Motor evoked potentials from the pelvic floor in patients with multiple sclerosis

The use of motor evoked potentials (MEPs) to study the integrity of pelvic floor motor innervation is poorly described in the literature. This study evaluated the clinical use of pelvic floor MEPs in 16 women with multiple sclerosis. Lower urinary tract dysfunction was assessed with urodynamic investigations. Transcutaneous magnetic stimulation was applied over the motor cortex and spinal roots, and MEPs were recorded from the puborectalis, the external urethral sphincter, and the abductor hallucis muscles. In many patients, responses from the pelvic floor muscles could not be evoked, and central motor conduction times for the puborectalis motor pathways could only be calculated in 56%. There was a poor correlation of abnormal conduction to lower urinary tract dysfunction. It is concluded, that unevokable responses from pelvic floor muscles in a patient with multiple sclerosis should be interpreted with care, and that pelvic floor MEPs have a limited clinical value in the investigation of suspected demyelinating disease.