Management of the uninhibited bladder by selective sacral neurectomy

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1 Management of the uninhibited bladder by selective sacral neurectomy MCHAEL J. TORRENS, F.R.C.S., AND HUW B. GRFFTH, M.R.C.P., F.R.C.S. Department of Urology, Ham Green Hospital, and Department of Neurosurgery, Frenchay Hospital, Bristol, England ~" The authors report the treatment of incontinence due to uninhibited bladder contractions by selective sacral neurectomy in nine patients, four without evidence of neurological disease. A detailed and objective analysis of bladder and urethral function, together with quantitation of clinical features, was made before and after operation. Seven patients were either cured or greatly improved. The overall increase in bladder capacity and reduction of uninhibited activity were statistically significant. The resting urethral sphincter pressure was unchanged, but the contractility of the voluntary external sphincter was slightly impaired. Criteria for such neurectomies are discussed. KEY WORDS 9 selective sacral neurectomy 9 incontinence 9 uninhibited bladder 9 vesicourethral innervation 9 sacral rhizotomy T HERE is much current interest and controversy concerning the management of the hyperactive bladder, la The extent of the problem is reflected by our series of 304 incontinent patients reviewed over a 2-year period. Uninhibited bladder contractions caused or potentiated the incontinence in 146 cases (48%), although only 12% had objective neurological abnormalities. We have tried to assess the place of sacral neurectomy in the treatment of these patients. Denervation as a treatment for the reflex or uninhibited bladder has been advocated for many years, 2 yet carried out only sporadically. nitially the objective was complete denervation in paraplegic patients to allow autonomous activity? ~o As the need for partial denervation in less severe problems was realized, pelvic neurotomy 14 and local perivesical denervation 2~ were introduced. These are procedures in which it is difficult to judge the extent of the denervation carried out. The accessibility of the sacral roots at the level of the sacral foramina led Heimburger, et al.fl to develop selective sacral root blocks with local anesthetic as a reversible test procedure. Meirowsky, et al., 7 carried these out prior to selective sacral neurectomy. The results of operation however remain unpredictable.~l,13.16 Clinical Material and Methods Seventeen patients underwent selective sacral nerve blocks under radiographic control. These were selected by the extreme severity of their symptoms; all were incontinent both day and night. Eight cases were of lifelong idiopathic enuresis with diurnal urge incontinence, eight patients had developed ]76 J. Neurosurg. Volume 44 February, 1976

2 Sacral neurectomy for uninhibited bladder secondary urge incontinence and enuresis, of whom four had neurological disease, and one patient had interstitial cystitis. Enuresis in this context is defined as an otherwise normal reflex act of micturition occurring while the patient is asleep. The significance of uninhibited bladder activity and sphincter pressure in enuresis is the subject of a separate report. 18 After nerve blocks, nine patients were selected for sacral neurectomy; five were lifelong enuretics. Four patients had acquired urge incontinence; of these two had multiple sclerosis and one had suffered a posteroinferior cerebellar artery thrombosis. All patients underwent a routine urodynamic analysis consisting of the following tests: 1. A cystometrogram with constant recording of bladder and intra-abdominal pressure, during filling with saline at 37 ~ C, at a constant rate of 50 mlmin 2. Pressure-flow analysis during micturition 3. Recording of urethral sphincter pressure, at rest and during voluntary contraction, by the urethral pressure profile technique. 