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PURPOSE: Chronic stimulation of the sacral nerves has now become one of the most accepted stimulation therapies for functional lower urinary tract symptoms refractory to conservative treatment. Despite the existence of a large amount of literature on sacral neuromodulation (SNM) showing a fairly high percent of significant improvement in clinical outcome there are few experimental studies of SNM stimulus parameters and/or neurophysiological monitoring. We evaluated the specific action of SNM on the primary sensory cortical area. Somatosensory evoked potentials (SEPs) of the pudendal and posterior tibial nerves were evaluated in patients implanted with a monolateral permanent quadripolar electrode. MATERIALS AND METHODS: A total of 24 patients underwent stage 1 monolateral sacral nerve implantation. Three SEP patterns were evaluated; namely before implantation, 1 month after stage 1 with stimulation set at 21 Hz and again with a pulse rate of 40 Hz. RESULTS: In all patients SNM produced a significant decrease in pudendal SEP latency of the first positive deflection between baseline SNM stimulation at different pulse rates at the ipsilateral and contralateral implant sites. This finding was evidence of the effect of S3 SNM on the cortical sensory area and the specificity of pudendal SEPs in measuring how SNM modulates the afferent pathway from the spinal nerve to the cortical sensory area. CONCLUSIONS: Our study confirms previous observations that SNM acts by the afferent pathway at the cortical site level and it sheds light on so-called idiopathic lower urinary tract symptoms. A modification of SEPs induced by SNM seems to be a prognostic factor of clinical outcomes. The action of SNM on the afferent pathway from the sacral area to the somatosensory cortex is specific and neurophysiological evaluation via pudendal SEPs provides evidence to this effect.
PURPOSE: We investigated the action of sacral neuromodulation in restoring voiding function in women with urinary retention attributable to sphincter overactivity (Fowler's syndrome). MATERIALS AND METHODS: We recruited women within retention who were able to void following neuromodulation by temporary test stimulation or a permanent implant. Urethral pressure profiles, cystometry and sphincter electromyography were performed before and after neuromodulation. RESULTS: A total of 30 women 19 to 52 years old were recruited, including 21 with a permanent implant and 9 undergoing temporary stimulation. Mean maximum urethral closure pressure was elevated compared to expected pressure and it did not change significantly after neuromodulation. The electromyographic abnormality persisted during neuromodulation and voiding was often done with an interrupted flow. There was a slight increase in detrusor contractility. CONCLUSIONS: This evidence suggests that neuromodulation does not restore voiding in these patients by a direct relaxant effect on the sphincter. The modest increase in detrusor pressure appears to be sufficient to overcome the resistance of the overactive sphincter.
PURPOSE: We assessed the efficacy of sacral neuromodulation as an alternative therapeutic option in women with an artificial urinary sphincter (AUS) who had de novo irritative urinary symptoms (urgency/frequency) refractory to conventional treatment. MATERIALS AND METHODS: Between 1984 and 2002 we implanted an AUS in 350 women and detrusor overactivity developed in 14. Six of the 14 patients responding positively to a percutaneous nerve evaluation test (greater than 50% subjective/objective improvement) were implanted with an S3 neuromodulator within 42.8 weeks (range 21 to 106) of AUS implantation. Followup included analysis of the voiding diary, a pad test and urodynamic assessment. RESULTS: After 30.5 months followup (range 14 to 40) 1 patient was dry, 4 were improved and treatment failed in 1. At 12 months mean voiding frequency daily had decreased from 17 (range 12 to 23) to 8 (range 4 to 12) and the mean number of leakages episodes daily had decreased from 14.7 (range 8.5 to 17) to 6 (range 4 to 10). Mean voided volume had increased from 121.7 (range 90 to 170) to 180 ml (range 120 to 225), mean first desire to void volume had increased from 117 (range 88 to 190) to 183 ml (range 130 to 275) and mean functional bladder capacity had increased from 325 (range 200 to 530) to 372 ml (range 250 to 580). Uninhibited bladder contractions had resolved in 4 of 5 patients. CONCLUSIONS: In women who already have an AUS with urge incontinence sacral neuromodulation can help resolve symptoms. Because this therapy does not compromise the potential for future treatment, it appears to be an alternative option in these patients. It can postpone or avoid more mutilating surgery and self-catheterization.
