Sensing in Sacral Neuromodulation: A Feasibility Study in Subjects With Urinary Incontinence and Retention

OBJECTIVES

Sacral neuromodulation (SNM) therapy standard of care relies on visual-motor responses and patient-reported sensory responses in deciding optimized lead placement and programming. Automatic detection of stimulation responses could offer a simple, consistent indicator for optimizing SNM. The purpose of this study was to measure and characterize sacral evoked responses (SERs) resulting from sacral nerve stimulation using a commercial, tined SNM lead.

MATERIALS AND METHODS

A custom external research system with stimulation and sensing hardware was connected to the percutaneous extension of an implanted lead during a staged (tined lead) evaluation for SNM. The system collected SER recordings across a range of prespecified stimulation settings (electrode configuration combinations for bipolar stimulation and bipolar sensing) during intraoperative and postoperative sessions in 21 subjects with overactive bladder (OAB) and nonobstructive urinary retention (NOUR). Motor and sensory thresholds were collected during the same sessions.

RESULTS

SERs were detected in all 21 subjects. SER morphology (number of peaks, magnitude, and timing) varied across electrode configurations within and across subjects. Among subjects and electrode configurations tested, recordings contained SERs at motor threshold and/or sensory threshold in 75% to 80% of subjects.

CONCLUSIONS

This study confirmed that implanted SNM leads can be used to directly record SERs elicited by stimulation in subjects with OAB and NOUR. SERs were readily detectable at typical SNM stimulation settings and procedural time points. Using these SERs as possible objective measures of SNM response has the capability to automate patient-specific SNM therapy, potentially providing consistent lead placement, programming, and/or closed-loop therapy.

Fecal Incontinence in the Elderly

Fecal incontinence can be a challenging and stigmatizing disease with a high prevalence in the elderly population. Despite effective treatment options, most patients do not receive care. Clues in the history and physical examination can assist the provider in establishing the diagnosis. Direct inquiry about the presence of incontinence is key. Bowel disturbances are common triggers for symptoms and represent some of the easiest treatment targets. We review the epidemiology and impact of the disease, delineate a diagnostic and treatment approach for primary care physicians to identify patients with suspected fecal incontinence and describe appropriate treatment options.

Sacral Nerve Stimulation in Parkinson's Disease Patients With Overactive Bladder Symptoms

OBJECTIVE

To assess the efficacy, safety, and outcomes of sacral nerve stimulation (SNS) for Parkinson's disease (PD) patients with overactive bladder symptoms.

METHODS

We retrospectively reviewed PD patients who underwent Stage I SNS. Demographics, urodynamic data, and baseline voiding function were analyzed. Efficacy and safety of treatment were determined by rate of progression to Stage II, explantation, and surgical revision. Long-term outcomes were assessed using voiding diaries and/or clinic notes.

RESULTS

Sixty percent (9/15) experienced ≥50% improvement in urinary parameters and proceeded to Stage II. There was no significant difference in age, body mass index, comorbidities, PD disease duration, or levodopa equivalent daily dose between successful and nonsuccessful Stage I patients. However, 100% of female patients experienced Stage I success compared to 44% of male PD patients (P = .04). Individuals with >12-month follow-up experienced an average reduction of 6 voids/day. No patients required revision or explantation of their device at latest clinic follow-up (22.2 ± 7.8 months). Higher maximal urethral closure pressures, detrusor pressure at maximum flow rate (PdetQmax), post-void residual volume, and mean bladder outlet obstruction index were observed in the Stage I trial failures.

CONCLUSION

At our institution, PD patients have a similar rate of progression to Stage II compared to the general population. SNS is an effective therapy that should be considered among the treatment options for PD patients with overactive bladder symptoms. Urodynamic parameters associated with obstruction may be predictive of SNS failure in PD patients and may help guide patient selection, however further studies are needed.

Sacral Nerve Stimulation in the Treatment of Bowel Disorders

Defecation problems occur in patients of all ages, but are more prevalent in the elderly, postpartum women, and patients with chronic and debilitating medical conditions. Most of the time, these problems respond to medical therapy and nonsurgical options, but it is not uncommon for patients to require surgical intervention. Sacral nerve stimulation (SNS) presents an alternative for patients with bowel dysfunction combining proven therapeutic benefits and limited surgical risks. Here we describe the common indications for SNS, patient selection, technical details of the procedure, published outcomes, and complications that can arise. Based on our review, SNS is an effective treatment option for fecal incontinence and may reduce the patients' clinical symptoms and help restore their quality of life. Future research studies may expand the role of this modality for other bowel disorders.

Sacral Neuromodulation for Genitourinary Problems

Sacral neuromodulation (SNM) is a minimally invasive therapeutic option for many voiding dysfunction conditions. It is approved by the US FDA for refractory overactive bladder with and without incontinence and nonobstructive retention. Since SNM has shown a favorable response for these approved indications, other therapeutic applications have been proposed for various conditions such as painful bladder syndrome, chronic pelvic pain and neurological voiding dysfunction in both adult and pediatric age groups. SNM therapy with the most commonly used dedicated SNM device (InterStim) involves insertion of electrode(s) in the third and/or fourth sacral foramen next to the nerve root. The electrode is then connected to a battery-operated pulse generator. All patients need to have a test trial period before definitive device insertion. Here we discuss SNM therapy in functional urinary disorders and the technique of device insertion with the potential pitfalls.

Cervical stimulation activates A1 and locus coeruleus neurons that project to the paraventricular nucleus of the hypothalamus

In female rats, stimulation of the uterine cervix during mating induces two daily surges of prolactin. Inhibition of hypothalamic dopamine release and stimulation of oxytocin neurons in the paraventricular nucleus (PVN) are required for prolactin secretion. We aim to better understand how stimulation of the uterine cervix is translated into two daily prolactin surges. We hypothesize that noradrenergic neurons in the A1, A2, and locus coeruleus (LC) are responsible for conveying the peripheral stimulus to the PVN. In order to determine whether projections from these neurons to the PVN are activated by cervical stimulation (CS), we injected a retrograde tracer, Fluoro-Gold (FG), into the PVN of ovariectomized rats. Fourteen days after injection, animals were submitted to artificial CS or handling and perfused with a fixative solution. Brains were removed and sectioned from the A1, A2, and LC for c-Fos, tyrosine hydroxylase (TH), and FG triple-labeling using immunohistochemistry. CS increased the percentage of TH/FG+ double-labeled neurons expressing c-Fos in the A1 and LC. CS also increased the percentage of TH+ neurons expressing c-Fos within the A1 and A2, independent of their projections to the PVN. Our data reinforce the significant contributions of the A1 and A2 to carry sensory information during mating, and provide evidence of a functional pathway in which CS activates A1 and LC neurons projecting to the PVN, which is potentially involved in the translation of CS into two daily prolactin surges.