1 All pressures were electrically transduced (EMT 34 transducer) and recorded on an Elema Sch6nander mingograph 81" where the established techniques of von Garrelts and Strandell 3,4 were used. The urodynamic analysis was repeated 90 minutes after the bilateral percutaneous injection of 1.5 ml of 0.5% bupivicaine through the posterior sacral foramina to anesthetize the sacral roots as they pass through the anterior sacral foramina. The injections were performed under radiological control and repeated at S-2, S-3, and S-4 in turn, with at least 48 hours elapsing between each pair of injections. Hypesthesia in the saddle area was seen but is not always a reliable indicator of root anesthetization, as the posterior primary ramus may not be affected by the anesthetic. The location and spread of the anesthetic was checked by concurrent injection of iophendylate contrast medium on some occasions. t was found to spread in the perineural tissues close to the nerve over a 3- to 4-cm length. The sacral nerves selected by anesthetic nerve blocks were then exposed extradurally by limited sacral laminectomy. The operative technique was designed to give the least postoperative morbidity by avoiding intradural manipulation and interference with the function of the lumbosacral junction. With the patient under a light general anesthetic with spontaneous respiration, a midline incision is made between S-1 and S-4 (Fig. 1 left). The relevant posterior sacral foramina are identified by counting up from S-4 foramen with reference to the sacral hiatus and to radiographs. A burr hole is then made in the lamina immediately cranial and medial to the selected foramen which exposes the nerve just before its exit (Fig. 1 right). We have found this method less damaging to the posterior primary ramus than enlarging the foramen medially and cranially as advocated by Meirowsky, et al. 7 Under the operating microscope the sacral nerve appears to have two or three preformed bundles. This observation has been confirmed by the analysis of transverse histological specimens. 5 These bundles may be separated easily by microdissection. The intact nerve and nerve bundles are stimulated individually with a specially constructed bipolar electrode with a squarewave generator (0 to 5 V, 10 cps, 0.5 Mcsec).t Bladder pressure is monitored through a fine urethral catheter, the urethral sphincter pressure is assessed by the profile technique, and a balloon is used in the anal sphincter. The same electromanometric transduction and recording methods are employed as in the urodynamic analysis. This stimulation is used to confirm the results of sacral nerve blocks. The selected nerves are then partially or totally cut or crushed as indicated and the wound is closed. A urethral catheter is usually left to drain for 2 days. Objective and quantitative assessment of postoperative symptoms and urodynamic parameters has been carried out 3 months postoperatively. The frequency of micturition and the volumes of urine voided are measured *Generator made by Electrophysiological ndustries, Ltd. temt 34 transducer and Elema Sch5nander mingograph 81 manufactured by Elema Sch~Snander, Postsack, Solna 1, Sweden. J. Neurosurg. Volume 44 February,

3 M. J. Torrens and H. B. Griffith FG. 1. Left: ncision and initial exposure in selective sacral neurectomy. Right: Burr-hole laminectomy and exposure of S-3 nerve root. by the patients themselves whose cooperation has been excellent throughout. Functional bladder capacity was assessed as the mean volume voided over a period of 1 week. The maximum bladder capacity is the largest urine volume voided. Frequency of enuresis is recorded over a period of 1 month. All these values can be compared with similar recordings made preoperatively. Case 1 Case Reports This 42-year-old woman was healthy except for a 5-year history of frequent diurnal urge incontinence accompanied by suprapubic pain. There was occasional enuresis. No organic cause could be found for her complaints. n July, 1972, she underwent a partial bilateral S-3 nerve section. This resulted in a complete symptomatic cure which persists 2 years after surgery. Paresthesias in the buttocks were present for 6 weeks after the operation. Case 2 This 53-year-old woman was continuously wet for 5 years due to reflex incontinence following a posterior inferior cerebellar artery thrombosis. She was unable to retain a catheter because of bladder spasm. n August, 1973, both S-3 nerve roots were crushed and the left S-4 root cut. This resulted in abolition of her reflex incontinence although some stress incontinence remained. She is now able to tolerate a catheter without discomfort. Case 3 This 32-year-old woman had multiple sclerosis, with frequent flooding incontinence and occasional enuresis for 4 years. There was occasional paradoxical retention due to sphincter discoordination. She also had difficulty in walking due to leg spasticity. n January, 1973, the $2-4 nerve roots were explored bilaterally with dissection of both S-2 nerves. A bilateral S-3 crush was performed. Postoperatively her walking was greatly improved due to reduction of hamstring 178 J. Neurosurg. Volume 44 February, 1976

