Phrenic nerve studies predict survival in amyotrophic lateral sclerosis

Abstract

Objective: Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disease associated with short survival due to respiratory failure. We aimed to test the predictive value of the phrenic nerve motor response for survival, in a large population of ALS patients.

Methods: We included 254 ALS patients followed in our tertiary centre from 1997 to 2006, in whom phrenic nerve stimulation was performed according to the study inclusion and exclusion criteria. ALS was spinal onset in 175 and bulbar onset in 79 patients. The following features were recorded at entry: gender, age at presentation, onset region, diagnostic delay, forced vital capacity (FVC), ALS functional rating scale (ALS-FRS) including the respiratory subscore of the reviewed ALS-FRS and mean amplitude of motor responses by phrenic nerve stimulation (PhrenAmpl).

Results: Survival analysis was evaluated by Kaplan-Meier log-rank test and multivariate Cox proportional hazards. Independent factors negatively affecting survival were bulbar onset, short diagnostic delay, FVC and small PhrenAmpl for the total population. Small PhrenAmpl and short diagnostic delay were also independent factors for both spinal and bulbar-onset patients; age at onset and FVC were also independent predictors in bulbar-onset patients.

Conclusion: Phrenic nerve stimulation is a non-volitional test that can be performed quickly in most patients; it is a powerful predictor of survival in ALS.

Significance: Phrenic nerve stimulation should be considered as an additional test for respiratory assessment in ALS.