[Influence of femoral catheter stimulation intensity on post-surgical analgesia after total knee replacement]

INTRODUCTION

Stimulating catheters allow the catheter point to be positioned near the nerve, thus reducing the amount of local anaesthetic required for a successful block. There is currently a debate on what is the stimulation intensity required to provide adequate analgesia, although it does seem that if it is obtained with 1mAmp or less the block is more effective. The objective of the study was to demonstrate whether different neurostimulation intensities with the stimulating catheter at femoral nerve level, had an influence on the adequacy of post-surgical analgesia during the 48h after total knee arthroplasty.

MATERIAL AND METHODS

A comparative, prospective and randomised study was conducted on patients subjected to total knee replacement. After surgery with subarachnoid anaesthesia, a continuous femoral block was performed with a stimulating catheter at a neurostimulation intensity 0.2 and 0.5mAmp in Group 1, between 0.6 and 1mAmp in Group 2, equal or higher than 1.1mAmp in Group 3, and in Group 4 the catheter was introduced between 3-5cm without looking for a motor response. A dose of 0.2% ropivacaine 0.4mL/kg and an infusion at 5mL/h, with boluses of 10mL/30min, was administered via the catheter. Sciatic nerve block was also performed on all patients with 20ml of 0.5% ropivacaine. The patient demographics were recorded, as well as, post-surgical analgesia details, sensory and motor block in each area, boluses requested, rescue analgesia, and undesirable effects at 8, 16, 24, 36 and 48h.

RESULTS

A total of 124 patients were included, 32 in Group 1 (25.8%), 21 in Group 2 (16.9%), 31 in Group 3 (25%), and 40 in group 4 (32.3%). The 4 groups were homogeneous as regards age, height, weight and ASA. There were no statistically significant differences found in the post-operative pain, except during movement in the femoral area at 36 hours (p=.032). There were also no statistically significant differences found in the sensory block in the femoral area at 48 hours (p=.019) and in the femoral cutaneous nerve block at 8 hours (p=.049) or at 24 hours (p=.045). As regards motor block, differences were only found in the obturator nerve at 24 hours (p=.016). There were no differences in rescue analgesia, patient controlled analgesia (PCA) boluses requested or administered, except that the number of boluses requested at 16 hours was less in Group 3 (p=.049). There were also no significant differences in undesirable effects or in the level of satisfaction of the patients between the four groups.

CONCLUSIONS

In our study, no influence was found on the level of analgesia provided after knee replacement surgery with the neurostimulation intensity to which the neuromuscular system involved responded when a stimulating catheter is inserted at femoral level.

Maximum acceptable weight of lift reflects peak lumbosacral extension moments in a functional capacity evaluation test using free style, stoop and squat lifting

It is unclear whether the maximum acceptable weight of lift (MAWL), a common psychophysical method, reflects joint kinetics when different lifting techniques are employed. In a within-participants study (n = 12), participants performed three lifting techniques--free style, stoop and squat lifting from knee to waist level--using the same dynamic functional capacity evaluation lifting test to assess MAWL and to calculate low back and knee kinetics. We assessed which knee and back kinetic parameters increased with the load mass lifted, and whether the magnitudes of the kinetic parameters were consistent across techniques when lifting MAWL. MAWL was significantly different between techniques (p = 0.03). The peak lumbosacral extension moment met both criteria: it had the highest association with the load masses lifted (r > 0.9) and was most consistent between the three techniques when lifting MAWL (ICC = 0.87). In conclusion, MAWL reflects the lumbosacral extension moment across free style, stoop and squat lifting in healthy young males, but the relation between the load mass lifted and lumbosacral extension moment is different between techniques.

PRACTITIONER SUMMARY

Tests of maximum acceptable weight of lift (MAWL) from knee to waist height are used to assess work capacity of individuals with low-back disorders. This article shows that the MAWL reflects the lumbosacral extension moment across free style, stoop and squat lifting in healthy young males, but the relation between the load mass lifted and lumbosacral extension moment is different between techniques. This suggests that standardisation of lifting technique used in tests of the MAWL would be indicated if the aim is to assess the capacity of the low back.

A unique approach to severe constipation

Sacral neuromodulation used for urge urinary incontinence, urgency-frequency, and nonobstructive urinary retention, has incidentally been noted to normalize bowel function. This 48-year old female with severe constipation who had failed all conservative treatment measures returned to normal defecatory function after sacral neuromodulation under the supervision of a nurse practitioner.

[Sacral nerve stimulation in the treatment of the lower urinary tract function disorders]

Functional disorders of the female lower urinary tract like urge incontinence, idiopathic urinary retention and symptoms of urgency-frequency occasionally do not respond properly to classical behavioral and pharmacological therapy Therefore, additional alternative therapies are needed to alleviate these bothersome symptoms. Sacral neuromodulation (SNS) utilize mild electrical pulses which activate or suppress neural reflexes responsible for voiding by stimulating the sacral nerves that innervate the bladder, external urethral sphincter and pelvic floor muscles. The exact mechanism of SNS action is not yet fully understood but it is assumed that it influences the neuroaxis at different levels of the central nervous system and restores the balance between inhibitory and activatory control over the voiding reflex. There is numerous evidence on the success of SNS not only in the treatment of refractory urge incontinence in adult and children but also in idiopathic urinary retention and symptoms of urgency-frequency

Sacral nerve stimulation increases activation of the primary somatosensory cortex by anal canal stimulation in an experimental model

BACKGROUND

Sacral and posterior tibial nerve stimulation may be used to treat faecal incontinence; however, the mechanism of action is unknown. The aim of this study was to establish whether sensory activation of the cerebral cortex by anal canal stimulation was increased by peripheral neuromodulation.

METHODS

A multielectrode array was positioned over the right primary somatosensory cortex of anaesthetized rats. A brief burst of electrical stimulation was applied to either the left sacral root or the left posterior tibial nerve, and evoked potentials from anal canal stimulation were signal-averaged at intervals over 1 h. At the end of the experiment, the cerebral cortex was removed and probed for polysialylated neural cell adhesion molecule (PSA-NCAM).

RESULTS

Sacral nerve root and posterior tibial nerve stimulation significantly increased the peak amplitude of primary cortical evoked potentials by 54.0 and 45.1 per cent respectively. This change persisted throughout the period of observation. The density of PSA-NCAM-positive cells in the somatosensory cortex underlying the electrode array was increased by approximately 50 per cent in the sacral nerve-stimulated group.

CONCLUSION

Brief sacral neuromodulation induces profound changes in anal canal representation on the primary somatosensory cortex, providing a plausible hypothesis concerning the mechanism of action of neuromodulation in the treatment of faecal incontinence.