4 Sacral neurectomy for uninhibited bladder spasticity, and a symptomatic cure of her incontinence resulted. Case 4 This 36-year-old man had had enuresis every night for 5 years due to multiple sclerosis. He also complained of diurnal urge incontinence about three times weekly, and was impotent and grossly constipated. He exhibited sphincter discoordination. n September, 1972, he underwent a partial left S-3 nerve section. The clinical effects were unsatisfactory and the operation was followed by bilateral Phenol injections at S-2 and S-3 levels. This reduced his enuresis to twice a week and he was satisfactorily controlled by the addition of antidiuretic hormone and anticholinergic drugs. Case 5 This 21-year-old man complained of intense frequency with life-long enuresis and urge incontinence several times a day. There was no neurological deficit. n April, 1973, he underwent a right S-3 nerve crush which reduced his enuresis to once a week and greatly improved his frequency. The urge incontinence was abolished. He complained of paresthesias in the buttocks for 4 weeks after the operation. Case 6 This 26-year-old man had had life-long enuresis about five times a week with occasional urge incontinence. There was no neurological deficit. n May, 1973, his left S- 3 nerve root was crushed. After this the enuresis was reduced to twice a week and the urge incontinence abolished. Case 7 This 21-year-old man had had life-long enuresis every night with diurnal urge incontinence. There was no neurological deficit. n August, 1973, bilateral S-3 nerve crush was carried out. This reduced his enuresis to once a week and abolished the diurnal symptoms. One year after operation the enuresis had increased in frequency again. Case 8 This 20-year-old woman complained of life-long enuresis every night with diurnal urge incontinence. She also suffered from epilepsy and had mild neurofibromatosis but no neurological signs. n May, 1973, she underwent a bilateral S-3 nerve crush and the left S-4 nerve was cut. Postoperatively there was no significant change in her symptoms but a small residual urine was created. Case 9 This 25-year-old woman had had life-long enuresis every night with diurnal urge incontinence. She was epileptic, but had no neurological deficit. n August, 1973, a left S-4 nerve crush was performed. There was no significant improvement in her symptoms after operation, but no residual urine was noted. A second neurectomy of S-3 on the right side was performed in May, 1974, after intraoperative stimulation. This cured her diurnal frequency and urge incontinence, but the enuresis remains. Results Selective Sacral Nerve Blocks The results of blocks in 17 patients have been reported in detail elsewhere. 17 The combined results are summarized in Table 1 which records the mean percentage change from the normal state after root anesthetization. Paired data are analyzed and significance is assessed by students t test (twotailed). t is evident that bladder capacity is greatly increased without significant reduction of sphincter activity. The flow rate, although reduced after S-3 block, is still entirely adequate. The S-3 nerve root seems to be the most important in subserving bladder control. Root block at S-4 increases resting sphincter tone in the urethra; this suggests that it carries an inhibitory nerve supply to the urethral smooth muscle. No decrease in sexual potency was reported by the male patients in the 12 hours after the injections. One patient (Case 4) was restored temporarily to potency after 5 years of impotence. lntraoperative Nerve Root Stimulation All the roots at $2-5 can be conveniently exposed by burr-hole laminectomy at the S-2 level. The exposed nerves were stimulated at J. Neurosurg. Volume 44 February,

