Review of Sacral Electrical Stimulation in the Management of the Neurogenic Bladder G.H. Creasey, MD Spinal Cord Injury Unit, MetroRealth Centerfor Rehabilitation, Cleveland, OR
D.R. Bodner, MD Department of Urology, Case u-istern Reserve University, Cleveland, OR In patients with spinal cord injury above the conus medullaris, electrical stimulation of the sacral anterior nerve roots can produce micturition with low reswual volumes of urine and reduced urinary tract infection. Vowing pressures appear to be maintained at safe levels by the use of an intermittent pattern of stimulation. The procedure is usually combined with division of the sacral posterior roots, which increases bladder capacity and continence; this also increases bladder compliance, which may be protective for the upper urinary tracts. The procedure has now been applied in about 900 patients with spinal cord injury, some of whom have been followed up for over 15 years. The nerves do not appear to be damaged by long-term stimulation and technical faults with the equipment are now uncommon. Keywords: Electric stimulation; bladder; paraplegia; quadriplegia; spinal nerve roots
Electrical stimulation can be applied to the body for several different purposes. Diagnostic electrical stimulation is widely used to distinguish innervated from denervated muscle and to test for the integrity of neural pathways. Attempts to produce benefit which persists after cessation of stimulation are sometimes given the term of therapeutic electrical stimulation. This should be distinguished from functional electrical stimulation, in which useful function is only produced during stimulation, although this may have long-term benefit to the patient. The cardiac defibrillator is an example of therapeutic stimulation, whereas functional stimulation is exemplified by the pacemaker. In the lower urinary tract, many attempts have been made over the last few decades to improve function by electrical stimulation. Most of these can be considered as aiming to achieve therapeutic stimulation, by obtaining lasting improvement
as a result of stimulation applied to the surface of the body briefly or intermittendy. However, the availability of more reliable devices, which can be implanted permanendy into the body, has made it possible and convenient to apply stimulation repeatedly or continuously in the long term for restoration of function. In considering the application of electrical stimulation to improve function of the lowerurinary tract, a distinction should be made as to whether the intention is to improve continence, voiding, or both.
Continence Improvement of continence may depend on reduction of unwanted bladder contraction, improvement in sphincter tone, or both. Relaxation of the bladder. Electrical stimulation of sacral afferent nerves has frequendy been NeuroRehabil1994; 4(4):266-274 Copyright © 1994 by Butterworth-Heinemann
Sacral Electrical Stimulation
shown to reduce incontinence, probably by reducing hyperactivity of the bladder, whether applied via electrodes in the anus or vagina, on the sacral dermatomes, on the pudendal nerves, epidurally, or on the sacral nerves in the spinal canal. This may be part of the mechanism of neuromodulation as applied to the lower urinary tract. 1 Contraction of the sphincter. Stimulation of sacral afferent nerves can produce reflex activation of the efferent nerves to the sphincter, but this reflex is likely to accommodate too rapidly to provide lasting contraction. The external urethral sphincter can also readily be made to contract by electrical stimulation of efferent fibers in the pudendal nerve via electrodes in the anus or vagina, or by stimulation of sacral nerves or roots via implanted electrodes. However, fatigue is likely to reduce the pressure generated in the urethra to a level which can be overcome by a strong bladder contraction. Stimulation via external devices has been used with some benefit in patients with non-neurogenic bladders, although the inconvenience of repeated application of the electrodes has limited such use. 2 The improvement in continence derived from external stimulators has probably been mainly due to their effect in reducing bladder contraction.
Voiding In patients with a neurogenic bladder, attempts to improve voiding by using electrical stimulation to produce bladder contraction have used electrodes on the bladder itself,3,4 the pelvic splanchnic nerves,5,6 the conus medullaris, 7 the sacral nerves, 8 and the sacral anterior roots. 9 All of these techniques have had to contend with the fact that contraction of the bladder has usually been accompanied by contraction of the external urethral sphincter, produced either reflexly from stimulation of sensory fibers or by direct activation of somatic motor fibers. Nashold et al. inserted electrodes into the conus medullaris in an attempt to stimulate the sacral parasympathetic nucleus without stimulation of the anterior horn cells supplying the external sphincter, and produced clinical benefit in a few patients, but this technique is no longer in use. Tanagho 10 and Schmidt 11 have produced clinical benefit in a similar number of
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patients with spinal cord injury by placing electrodes on the sacral nerves containing motor and sensory fibers, often combining the implantation with division of the sensory fibers extradurally or intradurally. Brindley 9,12,13 has developed a technique of implanting electrodes intradurally on the sacral anterior roots, thereby reducing stimulation of sensory nerves although still activating somatic efferent fibers when parasympathetic fibers are activated. It is possible to produce voiding by making use of the fact that the striated muscle of the sphincter contracts and relaxes more rapidly than the smooth muscle ofthe detrusor. Intermittent bursts of stimulation can be timed so that the peaks of contraction of sphincter and bladder are out of phase with each other; while the sphincter relaxes rapidly at the end of each burst, pressure in the bladder is sufficiently maintained to produce micturition between the bursts (see Figure 1). The implantation of a stimulator to produce effective micturition is often combined with posterior sacral rhizotomy for the reasons given below. The technique is in use in over 15 countries and has been of clinical benefit to about 800 patients, most with suprasacral spinal cord injury; follow-up now extends to over 15 years in some of
PRESSURE
FLOW
110'~~~: 10 sec
INTERMITTENT STIMULATION Figure 1. Pressure recorded in the human male bladder via a 4FG ureteric catheter inserted through the urethra, and urine flow rate, following stimulation with the Finetech-Brindley bladder controller. Note that urine flows in the intervals between stimulation.
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these patients. The remainder of this article will therefore be devoted to a review of the Brindley technique.
