Phrenic nerve studies predict survival in amyotrophic lateral sclerosis

► Phrenic nerve study is an accessible, non-volitional test, to investigate diaphragm motor neuron pool. ► Phrenic nerve motor response amplitude is a significant predictor factor of survival for both spinal and bulbar-onset amyotrophic lateral sclerosis (ALS) patients. ► Phrenic nerve motor response should be part of the available tools to test respiratory function in ALS patients.