PHRENIC-NERVE CONDUCTION AND DIAPHRAGMATIC MOTOR EVOKED-POTENTIALS - EVALUATION OF RESPIRATORY DYSFUNCTION

Objective To investigate preliminarily the value of phrenic nerve cond uction (PNC) and diaphragmatic motor evoked potentials (MEPs) in the e valuation of various respiratory dysfunction (RDF). Methods Thirty-fou r patients with various RDF, (19 patients with neurogenical diseases a nd 15 patients with respiratory disorders) were investigated. Fifty he althy volunteers sewed as controls. The phrenic nerve was cutaneously stimulated by electrical pulse current at the midpoint of the posterio r border of the sternomastoid muscle, and the diaphragmatic muscle com pound action potentials (DCAP) were recorded between the 7th and 8th i ntercostal space and xiphoid process. When the magnetic transcranial s timulation (MTS) of the cortex was given, the recordings were made und er the condition of maximal deep inspiration. Results Ail patients wit h myopathies had normal PNC. The patients with Guillain Barre syndrome (GBS), hereditary motor and sensory neuropathy (HMSN) and myasthenic crisis had abnormal PNC. The findings in PNC studies remarkably correl ated with RDF, while serial examinations were performed in the patient s with GBS and myasthenia gravis (MG). In 7 patients with sleep apnea syndrome (SAS), 4 had abnormal PNC, and 2 of 3 patients with chronic o bstructive pulmonary diseases (COPD), and I of 5 patients with chest t ightness or breathlessness on the supine position showed decreased amp litude. When MEPs were recorded, 3 of 5 patients showed abnormal SAS ( 1 had no response, 2 lower amplitude). Three patients with COPD had no rmal MEP. Conclusions PNC studies could not only evaluate neuromuscula r RDF and predict the outcome of diseases, but also supply additional information about diaphragmatic dysfunction for the RDF caused by resp iratory disorders. The results of PNC and diaphragmatic MEP may differ entiate the types of SAS.