SELECTION OF PATIENTS Patients with complete spinal cord injury above the conus medullaris and inefficient reflex micturition may be considered for an implanted stimulator at any time after the first year of injury, particularly if they have complications such as frequent or chronic urine infection or autonomic dysreflexia triggered by bladder or bowel. In patients with incomplete injuries, it is wise to wait until two years after injury to allow any recovery to occur, and it is necessary to determine, by testing for pain sensation in the sacral dermatomes, whether the implant is likely to be painful. Patients with recurrent infection have more to gain from effective voiding than those without. Those with detrusor hyper-reflexia causing persistently high bladder pressures endangering renal function or with autonomic dysreflexia triggered by bladder or bowel are likely to benefit from posterior rhizotomy; this operation provides the opportunity to implant a stimulator which then provides them with a preferable alternative to intermittent catheterization. Women with reflex incontinence have more to gain from posterior rhizotomy than men, because of the lack of satisfactory urine collecting devices for females and the fact that they have less to lose from the rhizotomy. Men with poor or absent reflex erection have more to gain and less to lose than those whose reflex erections already suffice for coitus. Paraplegic men are more likely to benefit from continence, while some tetraplegic men may continue to wear an appliance during the day because of difficulty in transferring from a wheelchair. Some patients with multiple sclerosis are suitable, subject to the reservations above. A few adult patients with meningomyelocele may also be suitable, but the growth of young children would be likely to displace the electrodes if implanted in them. 14
Combination of Implantation with Posterior Rhizotomy The major advantages of posterior rhizotomy are: 1. The abolition of uninhibited reflex bladder contractions, thereby increasing bladder capacity and abolishing reflex incontinence 2. Restoration of bladder compliance to normal (except in those cases where poor compliance is due to fibrosis), thereby protecting the upper tracts 3. Abolishing reflex contraction of the sphincter, thereby reducing detrusor-sphincter dyssynergia 4. The abolition of autonomic dysreflexic attacks triggered from bladder or rectum. The disadvantages of posterior rhizotomy include: 1. The loss of reflex erection and reflex ejaculation if these are present. Erection is commonly produced by the implant and even more effectively by injection of papaverine into the corpora cavernosa. Seminal emission can now be produced from a high proportion of spinal cord injured men by rectal probe electrostimulation. 2. The loss of reflex micturition. The micturition produced by the implant is usually more effective than reflex micturition, but if the implant is not used for any reason a patient will usually have to resort to intermittent catheterization. 3. The loss of perineal sensation if present. A decision about posterior rhizotomy should therefore be made in each case. It is now, however, the usual practice for the implantation to be accompanied by posterior rhizotomy.
PREOPERATIVE INVESTIGATION It is essential that a patient undergoing implantation of a sacral anterior root stimulator should have intact parasympathetic efferent fibers in the
Sacral Electrical Stimulation
sacral anterior roots, capable of producing bladder contraction. This can usually be adequately determined by cystometry,14 but in case of doubt, electrical stimulation can be applied to these nerves as they travel in the pelvic plexus by using a rectal electrode l5 or by inserting needle electrodes temporarily in the posterior sacral foramina. 16 Urinary tract function should be documented thoroughly, particularly to confirm adequate bladder capacity and exclude severe fibrosis of the bladder walJ.l7 If the patient is able to void, the pressure at which this occurs should be compared with voiding pressure after operation. Ureteric reflux and hydronephrosis are not necessarily contra-indications and may in fact be indications for posterior rhizotomy. Documentation of penile erection and bowel function is also desirable, particularly if posterior rhizotomy is planned. Imaging of the lumbosacral spine is of value for confirming adequate access to the spinal canal and excluding structural abnormalities. Separation of the spinal roots intradurally can be complicated by adhesions due to previous subarachnoid hemorrhage (such as from a bullet or stab wound) or spinal meningitis or myelography with an oily contrast medium,14 and magnetic resonance imaging (particularly with gadolinium enhancement) may aid in the preoperative detection of these adhesions. 18
SURGICAL IMPLANTATION The surgical technique developed by Brindley l4 involves a laminectomy from L4-S2 and opening of the dura to expose the cauda equina. The sacral anterior roots supplying the bladder are identified by per-operative stimulation while recording bladder pressure, and electrodes are placed around these roots. Cables from the electrodes are brought out through a grommet sutured to the dura, which is then closed, and tunneled subcutaneously to a pocket on the front of the chest or abdomen where a radio receiver is implanted. The procedure is usually combined with intradural division of the posterior roots of S2-S5.
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Alternatively the posterior roots can be divided at their entry into the conus medullaris. This can be done in a separate operation before or after electrode implantation, and may be the only form of rhizotomy possible when adhesions of the cauda equina are present.
POSTOPERATIVE TESTING The implant should be tested on the third or fourth postoperative day and again at one week; reduced responses at one week, particularly of somatic muscles, may indicate Wallerian degeneration caused by axonotmesis at operation. The patient can, however, be reassured that the motor responses seen at three days are likely to return. 14 Urodynamic studies are used to guide the setting of stimulus parameters to give an acceptable voiding pressure and rate and pattern of flow, and to document the urological effects of any rhizotomy. The stimulus program should be checked between one and three months after the operation since the response of the bladder may change with repeated use; thereafter adjustment is recommended at least every two years, provided that urinary tract function is followed carefully.
RESULTS Results obtained in the first 50 patients to receive the Finetech-Brindley stimulator were reported by Brindley et al. in 1986 and 1990. Reports have been published from other centers in Britain, 19-23 France,24,25 Germany,26 Austria,27 Denmark,28 and New Zealand 29 ; and Van Kerrebroeck 3o has collected data on 184 patients treated in 22 centers. The stimulator was the subject of conferences at Le Mans in France in 1989 31 and Halifax in Nova Scotia in 1992. 32 By the end of 1993 about 900 implants had been performed, almost all in patients with spinal cord injury, at over 42 centers in 16 countries.
Micturition The majority of subjects with the Finetech stimulator use it routinely for producing micturition at home four to six times per day. Ofthe 184 patients
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reported by Van Kerrebroeck,30 157 (85%) used the stimulator alone; a further 4 required a subsequent sphincterotomy in order to use it and a further 8 combined its use with intermittent catheterization, resulting in an overall stimulator usage rate of over 90%.
Continence of Urine
McDonagh et al. 33 reviewed 15 incontinent patients who had had complete sacral posterior rhizotomy in conjunction with implantation of the Finetech stimulator, and reported that 13 no longer required any form of incontinence appliance. Detrusor hyper-reflexia was abolished in all but 1 patient, who remained incontinent, as did 1 patient who had had two previous transurethral sphincterotomies. Of 41 early users followed up for 5-13 years, 35 reported continence day and night; of the 6 who were not continent, 4 had had previous bladder-neck resections. 34 In later multicenter data, continence is reported to have been achieved in 159 of 184 patients (86%). Stress incontinence and reflex incontinence accounted for approximately equal numbers of those who did not achieve continence. 3o
Residual Urine In the report by Van Kerrebroeck 30 on 184 cases, of whom 170 were using the Finetech stimulator, residual volume in the bladder following implantdriven micturition was reduced in 151 patients (89% of users) to less than 30 ml and in 95% of users to less than 60 ml. No user had a residual greater than 200 ml.
