Method for Deriving Motor Evoked Potentials of The Diaphragm Muscle After Transcranial And Cervical Magnetic Stimulation

Objective The aim of the study was to test the applicability of transcranial magnetic stimulation (TMS) for assessing the integrity of the cortico-dia-phragmatic motor system with suspected disorders of respiratory function. Methods Transcranial and cervical magnet stimulations were carried out. Diaphragmatic response was derived by using surface electrodes placed in the 7(th) intercostal space. The stimulation was performed at least 3 times and the shortest latency of cortico-muscular and peripheral motor latency was used to determine central motor conduction time (CMCT). Subjects with TSM-diagnosed disturbance of the central motor pathway to the arms and feet were excluded. Descriptive statistics were conducted and further analyses were carried out. Results 58 subjects without any clinical signs of a respiration disorder were examined, of whom 7 were excluded from further analysis. The mean value of the CMCT (+/- 2SD) to the left hemidiaphragm was 10.7 +/- 4.0 ms and 10.8 +/- 3.6 ms to the right hemidiaphragm. The latenci-es were normally distributed. No significant correlation was found between the height and the cortico-muscular latency to the left (p = 0.23) and the right hemidiaphragm (p = 0.20), and in addition between age and the CMCT to the left (p = 0.62) and right hemidiaphragm (p = 0.76). Conclusions Magnetic stimulation is feasible as a non-invasive tool for examination of the function of the central motor pathway to the diaphragm.