Objective: To provide an additional contribution to the differential diagnosis of Charcot-Marie-Tooth disease type 1A (CMT1A) and chronic inflammatory demyelinating polyneuropathy (CIDP) by analyzing distal duration and proximal/distal amplitude and duration ratios on different nerves in these diseases that show demyelinating peripheral neuropathy features.
Material and Methods: We retrospectively reviewed the electromyography (EMG) findings of patients aged 18-80 years who were followed up with a diagnosis of acquired and hereditary demyelinating type polyneuropathy in the neuromuscular diseases outpatient clinic in our center. We analyzed the distal CMAP duration and amplitude, proximal and distal compound muscle action potential, and duration ratios on each nerve in the patient groups, separately.
Results: The CIDP group had significantly longer Peroneal nerve distal duration than the CMT1A group (p=0.04). Median, ulnar, and tibial nerve distal durations were similar between the groups (p=0.84, p=0.86, and p=0.13, respectively). The median nerve, ulnar nerve, and peroneal nerve proximal/distal amplitude ratios were not different between the CMT1A and CIDP groups (p=0.99, p=0.38, and p=0.16, respectively). The tibial nerve proximal/distal amplitude ratio in the CIDP group was lower than in the CMT1A group (p=0.003). Median, ulnar, peroneal, and tibial nerve proximal/distal duration ratios were statistically similar among the groups (p=0.21, p=0.66, p=0.62, and p=0.46, respectively).
Conclusion: This study may help to improve the management of challenging patients where there is an overlap between hereditary and inflammatory neuropathies. The different electrodiagnostic models of various acquired and hereditary demyelinating polyneuropathies should be clinically recognized.
Charcot-Marie-Tooth disease type 2 caused by homozygous MME gene mutation superimposed by chronic inflammatory demyelinating polyneuropathy