Comparative study of central motor conduction time by using magnetic stimulation and F-wave study in normal subjects

Introduction: Central motor conduction time (CMCT) includes time for excitation of the corticospinal pathways and transmission along those tracts. Data obtained by cortical magnetic stimulation are helpful in some clinical situations such as multiple sclerosis, cervical spondylosis, motor neuron disease, and etc. However, using different methods for peripheral motor conduction time (PMCT) demonsrates two different results. In this study, we used two methods to compare CMCT from F- wave latency and spinal root magnetic stimulation. Also, this study was performed to determine normal values, effects of sex, age and upper limb length. Matrials and Methods: Magnetic stimulation of the cortex and cervical spinal roots was performed on 39 healthy subjects. Responces were recorded from the abductor pollicis brevis (APB) muscle. F-wave study was performed in the median nerve. Subtraction of total motor conduction time (TMCT: cortical response) and PMCT by F-wave and cervical root stimulation, shows CMCT. Results: The results showed 19.7 ms for TMCT, 7.3 ms for CMCT of root stimulation and 4.8 for F-wave based CMCT. CMCT to the APB correlates with upper limb length but no with age or sex. Conclusions: The CMCT calculated by subtracting F- wave latencies measured to APB after transcranial stimulation was shorter than the one obtained after magnetic root stimulation.