Modeling of Lung Function Recovery in Neuralgic Amyotrophy With Diaphragm Impairment

Abstract

Neuralgic amyotrophy is an inflammatory peripheral nerve disorder in which phrenic nerve involvement can lead to diaphragm paralysis. The prevalence, magnitude, and time course of diaphragm recovery are uncertain. This study modeled the course of recovery of lung function in 16 subjects with diaphragm impairment from neuralgic amyotrophy. The first and last available vital capacity, sitting-to-supine decline in vital capacity, and maximal inspiratory pressures were compared. An asymptotic regression model analysis in 11 subjects with at least partial recovery provided estimates of the vital capacity at onset (47%, 95% CI 25-68%), the final vital capacity (81%, 95% CI 62-101%), and the half-time to recovery (22 months, 95% CI 15-43 months). In those subjects, there was a significant improvement between the first and last measured FVC (median 44-66%, P = .004) and maximal inspiratory pressure (mean 34-51%, P = .004). Five subjects (31%) with complete recovery had a final sitting-to-supine drop of vital capacity of 16% and a maximal predicted inspiratory pressure of 63%. Sixty-nine percent of subjects with diaphragm impairment from neuralgic amyotrophy experience recovery of lung function and diaphragm strength, but recovery is slow and may be incomplete.