Functional variability of sacral roots in bladder control

The predictive value of intraoperative bulbocavernosus reflex monitoring for postoperative voiding function in patients with conus medullaris and cauda equina tumors: a retrospective single center study

BACKGROUND CONTEXT

Surgical resection is the preferred treatment in most conus medullaris and cauda equina tumor (CMCET) cases. However, total resection is usually challenging to obtain and has a strong possibility of causing various complications if forcibly attempted. Intraoperative neurophysiological monitoring (IONM) has become a necessary adjunctive tool for CMCET resection.

PURPOSE

The current study aimed to evaluate the application value of bulbocavernosus reflex (BCR) monitoring in CMCET surgery.

STUDY DESIGN

A retrospective clinical study.

PATIENT SAMPLE

The medical records of patients who underwent CMCET resection by the same neurosurgical team at our hospital from September 2020 to June 2022 were retrospectively reviewed. IONM was conducted in all surgeries. According to inclusion criteria and exclusion criteria, ultimately, 105 patients were enrolled in the study.

OUTCOME MEASURES

The voiding function was assessed before surgery, 1 month after, and 6 months after surgery using the Neurogenic Bladder Symptom Score (NBSS). If the NBSS obtained 1 month after surgery exceeds 9 points than that before surgery, it can be considered that the patient suffered new-onset postoperative voiding dysfunctions (PVDs). Moreover, if the NBSS could restored (less than 9 points higher than before the surgery) at 6 months after surgery, it was defined as a short-term PVD. Otherwise, it was defined as a long-term PVD.

METHODS

The amplitude reduction ratios (ARRs) of bilateral BCR waveforms were calculated and compared between patients with PVDs and those without. The receiver operating characteristic curve analysis was subsequently applied to determine the cut-off value of the maximal and minimal ARRs for predicting PVDs.

RESULTS

The maximal and minimal ARRs were significantly correlated with short-term and long-term PVDs (p<.001 for all comparisons, Mann-Whitney U test). The threshold values of maximal ARR for predicting short-term and long-term PVD were 68.80% (AUC=0.996, p<.001) and 72.10% (AUC=0.996, p<.001), respectively. While those of minimal ARR were 50.20% (AUC=0.976, p<.001) and 53.70% AUC=0.999, p<.001).

CONCLUSIONS

The amplitude reduction of intraoperative bilateral BCR waveforms showed high predictive value for PVDs.

Intraoperative Neurophysiological Monitoring in Tethered Cord Syndrome Surgery: Predictive Values and Clinical Outcome

INTRODUCTION

"Tethered cord syndrome" (TCS) refers to a congenital abnormality associated with neurological signs and symptoms. The aim of surgery is to prevent or arrest their progression. This study reports a retrospective case series of tethered cord syndrome surgeries, supported by intraoperative neurophysiological monitoring.

METHODS

The case series comprises 50 surgeries for tethered cord syndrome in which multimodal intraoperative neurophysiological monitoring was performed using motor evoked potentials (transcranial motor evoked potentials [TcMEPs]), tibial nerve somatosensory evoked potentials (TNSEPs), and pudendal-anal reflex (PAR). The intraoperative neurophysiological monitoring results are reported and correlated with clinical outcomes.

RESULTS

Sensitivity, specificity, and negative predictive value were high for TcMEPs and TNSEPs, while PAR exhibited low sensitivity and positive predictive value but high specificity and negative predictive value. Fisher's exact test revealed a significant correlation between changes in TcMEPs, TNSEPs, and clinical outcome ( P < 0.000 and P = 0.049 respectively), but no correlation was detected between PAR and urinary/anal function ( P = 0.497).

CONCLUSIONS

While TcMEPs and TNSEPs were found to be reliable intraoperative neurophysiological monitoring parameters during tethered cord syndrome surgery, PAR had low sensitivity and positive predictive value probably because the reflex is not directly related to bladder function and because its multisynaptic pathway may be sensitive to anesthetics. New onset muscle weakness and sensory deficits were related to postoperative changes in TcMEPs and TNSEPs, whereas changes in PAR did not predict bladder/urinary impairment. Urinary deficits may be predicted and prevented with other neurophysiological techniques, such as the bladder-anal reflex.