Urodynamics and Effects on the Urinary Tract
Van Kerrebroeck 17 and others9,33,35 have reported the results of urodynamic investigation showing increases in bladder capacity and compliance, which are probably mainly due to posterior rhizotomy. Concern was initially expressed that the cocontraction of bladder and external sphincter would lead to dangerously high bladder pressures, resulting in trabeculation of the bladder, ureteric reflux, and hydronephrosis. When the sphincter
is closed, the pressure in the bladder depends on the stimulus parameters applied to the parasympathetic efferent fibers, particularly the stimulus amplitude, pulse width, frequency, burst length, and gap length, and these parameters can be varied to control the detrusor pressure. Detrusor pressure has been recorded during stimulation and voiding by several groups;17,27,29,35 in general, data available to date indicates that trabeculation, ureteric reflux, and hydronephrosis have tended to decrease in patients who have undergone implantation and posterior rhizotomy. In the first 50 patients to receive the Finetech implant, bladder trabeculation as observed on intravenous urography or cystography was reported to have decreased in 13 patients when followed up at one to nine years. No patient in this group showed evidence of increased trabeculation. 9 In the same group, no patients showed reflux at postoperative cystography who had not done so preoperatively. Seven showed reflux on one or both sides preoperatively and four of these did not do so postoperatively. Three continued to reflux at four years, ten months, and five months follow-up respectively. In a multicenter review of 184 patients, reflux was present in 7 patients before the operation. After implantation it was improved or abolished in 7 of these and persisted in 2. No patient in this group developed reflux with the use of the stimulator. 30 In another series of 22 patients, 3 had abnormal upper tracts prior to implantation and of these, 2 resolved and 2 deteriorated. After undergoing sphincterotomy the latter 2 were able to continue using the stimulator. One patient developed hydronephrosis after implantation. 22 In the multicenter review not including the above patients, eight of 184 subjects showed upper-tract dilatation preoperatively. Of these, the dilatation improved in 7 and deteriorated in 1. No patient in this series was found to develop uppertract dilatation for the first time after implantation of the stimulator. Further long-term follow-up of these patients is desirable to confirm these findings and to distinguish the benefits of stimulation from those of posterior rhizotomy.
Sacral Electrical Stimulation
Urine Infection Apart from an early paper by Brindley,34 culture results have not been reported in detail, but a substantial decrease in symptomatic urine infection with or without pyrexia has however been reported by many groups following the use of the implant. 9.24.27.29-31
Autonomic Dysreflexia Among the first 50 patients to receive the implant, stimulation sometimes caused mild headache; blood pressure changes were not reported. The headache was no worse than that caused by reflex micturition in the same patient and did not prevent use of the device. However, one tetraplegic patient operated on subsequently has been unable to use the implant because of dysreflexia. 34 Autonomic dysreflexia was subsequently reported to be a problem in 26 of 184 patients before operation but in only 10 postoperatively. No patient in this series developed autonomic dysreflexia following the surgery.30 In some patients autonomic dysreflexia present before operation has improved with the control of infection, and the dysreflexia is abolished by the posterior rhizotomy commonly performed at the time of implantation.
COMPLICATIONS Among the early patients, three were unable to use the Finetech implant because of pain on stimulation, and four others found use of the stimulator to some extent painful. 34 All these patients had preserved pain sensitivity in the sacral dermatomes preoperatively. A modified implant has now been developed for use in such patients. Neuropraxia or axonotmesis of one or more nerve roots at the time of operation can be most sensitively detected by testing for any loss of skeletal muscle responses to the use of the stimulator during the first postoperative week, and may also become evident as a loss of bladder response. Judged by somatic criteria, Sauerwein et al. reported that in early cases it was common in intradural operations and very common in extradural implants, although less frequent as surgeons
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gained experience. 26 ,36 Anterior roots almost always recover but bladder responses may take from two to six months to return, thus delaying the use of the implant for micturition. Accidental damage to posterior roots has in no case been followed by functional recovery; deliberate posterior rhizotomy is now recommended for most cases. 14 Several patients have now been using the Finetech stimulator for between 10 and 15 years without apparent deterioration in nerve function. The histological appearance of stimulated nerves was reported as normal in the case of two patients who died (one by suicide and one from myocardial infarction) after using the implant for 3 and 5 years respectively. 9 Among the first 50 Finetech implants, 7 had a persistent collection of cerebrospinal fluid along the line of the subcutaneous cables to the receiver. This was dealt with by local repair of the dura. Seven others had a collection which subsided spontaneously. 9 The implant has now been modified by the addition of a grommet to seal the cables to the dura, and the incidence of this complication appears to have been greatly reduced, although figures have not yet been published. Infection of the Finetech implants has been rare, particularly since a technique of coating them with antibiotics was introduced in 1982. Rushton 37 reported that lout of 104 coated implants had become infected, and in this case infection appeared to have been introduced at a subsequent operation to close a leak of cerebrospinal fluid. Among early implants not coated with antibiotic, 2 out of 40 became infected. The infection rate for a variety of implants has been shown to be significantly reduced by the antibiotic coating, but not by systemic perioperative antibiotics. Technical faults in the implanted equipment have been rare. The commonest site for faults has been in cables, which are sometimes mechanically damaged by movement. Repair or replacement of the Finetech device has been possible in all cases where this has been attempted and no fault is known to have led to permanent discontinuation of use of the implant. Failures in the external transmitter have primarily been due to breaks in the antenna lead and
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have been more common, but do not require reoperation.
DISCUSSION Continence Increases in bladder capacity measured by cystometry are probably largely attributable to posterior rhizotomy. Accidental damage to posterior roots may have played a part in some patients where rhizotomy was not attempted. A decrease in residual urine, as a result of stimulated voiding, also allows a patient a longer period of bladder filling before reaching capacity. Reduction of infection should also improve the compliance of the bladder and reduce the likelihood of contraction in response to spinal or nonspinal reflexes.
ons to the bladder and in the large myelinated axons to the striated sphincter. However, at higher currents, action potentials can be arrested at the anodes by hyperpolarization of the large axons, while allowing action potentials to proceed in the smaller axons to the bladder. As a result, contraction of the bladder can be produced with little contraction of the external sphincter. (See Figure 2.) In this animal model, activation of the small axons also produces contraction of smooth muscle in the bladder neck and tumescence of the penis in the male, and both these factors hinder urine flow. However, the technique appears to have promise as a means of producing continuous stream micturition in man with lower voiding pressures, by reducing substantially the urethral resistance offered by the external sphincter.
