Diaphragmatic CMAP amplitude from phrenic nerve stimulation predicts functional decline in ALS

Area of Science:

• Neurology
• Respiratory Medicine
• Clinical Research

Background:

• Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease affecting motor neurons.
• Functional decline in ALS patients is a critical outcome measure.
• Respiratory muscle weakness, particularly involving the phrenic nerve, significantly impacts ALS progression.

Purpose of the Study:

• To determine if phrenic nerve motor amplitude (PhrenicAmp) independently predicts functional decline in ALS patients.
• To assess the predictive value of PhrenicAmp and forced vital capacity (FVC) for functional loss in ALS patients with bulbar dysfunction.

Main Methods:

• A cohort of 249 ALS patients with baseline PhrenicAmp and FVC measurements was analyzed.
• Functional decline was quantified by the percentage reduction in the revised ALS Functional Rating Scale (ALSFRS-R).
• Mixed-effects regression models were employed to evaluate the relationship between respiratory measures and functional decline.

Main Results:

• Baseline PhrenicAmp and FVC were significantly correlated with ALSFRS-R scores.
• Both PhrenicAmp and FVC correlated with functional decline over time in the overall ALS population.
• PhrenicAmp, but not FVC, emerged as a significant independent predictor of functional decline in ALS patients, including those with bulbar dysfunction.

Conclusions:

• Phrenic nerve motor amplitude at baseline is a robust independent predictor of functional decline in amyotrophic lateral sclerosis.
• This finding holds true irrespective of the presence or absence of bulbar dysfunction in ALS patients.