Electrodiagnostic evidence of phrenic nerve demyelination in Charcot-Marie-Tooth disease 1A

To determine whether neurophysiologic findings correlate to clinical respiratory signs or spirometric abnormalities in patients with hereditary motor and sensory neuropathy type 1 (Charcot-Marie-Tooth disease).

A total of 11 patients with hereditary motor and sensory neuropathy type 1A, genetically identified, (age range, 10-58 yr) were included and studied by physical pulmonary examination, chest radiography, respiratory function tests, and bilateral transcutaneous phrenic nerve conduction.

No patient complained of respiratory symptoms or revealed abnormal spirometric or maximal respiratory pressure data, despite a phrenic nerve conduction significantly slower (P < 0.0001; median conduction time, 18.6 msec; 95th percentile, 31.97 msec) than that recorded in the control group of healthy subjects (median, 6.05 msec; 95th percentile, 8.82 msec); the amplitudes of compound muscle action potentials were not statistically different from the controls.

Our study confirms a dramatic phrenic nerve involvement in absence of clinical and laboratory evidence of diaphragmatic weakness; further studies and an adequate follow-up are necessary to discover whether the disease progress might encompass respiratory dysfunction at later stages.