5 TABLE 1 M. J. Torrens and H. B. Griffith Bladder and sphincter responses to sacral root blocks in 17 patients* Resting Contracted Root Block Bladder Urinary Sphincter Sphincter Level Capacity Flow Rate Pressure Pressure Yo p % p Yo p Yo p S-2 q- 158 < NS - 1 NS - 13 NS S < < NS -- 6 NS S-4 q- 124 < q- 1 NS + 28 = NS * Mean percentage changes of paired data before and after blocks. operation to confirm the sacral block findings and assess the relative contribution of the dissected nerve bundles to bladder and sphincter innervation. The results of stimulating an undissected single nerve are shown in Fig. 2 upper. The bladder response is a sustained tonic contraction with a latency of 5 to 8 seconds. The usual urethral sphincter response is an immediate but poorly sustained contraction followed by a sustained relaxation. This relaxation is further evidence that inhibitory fibers are contained in the sacral outflow to the sphincters. Both bladder and sphincter responses were most commonly found on stimulating the S-3 nerve. Differential stimulation of nerve bundles after dissection was performed in five of the nine cases. The results showed that the bundles are functionally distinct before their entry into the sacral plexus. Some are related more to sphincter function and others concerned mainly with bladder innervation (Fig. 2 lower). n three of these five cases the bladder innervation was carried in the anterolateral fiber bundles. n the remaining two cases the lateral fiber bundles again seemed to convey fibers destined for the bladder while the medially placed bundles appeared to innervate the sphincters. Selective Sacral Neurectomy The nerves for section were selected by combining the information obtained by preoperative nerve blocks and intraoperative nerve stimulation. n eight of the nine cases S-3 was selected. n one case S-4 was cut and this case showed no postoperative improvement. Most female patients had bilateral nerve operations. The first male patients we treated had unilateral operations because of the fear of impotence. However, as no change of potency was observed a bilateral operation at one level was performed subsequently in one man with no diminution of potency. Those patients who had a bilateral nerve operation required an indwelling catheter for periods up to a week. The patients suffered very little postoperative discomfort and could walk as soon as they recovered from the anesthetic. Six of the nine patients were discharged as soon as their skin sutures were removed, one patient was discharged before the stitches were removed, and two who had difficulty in walking preoperatively required a rather longer spell of rehabilitation. Two cases had paresthesias in the buttock which persisted for 4 to 6 weeks after operation. These then completely disappeared with time, and no postoperative numbness in the saddle area lasted more than 2 or 3 days. The response to selective sacral neurectomy at 3 months has been assessed as objectively as possible. These results are recorded below and also summarized in Table 2. Overall there have been two complete symptomatic cures, five patients are considerably improved, and two are unchanged. Summary of Results Cystometrogram Capacity. The cystometrogram capacity was increased in six of the nine patients postoperatively (Fig. 3). The mean change was from 176 ml (+ SD 112) to 315 ml (+ SD 135, p < 0.01). This represents an increase of 70%. The capacity failed to increase in the two women with epilepsy and in one other case with considerable detrusor ]80 J. Neurosurg. Volume 44 February, 1976

6 Sacral neurectomy for uninhibited bladder Fm 2. Bladder and sphincter responses following stimulation of sacral roots ($2-4). Small regular fluctuations are due to respiration. The duration of stimulation is shown by the narrow dotted line. Upper: Results of stimulating theintact sacral nerves. Lower: Differential innervation of bladder and sphincter revealed by stimulating the dissected nerve bundles. TABLE 2 Results of sacral neureetomy* Case No. Roots Diurnal Urge Frequency No. Sectioned ncontinence (xday) Cysto- Unin- Sphincter Pressure Enuresis metro- hibited (mm Hg) (xweek) gram Activity Capacity (mm (ml) Hgml) Rest Squeeze Comment stress uncharted i ? 7~A * Figures show preoperativepostoperative value cured improved cured improved improved improved improved unchanged unchanged J. Neurosurg. Volume 44 February,