[Identification of the lumbosacral nerve plexus during the extreme lateral interbody fusion procedure]

PURPOSE OF THE STUDY

The aim of this clinical observation study was to determine the extent to which muscle relaxation induced by anesthesia must be intra-operatively reversed for a reliable identification, by intra-operative monitoring, of the lumbosacral (LS) nerve roots during extreme lateral interbody fusion (XLIF). MATERAL AND METHODS: General anesthesia (midazolam, propofol, sufentanil, oxygen/air/sevofluran - rocuronium) was administrated to all pa - tients. Train-of-four (TOF) stimulation of the ulnar nerve at 10-second intervals and an electromyographic response of the adductor pollicis muscle were used, and the duration of neuromuscular block was measured by the value of the TOF-ratio. When the level of recovery from neuromuscular block was TOF-count = 2, reversion to normal function was still accelerated by sugammadex administration at a dose of 2 mg.kg-1. Subsequently, it was determined at which level of muscle relaxation subsidence the first responses to LS nerve root stimulation were evident. Intra-operative neurophysiologial monitoring (IOM) with use of the NIM - Neuro® 3.0 device allowed for assessment of a triggered electromyographic reaction (tEMG) of LS roots to stimulation during surgery. The neuromuscular reactions were evaluated in 11 patients, five men and six women. The results were analysed by descriptive statistics and presented as median and interquartile-range values.

RESULTS

In all patients a reliable monitoring of the depth of muscle relaxation was established. The value of supramaximal impulse was 46 mA (38 to 64 mA). The period from rocuronium administration to a spontaneous recovery of the TOF-count = 2 took 33 min (29 to 35 min). Duration from sugammadex administration to a TOF ratio of . 0.70 was 90 seconds (50 to 140) and to a TOF ratio of . 0.90 was 190 seconds (100 to 220 s). A reliable tEMG response of LS nerve roots to electric stimulation at 10 mA intensity was recorded at a TOF ratio of 0.68 (0.56 to 0.77) and at a 5 mA intensity it was reliable at a TOF ratio of 0.86 (0.75 to 0.90).. None of the patients reported radicular symptoms after surgery.

DISCUSSION

From the anatomy of the greater psoas muscle and varied patterns of its LS plexus it is obvious that none of the zones is absolutely safe. In XLIF procedures it is therefore recommended to disect the psoas muscle under both visual and IOM control. Intra-operative checking of the depth of muscle relaxation then will provide information that conditions not affected by rocuronium administration and necessary for the detection of LS roots have been provided.

CONCLUSIONS

1. For a reliable intra-operative identification of LS nerve roots by electric stimulation at a 10 mA intensity it is recommended to achieve the value of TOF ratio equal to at least 0.70. When stimulation at a lower intensity (5 mA) is used, a TOF ratio of . 0.90 is necessary. 2. Administration of sugammadex to reverse an action of the muscle relaxant rocuronium is an effective and quick method to achieve the values required.

Protecting the genitofemoral nerve during direct/extreme lateral interbody fusion (DLIF/XLIF) procedures

A 77-year-old male presented with a history of severe lower back pain for 10 years with radiculopathy, positive claudication type symptoms in his calf with walking, and severe "burning" in his legs bilaterally with walking. Magnetic resonance imaging (MRI) revealed lumbar stenosis at the L3-L4 and L4-L5 levels. During the direct or extreme lateral interbody fusion (DLIF/XLIF) procedure, bilateral posterior tibial, femoral, and ulnar nerve somatosensory evoked potentials (SSEPs) were recorded with good morphology of waveforms observed. Spontaneous electromyography (S-EMG) and triggered electromyography (T-EMG) were recorded from cremaster and ipsilateral leg muscles. A left lateral retroperitoneal transpsoas approach was used to access the anterior disc space for complete discectomy, distraction, and interbody fusion. T-EMG ranging from 0.05 to 55.0 mA with duration of 200 microsec was used for identification of the genitofemoral nerve using a monopolar stimulator during the approach. The genitofemoral nerve (L1-L2) was identified, and the guidewire was redirected away from the nerve. Post-operatively, the patient reported complete pain relief and displayed no complications from the procedure. Intraoperative SSEPs, S-EMG, and T-EMG were utilized effectively to guide the surgeon's approach in this DLIF thereby preventing any post-operative neurological deficits such as damage to the genitofemoral nerve that could lead to groin pain.

Predictors of the outcome of percutaneous nerve evaluation for faecal incontinence

BACKGROUND

The aim was to identify patient-related and operative factors that might predict the outcome of percutaneous nerve evaluation (PNE).

METHODS

Demographic data (age, sex, body mass index), primary cause of incontinence, number and type of incontinence episodes, results of endoanal ultrasonography and manometry, and operative factors from 244 patients who underwent PNE for faecal incontinence were reviewed. Each factor was assessed according to the outcome, and explored by univariable and multivariable analysis to identify predictors.

RESULTS

Some 191 patients (78.3 per cent) had a successful PNE. A low amplitude of sensory threshold during PNE (odds ratio (OR) 0.69 (95 per cent confidence interval 0.59 to 0.81); P < 0.001) and lead placement anterior to the sacral cortex (OR 9.06 (4.70 to 17.45); P < 0.001) were positive predictive factors for successful outcome of PNE. Neither a defect nor an abnormality of either the external (OR 0.88 (0.39 to 1.97); P = 0.749) or internal (OR 0.62 (0.27 to 1.42); P = 0.255) anal sphincter was a negative predictive factor. Demographic variables, number of incontinence episodes and the motor response threshold did not predict outcome.

CONCLUSION

No preoperative predictor of PNE outcome could be identified. Predictors were limited to operative lead placement and sensory response during PNE.

Sacral nerve stimulation induces changes in the pelvic floor and rectum that improve continence and quality of life

PURPOSE

Sacral nerve stimulation (SNS) can improve fecal incontinence, though the exact mechanism is not known. This study examines the following hypotheses: SNS leads to contraction of the pelvic floor, influences rectal perception, and improves continence and quality of life.

METHODS

Fourteen patients with sacral nerve stimulators implanted for fecal incontinence were examined prospectively. Morphological and functional assessment was done by endosonography, manometry, and volumetry with the stimulator turned on and off in direct succession. Questionnaires were used to determine incontinence and quality of life.

RESULTS

With the stimulator turned on, rectal filling conditions were perceived only at higher volumes; in particular, the defecation urge was sensed only at higher volumes. There was also a reduction in the diameters of the external and internal anal sphincters and a decrease in the distance between the anal mucosa and the symphysis as a sign of pelvic floor elevation. Six months after surgery, continence and quality of life were markedly better than before the operation.

CONCLUSIONS

We were able to confirm the hypotheses given above. The improvements of pelvic floor contraction and rectal perception are rapid adjustment processes in response to stimulation of sacral nerves S3/S4 when turning on the stimulator.

Artifact on electromyography produced by an implanted sacral nerve stimulator

A patient with muscle cramps was referred for nerve conduction studies and electromyography. Her study demonstrated bursts of spontaneous electromyography activity, which waxed and waned in amplitude with a "dive bomber"-like sound. The abnormal finding was found to be an artifact from an implanted sacral nerve stimulator for bladder incontinence.

Sacral nerve function in patients with soiling more than 10 years after low anterior resection for lower rectal cancer

BACKGROUND/AIMS

To assess the neurological function of the puborectalis muscles (PM) in patients with or without soiling after low anterior resection (LAR) for lower rectal cancer, we examined the sacral nerve terminal motor latency (SNTML) of the PM.