Detrusor-sphincter Dyssynergia Continuous stimulation of sacral anterior roots sufficient to produce contraction of the detrusor also produces contraction of the external sphincter, and has been found in the past to lead to poor voiding and high intravesical pressures which may be dangerous to the upper tracts unless measures are taken to reduce sphincter contraction. Intermittent stimulation has been used to produce bladder and sphincter contractions out of phase with each other, adjusting the timing and magnitude of the stimuli to control voiding pressures. This approach has resulted in a high proportion of patients voiding with stimulation, and the longterm results to date indicate that ureteric reflux and hydronephrosis have more often improved than deteriorated with use of the stimulator. Brindley 12 suggested the use of anodal block to prevent propagation of action potentials in the large somatic axons to the external sphincter while allowing propagation in the small parasympathetic fibers to the detrusor, and demonstrated the principle experimentally. In our laboratory this has been developed using tripolar electrodes chronically implanted in dogs and activated with wide quasitrapezoidal stimuli. When using lowstimulus amplitudes, these stimuli generate action potentials at the cathodes both in the small myelinated preganglionic parasympathetic efferent ax-
SUMMARY In patients with spinal cord injury above the conus medullaris, electrical stimulation of the sacral anterior nerve roots can produce micturition with low residual volumes of urine and reduced urinary tractinfection. Voiding pressures appear to be maintained at safe levels by the use of an intermittentpattern of stimulation. The procedure is usually ~,-------------------------------,
BLADDER URETHRA
o
0.1
Current (mA)
0.5
Pressures recorded in the canine male urethra and bladder using microtip pressure transducers inserted via the urethra. Stimulation applied to S2 anterior root of one side via a tripolar cuff electrode, using a quasi trapezoidal waveform of pulse width 500 IJ..sec with exponential training edge of 500 IJ..sec and frequency 20 Hz. Figure 2.
Sacral Electrical Stimulation
combined with division of the sacral posterior roots, which increases bladder capacity and continence; this also increases bladder compliance, which may be protective fur the upper-urinary tracts. The procedure has now been applied in about
273
900 patients with spinal cord injury, some of whom have been followed up for over 15 years. The nerves do not appear to be damaged by long-term stimulation, and technical faults with the equipment are now uncommon.
REFERENCES 1. Thon WF, Baskin LS, Jonas U, Tanagho EA, Schmidt RA Neuromodulation of voiding dysfunction and pelvic pain. World] Urol 1991; 9:138-141. 2. Edwards L, Malvern]. Electronic control of continence: A critical review of the present situation. Brit] Urol1972; 44:467-472. 3. Bradley WE, Timm Gw, Chou SN. A decade of experience with electronic stimulation of the micturition reflex. UrolInt 1971; 26:283-303. 4. Halverstadt DB, Parry WL. Electronic stimulation of the human bladder: Nine years later.] Urol1975; 113:341-344. 5. Burghele T. Electrostimulation of the neurogenic urinary bladder. In: Lutzmeyer W, et al. eds. Urodynamics. Berlin: Springer-Verlag, 1973, 319-322. 6. Kaeckenbeeck B. Electrostimulation de la vessie des paraplegiques. Technique de Burghele-IchimDemetrescu. Acta Urol Belg 1979; 47:137-140. 7. Nashold BS, Friedman H, Grimes]. Electrical stimulation of the conus medullaris to control the bladder in the paraplegic patient: A ten year review. Appl Neurophysioll981; 44:225-232. 8. Tanagho EA, Schmidt RA. Electrical stimulation in the clinical management of the neurogenic bladder.] Urol1988; 140:1331-1339. 9. Brindley GS, Polkey CE, Rushton DN, et al. Sacral anterior root stimulators for bladder control in paraplegia: The first 50 cases.] Neurol Neurosurg Psychiat 1986; 49: 11 04-1114. 10. Tanagho EA, Schmidt RA, Orvis BR. Neural stimulation for control of voiding dysfunction: A preliminary report in 22 patients with serious neuropathic voiding disorders. ] Urol 1989; 142:340-345. 11. Schmidt RA Advances in genitourinary neurostimulation. Neurosurgery 1986; 19: 1041-1044. 12. Brindley GS, Craggs MD. A technique for anodally blocking large nerve fibres through chronically implanted electrodes.] Neurol Neurosurg Psychiatr 1980; 43: 1083-1090. 13. Brindley GS, Rushton DN. Long-term follow-up of patients with sacral anterior root stimulator implants. Paraplegia 1991; 28:469-475. 14. Brindley GS. The Finetech-Brindley bladder control-
ler: Notes for surgeons and physicians. Finetech Ltd., 13 Tewin Court, Welwyn Garden City, Herts, England, 1991. 15. Brindley GS, Electroejaculation: Its technique, neurological indications and uses.] Neurol Neurosurg Psychiat 1981; 44:9-18. 16. Markland C, Merrill D, Chou S, et al. Sacral nerve root stimulation: A clinical test of detrusor innervation.] Urol 1972; 107:772-776. 17. Van Kerrebroeck PEV, Koldewijn EL, Wijkstra H, et al. Urodynamic evaluation before and after intradural posterior sacral rhizotomies and implantation of the Finetech-Brindley anterior sacral root stimulator. Urodinamica 1992; 1:7-16. 18. Ross JS, Masaryk TJ, Modic MT, et al. MR imaging oflumbar arachnoiditis. Am] Neuro Radiology 1987; 8:885-892. 19. Binnie NR, Smith AN, Creasey GH, et al. Motility effects of electrical anterior sacral nerve root stimulation of the parasympathetic supply of the left colon and rectum in paraplegic subjects. ] Gastrointestinal Motility 1990; 2(1):12-17. 20. Binnie NR, Smith AN, Creasey GH, et al. Constipation associated with chronic spinal cord injury: The effect of pelvic parasympathetic stimulation by the Brindley stimulator. Paraplegia 1991; 29:463-469. 21. MacDonagh R, Smallwood R, Forster D, et al. Control of defecation in patients with spinal injuries by stimulation of sacral anterior nerve roots. Brit Med] 1990a; 300:1494-1497. 22. Robinson LQ, Grant A, Weston P, et al. Experience with the Brindley anterior sacral root stimulator. Br] Urol 1988; 62:553-557. 23. VarmaJS, Binnie NR, Smith AN, etal. Differential effects of sacral anterior root stimulation on anal sphincter and colorectal motility in spinally injured man. Brit] Surg 1986; 73:478-482. 24. Egon G, Colombel P, des Roseaux F, et al. Electrostimulation des racines sacrees anterieures chez Ie paraplegique. Annales de Readaptation et de Medecine Physique 1989; 32:47-57. 25. Herlant M, Colombel P. Electrostimulation intradurale des racine sacrees anterieures chez les
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paraplegiques. Annales de Readaptation et de Medecine Physique 1986; 29:405-411. Sauerwein D. Die operative Behandlung del' spastischen Blasenlahmung bei Querschnittlahmung [Surgical treatment of spastic bladder paralysis in paraplegic patients. Sacral deafferentation with implantation of a sacral anterior root stimulator]. Urologe A 1990; 29: 196-203. Madersbacher H, Fischer H, Ebner A. Anterior sacral root stimulator (Brindley): experiences especially in women with neurogenic urinary incontinence. Neurourol Urodyn 1988; 7:593-601. Nordling], Hald 'l~ Kristensen]K, et al. Implanterbar radiostyret sakralrodstimulator til kontrolleret vandledning [An implantable radio-controlled sacral nerve root stimulator for control of urination]. Ugeskr Laeger 1988; 150:978-980. Arnold EP, Gowland Sp, MacFarlane MR, et al. Sacral anterior root stimulation of the bladder in paraplegics Aust NZJ Surg 1986; 56:319-324. Van Kerrebroeck PEV. World wide experience with the Finetech-Brindley sacral anterior root stimulator. Neurourol Urodyn 1993; 12(5):497-503. Colombe! P, Egon G. Lclectrostimulation des
32. 33.
