Evaluation of the sacroanal motor pathway by magnetic and electric stimulation in patients with fecal incontinence

PURPOSE: The aim of this controlled study was to examine whether it was fea sible to use magnetic stimulation as a new diagnostic tool to evaluate the motor function of the sacral roots and the pudendal nerves in patients with fecal incontinence. PATIENTS AND METHODS: Nineteen consecutive patients (1 7 females) with a median age of 67 (range, 36-78) years referred for fecal incontinence and 14 healthy volunteers (six females) with a median age of 4 2 (range, 23-69) pears were examined. Latency times of the motor response o f the external anal sphincter were measured after electric transrectal stim ulation of the pudendal nerve and magnetic stimulation of the sacral roots. RESULTS: The success rates of pudendal nerve terminal motor latency and sa cral root terminal motor latency measurements were 100 and 85 percent, resp ectively, in the control group and 94 and 81 percent, respectively, in the fecal incontinence group. Median left pudendal nerve terminal motor latency was 1.88 (range, 1.4-2.9) milliseconds in the control group and 2.3 (range , 1.8-4) milliseconds in the fecal incontinence group (P < 0.006), Median r ight pudendal nerve terminal motor latency was 1.7 (range, 1.3-3.4) millise conds in the control group and 2.5 (range, 1.7-6) milliseconds in the fecal incontinence group (P < 0.003). Median left sacral root terminal motor lat ency was 3.3 (range, 2.1-6) milliseconds in the control group and 3.7 (rang e, 2.8-4.8) milliseconds in the fecal incontinence group (P < 0.03). Median right sacral root terminal motor latency was 3 (range, 2.6-5.8) millisecon ds in the control group and 3.9 (range, 2.5-7.2) milliseconds in the fecal incontinence group (P = 0.15). CONCLUSIONS: Combined pudendal nerve termina l motor latency and sacral root terminal motor latency measurements may all ow us to study both proximal and distal pudendal nerve motor function in pa tients with fecal incontinence. Values of sacral root terminal motor latenc y have to be interpreted cautiously because of the uncertainty about the ex act site of magnetic stimulation and die limited magnetic field strength.