METHODOLOGY

The latency of the response in the PM following transcutaneous magnetic stimulation of the cauda equina at the levels from S3 to S4 by SNTML was measured in 24 patients after LAR. They were divided into a group with soiling (10 cases; 8 men and 2 women, aged 55 to 70 years with a mean age of 61.6 years) and one without soiling (14 cases; 10 men and 4 women, aged 50 to 69 years with a mean age of 60.3 years), and results were compared with data obtained from 25 control subjects (16 men and 9 women, aged 48 to 71 years with a mean age of 62.1 years). Postoperative monitoring of patients was initiated after a period of more than 10 years (121-144 months; mean: 128.2 months).

RESULTS

1) Distance of anastomosis from the dentate line measured with rectoscopy: Patients with and without soiling registered respective coloproctostomy distances of 2.5 +/- 0.6 (2-3.8) and 5.1 +/- 1.2 (3.0-6.5) cm, with the former showing a tendency (p < 0.0001) toward shorter distances. 2) Values of the SNTML: Patients with soiling (6.9 +/- 2.1 ms) exhibited significant extensions compared with patients without soiling (4.2 +/- 0.6 ms), and control subjects (3.9 +/- 0.6ms) (p < 0.0001, respectively). Moreover, patients without soiling showed more extended SNTML than control subjects at all sites. The conduction delay of SNTML in the patients with soiling was longest, followed by that in those without any soiling, then that in the control subjects.

CONCLUSIONS

Soiling after LAR may be caused by damage to the sacral motor nerves.

[Sacral nerve stimulation, an effective treatment for fecal incontinence]

Sacral nerve stimulation (SNS) became recently an essential therapeutic modality in the treatment of anal incontinence. Indications range from anorectal functional disorders to limited sphincteric lesions. An electrode is inserted through a sacral foramen, generally S3, to stimulate the corresponding nerve root. Patient's selection needs a meticulous multidisciplinary approach. Improved continence of more than 50% is frequently encountered and quality of life is significantly improved after implantation. SNS is a minimal-invasive technique, with very few risks of complications.

Differential sympathetic outflow elicited by active muscle in rats

The present study was undertaken to test the hypothesis that activation of the muscle reflex elicits less sympathetic activation in skeletal muscle than in internal organs. In decerebrate rats, we examined renal and lumbar (mainly innervating hindlimb blood vessels) sympathetic nerve activities (RSNA and LSNA, respectively) during 1 min of 1) repetitive (1- to 4-s stimulation-to-relaxation) contraction of the triceps surae muscle, 2) repetitive tendon stretch, and 3) repetitive contraction with hindlimb circulatory occlusion. During these interventions, RSNA and LSNA responded synchronously as tension developed. The increase was greater in RSNA than in LSNA [+51 +/- 14 vs. +24 +/- 5% (P < 0.05) with contraction, +46 +/- 8 vs. +17 +/- 4% (P < 0.05) with stretch, +76 +/- 20 vs. 39 +/- 7% (P < 0.05) with contraction during occlusion] during all three interventions: repetitive contraction (n = 10, +508 +/- 48 g tension from baseline), tendon stretch (n = 12, +454 +/- 34 g), and contraction during occlusion (n = 9, +473 +/- 33 g). Additionally, hindlimb circulatory occlusion significantly enhanced RSNA and LSNA responses to contraction. These data demonstrate that RSNA responses to muscle contraction and stretch are greater than LSNA responses. We suggest that activation of the muscle afferents induces the differential sympathetic outflow that is directed toward the kidney as opposed to the limbs. This differential outflow contributes to the distribution of cardiac output observed during exercise. We further suggest that as exercise proceeds, muscle metabolites produced in contracting muscle sensitize muscle afferents and enhance sympathetic drive to limbs and renal beds.

2006 Young Investigator Award Winner: lumbosacral nerve root displacement and strain: part 2. A comparison of 2 straight leg raise conditions in unembalmed cadavers

STUDY DESIGN

An inferential cadaveric study.

OBJECTIVES

To compare the displacement and strain of the lumbosacral nerve roots during different conditions of straight leg raise (SLR) with intact foraminal ligaments.

SUMMARY OF BACKGROUND DATA

Clinicians use sensitizing movements such as dorsiflexion during neurodynamic testing, assuming that these prepositions influence the displacement or strain to the lumbosacral nerve roots. Little is known about the effect of these prepositions on neurodynamic behavior.

METHODS

Lower limbs and associated nerve roots of 5 unembalmed cadavers (n = 10) were used to evaluate the displacement and strain of the L4, L5, and S1 roots during 2 different SLR conditions. Fluoroscopic images of intraneural metal markers were digitized to evaluate displacement and strain during SLR with no preposition (SLR NPP) of the ankle and SLR with dorsiflexion preposition (SLR DF) of the ankle, respectively.

RESULTS

SLR NPP produced larger distal displacement at L5 and S1, (P < 0.001) when compared with SLR DF. Displacement comparisons at L4 were nonsignificant (P = 0.051). While nonsignificant, medium to large effect sizes (0.60-0.96) suggest that SLR DF may produce more strain than the SLR NPP condition.

CONCLUSIONS

Prepositions of the SLR test alter the displacement and possibly the strain of the lumbosacral nerve roots in the lateral recess.

2006 Young Investigator Award Winner: lumbosacral nerve root displacement and strain: part 1. A novel measurement technique during straight leg raise in unembalmed cadavers

STUDY DESIGN

A descriptive cadaveric study incorporating a novel nerve root marking technique.

OBJECTIVES

To describe the displacement and strain of the lumbosacral nerve roots in the lateral recess during straight leg raise (SLR) without disrupting the foraminal ligaments.

SUMMARY OF BACKGROUND DATA

Previous studies document 2 to 8 mm of lumbosacral nerve root displacement during SLR. Prior dissection methods incorporated laminectomy and facetectomy.

METHODS

Lower limbs and associated nerve roots of 5 unembalmed cadavers (n = 10) were studied. Metal markers were inserted intraneurally within the lateral recess of L4, L5, and S1 with a modified spinal needle. Fluoroscopic images were digitized to evaluate displacement and strain during SLR.

RESULTS

The lumbosacral nerve roots in the lateral recess moved less and experienced less strain during SLR than described in previously published reports. Statistically significant distal displacement occurred at hip positions greater than 60 degrees of flexion at all nerve root levels (P < 0.01).

CONCLUSIONS

The lumbosacral nerve roots (L4, L5, S1) moved less and underwent less strain during SLR testing than previously reported and may require hip motion greater than 60 degrees to produce substantive displacement in the lateral recess. Additional research is needed to examine the effects of prepositioning during SLR.