PURPOSE: We report a prospective randomized controlled study to evaluate the possible benefits of sacral neuromodulation (SNM) for the management of neurogenic bladder dysfunction in children. MATERIALS AND METHODS: We included in the study subjects between the ages of 5 and 21 years presenting with urinary incontinence due to neurogenic bladder. Before study inclusion all previous treatment was discontinued. Patients were randomly divided into the control group treated conventionally and the implant group treated with SNM. Treatment outcome was compared every 3 months for a minimum of 12 months based on clinical examination, voiding diary and urodynamic evaluation. RESULTS: A total of 26 boys and 16 girls with a mean age of 11.9 years were enrolled in this study. There were 21 patients in each group. The main underlying etiology was spina bifida. The 2 groups were comparable with regard to sex, age and urodynamic variables. Total disappearance of urinary leakage was observed in 1 patient who underwent implantation but he still required intermittent catheterization. Comparison of urodynamic variables disclosed no significant statistical difference except with regard to functional bladder capacity which was better in the control group and the leak point pressure which was better in the implant group (p <0.05). Evaluation of interindividual variations in the implant group revealed significant improvement in compliance and functional bladder capacity at 6 and 9 months but not at 12 months. Nine patients in the implant group reported improvement in intestinal transit, 5 total disappearance of urinary infection and 6 persistent sensation of a full bladder. No patient in the control group reported any improvement. Revision surgery was required in 3 cases due to lead migration, faulty connection and wound infection. CONCLUSIONS: SNM is a promising new therapeutic modality. Implant placement is minimally invasive, nondestructive and reversible. Use in children with neurogenic bladder has not been previously reported. Although some improvement was noted in patients treated with SNM, the difference with the control group was not significant. A larger multicenter study is warranted to evaluate SNM.
OBJECTIVE: To obtain quantitative biomechanical data on the effects of different angles of straight-leg raising on intrathecal movements and tensions in the lumbosacral nerve roots in human cadavers. DESIGN: Eight embalmed human cadavers with no gross spinal pathology and no limitations in hip motion were used. We performed reverse straight-leg raising by hanging the left leg down from the table with the knee extended while measuring the movement and tension of nerve roots L2, L3, L4, L5, and S1 in 10-degree intervals for straight-leg raising from 0 to 70 degrees. RESULTS: The mean intrathecal movements at 70 degrees were 0.55 mm, 0.54 mm, 0.96 mm, 1.54 mm, and 2.31 mm for roots L2, L3, L4, L5, and S1, respectively. The movements were statistically significant at >50 degrees for root L5 and at >40 degrees for root S1 (P < 0.05). The tension in the nerve roots with increasing angle of straight-leg raising increased from roots L2 to S1. The mean tensions at 70 degrees of straight-leg raising were 141.25 g, 168.75 g, 228.75 g, 280.00 g, and 493.75 g for roots L2, L3, L4, L5, and S1, respectively. The difference in tension was significant at >70 degrees for roots L2, L3, and L4 roots, at >40 degrees for root L5 root, and at >10 degrees for root S1 (P < 0.05). CONCLUSIONS: The intrathecal movement and tension of the lumbosacral roots induced by straight-leg raising were <2.5 mm and <500 g, respectively. The movement and tension induced by straight-leg raising tended to be greater in more distal segmental roots.
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We investigated leg-powered cycling in a recumbent tricycle for a paraplegic using functional electrical stimulation (FES) with the lumbo-sacral anterior root stimulator implant (LARSI). A female complete T9 paraplegic had a stimulator for the anterior L2 to S2 spinal roots (bilaterally) implanted in 1994. She was provided with equipment for daily FES cycling exercise at home. The cycling controller applies a pattern of stimulation in each of 16 crank angle phases. A 7-bit shaft encoder measures the crank angle with adequate precision. Each pattern was originally chosen to give the greatest propulsive force in that position when there was no motion. However, dynamically, some reduction in co-contraction is needed; also the patterns are applied with a preset advance time. Maximal power is obtained with an advance of 250 ms, which compensates for muscle response delay and accommodates changes in cadence (from about 25 to 85 rpm). With this system, she has cycled 1.2 km at a time on gently undulating road. We found that spinal root stimulation gives sufficient control over the muscles in the legs to produce a fluid cycling gait. We propose that root stimulation for leg cycling exercise may be a practicable and valuable function for paraplegics following spinal cord injury.