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racines sacrces antcrieures. Ann Urol Paris 1991; 25:48-52. Madersbacher H, Fischer J. Sacral anterior root stimulation: Prerequisites and indications. Neurourol Urodyn 1993; 12(5):489-494. MacDonagh RP, Forster DM, Thomas DG. Urinary continence in spinal injury patients following complete sacral posterior rhizotomy. Br ] Urol 1990b; 66:618-622. Brindley GS, Polkey CE, Rushton DN. Sacral anterior root stimulators for bladder control in paraplegia. Paraplegia 1982; 20:365-381. Cardozo L, Krishnan KR, Polkey CE, et al. Urodynamic observations on patients with sacral anterior root stimulators. Paraplegia 1984; 22:201209. Sauerwein D, Ingunza W, Fischer ], et al. Extradural implantation of sacral anterior root stimulators. ] Neurol Neurosurg Psychiatry 1990; 53:681-684. Rushton DN, Brindley GS, Polkey CE, et al. Implant infections and antibiotic-impregnated silicone rubber coating. ] Neurol Neurosurg Psychiatry 1989; 52(2):223-229.
D.R. Bodner, MD Department of Urology, Case u-istern Reserve University, Cleveland, OR In patients with spinal cord injury above the conus medullaris, electrical stimulation of the sacral anterior nerve roots can produce micturition with low reswual volumes of urine and reduced urinary tract infection. Vowing pressures appear to be maintained at safe levels by the use of an intermittent pattern of stimulation. The procedure is usually combined with division of the sacral posterior roots, which increases bladder capacity and continence; this also increases bladder compliance, which may be protective for the upper urinary tracts. The procedure has now been applied in about 900 patients with spinal cord injury, some of whom have been followed up for over 15 years. The nerves do not appear to be damaged by long-term stimulation and technical faults with the equipment are now uncommon. Keywords: Electric stimulation; bladder; paraplegia; quadriplegia; spinal nerve roots
Electrical stimulation can be applied to the body for several different purposes. Diagnostic electrical stimulation is widely used to distinguish innervated from denervated muscle and to test for the integrity of neural pathways. Attempts to produce benefit which persists after cessation of stimulation are sometimes given the term of therapeutic electrical stimulation. This should be distinguished from functional electrical stimulation, in which useful function is only produced during stimulation, although this may have long-term benefit to the patient. The cardiac defibrillator is an example of therapeutic stimulation, whereas functional stimulation is exemplified by the pacemaker. In the lower urinary tract, many attempts have been made over the last few decades to improve function by electrical stimulation. Most of these can be considered as aiming to achieve therapeutic stimulation, by obtaining lasting improvement
as a result of stimulation applied to the surface of the body briefly or intermittendy. However, the availability of more reliable devices, which can be implanted permanendy into the body, has made it possible and convenient to apply stimulation repeatedly or continuously in the long term for restoration of function. In considering the application of electrical stimulation to improve function of the lowerurinary tract, a distinction should be made as to whether the intention is to improve continence, voiding, or both.
Continence Improvement of continence may depend on reduction of unwanted bladder contraction, improvement in sphincter tone, or both. Relaxation of the bladder. Electrical stimulation of sacral afferent nerves has frequendy been NeuroRehabil1994; 4(4):266-274 Copyright © 1994 by Butterworth-Heinemann
Sacral Electrical Stimulation
shown to reduce incontinence, probably by reducing hyperactivity of the bladder, whether applied via electrodes in the anus or vagina, on the sacral dermatomes, on the pudendal nerves, epidurally, or on the sacral nerves in the spinal canal. This may be part of the mechanism of neuromodulation as applied to the lower urinary tract. 1 Contraction of the sphincter. Stimulation of sacral afferent nerves can produce reflex activation of the efferent nerves to the sphincter, but this reflex is likely to accommodate too rapidly to provide lasting contraction. The external urethral sphincter can also readily be made to contract by electrical stimulation of efferent fibers in the pudendal nerve via electrodes in the anus or vagina, or by stimulation of sacral nerves or roots via implanted electrodes. However, fatigue is likely to reduce the pressure generated in the urethra to a level which can be overcome by a strong bladder contraction. Stimulation via external devices has been used with some benefit in patients with non-neurogenic bladders, although the inconvenience of repeated application of the electrodes has limited such use. 2 The improvement in continence derived from external stimulators has probably been mainly due to their effect in reducing bladder contraction.
Voiding In patients with a neurogenic bladder, attempts to improve voiding by using electrical stimulation to produce bladder contraction have used electrodes on the bladder itself,3,4 the pelvic splanchnic nerves,5,6 the conus medullaris, 7 the sacral nerves, 8 and the sacral anterior roots. 9 All of these techniques have had to contend with the fact that contraction of the bladder has usually been accompanied by contraction of the external urethral sphincter, produced either reflexly from stimulation of sensory fibers or by direct activation of somatic motor fibers. Nashold et al. inserted electrodes into the conus medullaris in an attempt to stimulate the sacral parasympathetic nucleus without stimulation of the anterior horn cells supplying the external sphincter, and produced clinical benefit in a few patients, but this technique is no longer in use. Tanagho 10 and Schmidt 11 have produced clinical benefit in a similar number of
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patients with spinal cord injury by placing electrodes on the sacral nerves containing motor and sensory fibers, often combining the implantation with division of the sensory fibers extradurally or intradurally. Brindley 9,12,13 has developed a technique of implanting electrodes intradurally on the sacral anterior roots, thereby reducing stimulation of sensory nerves although still activating somatic efferent fibers when parasympathetic fibers are activated. It is possible to produce voiding by making use of the fact that the striated muscle of the sphincter contracts and relaxes more rapidly than the smooth muscle ofthe detrusor. Intermittent bursts of stimulation can be timed so that the peaks of contraction of sphincter and bladder are out of phase with each other; while the sphincter relaxes rapidly at the end of each burst, pressure in the bladder is sufficiently maintained to produce micturition between the bursts (see Figure 1). The implantation of a stimulator to produce effective micturition is often combined with posterior sacral rhizotomy for the reasons given below. The technique is in use in over 15 countries and has been of clinical benefit to about 800 patients, most with suprasacral spinal cord injury; follow-up now extends to over 15 years in some of
PRESSURE
FLOW
110'~~~: 10 sec
INTERMITTENT STIMULATION Figure 1. Pressure recorded in the human male bladder via a 4FG ureteric catheter inserted through the urethra, and urine flow rate, following stimulation with the Finetech-Brindley bladder controller. Note that urine flows in the intervals between stimulation.
