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.