS) can be challenging when clinical and electrophysiological findings are insufficient. We aimed to investigate the potential role of cervical Skeletal Muscle Index (SMI), as a supportive diagnostic marker in ALS, particularly in relation to disease duration.

METHODS

A total of 22 ALS patients and 25 age- and sex-matched controls were retrospectively included. The cross-sectional area (CSA) of cervical muscles was measured on axial T1-weighted magnetic resonance imaging (MRI) at the C3 vertebra level. SMI was calculated by normalizing the total CSA to patient height (mm2/m2). ALS patients were stratified based on the timing of MRI: within six months of symptom onset and after six months.

RESULTS

There were no significant differences in age, sex, BMI, or total muscle volume between patients and controls. Although mean SMI was slightly lower in ALS patients (p = 0.177), this difference was not statistically significant. Among ALS patients, those who underwent MRI more than six months after symptom onset had significantly lower SMI values compared to both those who underwent MRI within six months and controls (respectively, p = 0.014, p = 0.018). No significant SMI difference was observed between ALS patients who underwent MRI within six months and controls (p = 0.626).

CONCLUSION

Cervical SMI measurements at the C3 vertebral level may support ALS diagnosis, particularly in patients with longer disease duration. SMI may also provide insight into early muscle loss due to denervation.