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NEUROREHABILITATION / OCTOBER 1994
these patients. The remainder of this article will therefore be devoted to a review of the Brindley technique.
SELECTION OF PATIENTS Patients with complete spinal cord injury above the conus medullaris and inefficient reflex micturition may be considered for an implanted stimulator at any time after the first year of injury, particularly if they have complications such as frequent or chronic urine infection or autonomic dysreflexia triggered by bladder or bowel. In patients with incomplete injuries, it is wise to wait until two years after injury to allow any recovery to occur, and it is necessary to determine, by testing for pain sensation in the sacral dermatomes, whether the implant is likely to be painful. Patients with recurrent infection have more to gain from effective voiding than those without. Those with detrusor hyper-reflexia causing persistently high bladder pressures endangering renal function or with autonomic dysreflexia triggered by bladder or bowel are likely to benefit from posterior rhizotomy; this operation provides the opportunity to implant a stimulator which then provides them with a preferable alternative to intermittent catheterization. Women with reflex incontinence have more to gain from posterior rhizotomy than men, because of the lack of satisfactory urine collecting devices for females and the fact that they have less to lose from the rhizotomy. Men with poor or absent reflex erection have more to gain and less to lose than those whose reflex erections already suffice for coitus. Paraplegic men are more likely to benefit from continence, while some tetraplegic men may continue to wear an appliance during the day because of difficulty in transferring from a wheelchair. Some patients with multiple sclerosis are suitable, subject to the reservations above. A few adult patients with meningomyelocele may also be suitable, but the growth of young children would be likely to displace the electrodes if implanted in them. 14
Combination of Implantation with Posterior Rhizotomy The major advantages of posterior rhizotomy are: 1. The abolition of uninhibited reflex bladder contractions, thereby increasing bladder capacity and abolishing reflex incontinence 2. Restoration of bladder compliance to normal (except in those cases where poor compliance is due to fibrosis), thereby protecting the upper tracts 3. Abolishing reflex contraction of the sphincter, thereby reducing detrusor-sphincter dyssynergia 4. The abolition of autonomic dysreflexic attacks triggered from bladder or rectum. The disadvantages of posterior rhizotomy include: 1. The loss of reflex erection and reflex ejaculation if these are present. Erection is commonly produced by the implant and even more effectively by injection of papaverine into the corpora cavernosa. Seminal emission can now be produced from a high proportion of spinal cord injured men by rectal probe electrostimulation. 2. The loss of reflex micturition. The micturition produced by the implant is usually more effective than reflex micturition, but if the implant is not used for any reason a patient will usually have to resort to intermittent catheterization. 3. The loss of perineal sensation if present. A decision about posterior rhizotomy should therefore be made in each case. It is now, however, the usual practice for the implantation to be accompanied by posterior rhizotomy.
PREOPERATIVE INVESTIGATION It is essential that a patient undergoing implantation of a sacral anterior root stimulator should have intact parasympathetic efferent fibers in the
Sacral Electrical Stimulation
sacral anterior roots, capable of producing bladder contraction. This can usually be adequately determined by cystometry,14 but in case of doubt, electrical stimulation can be applied to these nerves as they travel in the pelvic plexus by using a rectal electrode l5 or by inserting needle electrodes temporarily in the posterior sacral foramina. 16 Urinary tract function should be documented thoroughly, particularly to confirm adequate bladder capacity and exclude severe fibrosis of the bladder walJ.l7 If the patient is able to void, the pressure at which this occurs should be compared with voiding pressure after operation. Ureteric reflux and hydronephrosis are not necessarily contra-indications and may in fact be indications for posterior rhizotomy. Documentation of penile erection and bowel function is also desirable, particularly if posterior rhizotomy is planned. Imaging of the lumbosacral spine is of value for confirming adequate access to the spinal canal and excluding structural abnormalities. Separation of the spinal roots intradurally can be complicated by adhesions due to previous subarachnoid hemorrhage (such as from a bullet or stab wound) or spinal meningitis or myelography with an oily contrast medium,14 and magnetic resonance imaging (particularly with gadolinium enhancement) may aid in the preoperative detection of these adhesions. 18
SURGICAL IMPLANTATION The surgical technique developed by Brindley l4 involves a laminectomy from L4-S2 and opening of the dura to expose the cauda equina. The sacral anterior roots supplying the bladder are identified by per-operative stimulation while recording bladder pressure, and electrodes are placed around these roots. Cables from the electrodes are brought out through a grommet sutured to the dura, which is then closed, and tunneled subcutaneously to a pocket on the front of the chest or abdomen where a radio receiver is implanted. The procedure is usually combined with intradural division of the posterior roots of S2-S5.
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Alternatively the posterior roots can be divided at their entry into the conus medullaris. This can be done in a separate operation before or after electrode implantation, and may be the only form of rhizotomy possible when adhesions of the cauda equina are present.
POSTOPERATIVE TESTING The implant should be tested on the third or fourth postoperative day and again at one week; reduced responses at one week, particularly of somatic muscles, may indicate Wallerian degeneration caused by axonotmesis at operation. The patient can, however, be reassured that the motor responses seen at three days are likely to return. 14 Urodynamic studies are used to guide the setting of stimulus parameters to give an acceptable voiding pressure and rate and pattern of flow, and to document the urological effects of any rhizotomy. The stimulus program should be checked between one and three months after the operation since the response of the bladder may change with repeated use; thereafter adjustment is recommended at least every two years, provided that urinary tract function is followed carefully.
RESULTS Results obtained in the first 50 patients to receive the Finetech-Brindley stimulator were reported by Brindley et al. in 1986 and 1990. Reports have been published from other centers in Britain, 19-23 France,24,25 Germany,26 Austria,27 Denmark,28 and New Zealand 29 ; and Van Kerrebroeck 3o has collected data on 184 patients treated in 22 centers. The stimulator was the subject of conferences at Le Mans in France in 1989 31 and Halifax in Nova Scotia in 1992. 32 By the end of 1993 about 900 implants had been performed, almost all in patients with spinal cord injury, at over 42 centers in 16 countries.
Micturition The majority of subjects with the Finetech stimulator use it routinely for producing micturition at home four to six times per day. Ofthe 184 patients
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NEUROREHABILITATION / OCTOBER 1994
reported by Van Kerrebroeck,30 157 (85%) used the stimulator alone; a further 4 required a subsequent sphincterotomy in order to use it and a further 8 combined its use with intermittent catheterization, resulting in an overall stimulator usage rate of over 90%.