7 M. J. T o r r e n s a n d H. B. Griffith 400 w >- 300 o ,r 2 o 200 o n=s f = Z.83 p< PRE OPERA"fVE Fo. 3. Effect o f sacral n e u r e c t o m y metrogram capacity (ml). on cysto- hypertrophy and indistensibility due to the longstanding hyperactivity. A desire to void occurred normally, but the onset of this was delayed from 102 ml (-4-SD 68) to 215 ml (~ SD 132, p < 0.05). Average Volume Voided. The average volume voided is considered to be an index of functional bladder capacity. This is assessed by calculating the total urinary output over the period of a week and dividing this by the urinary frequency. This was increased in four cases but failed to increase in another three patients who all carried a residual urine. Two of these patients had multiple sclerosis. The overall mean increase was from 140 ml ( SD52) to 176 ml ( + S D 7 6, p not significant). However the maximum volume voided was significantly increased from 300 ml (! S D 100) to 396 ml ( + S D 161, p < 0.02). Uninhibited Bladder Activity. The index of uninhibited bladder activity used is the summated height of all uninhibited contractions divided by cystometrogram capacity, and expressed as mm Hgml. Uninhibited activity was reduced postoperatively in eight of the nine cases (Fig. 4). The overall mean change was from 1.25 mm Hgml ( i SD 100) to 0.47 mm Hgml ( i SD 0.55, p < 0.05). There would thus appear to be a generally significant improvement in bladder function. The tone of the resting urethral sphincter, 182 n:9 t = Z.10 p < 0.05 A PRE OPERATVE 3 4 Fm 4. Effect of sacral neurectomy on uninhibited bladder contractions (ram Hgml). which is substantially involuntary, was insignificantly increased (Fig. 5) after operation from 62.3 mm Hg (+ SD 24.7) to 68.5 mm Hg ( SD 32.8, p not significant). However the pressure produced by voluntary sphincter contraction was reduced slightly in eight of the nine cases (Fig. 6). This significant alteration was from mm Hg (+ SD 54.3) to 84.2 mm Hg (+ SD 37.4, p < 0.05). Urinary Flow Rate. t is important to stress that the patients were able to pass urine normally after this operation. The urinary flow rate was increased slightly in the majority of cases postoperatively. This is in contrast with the effects of sacral root blocks (Table 1). The mean change was from 23.1 mlsec ( i SD 11.1) to 26.8 mlsec (+ SD 13.0, p not significant). However, the mean volume voided at the test also increased from 175 to 32 ml. Since the flow rate is proportional to the volume voided, operation has made no effective difference to urinary flow rates. Micturition Pressure. The intravesical micturition pressure shows no change, and the measurement of intraabdominal pressure shows that patients do not have to strain postoperatively in order to void. Only one patient developed a residual urine where this had not been present preoperatively. n those patients with multiple sclerosis who had a preoperative residuum, residual urine was not inj. Neurosurg. Volume 44 February, 1976

8 Sacral neurectomy for uninhibited bladder 250 i 200,- LU :> ~- 150 ~ ," j mo 9, o ~ mo o n:9 : 0.25 p=fls 50 ~ 150 o % 9 n=9 t = 2.53 p < oo 9 5O J PRE O P E R A T V E 200 i 250 i 0 5O PRE OPERATVE FG. 5. Effect of sacral neurectomy on resting urethral sphincter pressure (ram Hg). Fm 6. Effect of sacral neurectomy on voluntary urethral sphincter contraction (mm Hg). creased when considered as a percentage of capacity. Enuresis. Objective assessment of symptoms showed that enuresis was cured in two cases, substantially improved in four cases, and unchanged in three. n the group that was improved, the change in mean frequency of enuresis was from 5.5 to 1.5 times a week. The cases that failed were the two young women with epilepsy and one case of severe reflex incontinence with totally inadequate sensation. This patient continually extruded her catheter preoperatively but now is adequately controlled by this method. Urinary Frequency. Urinary frequency shows a trend toward improvement although this is not significant. The overall change is from 10.5 times a day ( SD 5.47) to 7.5 times a day (:t: SD 2.2, p not significant). Urge ncontinence. This disappeared in five of the nine cases, and continues to be well controlled in the long-term follow-up. Sexual Potency and Bowel Function. There was no deterioration of sexual potency among the four men operated on. One patient with multiple sclerosis who had been impotent for 5 years had potency transiently restored. Another patient reported a marked increase in the frequency of sexual activity. No significant disturbance of bowel function has been recorded and in particular no constipation has occurred. The patient