Chronic inflammatory demyelinating polyneuropathy, phrenic nerve and respiratory symptoms

Respiratory involvement in chronic inflammatory demyelinating polyneuropathy (CIDP) has been very recently described. Phrenic nerve conduction studies have been described as useful to detect respiratory impairment in these patients. This study describes two patients with CIDP, in whom neurophysiological studies of the respiratory muscles were performed. The first patient had severe respiratory insufficiency, and phrenic nerve studies disclosed no motor responses and electromyography (EMG) of the diaphragm confirmed severe loss of motor units, bilaterally. On treatment, we documented clinical and neurophysiological improvement. In the second patient, phrenic nerve studies showed abnormal results; however, EMG of the diaphragm ruled out loss of motor units. The first case represents the risk of phrenic nerve involvement in this disorder, and the potential recovery on treatment. The second case illustrates that the temporal dispersion of the motor responses can be misleading, and EMG of diaphragm should be performed to confirm the loss of motor units.