Nonbinary 2D Distribution Tool Maps Autonomic Nerve Fiber Clustering in Lumbosacral Ventral Roots of Rhesus Macaques

Neuromodulation of the peripheral nervous system (PNS) by electrical stimulation may augment autonomic function after injury or in neurodegenerative disorders. Nerve fiber size, myelination, and distance between individual fibers and the stimulation electrode may influence response thresholds to electrical stimulation. However, information on the spatial distribution of nerve fibers within the PNS is sparse. We developed a new two-dimensional (2D) morphological mapping tool to assess spatial heterogeneity and clustering of nerve fibers. The L6-S3 ventral roots (VRs) in rhesus macaques were used as a model system to map preganglionic parasympathetic, γ-motor, and α-motor fibers. Random and ground truth distributions of nerve fiber centroids were determined for each VR by light microscopy. The proposed tool allows for nonbinary determinations of fiber heterogeneity by defining the minimum distance between nerve fibers for cluster inclusion and comparisons with random fiber distributions for each VR. There was extensive variability in the relative composition of nerve fiber types and degree of 2D fiber heterogeneity between different L6-S3 VR levels within and across different animals. There was a positive correlation between the proportion of autonomic fibers and the degree of nerve fiber clustering. Nerve fiber cluster heterogeneity between VRs may contribute to varied functional outcomes from neuromodulation.

Posterior Surgical Ligation and Cyst Decompression -via Needle Puncture- of a Large Anterior Sacral Pelvic Meningocele Through Posterior Sacral Laminectomy

The first documented description of an anterior sacral meningocele was Bryant's in 1823. Anterior sacral meningocele patients have constipation as a universal symptom; urinary incontinence is also common. All the symptoms are directly related to the pressure from a pelvic mass on adjacent structures. When the patient stands, a headache often develops because the spinal fluid pressure decreases as the meningocele sac fills. Finally, a scimitar-shaped sacrum on a neuroradiological anteroposterior plain assessment is pathognomonic. The coccyx may be absent, and the lower sacral laminae may be absent or incomplete. The surgical options for this rare clinical condition are still matter of debate.Anterior sacral meningocele is a pathology that lacks a current classification and neurosurgical therapeutic standards, even though a similar dynamic has been shown by the related traumatic pseudomeningocele. Anterior approaches (retro- and transperitoneal meningocele neck occlusion with internal cerebrospinal fluid (CSF) cyst drainage) and posterior approaches (posterior sacral laminectomy, dural sac ligation, and CSF cyst drainage) are the available surgical strategies.We now report the case of an adult patient for whom a posterior approach was suggested and performed and report her postoperative surgical follow-up. The surgical rationale is also discussed.

Intraoperative Neuromonitoring for Pediatric Pelvic Tumors

Background

Tumors of the pre-sacral and sacral spaces are a rare occurrence in children. Total tumor excision is required due to the significant risk of relapse in the event of partial surgery, but the surgical procedure may lead to postoperative problems such as urinary, sexual, and anorectal dysfunctions. Intraoperative neuromonitoring (IONM) has gained popularity in recent years as a strategy for preventing the onset of neurologic impairments by combining several neurophysiological techniques. The aim of our study is to describe the experience of Bambino Gesù Children's Hospital in the use of IONM in pediatric pelvic surgery.

Materials and Methods

The data of patients treated for pelvic malignancies at Bambino Gesù Children's Hospital from 2015 to 2019 were retrospectively collected. All patients were assessed from a neurologic and neuro-urologic point of view at different time-points (before and immediately after surgery, after 6 months, and 1-year follow-up). They were all monitored during a surgical procedure using multimodal IONM including transcranial motor evoked potentials (TcMEP), triggered-EMG (t-EMG), pudendal somatosensory evoked potentials (PSSEP), and bulbocavernosus reflex (BCR).

