Neurophysiological assessment of the central motor pathway to the external urethral sphincter in man

A recently developed neurophysiological method by which the motor cortex in man can be electrically stimulated has been applied to the assessment of the central motor pathway to the external urethral sphincter. It was observed that there was parallel activation of the anal sphincter, the pelvic floor and the lower limb muscles, voluntary facilitation and marked inhibition during micturition. This method can be used to assess the volitional and the various segmental and suprasegmental influences on the behaviour of the external urethral sphincter. Unfortunately, the poor tolerance of subjects to the scalp sensations caused by the electrical stimulus is a major limitation to its clinical use, though this should be obviated by the introduction of a cortical magnetic stimulator.