Continence of Urine
McDonagh et al. 33 reviewed 15 incontinent patients who had had complete sacral posterior rhizotomy in conjunction with implantation of the Finetech stimulator, and reported that 13 no longer required any form of incontinence appliance. Detrusor hyper-reflexia was abolished in all but 1 patient, who remained incontinent, as did 1 patient who had had two previous transurethral sphincterotomies. Of 41 early users followed up for 5-13 years, 35 reported continence day and night; of the 6 who were not continent, 4 had had previous bladder-neck resections. 34 In later multicenter data, continence is reported to have been achieved in 159 of 184 patients (86%). Stress incontinence and reflex incontinence accounted for approximately equal numbers of those who did not achieve continence. 3o
Residual Urine In the report by Van Kerrebroeck 30 on 184 cases, of whom 170 were using the Finetech stimulator, residual volume in the bladder following implantdriven micturition was reduced in 151 patients (89% of users) to less than 30 ml and in 95% of users to less than 60 ml. No user had a residual greater than 200 ml.
Urodynamics and Effects on the Urinary Tract
Van Kerrebroeck 17 and others9,33,35 have reported the results of urodynamic investigation showing increases in bladder capacity and compliance, which are probably mainly due to posterior rhizotomy. Concern was initially expressed that the cocontraction of bladder and external sphincter would lead to dangerously high bladder pressures, resulting in trabeculation of the bladder, ureteric reflux, and hydronephrosis. When the sphincter
is closed, the pressure in the bladder depends on the stimulus parameters applied to the parasympathetic efferent fibers, particularly the stimulus amplitude, pulse width, frequency, burst length, and gap length, and these parameters can be varied to control the detrusor pressure. Detrusor pressure has been recorded during stimulation and voiding by several groups;17,27,29,35 in general, data available to date indicates that trabeculation, ureteric reflux, and hydronephrosis have tended to decrease in patients who have undergone implantation and posterior rhizotomy. In the first 50 patients to receive the Finetech implant, bladder trabeculation as observed on intravenous urography or cystography was reported to have decreased in 13 patients when followed up at one to nine years. No patient in this group showed evidence of increased trabeculation. 9 In the same group, no patients showed reflux at postoperative cystography who had not done so preoperatively. Seven showed reflux on one or both sides preoperatively and four of these did not do so postoperatively. Three continued to reflux at four years, ten months, and five months follow-up respectively. In a multicenter review of 184 patients, reflux was present in 7 patients before the operation. After implantation it was improved or abolished in 7 of these and persisted in 2. No patient in this group developed reflux with the use of the stimulator. 30 In another series of 22 patients, 3 had abnormal upper tracts prior to implantation and of these, 2 resolved and 2 deteriorated. After undergoing sphincterotomy the latter 2 were able to continue using the stimulator. One patient developed hydronephrosis after implantation. 22 In the multicenter review not including the above patients, eight of 184 subjects showed upper-tract dilatation preoperatively. Of these, the dilatation improved in 7 and deteriorated in 1. No patient in this series was found to develop uppertract dilatation for the first time after implantation of the stimulator. Further long-term follow-up of these patients is desirable to confirm these findings and to distinguish the benefits of stimulation from those of posterior rhizotomy.
Sacral Electrical Stimulation
Urine Infection Apart from an early paper by Brindley,34 culture results have not been reported in detail, but a substantial decrease in symptomatic urine infection with or without pyrexia has however been reported by many groups following the use of the implant. 9.24.27.29-31
Autonomic Dysreflexia Among the first 50 patients to receive the implant, stimulation sometimes caused mild headache; blood pressure changes were not reported. The headache was no worse than that caused by reflex micturition in the same patient and did not prevent use of the device. However, one tetraplegic patient operated on subsequently has been unable to use the implant because of dysreflexia. 34 Autonomic dysreflexia was subsequently reported to be a problem in 26 of 184 patients before operation but in only 10 postoperatively. No patient in this series developed autonomic dysreflexia following the surgery.30 In some patients autonomic dysreflexia present before operation has improved with the control of infection, and the dysreflexia is abolished by the posterior rhizotomy commonly performed at the time of implantation.
COMPLICATIONS Among the early patients, three were unable to use the Finetech implant because of pain on stimulation, and four others found use of the stimulator to some extent painful. 34 All these patients had preserved pain sensitivity in the sacral dermatomes preoperatively. A modified implant has now been developed for use in such patients. Neuropraxia or axonotmesis of one or more nerve roots at the time of operation can be most sensitively detected by testing for any loss of skeletal muscle responses to the use of the stimulator during the first postoperative week, and may also become evident as a loss of bladder response. Judged by somatic criteria, Sauerwein et al. reported that in early cases it was common in intradural operations and very common in extradural implants, although less frequent as surgeons
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gained experience. 26 ,36 Anterior roots almost always recover but bladder responses may take from two to six months to return, thus delaying the use of the implant for micturition. Accidental damage to posterior roots has in no case been followed by functional recovery; deliberate posterior rhizotomy is now recommended for most cases. 14 Several patients have now been using the Finetech stimulator for between 10 and 15 years without apparent deterioration in nerve function. The histological appearance of stimulated nerves was reported as normal in the case of two patients who died (one by suicide and one from myocardial infarction) after using the implant for 3 and 5 years respectively. 9 Among the first 50 Finetech implants, 7 had a persistent collection of cerebrospinal fluid along the line of the subcutaneous cables to the receiver. This was dealt with by local repair of the dura. Seven others had a collection which subsided spontaneously. 9 The implant has now been modified by the addition of a grommet to seal the cables to the dura, and the incidence of this complication appears to have been greatly reduced, although figures have not yet been published. Infection of the Finetech implants has been rare, particularly since a technique of coating them with antibiotics was introduced in 1982. Rushton 37 reported that lout of 104 coated implants had become infected, and in this case infection appeared to have been introduced at a subsequent operation to close a leak of cerebrospinal fluid. Among early implants not coated with antibiotic, 2 out of 40 became infected. The infection rate for a variety of implants has been shown to be significantly reduced by the antibiotic coating, but not by systemic perioperative antibiotics. Technical faults in the implanted equipment have been rare. The commonest site for faults has been in cables, which are sometimes mechanically damaged by movement. Repair or replacement of the Finetech device has been possible in all cases where this has been attempted and no fault is known to have led to permanent discontinuation of use of the implant. Failures in the external transmitter have primarily been due to breaks in the antenna lead and
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NEUROREHABILITATION I OCTOBER 1994
have been more common, but do not require reoperation.