Results

During the study period, ten children underwent pelvic tumor removal at our Institution. In all cases, intraoperative neurophysiological recordings were stable and feasible. The preservation of neurophysiological response at the same intensity during surgical procedures correlated with no new deficits for all neurophysiological techniques.

Discussion

Although the impact of the IONM on surgical strategies and clinical follow-up is unknown, this preliminary experience suggests that the appropriate use of several neurophysiological techniques can influence both the radicality of pelvic tumor removal and the neurological and urological outcome at clinical follow-up. Finally, because of the highly complex anatomy and inter-individual variances, this is especially useful in this type of surgery.

Sacral neuromodulation: sacral anatomy and optimal lead placement

INTRODUCTION AND HYPOSTHESIS

To develop an instructional video that correlates cadaveric anatomy with fluoroscopic images to assist in conceptualization of optimal placement of the foramen needle and lead to complete an efficient and successful sacral neuromodulation (SNM) procedure.

METHODS

A SNM procedure was performed and recorded on a fresh female cadaver. Fluoroscopic images were obtained during the procedure to highlight the bony relationships to the S3 foramen and nerve. Dissection of the anterior and posterior sacrum was completed to highlight the tract of the S3 nerve. Techniques to increase the likelihood of optimal foramen needle and thus lead placement were highlighted.

CONCLUSIONS

This video demonstrates how achieving optimal foramen needle placement within the S3 foramen is key to optimal lead placement. Understanding the relationship of the bony landmarks on fluoroscopy to the S3 nerve and foramen, seen in the cadaveric dissections, are important in understanding how to achieve optimal lead placement. This optimization should lead to decreased operating room time, maximization of programming options, and decreased amplitude requirements.

Incidence, prognosis, and risk factors for bladder and bowel dysfunction due to incidental dural tears in lumbar microendoscopic surgery

BACKGROUND CONTEXT

Despite the common occurrence of incidental dural tears, the incidence and prognosis of bladder and bowel dysfunction (BBD) due to incidental dural tears in lumbar spinal surgery are not well known because of the lack of reported cases.

PURPOSE

To analyze the incidence, prognosis, and risk factors for BBD after lumbar microendoscopic surgery with or without incidental dural tears.

STUDY DESIGN/SETTING

A retrospective cohort study.

PATIENT SAMPLE

We analyzed 2,421 patients who underwent lumbar microendoscopic surgery and investigated patients with BBD after an incidental durotomy during surgery.

OUTCOME MEASURES

Patients were divided into three groups on the basis of dysuria and defecation disorders: severe BBD, mild BBD, and no BBD. The post void residual volumes before and after surgery were compared using an ultrasound bladder scanner or bladder catheterization after confirmation of urination. Bowel dysfunction was evaluated by subjective symptomatic deterioration and the increase in the frequency and duration of postoperative medical care.

METHODS

Risk factors for BBD were analyzed using surgical video documentation to determine the dural tear site and cauda equina exposure from the dural sac. Patients with BBD were prospectively followed up for prognosis determination. The chi-square test was used to compare the incidence of BBD between patients with dural tears and those without. Propensity score-adjusted logistic regression analysis was performed to evaluate the effects of various factors on the incidence of postoperative BBD.

RESULTS

The incidence of dural tears was 6.9% (168/2,421). The overall incidence of BBD was 3.0% (73/2,421), while the incidences of BBD (mild+severe BBD) and severe BBD due to incidental dural tears were 1.2% (30/2,421) and 0.8% (20/2,421), respectively. The incidence of BBD in patients with dural tears and those without tears was 17.9% [30/168] and 1.9% [43/2,253; p<.001]), respectively. BBD rates at 1 week, 1 month, 3 months, 6 months, and 1 year after surgery were 64.0%, 44.0%, 40.0%, 28.0%, and 13.6%, respectively. Logistic regression analysis revealed that the male sex (odds ratio [OR], 4.20), dural tears in the central area (OR, 10.15), and exposure of the cauda equina (OR, 51.04) were significant risk factors.