Nonuniformity in the von Bezold-Jarisch reflex

The von Bezold-Jarisch reflex (BJR) is a vagally mediated chemoreflex from the heart and lungs, causing hypopnea, bradycardia, and inhibition of sympathetic vasomotor tone. However, cardiac sympathetic nerve activity (CSNA) has not been systematically compared with vasomotor activity during the BJR. In 11 urethane-anesthetized (1-1.5 g/kg iv), artificially ventilated rats, we measured CSNA simultaneously with lumbar sympathetic activity (LSNA) while the BJR was evoked by right atrial bolus injections of phenylbiguanide (0.5, 1.0, 1.5, and 2 microg). Nerve and heartbeat responses were analyzed by calculating normalized cumulative sums. LSNA and heartbeats were always reduced by the BJR. An excitatory "rebound" component often followed the inhibition of LSNA but never outweighed it. For CSNA, however, excitation usually (in 7 of 11 rats) outweighed any initial inhibition, such that the net response to phenylbiguanide was excitatory. The differences in net response between LSNA, CSNA, and heartbeats were all significant (P < 0.01). A second experimental series on seven rats showed that methyl atropine (1 mg/kg iv) abolished the bradycardia of the BJR, whereas subsequent bilateral vagotomy substantially reduced LSNA and CSNA responses, both excitatory and inhibitory. These findings show that, during the BJR, 1) CSNA is often excited, 2) there may be coactivation of sympathetic and parasympathetic drives to the heart, 3) divergent responses may be evoked simultaneously in cardiac vagal, cardiac sympathetic, and vasomotor nervous pathways, and 4) those divergent responses are mediated primarily by the vagi.

Acupuncture stimulation to the sacral segment affects state of vigilance in rats

The effects of acupuncture stimulation to the sacral segment on electroencephalograms (EEGs) and activity of locus coeruleus (LC) neurons were examined in urethane-anesthetized rats. In 71 of 112 trials, when EEGs displayed small amplitude and high frequency, stimulation to the sacral segment-induced large amplitude and slow EEGs with a latency of <450s and duration ranged from 32s to >42 min. Stimulus-induced EEGs comprised significant increases in delta power and significant decreases in theta and beta powers. After intraperitoneal administration of bicuculline, stimulation to the sacral segment failed to induce changes in EEG pattern. Firing rate of noradrenergic LC neurons decreased significantly from 2.9+/-1.5 to 1.1+/-0.8 Hz (n=11, p<0.001). Decreased neuronal activity exhibited close relationships with increased EEG amplitude. These results suggest that acupuncture stimulation to the sacral segment changes the state of animals from light anesthesia to deep anesthesia, and that this change is mediated by GABAergic systems suppressing the activity of noradrenergic LC neurons.

Anatomical significance of the nerve to the pyramidalis muscle: a morphological study

Characteristics of the nerve to the pyramidalis muscle (NPy), including its origin, course and distribution, were observed (macroscopically) in detail in the present study. The spinal segments that give rise to the nerve vary considerably and involve Th12-L2. The course and distribution of the nerve also vary widely. The NPy is given off from one of the following: (i) the anterior cutaneus branch (Rca) of the intercostals nerve; (ii) the ilioinguinal (li) nerve; or (iii) the genital branch (Rg) of the genitofemoral nerve. The NPy can be classified into nine types according to features of the course and branching pattern of the Rca and li. In three of 67 cases, the pyramidalis muscle had two nerves. Double-innervated pyramidalis muscles received one nerve from a transitional-type Rca (Rcat) and a second nerve derived from one of the superficial Rca (Rcas), li or Rg. The NPy derived from the deep Rca (Rcap; Type 1), Rcat (Type 2) and containing their features as well as the Type 9 (Rcat + li + Rg) reach the muscle from behind. Types 3-8 (not containing features of the Rcap and Rcat) enter the muscle from its surface. The branch that gives off the NPy is determined by the level of segmental origin, with the segmental origin of branches from the Rca (Types 1-4), li (Types 5-6) and Rg (Types 7-9) getting lower in that order. The level of segmental origin of the NPy derived from different Rca becomes lower in the following order: Rcap (Type 1), Rcat (Type 2), Rcas (Type 3), Rcas' (Rcas entering the inguinal canal; Type 4). When the origin of the NPy is from a lower segment, the origin of the boundary nerve (Rcap/Rcas) is also deviated downward. The changes in the NPy are related to the deviation of the entire lumbar plexus.

Sacral nerve stimulation for neuromodulation of the lower urinary tract

Patients with symptoms of overactive bladder syndrome or non-obstructive urinary retention, refractory to conservative therapy, can nowadays be treated minimally invasively with sacral nerve stimulation (SNS). The use of electric currents to treat urological pathology has a long history but SNS therapy only received FDA approval in 1997. The mechanisms of action are still not known so there are different theories explaining the modulation effect. Recent studies have shown a central modulation effect. Predictive factors which can help to identify the perfect candidates are not known. Over the years the technique of SNS has become less invasive and because of two stage implantation test results have proven to be more reliable. The clinical results for this therapy have proven to be safe and effective and with the technical improvements over the years the re-operation and complication rates have decreased significantly. The clinical results have led to expanding indications because of positive effects in other symptoms. In the field of urology this has resulted in the use of SNS therapy for interstitial cystitis, neurogenic lower urinary dysfunction, and pediatric voiding dysfunction. In the field of gastro-intestinal pathology, SNS therapy is used to treat faecal incontinence and constipation.

Adductor T and H reflexes in humans

In the belief that changes in the adductor reflex (AR) may be helpful in evaluating lumbar root and plexus lesions, expression of the AR was studied in 43 healthy human subjects. ARs elicited with an electronic reflex hammer were recorded from the inner side of the proximal thigh using needle and surface electrodes, and patellar reflexes (PRs) were recorded simultaneously. These reflexes were obtained by tapping the ipsilateral medial aspect of the knee, the contralateral patellar tendon, the ipsilateral and contralateral anterior superior iliac spines, and the Achilles tendon. The H reflex of the obturator nerve was also evaluated in 17 cases. ARs were evoked consistently by tapping the ipsilateral medial aspect of the knee and by contralateral patellar tap, and by tapping ipsilateral and contralateral anterior superior iliac spines when a needle recording electrode was used. Sometimes an Achilles tendon tap also elicited the AR ipsilaterally. By contrast, the PR could only be elicited by a tap to the ipsilateral patellar tendon. ARs have somewhat different features than other well-known tendon reflexes such as the PR and are recorded consistently when a needle electrode is used, being elicited from both distal and proximal areas of the legs by tapping the Achilles tendon or anterior superior iliac spines unilaterally or bilaterally. Their role in evaluating lumbar root disease and monitoring adductor spasticity merits investigation.

Locomotor-related networks in the lumbosacral enlargement of the adult spinal cat: activation through intraspinal microstimulation

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.

Use of Sequential Electrical Nerve Stimuli (SENS) for Location of the Sciatic Nerve and Lumbar Plexus

BACKGROUND AND OBJECTIVES

Conventional electrical stimulation has been done by continuous adjustment of current amplitude at a single, set pulse duration (conventionally, 0.1 ms). This study evaluated a novel technique for nerve location by utilization of a peripheral-nerve stimulator (PNS) programmed to deliver sequential electrical nerve stimuli (SENS). A repeating series of alternating sequential pulses of 0.1, 0.3, and 1.0 ms at 1/3-second period intervals between pulses were generated so that at a greater distance from the nerve, only higher-duration pulses would stimulate the targeted nerve and result in 1 or 2 motor responses (MR) per second. Three MR per second at 0.5 mA or less signified the conventional endpoint for nerve location (</=0.5 mA, 0.1 ms) because that value indicated that the 0.1-ms pulse was effective. The conventional 0.1-ms pulse served as a built-in control to which the SENS was compared.

