Translumbar and transsacral magnetic neurostimulation for the assessment of neuropathy in fecal incontinence

BACKGROUND: Neurologic dysfunction causes fecal incontinence, but current techniques for its assessment are limited and controversial. OBJECTIVE: The purpose of this work was to investigate spino-rectal and spino-anal motor-evoked potentials simultaneously using lumbar and sacral magneticstimulation in subjects with fecal incontinence and healthy subjects and to compare motor-evoked potentials and pudendal nerve terminal motor latency in subjects with fecal incontinence. DESIGN: This was a prospective, observational study. SETTINGS: The study took place in 2 tertiary care centers. PATIENTS: Subjects included adults with fecal incontinence and healthy subjects. INTERVENTIONS: Translumbar and transsacral magnetic stimulations were performed bilaterally by applying a magnetic coil to the lumbar and sacral regions in 50 subjects with fecal incontinence (1 or more episodes per week) and 20 healthy subjects. Both motor-evoked potentials and pudendal nerve terminal motor latency were assessed in 30 subjects with fecal incontinence. Stimulation-induced, motor-evoked potentials were recorded simultaneously from the rectum and anus with 2 pairs of bipolar ring electrodes. MAIN OUTCOME MEASURES: Latency and amplitude of motor-evoked potentials after lumbosacral magnetic stimulation and agreement with pudendal nerve terminal motor latency were measured. RESULTS: When compared with control subjects, 1 or more lumbo-anal, lumbo-rectal, sacro-anal, or sacrorectal motor-evoked potentials were significantly prolonged (p < 0.01) and were abnormal in 44 (88%) of 50 subjects with fecal incontinence. Positive agreement between abnormal motor-evoked potentials and pudendal nerve terminal motor latency was 63%, whereas negative agreement was 13%. Motor-evoked potentials were abnormal in more (p < 0.05) subjects with fecal incontinence than pudendal nerve terminal motor latency, in 26 (87%) of 30 versus 19 (63%) of 30, and in 24% of subjects with normal pudendal nerve terminal motor latency. There were no adverse events. LIMITATIONS: Anal EMG was not performed. CONCLUSIONS: Translumbar and transsacral magnetic stimulation-induced, motor-evoked potentials provide objective evidence for rectal or anal neuropathy in subjects with fecal incontinence and could be useful. The test was superior to pudendal nerve terminal motor latency and appears to be safe and well tolerated.