CONCLUSIONS

The incidence of dural tears in lumbar microendoscopic surgeries are associated with an increased incidence of BBD. The recovery rate for BBD due to incidental dural tears is generally good; however, some patients experience long-term symptoms. Clinicians should be aware that incidental dural tears with cauda equina exposure can increase the risk of BBD.

Can sacral development as a marker for caudal regression help identify associated urologic anomalies in patients with anorectal malformation?

BACKGROUND AND AIM

The sacral ratio (SR) is a well-established tool to quantify sacral development in patients with anorectal malformations (ARM) and can be used as a predictor of fecal continence. We hypothesized that a lower SR correlated with the presence of urologic and renal malformations.

METHODS

We retrospectively reviewed the medical records of patients with ARM treated at our center from 2014 to 2016. We measured the lateral SR as a marker for sacral development and assessed the spine for the presence of tethered cord (TC). Urological and renal anomalies, including single kidney, hydronephrosis, hypospadias, vesicoureteral reflux (VUR), ectopic ureter, and penoscrotal transposition were assessed. Analysis of variance (ANOVA), t-tests, and multivariable linear regression were used to test for differences in SR with consideration of associated urologic malformations and tethered cord.

RESULTS

283 patients with ARM were included for analysis (156 females). The median age was 39months (10-90). Among these, 178 (55.6%) had 1 or more urologic malformations, and 81 (25.3%) had a TC. Hydronephrosis, high-grade VUR (3-5), solitary kidney, and tethered cord were significantly associated with lower SR (p<0.01). In multivariable regression models, the presence of urologic abnormalities remained significantly associated with lower a SR despite the presence or absence of TC (p<0.001).

CONCLUSION

SR is a potentially useful indicator of certain urologic anomalies including hydronephrosis, high grade VUR, and solitary kidney in patients with ARM. This association is independent of the presence of TC. A sacral ratio as a part of the VACTERL screening can help the surgeon identify which patients need closer urologic follow up.

LEVEL OF EVIDENCE

IV.

Predictive value of intraoperative bulbocavernosus reflex during untethering surgery for post-operative voiding function

OBJECTIVE

To evaluate the clinical significance of intraoperative bulbocavernosus reflex (BCR) during untethering surgery in predicting post-operative voiding function.

METHODS

We conducted a retrospective review of pediatric patients who underwent untethering surgery with available intraoperative baseline BCR. BCR response during surgery was classified into loss or maintenance. Post-operative voiding function was determined as worsened or maintained based on history, postvoid residual urine measurement, and urodynamic study (UDS). Data regarding demographics, diagnosis, pre-operative voiding difficulty, re-untethering, syrinx, and abnormalities in electromyography were collected for analysis.

RESULTS

We included 106 patients, with a mean age of 3.3 years, and 49 patients were male. BCR was lost in 15 patients during surgery and voiding function worsened in 14 patients after surgery. Lumbosacral lipoma was the most common diagnosis, and 16 patients were diagnosed with lipomyelomeningocele (LMMC). The sensitivity and specificity of intraoperative BCR for post-operative worsening of voiding function were 35.7%, and 88.5% at 6 months, respectively. The diagnosis of LMMC was statistically significant in a logistic regression analysis. The specificity of BCR at 6 months in patients with diagnosis other than LMMC was 93.4%, and intraoperative BCR was significant in a logistic regression analysis.

CONCLUSIONS

Intraoperative BCR during untethering could predict bladder function 6 months post-operatively with high specificity (88.5%), particularly in cases other than LMMC (93.4%), indicating that voiding function deterioration will not occur if intraoperative BCR is preserved.

SIGNIFICANCE

Intraoperative BCR during untethering surgery is a useful tool to predict post-operative voiding outcome.

International Continence Society best practice statement for use of sacral neuromodulation

AIMS

Sacral neuromodulation (SNM) is an accepted therapy for a variety of conditions. However, despite over 20 years of experience, it remains a specialized procedure with a number of subtleties. Here we present the recommendations issued from the International Continence Society (ICS) SNM Consensus Panel.