METHODS

Sixteen sciatic/psoas blocks were performed on 8 patients. Nerve location was by SENS, with an 80-mm block needle. Needle advance began at 1.0 mA until MR. If 1 or 2 MR/s occurred, the needle was advanced until 3 MR/s were obtained. When 3 MR/s occurred at 0.5 mA or less, needle position was fixed (final position), and mA further decreased until MR disappeared. Two digital video cameras separately recorded needle depth and MR for analysis. Final needle position was designated as zero, and distance was calculated relative to it.

RESULTS

In 12 of 16 of the performed blocks, SENS resulted in advanced notification (1 or 2 MR/s), which yielded additional visual feedback compared with control before final nerve location and, thus, increased range. In 15 of 16 blocks, MR did not disappear, once elicited, through final needle location.

CONCLUSIONS

SENS resulted in increased sensitivity without compromising specificity of nerve location.

Ultrasound imaging of sacral reflexes

OBJECTIVES

To investigate the reliability of examination of the guarding reflex of the pelvic floor by dynamic perineal ultrasonography in children with bladder dysfunction and in controls.

METHODS

A total of 40 patients with nonneurogenic bladder/sphincter dyssynergia, 40 with spina bifida, and 40 controls underwent a dynamic ultrasound examination of the pelvic floor while coughing and while being tapped on the abdominal wall. The reflex action of the puborectal muscle in females, and the combined action of the puborectal muscle and external sphincter muscle in males, were recorded.

RESULTS

Of the 40 patients with nonneurogenic bladder/sphincter dyssynergia, 38 had a normal reflex action of the puborectal muscle during the abdominal tap and 36 had a normal reflex action when coughing. Two of these patients had unexplained underactive bladder syndrome and were using clean intermittent catheterization, and two could not be assessed because of hypermobility of the bladder neck when coughing but had a normal reaction during abdominal tapping. Of the 40 patients with spina bifida, none had puborectal activity during coughing and 5 had some puborectal activity during tapping. Of the 40 controls, 39 had normal reflex activity during both coughing and tapping.

CONCLUSIONS

The question of whether a child has nonneurogenic or neuropathic bladder/sphincter dysfunction is often difficult to answer on the basis of urodynamic studies alone. Dynamic perineal ultrasound recording of the S2-S4 reflex arches provides reliable additional information and is noninvasive to the patient.

[Use of permanent electrodes in the peripheral nerve evaluation test (PNE-Test) in comparison to conventional wire electrodes]

PURPOSE

Prior to implantation of a chronic sacral neurostimulator, it is important to establish which patients might profit from this kind of therapy in order to ensure, by means of a PNE (peripheral nerve evaluation) test, that the implantation of a permanent stimulating device is effective. In this study we compared the two different techniques used in our department (implantation of the permanent neurostimulation electrodes, the so-called "two-stage-implantation" vs. conventional PNE).

MATERIALS AND METHODS

We performed a sacral nerve stimulation in 53 patients (mean age: 49.7 years, range: 14 - 75 years) over a minimum of 5 days. In 42 patients we performed a conventional PNE, 11 patients underwent "two-stage implantation" with implantation of the permanent electrodes.

RESULTS

52 of 53 patients received bilateral test stimulation (9 % at S2, 91 % at S3). One patient underwent unilateral PNE (S3) because of an anatomic deformity of the os sacrum. In 20 cases the conventional PNE-test (cPNE) was successful according to standard criteria (47.6 % of all cPNE). The response rate of "two-stage implantation" with implantation of the permanent electrodes was 81.8 % (9 of 11 patients).

CONCLUSIONS

The success rate of implantation of permanent neurostimulation electrodes in selecting patients for the permanent implant is significantly higher than the conventional PNE. In this group patients with neurogenic and overactive bladder dysfunctions showed the highest response rates to sacral nerve stimulation and are the most likely to benefit from sacral neuromodulation.

The sympathoinhibitory effects of systemic cholecystokinin are dependent on neurons in the caudal ventrolateral medulla in the rat

The gastrointestinal hormone CCK inhibits a subset of presympathetic neurons in the rostroventrolateral medulla (RVLM) that may be responsible for driving the sympathetic vasomotor outflow to the gastrointestinal circulation. We tested the hypothesis that the central neurocircuitry of this novel sympathoinhibitory reflex involves a relay in the caudal ventrolateral medullary (CVLM) depressor area. Blood pressure and greater splanchnic sympathetic nerve discharge (SSND) or lumbar sympathetic nerve discharge (LSND) were monitored in anesthetised, paralyzed male Sprague-Dawley rats. The effects of phenylephrine (PE, 10 microg/kg iv; baroreflex activation), phenylbiguanide (PBG, 10 microg/kg iv; von Bezold-Jarisch reflex) and CCK (4 or 8 microg/kg iv) on SSND or LSND, were tested before and after bilateral injection of 50-100 nl of the GABAA agonist muscimol (1.75 mM; n=6, SSND; n=7, LSND) or the excitatory amino acid antagonist kynurenate (55 mM; n=7, SSND) into the CVLM. PE and PBG elicited splanchnic and lumbar sympathoinhibitory responses that were abolished by bilateral muscimol or kynurenate injection into the CVLM. Similarly, the inhibitory effect of CCK on SSND was abolished after neuronal inhibition within the CVLM. In contrast, CCK-evoked lumbar sympathoexcitation was accentuated following bilateral CVLM inhibition. In control experiments (n=7), these agents were injected outside the CVLM and had no effect on splanchnic sympathoinhibitory responses to PE, PBG, and CCK. In conclusion, neurons in the CVLM are necessary for the splanchnic but not lumbar sympathetic vasomotor reflex response to CCK. This strengthens the view that subpopulations of RVLM neurons supply sympathetic vasomotor outflow to specific vascular territories.

Role of peripheral innervation in p-chloroamphetamine-induced ejaculation in anesthetized rats

The occurrence of ejaculation, which consists of 2 distinct phases (emission and expulsion), requires a tight coordination of peripheral autonomic and somatic nerves. However, some aspects of the mechanism of ejaculation are not clearly defined. To clarify this issue, we used the p-chloroamphetamine (PCA)-induced ejaculation model in anesthetized rats and investigated the effects of selective peripheral nerves lesions on seminal vesicle and bulbospongiosus (BS) muscle activities as representing physiological markers of emission and expulsion phases, respectively. In intact rats, ejaculation induced with PCA (intraperitoneal 5 mg/kg) correlated with coordinated increases in seminal vesicle pressure (SVP) and BS electromyographic activity. PCA-induced ejaculation was still observed in rats with bilateral lesion of hypogastric nerves (HNx), lumbar paravertebral sympathetic chain (LSCx), or dorsal nerves of the penis (DNPx). Conversely, bilateral section of pelvic nerves (PNx) or L6-S1 dorsal roots (DRx) abolished PCA-induced ejaculation. The amplitude of SVP increases induced by PCA was reduced in PNx, HNx, and LSCx rats, whereas it was unchanged in DRx and DNPx rats. The time interval between SVP increases and BS muscle contractions induced by PCA was comparable in the different neural lesion groups. In conclusion, PCA initiates both emission and expulsion independently from each other. In this model, afferents conveyed by the pelvic nerves appear to be unnecessary for occurrence of BS muscle contractions but are essential for a complete ejaculatory response.