It is commonly accepted that locomotor-related neuronal circuitry resides in the lumbosacral spinal cord. Pharmacological agents, epidural electrical stimulation, and sensory stimulation can be used to activate these instrinsic networks in in vitro neonatal rat and in vivo cat preparations. In this study, we investigated the use of low-level tonic intraspinal microstimulation (ISMS) as a means of activating spinal locomotor networks in adult cats with complete spinal transections. Trains of low-amplitude electrical pulses were delivered to the spinal cord via groups of fine microwires implanted in the ventral horns of the lumbosacral enlargement. In contrast to published reports, tonic ISMS applied through microwires in the caudal regions of the lumbosacral enlargement (L7-S1) was more effective in eliciting alternating movements in the hindlimbs than stimulation in the rostral regions. Possible mechanisms of action of tonic ISMS include depolarization of locally oscillating networks in the lumbosacral cord, backfiring of primary afferents, or activation of propriospinal neurons.
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Peripheral nerve blocks afford numerous benefits for lower extremity surgery. There is growing interest in continuous peripheral nerve blocks, mainly for treatment of postoperative pain, a field that represents a challenge to the anaesthesiologist. This paper seeks to review the efficacy of continuous lower limb blocks for postoperative pain relief. Not only do continuous peripheral nerve blocks afford specificity of analgesic area but current research has shown that they enhance postoperative analgesia and patient satisfaction. New techniques and devices are increasingly appearing, and catheters are constantly being developed and improved; an example being the stimulating catheter, which represents one of the newest advances in this area. The above techniques show that continuous postoperative analgesia with catheters in the lower extremities is not only possible, but indeed provides sustained effective postoperative analgesia, reduces use of opioids, and improves rehabilitation and patient well-being with minimal side-effects. These techniques could prove an alternative to postoperative pain treatment following ambulatory surgery.
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BACKGROUND AND AIM: An increase in recto-sigmoid colon activity through electrical stimulation of the sacral dermatomes has previously been reported. It has not been evaluated whether or not sacral dermatome stimulation has beneficial effects on constipation symptoms and anorectal function in constipated patients. Our aim was to evaluate short-term effects of magnetic stimulation of the sacral dermatomes on constipation symptoms and anorectal function in patients with idiopathic slow transit constipation. METHOD: Fourteen patients with idiopathic slow transit constipation were enrolled. Constipation symptoms, stool form and anorectal function were assessed before treatment, and at 3 and 6 weeks of treatment. Six-week treatment consisted of either a 3-week period of sham treatment or a 3-week period of magnetic stimulation of the S2-S3 dermatomes, which was performed in a randomized cross-over design. RESULTS: During the stimulation period, the frequency score of spontaneous bowel movements decreased in eight of the 14 patients (2.9 [2-3]vs 1.4 [0-2]), whose threshold volumes for urge to defecate and maximum tolerable volumes were significantly greater than those of the non-responders, and significantly decreased at the end of treatment. The degree of straining on defecation also significantly decreased in the responders. Responders had shorter right colonic transit time and longer left colonic transit time compared to the non-responders. Sham treatment did not affect constipation symptoms, stool form and rectal sensation. CONCLUSION: Sacral dermatome stimulation may offer potential for therapeutic benefit for a subset of patients with idiopathic slow transit constipation, particularly constipated patients with rectal hyposensation or hindgut dysfunction.