DISCUSSION Continence Increases in bladder capacity measured by cystometry are probably largely attributable to posterior rhizotomy. Accidental damage to posterior roots may have played a part in some patients where rhizotomy was not attempted. A decrease in residual urine, as a result of stimulated voiding, also allows a patient a longer period of bladder filling before reaching capacity. Reduction of infection should also improve the compliance of the bladder and reduce the likelihood of contraction in response to spinal or nonspinal reflexes.
ons to the bladder and in the large myelinated axons to the striated sphincter. However, at higher currents, action potentials can be arrested at the anodes by hyperpolarization of the large axons, while allowing action potentials to proceed in the smaller axons to the bladder. As a result, contraction of the bladder can be produced with little contraction of the external sphincter. (See Figure 2.) In this animal model, activation of the small axons also produces contraction of smooth muscle in the bladder neck and tumescence of the penis in the male, and both these factors hinder urine flow. However, the technique appears to have promise as a means of producing continuous stream micturition in man with lower voiding pressures, by reducing substantially the urethral resistance offered by the external sphincter.
Detrusor-sphincter Dyssynergia Continuous stimulation of sacral anterior roots sufficient to produce contraction of the detrusor also produces contraction of the external sphincter, and has been found in the past to lead to poor voiding and high intravesical pressures which may be dangerous to the upper tracts unless measures are taken to reduce sphincter contraction. Intermittent stimulation has been used to produce bladder and sphincter contractions out of phase with each other, adjusting the timing and magnitude of the stimuli to control voiding pressures. This approach has resulted in a high proportion of patients voiding with stimulation, and the longterm results to date indicate that ureteric reflux and hydronephrosis have more often improved than deteriorated with use of the stimulator. Brindley 12 suggested the use of anodal block to prevent propagation of action potentials in the large somatic axons to the external sphincter while allowing propagation in the small parasympathetic fibers to the detrusor, and demonstrated the principle experimentally. In our laboratory this has been developed using tripolar electrodes chronically implanted in dogs and activated with wide quasitrapezoidal stimuli. When using lowstimulus amplitudes, these stimuli generate action potentials at the cathodes both in the small myelinated preganglionic parasympathetic efferent ax-
SUMMARY In patients with spinal cord injury above the conus medullaris, electrical stimulation of the sacral anterior nerve roots can produce micturition with low residual volumes of urine and reduced urinary tractinfection. Voiding pressures appear to be maintained at safe levels by the use of an intermittentpattern of stimulation. The procedure is usually ~,-------------------------------,
BLADDER URETHRA
o
0.1
Current (mA)
0.5
Pressures recorded in the canine male urethra and bladder using microtip pressure transducers inserted via the urethra. Stimulation applied to S2 anterior root of one side via a tripolar cuff electrode, using a quasi trapezoidal waveform of pulse width 500 IJ..sec with exponential training edge of 500 IJ..sec and frequency 20 Hz. Figure 2.
Sacral Electrical Stimulation
combined with division of the sacral posterior roots, which increases bladder capacity and continence; this also increases bladder compliance, which may be protective fur the upper-urinary tracts. The procedure has now been applied in about
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900 patients with spinal cord injury, some of whom have been followed up for over 15 years. The nerves do not appear to be damaged by long-term stimulation, and technical faults with the equipment are now uncommon.
REFERENCES 1. Thon WF, Baskin LS, Jonas U, Tanagho EA, Schmidt RA Neuromodulation of voiding dysfunction and pelvic pain. World] Urol 1991; 9:138-141. 2. Edwards L, Malvern]. Electronic control of continence: A critical review of the present situation. Brit] Urol1972; 44:467-472. 3. Bradley WE, Timm Gw, Chou SN. A decade of experience with electronic stimulation of the micturition reflex. UrolInt 1971; 26:283-303. 4. Halverstadt DB, Parry WL. Electronic stimulation of the human bladder: Nine years later.] Urol1975; 113:341-344. 5. Burghele T. Electrostimulation of the neurogenic urinary bladder. In: Lutzmeyer W, et al. eds. Urodynamics. Berlin: Springer-Verlag, 1973, 319-322. 6. Kaeckenbeeck B. Electrostimulation de la vessie des paraplegiques. Technique de Burghele-IchimDemetrescu. Acta Urol Belg 1979; 47:137-140. 7. Nashold BS, Friedman H, Grimes]. Electrical stimulation of the conus medullaris to control the bladder in the paraplegic patient: A ten year review. Appl Neurophysioll981; 44:225-232. 8. Tanagho EA, Schmidt RA. Electrical stimulation in the clinical management of the neurogenic bladder.] Urol1988; 140:1331-1339. 9. Brindley GS, Polkey CE, Rushton DN, et al. Sacral anterior root stimulators for bladder control in paraplegia: The first 50 cases.] Neurol Neurosurg Psychiat 1986; 49: 11 04-1114. 10. Tanagho EA, Schmidt RA, Orvis BR. Neural stimulation for control of voiding dysfunction: A preliminary report in 22 patients with serious neuropathic voiding disorders. ] Urol 1989; 142:340-345. 11. Schmidt RA Advances in genitourinary neurostimulation. Neurosurgery 1986; 19: 1041-1044. 12. Brindley GS, Craggs MD. A technique for anodally blocking large nerve fibres through chronically implanted electrodes.] Neurol Neurosurg Psychiatr 1980; 43: 1083-1090. 13. Brindley GS, Rushton DN. Long-term follow-up of patients with sacral anterior root stimulator implants. Paraplegia 1991; 28:469-475. 14. Brindley GS. The Finetech-Brindley bladder control-
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paraplegiques. Annales de Readaptation et de Medecine Physique 1986; 29:405-411. Sauerwein D. Die operative Behandlung del' spastischen Blasenlahmung bei Querschnittlahmung [Surgical treatment of spastic bladder paralysis in paraplegic patients. Sacral deafferentation with implantation of a sacral anterior root stimulator]. Urologe A 1990; 29: 196-203. Madersbacher H, Fischer H, Ebner A. Anterior sacral root stimulator (Brindley): experiences especially in women with neurogenic urinary incontinence. Neurourol Urodyn 1988; 7:593-601. Nordling], Hald 'l~ Kristensen]K, et al. Implanterbar radiostyret sakralrodstimulator til kontrolleret vandledning [An implantable radio-controlled sacral nerve root stimulator for control of urination]. Ugeskr Laeger 1988; 150:978-980. Arnold EP, Gowland Sp, MacFarlane MR, et al. Sacral anterior root stimulation of the bladder in paraplegics Aust NZJ Surg 1986; 56:319-324. Van Kerrebroeck PEV. World wide experience with the Finetech-Brindley sacral anterior root stimulator. Neurourol Urodyn 1993; 12(5):497-503. Colombe! P, Egon G. Lclectrostimulation des
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