Sacral nerve stimulation can be successful in patients with ultrasound evidence of external anal sphincter disruption

PURPOSE

This study was designed to determine whether patients with fecal incontinence and endoanal ultrasound evidence of anal sphincter disruption may be successfully treated by sacral nerve stimulation.

METHODS

Five consecutive females with incontinence to solids and endoanal ultrasound evidence of anal sphincter disruption were treated by a two-week trial of sacral nerve stimulation. If successful, patients then proceeded to permanent sacral nerve stimulation implantation.

RESULTS

Five patients, aged 34 to 56 years, were treated by temporary sacral nerve stimulation. Four had symptoms starting after childbirth. Two had previously had an anterior sphincter repair. After a two-week trial, three females reported full continence and an improvement in all aspects of their Rockwood fecal incontinence quality of life scores. These three females underwent permanent sacral nerve stimulation implantation. The remaining two patients reported no improvement and underwent dynamic graciloplasty or end colostomy respectively.

CONCLUSIONS

Sacral nerve stimulation may successfully restore bowel continence in some patients with endoanal ultrasound evidence of a defect in their external anal sphincter.

Determination of therapeutic threshold in sacral nerve modulation for faecal incontinence

Background

The aim of the study was to determine the therapeutic stimulation threshold in patients with successful sacral nerve modulation for faecal incontinence.

Methods

Patients who had undergone successful permanent sacral nerve modulator implantation and had been followed up for a minimum of 3 months were included. The sensitivity threshold and motor threshold were determined and correlated with therapeutic response. Patients went home with the stimulator set at 0·6 V below the sensitivity threshold. Each week the voltage was increased by 0·2 V until the sensitivity threshold was reached. The effects on anorectal physiology and continence were recorded.

Results

Eight patients (seven women) with a median age of 58·5 years were included. The median follow-up was 6·3 months. The median sensibility threshold volume of rectal sensation was 50 ml, the median urge threshold volume was 140 ml and the median maximum tolerated rectal volume 240 ml. The median number of incontinence episodes and days per week affected by incontinence decreased from 5·0 and 3·8 before operation to 0·7 and 0·7 respectively after follow-up for 3 months. At anorectal manometry the median resting and stimulation anal canal pressures were 57 and 85 mmHg respectively, and remained constant over time. The therapeutic response threshold was significantly lower than the sensitivity threshold (median 1·6 versus 1·7 V; P = 0·042). The median motor threshold was 2·1 V, significantly higher than the sensitivity threshold (P = 0·009). The stimulation threshold for suboptimal therapeutic response was 1·4 V. In five of the eight patients the therapeutic response threshold was the same as the sensitivity threshold.

Conclusion

Sacral nerve modulation can produce a therapeutic effect below the sensitivity threshold. A lower stimulation voltage increases the lifespan of the pulse generator.

Use of chronic sacral nerve stimulation in neurological voiding disorders

AIM

Neurogenic low urinary tract dysfunctions unresponsive to medical and conservative therapy are difficult to manage. Nowadays they can be treated with Sacral Nerve Stimulation (SNS), even if clinical experiences reported in literature are still limited.

METHODS

We performed SNS in 6 patients with neurogenic bladder: 3 patients had incontinence-urgency (1 myelitis, 1 multiple sclerosis, 1 autonomic polineuropathy) and 3 patients had urinary retention (1 incomplete spinal cord lesion, 1 operation for discal hernia T5-T6, 1 hysterectomy).

RESULTS

Among cases with incontinence-urgency we achieved complete control of the bladder in 2 patients while in 1 patient the number of urinary losses was reduced of the 80%. In 2 patients with urinary retention we obtained complete recovery of the bladder function, while in 1 patient the number of cateterisms/die reduced of 50%, the urinary volume for micturion increased and residual urinary volume decreased. Results were unchanged during the follow-up (maximum 26 months), except for 1 patient in which a partial loss of effectiveness occurred.

CONCLUSIONS

Chronic electric stimulation of S3 sacral roots via an implanted neuroprotesis is therefore an effectiveness, save and promising therapeutic option in treatment of neurogenic bladder dysfunctions.

Extracellular voltage profile for reversing the recruitment order of peripheral nerve stimulation: a simulation study

Electrical stimulation of peripheral nerve activates large-diameter fibers before small ones. A physiological recruitment order, from small to large-diameter axons, is desirable in many applications. Previous studies using computer simulations showed that selective activation of small fibers could be achieved by reshaping the extracellular voltage profile along the nerve using an array of nine electrodes. In this study, several electrode-array configurations were tested in order to minimize the number of contacts. Electrode arrays of 5, 7, 9, and 11 contacts with 0.75 mm contact separation were performed in computer simulations of dog sacral root (S2). Electrode arrays of 5 and 7 contacts recruited 40% of small axons (<10 microm) when recruiting only 10% of larger axons. Effectiveness of 9- and 11-contact arrays decreased with the presence of epineurium and perineurium. The effectiveness of electrode arrays was independent of stimulation pulsewidth. The biphasic-pulse stimulation with the amplitude of the second phase set as low as possible should be used to prevent the excitation of large axons during the second phase and to minimize the electrode corrosion. Arrays of 5 and 7 contacts also decreased the recruitment curve slope to 26% and 51% of the tripolar electrode, respectively. This modeling study predicts that reversing the recruitment order of peripheral nerve stimulation could be achieved by reshaping the extracellular voltage using electrode arrays of 5 or 7 contacts.

Innovations in fecal incontinence: sacral nerve stimulation

OBJECTIVE

The aim of this study was to present an overview of sacral nerve stimulation in the treatment of fecal incontinence. We describe the evolution in technique, patient selection, and indications, and review results and complications.

METHODS

All articles on sacral nerve stimulation for fecal incontinence that were recovered on MEDLINE search were reviewed. With multiple articles from an institution, the most recent reports with the longest follow-up and largest cohort of patients were selected, unless information from earlier reports was relevant.

RESULTS

The technique of sacral stimulation is well established, carries little risk, and continues to be refined (e.g., a less invasive approach has been proposed). Patient selection is based on a two-stage diagnostic test stimulation (acute and subchronic), for which the predictive value is high. On this basis, permanent sacral nerve stimulation has proved effective in both single-center and multicenter trials in patients with a functional deficit but limited morphologic lesions or no morphologic lesions. The clinical benefit derives from multiple symptomatic improvements contributing to better bowel control and from substantially improved quality of life. The underlying mechanism of action remains undefined, but both somatic and autonomic function appears affected.