with multiple sclerosis obtained some spontaneous bowel action after 3 years of manual evacuation. J. Neurosurg. Volume 44, February, 1976 Discussion The aim of this technique is to increase functional bladder capacity by reducing uninhibited activity without compounding the problem of incontinence by interfering with sphincter function. The treatment has been extended to patients without neurological disease. Early results show that two patients have excellent results, five are improved, and two remain unchanged. This initial response to surgery is very encouraging as far as bladder function is concerned. No patient has been made worse by the procedure but there are two conspicuous problems. The procedure failed to improve two patients, and voluntary sphincter function has been depressed, although in no case has this been clinically significant. Both the failures were in young women who suffered from epilepsy. n one patient an S-4 nerve section was performed on the basis of sacral block results, which were not confirmed by stimulation at operation. This patient has since had her diurnal symptoms improved by an S-3 neurectomy. t is our conclusion that intraoperative stimulation is a more accurate means of localizing the innervation of the bladder than are sacral nerve 183

9 M. J. Torrens and H. B. Griffith blocks with anesthetic. We feel that intraoperative stimulation and recording is mandatory. Preoperative investigation by selective sacral nerve blocks is probably an unnecessary procedure except in cases of grossly asymmetrical, partial upper motor neuron lesions. n these cases, sacral blocks are the only way to identify preoperatively the final common pathway of asymmetrically mediated neural hyperactivity. n the other patient regarded as a failure, three nerve roots were ablated but urge incontinence and enuresis persisted. This patient had a thick-walled bladder that could not be distended under any form of anesthesia to more than 315 ml. We conclude that if the capacity after anesthesia is less than 400 ml, neurectomy should not be performed, and hydrostatic balloon distension or enterocystoplasy should be recommended. t is therefore essential that some test of maximum potential bladder capacity should be used in all cases. Although the analysis of sphincter pressure shows that the voluntary activity of the urethral sphincter is reduced after neurectomy, this has not affected the threshold of continence because the effect on the sphincter remains less profound than that on the bladder. Nevertheless, it is important that less destructive surgical techniques should be sought. The results of sacral rootlet stimulation have independently confirmed the observations made by Harman 5 and Toczek, et al., ~5 that the somatic and parasympathetic fibers are topographically distinct at nerve root level. Microscopic dissection should allow the isolation of detrusor innervation, and a selective rootlet neurectomy may then be performed. Section of the whole nerve root may still be indicated in cases which combine an uninhibited bladder with a spastic or discoordinated sphincter. Assessment of the results suggests that the best clinical response follows bilateral neurectomy at one level. A single nerve section is inadequate in these more severely incontinent patients. Triple nerve section may provoke a residual urine. The level for most operations would appear to be S-3, but this should always be confirmed by stimulation. The combination of adult enuresis and diurnal urge incontinence is particularly difficult to treat. The neuropathological and neuropsychiatric abnormalities in such cases remain items of extreme contention. The tech- nique cannot be recommended for those who suffer from enuresis without any diurnal symptoms. The follow-up at present lies between 1 and 3 years, and it is therefore too early to be optimistic about long-term results. t is to be expected that the bladder will regain tone after denervation. Sundin and DahlstrSm 12 have shown that a marked proliferation of alpha adrenergic endings occurs in the bladder after section of its parasympathetic innervation. Regression and recurrence of enuresis has been noted after the first year. The initial results are sufficiently encouraging for this form of treatment to be continued in patients with diurnal symptoms. The technique remains experimental and requires continuous reassessment but seems a relatively atraumatic procedure for the patient. We would offer the following criteria for the selection of incontinent patients for sacral neurectomy: 1. The case should be one of urge or reflex incontinence where more conservative treatment has failed. 