METHODS

Under the auspices of the ICS, eight urologists, three colorectal surgeons and two urogynecologists, covering a wide breadth of geographic and specialty interest representation, met in January 2017 to discuss best practices for neuromodulation. Suggestions for statements were submitted in advance and specific topics were assigned to committee members, who prepared and presented supporting data to the group, at which time each topic was discussed in depth. Best practice statements were formulated based on available data. This document was then circulated to multiple external reviewers after which final edits were made and approved by the group.

RESULTS

The present recommendations, based on the most relevant data available in the literature, as well as expert opinion, address a variety of specific and at times problematic issues associated with SNM. These include the use of SNM for a variety of underlying conditions, need for pre-procedural testing, use of staged versus single-stage procedures, screening for success during the trial phase, ideal anesthesia, device implantation, post-procedural management, trouble-shooting loss of device function, and future directions for research.

CONCLUSIONS

These guidelines undoubtedly constitute a reference document, which will help urologists, gynecologists, and colorectal surgeons optimize their use of SNM for refractory urinary urgency and frequency, UUI, NOR, and FI.

Stimulation of the pelvic nerve increases bladder capacity in the prostaglandin E2 rat model of overactive bladder

Overactive bladder (OAB) syndrome is a highly prevalent condition that may lead to medical complications and decreased quality of life. Emerging therapies focusing on selective electrical stimulation of peripheral nerves associated with lower urinary tract function may provide improved efficacy and reduced side effects compared with sacral neuromodulation for the treatment of OAB symptoms. Prior studies investigating the effects of pelvic nerve (PelN) stimulation on lower urinary tract function were focused on promoting bladder contractions, and it is unclear whether selective stimulation of the PelN would be beneficial for the treatment of OAB. Therefore our motivation was to test the hypothesis that PelN stimulation would increase bladder capacity in the prostaglandin E₂ (PGE₂) rat model of OAB. Cystometry experiments were conducted in 17 urethane-anesthetized female Sprague-Dawley rats. The effects of intravesical PGE₂ vs. vehicle and PelN stimulation after intravesical PGE₂ on cystometric parameters were quantified. Intravesical infusion of PGE₂ resulted in decreased bladder capacity and increased voiding efficiency without a change in bladder contraction area under the curve, maximum contraction pressure, or contraction duration. Bladder capacity was also significantly decreased compared with vehicle (1% ethanol in saline) confirming that the change in bladder capacity was mediated by PGE₂ PelN stimulation reversed the PGE₂-induced change in bladder capacity and increased the external urethral sphincter electromyogram activity at a specific stimulation condition (amplitude of 1.0 times threshold at 10 Hz). These results confirm that the urodynamic changes reported in conscious rats are also observed under urethane anesthesia and that PelN stimulation is a novel and promising approach for the treatment of the symptoms of OAB.

The Filum Terminale Revisited: A Histological Study in Human Fetuses

Previous studies have suggested that secondary neurulation provides no functional neurons but only the filum terminale. However, no studies have confirmed that the coccygeal and lower sacral nerves do not originate from the secondary neural tube but only from the primary tube. To obtain a better understanding of these relationships, we examined sagittal or frontal sections from 20 embryonic and fetal specimens ranging from 6 to 14 weeks of gestation. During the growth of the vertebral column as well as the subsequent upward migration of the caudal end of the dural sac, the secondary neural tube was stretched to maintain the original attachment to the coccyx or the lower sacral vertebra. The filum-like structure showed much individual variability but in all cases appeared to be derived from the stretched neural tube. Intermediate age morphology revealed that the secondary neural tube itself provided an initial filum terminale before the ascent of the dural sac. Given that the coccygeal and lower sacral nerves are likely to originate from the secondary neural tube, these parts of the tube persisted and differentiated into spinal neurons to form the anococcygeal nerves. Likewise, the filum terminale was also most likely to contain some neurons that persisted postnatally. Depending on the timing and site of degeneration of the secondary neural tube, individual variations could occur in proportion to the amount of sensory and motor elements in the anococcygeal nerve supply.