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| 번호 | 제목 | 등록일 | 조회수 |
|---|---|---|---|
| 10 | Evaluation of the Sacroanal Motor Pathway by Magnetic and Electric Stimulation in Patients with Fecal Incontinence [2001년 2월 DCR] | 2011-11-12 | 3339 |
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G. L. Morren, M.D.,S. Walter, M.D.,H. Lindehammar, M.D.,Olof Hallbook, M.D., Ph.D.,Rune Sjodahl, M.D., Ph.D., F.R.C.S.
From the Departments ofColorectal Surgery and Neurophysiology, University Hospital Zinkdping,
Linkdping, Sweden PURPOSE: The aim of this controlled study was to examine whether it was feasible 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 (17 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 42 (range, 23-69) years were examined. Latency times of the motor response of the external anal sphincter were measured after electric transrectal stimulation of the pudendal nerve and magnetic stimulation of the sacral roots. RESULTS: The success rates of pudendal nerve terminal motor latency and sacral root terminal motor latency measurements were 100 and 85 percent, respectively, 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 right pudendal nerve terminal motor latency was 1.7 (range, 1.3-3.4) milliseconds 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 latency was 3.3 (range, 2.1-6) milliseconds in the control group and 3.7 (range, 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) milliseconds 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 terminal motor latency and sacral root terminal motor
latency measurements may allow us to study both proximal and distal pudendal nerve motor function in patients with fecal incontinence. Values of sacral root terminal motor latency have to be interpreted cautiously because of the uncertainty about the exact site of magnetic stimulation and the limited magnetic field strength. DISCUSSION
The value of PNTML measurements in patients with FI is still under debate. 12' 19 A major problem is the absence of normal values matched for gender and age. Pudendal neuropathy defined as prolonged unilateral or bilateral PNTML has been associated with solid stool incontinence, 2° with the process of labor and vaginal delivery, 21 with rectal prolapse, 19 with idiopathic FI, 18 with failure after sphincteroplasty, 22 with persistent incontinence after surgical treatment of rectal prolapse, 23 and with soiling after ileal J-pouch-anal anastomosis. 7 PNTML assessment may be most important in diagnosing neurologic causes of FI. In a group of 225 patients with FI, pudendal neuropathy was found in 56 percent of patients with neurologic causes but in only 34 percent of patients with idiopathic incontinence. 19 PNTML assesses only the terminal portion of the pudendal nerve. Better diagnostic tools are needed to exclude nerve damage at a more proximal level of the efferent pathway between
the motor cortex and EAS. MSRS seems to be promising, but some major problems are encountered, First there is the generation of a major stimulus artifact that may obscure the onset of CMAPs, leading
to misinterpretation. Loening-Baucke et al. 6 report a long recovery of the stimulus artifact interfering with the latency measurement in 6 of 27 subjects. This problem made other investigators 1° develop new recording techniques using a modified St. Mark's electrode. The placement of the earth electrode between the site of stimulation and the site of registration led to a substantial reduction of the stimulus artifact and made recording of a reproducible CMAP possible in 18 of 21 subjects. This recording technique is uncomfortable to the patient and may need the presence of two investigators. In our study, we used an anal plug for CMAP recording and placed the earth electrode intrarectally. All patients were very comfortable during examination, and the single investigator was able to manipulate both the coil and keyboard of the electromyographic apparatus at the same time. The stimulus artifact was always shorter than one millisecond and never interfered with latency time measurement. There was one subject in each group in whom no CMAPs could be evoked by MSRS. Both had prolonged PNTMLs. Poor quality of the registered curves as judged on review led to the exclusion of 7 percent of the SRTML measurements in the control group and 11 percent in the FI group. This was mostly a result of low voltage amplitudes of the registered CMAPs because deflections could not consistently be identified. Worse electric contact between the registration electrodes and a weakened or fibrotic sphincter may contribute to low voltage amplitudes. However, in this study, no relation was found between the presence of FI or an EAS injury and CMAP amplitudes. Using a needle electrode instead of an intra-anal sponge electrode may improve registration, but in our view this does not outweigh the obvious disadvantages for the patient. Second, the exact site of nerve stimulation is unknown. Generator and coil design, the orientation
and position of the coil, stimulator output, and anatomic features may all influence the site of nerve stimulation. In this study we only registered the shortest reproducible SRTMLs and compared those with the PNTMLs of the corresponding site. Median differences were 1.2 milliseconds (left side) and 1.4 milliseconds (right side) in the control group and 1.3 milliseconds (left side) and 1.2 milliseconds (right side) in the FI group. This is consistent with the results of two other studies, v' 10 where mean differences between 1 and 1.6 milliseconds were found. These values correspond with a distance between 6 and 9.6 cm from the site of MSRS to the site of electric pudendal nerve stimulation, assuming a conduction velocity of 60 m per second. 24 Thus it appears that sacral root stimulation occurs at the exit from the sacral bone. In five measurements, the difference between PNTML and SRTML was equal to or less than 0.3 milliseconds, indicating that the distance between the two sites of stimulation was less than 2 cm. The pudendal nerve bends ventrally when passing behind the spina ischiadica. It is possible that this bend was the preferable site of magnetic stimulation in those five measurements. 25 This would also explain the differences in latencies after percutaneous electric and magnetic sacral root stimulation in the one patient described by Jost et al. 26 We found significantly prolonged PNTMLs on both sides in the FI group compared with the control group. The same was true for the left SRTML, but, when subtracting both values, no significant difference between the two groups was found. It may be that the patients in the FI group have a normal proximal but delayed distal conduction in the pudendal nerves. Other investigators using electric stimulation had similar results. 13 Because most patients in the F1 group were elderly females, in contrast with the control subjects, it remains unclear whether this distal pudendal neuropathy is an aging phenomenon or a causal factor. A third problem remains the limited magnetic field strength. We measured latency times at 100 percent of
the output that could be generated by the apparatus. However, because of the limited strength and penetration depth of the magnetic field, we cannot be sure that a supramaximal response in all subjects was consistently obtained, Because of the ongoing development of more powerful generators and specially designed coils, both a better penetration and localization of the magnetic field can be expected in the near future. |
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