CONCLUSION

Sacral nerve stimulation offers a safe treatment mode in a patient population in whom conservative treatment has failed and traditional surgical approaches would have limited success. The high predictive value of the diagnostic approach offers a unique therapeutic advantage.

Pattern of sensory innervation of the perineal skin in the female rat

Here we describe the nerves innervating the perineal skin together with their sensory fields in the adult female rat. Electrophysiological recording showed that the lumbosacral and L6-S1 trunks, in part by way of the sacral plexus, transmit sensory information from the perineal skin via four nerves: the viscerocutaneous branch of the pelvic nerve innervating the skin at the midline between the vaginal opening and anus, the sensory branch of the pudendal nerve innervating the clitoral sheath, the distal perineal branch of the pudendal nerve innervating a broad area of skin adjacent to the vaginal opening and anus, and the proximal perineal branch of the sacral plexus innervating a broad area of skin adjacent to the clitoris and vaginal opening. The sensory fields of three of these nerves overlapped to some degree: the viscerocutaneous branch of the pelvic and the distal perineal branch of the pudendal nerves at the midline skin between the vaginal opening and the anus, and the distal perineal branch of the pudendal nerve and the proximal perineal branch of the sacral plexus at the skin lateral to the vaginal opening. Such overlap might provide a safeguard helping to ensure that somatosensory input from the perineal region important for triggering reproductive and nonreproductive reflexes reaches the CNS.

Sacral nerve stimulation for treatment of fecal incontinence in a patient with muscular dystrophy: report of a case

Fecal incontinence is a common condition that causes major impairment of social life. Sacral nerve stimulation is a promising treatment in idiopathic fecal incontinence when conventional treatments have failed. However, new indications for sacral nerve stimulation are emerging. The present case shows that sacral nerve stimulation for treatment of fecal incontinence may be justified in other diseases in which fecal incontinence is a major problem.

Sacral neuromodulation in patients with fecal incontinence: a single-center study

PURPOSE

Fecal incontinence is a psychologically devastating and socially incapacitating condition. Conventional treatment is likely to improve continence in many patients; however, there remains a group with persisting symptoms who are not amenable for a simple surgical repair. We evaluated the effect of sacral neuromodulation in patients with structurally intact sphincters after failure of conventional treatment.

METHODS

Patients aged 18 to 75 years were evaluated. Incontinence was defined as involuntary loss of stool at least once per week, which was objectified by completion of a three-week bowel-habits diary during ambulatory electrode stimulation at the S3 or S4 foramen. Patients were qualified for permanent stimulation when showing a reduction of at least 50 percent in incontinence episodes or days.

RESULTS

Seventy-five patients (66 females; mean age, 52 (range, 26-75) years) were treated. Three patients had partial spinal cord injury, two patients a previous low-anterior resection, and nine patients had a previous sphincter repair. Evaluation after trial screening showed that 62 patients (83 percent) had improved continence. Median incontinence episodes per week decreased from 7.5 to 0.67 (P < 0.01), median incontinence days per week from 4 to 0.5 (P < 0.01). The symptomatic response stayed unchanged after implantation of a permanent electrode and pacemaker in 50 patients. After a median follow-up of 12 months, this effect could be sustained in 48 patients. Anal manometry during stimulation showed no increase of sphincter pressures.

CONCLUSIONS

Sacral neuromodulation is a feasible treatment option for fecal incontinence in patients with structurally intact sphincters.

Sacral nerve stimulation in fecal incontinence

PURPOSE

The effect of sacral nerve stimulation was studied in 45 patients with fecal incontinence.

METHODS

All patients were initially tested in general anesthesia. Sacral nerves 2, 3, and 4 were tested on both sides. If a perineal/perianal muscular response to sacral nerve stimulation could be obtained, electrodes were implanted for a three-week test-stimulation period. If sacral nerve stimulation resulted in at least a 50 percent reduction in incontinence episodes during the test period, a system for permanent sacral nerve stimulation was implanted.

RESULTS

When tested in general anesthesia, 43 of 45 patients had a muscular response to sacral nerve stimulation and had electrodes implanted for the three-week test period. Percutaneous electrodes were used in 34 patients, and 23 of these had at least a 50 percent reduction in incontinence episodes, whereas the electrodes dislocated in 7 patients and 4 had a poor response. Permanent electrodes with percutaneous extension electrodes were used primarily in 9 patients and after dislocation of percutaneous electrodes in an additional 6 patients; 14 of these had a good result. In the last patient, no clinical response to stimulation with the permanent electrode could be obtained. A permanent stimulation system was implanted in 37 patients. After a median of six (range, 0-36) months follow-up, five patients had the system explanted: three because the clinical response faded out, and two because of infection. Incontinence score (Wexner, 0-20) for the 37 patients with a permanent system for sacral nerve stimulation was reduced from median 16 (range, 9-20) before sacral nerve stimulation to median 6 (range, 0-20) at latest follow-up ( P < 0.0001). There was no differences in effect of sacral nerve stimulation in patients with idiopathic incontinence (n = 19) compared with spinal etiology (n = 8) or obstetric cause of incontinence (n = 5). Sacral nerve stimulation did not influence anal pressures or rectal volume tolerability.

CONCLUSIONS

Sacral nerve stimulation in fecal incontinence shows promising results. Patients with idiopathic, spinal etiology, or persisting incontinence after sphincter repair may benefit from this minimally invasive treatment.

Splanchnic and pelvic mechanosensory afferents signal different qualities of colonic stimuli in mice

BACKGROUND & AIMS

Mechanosensory information from the colon is conducted via lumbar splanchnic nerves (LSN) and sacral pelvic nerves (PN) to the spinal cord. The precise nature of mechanosensory information encoded by each pathway has remained elusive. Here, we characterize and directly compare the properties of mechanosensitive primary afferents from these 2 pathways.

METHODS

Using a novel in vitro mouse colon preparation, mechanosensitive primary afferents were recorded from the LSN and PN and distinguished based on their response to receptive field stimulation with 3 distinct mechanical stimuli: probing (70 mg-4 g), circular stretch (1-5 g), and mucosal stroking (10-1000 mg).

RESULTS

Five different classes of afferent were recorded from the LSN and PN. Three of these classes of afferent (serosal, muscular, and mucosal) were conserved between both pathways; however, their respective proportions, receptive field distributions, and response properties differed greatly. In general, these 3 classes of afferent recorded from the PN responded to lower stimulation intensities, displayed greater response magnitudes, and adapted less completely to mechanical stimulation compared with their LSN counterparts. In addition, the LSN and PN each contain a specialized class of afferent (mesenteric and muscular/mucosal), which is unique to their respective pathway.

CONCLUSIONS

The splanchnic and pelvic pathways contain distinct populations of mechanosensitive afferents. These afferents are capable of detecting an array of mechanical stimuli and are individually tuned to detect the type, magnitude, and duration of the stimulus. This knowledge contributes to our understanding of the role that these 2 pathways play in conveying mechanical information from the colon.