OBJECTIVES: In order to clarify the role of glutamate in the micturition reflex and in glutamatergic and glycinergic neuronal activity, we examined the effects of intrathecal (IT) injection of glutamate or MK-801 (an N-methyl-D-aspartate receptor antagonist) on bladder activity and on the glutamate and glycine levels in the lumbosacral cord of female rats with or without acute lower thoracic spinal cord injury (SCI). METHODS: Under urethane anesthesia, isovolumetric cystometry was performed in rats with or without SCI before and after IT injection of glutamate or MK-801 at the lumbosacral cord level. The glutamate and glycine levels of the whole lumbosacral cord were measured after IT injection of glutamate or MK-801 in both groups. RESULTS: In intact rats, IT glutamate (100 microg) prolonged the interval between bladder contractions and decreased the amplitude of contractions. IT MK-801 (3-100 microg) also prolonged the interval between bladder contractions and decreased the amplitude in intact rats. In SCI rats, cystometry demonstrated the disappearance of bladder contractions, and the glycine level in the lumbosacral cord was elevated. In intact rats, IT glutamate (0.3-100 microg) increased the glycine level in the lumbosacral cord. On the other hand, IT MK-801 (3-100 microg) decreased both glutamate and glycine levels in intact and SCI rats. CONCLUSIONS: These results suggest that glutamatergic neurons have stimulatory projections to both glutamatergic and glycinergic neurons in the lumbosacral cord, and that glutamatergic neurons inhibit the micturition reflex by stimulating glycinergic neurons.
Faecal incontinence is common, distressing to the patient and socially incapacitating. The treatment options depend on the severity and aetiology of incontinence. For mild cases of faecal incontinence, medical management and pelvic floor physiotherapy may be adequate. For more severe cases, surgery is often required. Patients who have a distinct sphincter defect are amenable to surgical repair. In many cases, there is a combination of diffuse structural damage of the anal sphincters with pudendal neuropathy. Conventional surgical repairs have a modest degree of success and the results tend to deteriorate with time. Neosphincter procedures such as artificial bowel sphincter and dynamic graciloplasty are potentially morbid and technically complex. Sacral nerve stimulation is innovative and has had a medium-term success with improvement of quality of life in over 80% of patients treated for faecal incontinence. These results are superior to other techniques in treating patients with severe refractory faecal incontinence, where current maximal therapy has failed. The technique is unique because there is a screening phase, which has a high predictive value. It is also associated with minimal complications that are usually minor. However, most published reports of sacral nerve stimulation for treatment of faecal incontinence were case studies and methods of assessing outcome were variable. Criteria for patient selection are evolving and are yet to be defined. The present paper critically reviews the publications to date on sacral nerve stimulation for treatment of faecal incontinence. This will form the basis for future evaluation of this emerging treatment of severe, intractable faecal incontinence. Randomized clinical trials like that of the Melbourne trial will further clarify the role and indications of sacral nerve stimulation for faecal incontinence.
The genitofemoral nerve (GFN) hypothesis for inguinoscrotal testicular descent proposes that calcitonin gene-related peptide (CGRP), released from the genitofemoral nerve, controls the migration of the gubernaculum from the inguinal region to the scrotum between 26 and 40 weeks of gestation. The processus vaginalis provides a channel through which the testis descends from the abdomen to the scrotum. Following descent of the testis the processus vaginalis undergoes luminal obliteration and disappearance between the internal inguinal ring and the upper pole of the testis. The mechanism underlying closure of the processus is unknown and failure for it to occur normally results in congenital inguinal hernia, scrotal hydrocele and possibly even an 'ascending' testis. Recent work in our laboratory suggests that CGRP, released from the genitofemoral nerve, may cause fusion and disappearance of the processus vaginalis. We propose that abnormalities in the GFN link a spectrum of disorders encompassing congenital undescended testis, inguinal hernia, scrotal hydrocele and ascending testis.
BACKGROUND: Differences in the dermatomal maps appearing in standard anatomic texts which are in common use may lead to diagnostic confusion in the assessment of patients who suffer from nerve root deficiency. This is particularly evident in the variable depiction of the L4 nerve root dermatome which is carried distally in the saphenous nerve. The purpose of this study is to establish the distal limit of L4 nerve root innervation in the foot by performing cadaveric dissection of the saphenous nerve. METHODS: Dissection of the dorsum of the medial foot and ankle was performed on 20 cadaveric specimens. RESULTS: The saphenous nerve was found to enter the dermis of the medial ankle region (mean = 14.75 mm) distal to the tip of the medial malleolus in the direction of the hallux. In three cases the nerve terminated proximal to the medical malleolus. In all cases the medial forefoot and hallux were supplied by the most medial branch of the superficial peroneal nerve. CONCLUSIONS: These findings suggest that the sensory component of the L4 nerve root terminates in most cases near the medical malleolus, well proximal to the bunion area of the forefoot.