2. Urodynamic assessment should confirm that the incontinence is due to uninhibited activity, exclude sphincter weakness and outflow-tract obstruction, and show that sensation from the bladder and urethra is relatively intact. 3. A potential functional capacity in excess of 400 ml must be demonstrated by caudal block, sacral root block, or general anesthetic. n incomplete upper motor neuron lesions with an asymmetrical or focal neurological deficit, selective sacral nerve blocks should be performed to elucidate focal abnormalities of bladder innervation. n all cases intraoperative nerve stimulation should confirm the root level supplying the majority of bladder fibers. Rootlet stimulation at this level should allow in future cases the isolation of bladder and sphincter innervation. The neurectomy usually should be bilateral at one root level. Where there is bladder hyperactivity with a normal sphincter, selective section of parasympathetic rootlets only may be indicated. Where bladder and sphincter spasm are combined, total root section can be carried out. ]84 J. Neurosurg. Volume 44 February, 1976

10 Sacral neurectomy for uninhibited bladder Acknowledgments We wish to thank the many surgeons in the Southwest who have referred their cases to us. References 1. Brown M, Wickham JEA: The urethral pressure profile. Br J Urol 41: , Editorial. Br J Child Dis 1: , Garrelts B yon: Analysis of micturition. A new method of recording the voiding of the bladder. Acta Chir Scand 112: , Garrelts B von, Strandell P: Continuous recording of urinary flow rate. Scand J Urol Nephrol 6: , Harman NB: The pelvic splanchnic nerves: an examination into their range and character. J Anat Physiol 33: , Heimburger RF, Freeman LW, Wilde N J: Sacral nerve innervation of the human bladder. J Neurosurg 5: , Meirowsky AM, Scheibert CD, Rose DK: ndications for neurosurgical establishment of bladder automaticity in paraplegia. J Uroi 67: , Misak S J, Bunts RC, Ulmer JL, et al: Nerve interruption procedures in the urologic management of paraplegic patients. J Urol 88: , Munro D: The rehabilitation of patients totally paralyzed below the waist: with special reference to making them ambulatory and capable of earning their living. 1. Anterior rhizotomy for spastic paraplegia. N Engl J Med 233: , Nagib A, Leal J, Voris HC: Successful control of selective anterior sacral rhizotomy for treatment of spastic bladder and ureteric reflux in paraplegics. Med Serv J Can 22: l, 1966 l l. Rockswold GL, Bradley WE, Chou SN: Differential sacral rhizotomy in the treatment of neurogenic bladder dysfunction. Pre- liminary report of six cases. J Neurosurg 38: , Sundin T, Dahlstr5m A: Sympathetic innervation of the urinary bladder and urethra in the normal state and after parasympathetic denerration at the spinal root level. An experimental study in cats. Scand J Urol Nephrol 7: , Susset JG, Pinheiro J, Otton P, et al: Ph6nolisation et neurotomie s61ective dans la traitement de la dysfonction v6sicale neurog6ne par 16sion centrale incomplete. J Uroi Nephrol (Paris) 75 [Suppl 12]: , Thiermann E: Der sacrale Zugang in der Urologic. Z Urol 46: , Toczek S, Gargour G, Wessenhop A J, et al: Selective sacral rhizotomy for improvement of spastic bladder function. Presented at the Symposium on Microneurosurgery, Cincinnati, Ohio, June 12, Toczek S, McCullough DC, Gargour GW, et al: Selective sacral rootlet rhizotomy for hypertonic neurogenic bladder. J Neurosurg 42: , Torrens M J: The effect of selective sacral nerve blocks on vesical and urethral function. J Urol 112: , Torrens M J, Collins CD: Urodynamic assessment in adult enuresis. Br J Urol 47: , Unstable Bladder Symposium. nstitute of Urology, University of London, October Worth PHL, Turner-Warwick R: The treatment of interstitial cystitis by cytolysis with observations on cystoplasty. Br J Urol 45:65-71, 1973 Mr. Torrens was the recipient of a Medical Research Council research fellowship. Address reprint requests to: Michael J. Torrens, F.R.C.S., Department of Neurosurgery, Frenchay Hospital, Bristol, BS16, 1LE, England. J. Neurosurg. Volume 44 February, 1976 ]85