Factors associated with Successful Responses to Ganglion Impar Block: A Retrospective Study.

Background: The ganglion impar (ganglion of Walther) block has been used to manage coccygeal and perineal (perianal and genital) pain due to both benign and malignant causes. However, the factors associated with successful responses to ganglion impar block are unknown. Therefore, in the present study, we aimed to identify the independent factors associated with successful responses to ganglion impar block in patients with chronic pain in coccygeal and perineal regions. Methods: From January 2008 to December 2017, we performed a retrospective review of 106 patients who underwent ganglion impar block. Patients were considered successful responders if they reported a decrease of more than 50% or 4 points on the 11-point (0 = no pain and 10 = worst possible pain) numerical rating scale 1 month after the procedure, while others were considered non-responders. Logistic regression analysis was performed to identify factors independently associated with successful responses at 1 month after the procedure. Results: Multivariable logistic regression analysis showed that cancer-related causes were significantly associated with successful responses at 1 month after ganglion impar block (odds ratio = 2.60, 95% confidence interval = 1.05 to 6.43, P = 0.038). Conclusion: Ganglion impar block may be more effective in cancer-related pain than pain due to benign causes.

Preoperative prediction of perineural invasion with multi-modality radiomics in rectal cancer.

Perineural invasion (PNI) as a grossly underreported independent risk predictor in rectal cancer is hard to identify preoperatively. We aim to predict PNI status in rectal cancer using multi-modality radiomics. In total, 396 radiomics features were extracted from T2-weighted images (T2WIs), diffusion-weighted images (DWIs), and portal venous phase of contrast-enhanced CT (CE-CT) respectively of 94 consecutive patients with histologically confirmed rectal cancer. T2WI score, DWI score, and CT score were calculated via the radiomics features selection and optimization. Discrimination, calibration, and clinical benefit ability were used to evaluate the performance of the radiomics scores in both training and testing datasets. CT score and T2WI score were independent risk predictors [CT score, OR (95% CI) = 4.218 (1.070-16.620); T2WI score, OR (95% CI) = 105.721 (3.091-3615.790)]. The concise score which combined CT score and T2WI score, showed the best performance [training dataset, AUC (95% CI) = 0.906 (0.833-0.979); testing dataset, AUC (95% CI) = 0.884 (0.761-1.000)] and good calibration (P > 0.05 in the Hosmer-Lemeshow test for the training and testing datasets). Decision curve analysis showed that the multi-modality radiomics nomogram had a higher clinical net benefit. The multi-modality radiomics score could be used to preoperatively assess PNI status in rectal cancer.

Altered sacral neural crest development in Pax3 spina bifida mutants underlies deficits of bladder innervation and function.

Mouse models of Spina bifida (SB) have been instrumental for identifying genes, developmental processes, and environmental factors that influence neurulation and neural tube closure. Beyond the prominent neural tube defects, other aspects of the nervous system can be affected in SB with significant changes in essential bodily functions such as urination. SB patients frequently experience bladder dysfunction and SB fetuses exhibit reduced density of bladder nerves and smooth muscle although the developmental origins of these deficits have not been determined. The Pax3 Splotch-delayed (Pax3Sp-d) mouse model of SB is one of a very few mouse SB models that survives to late stages of gestation. Through analysis of Pax3Sp-d mutants we sought to define how altered bladder innervation in SB might arise by tracing sacral neural crest (NC) development, pelvic ganglia neuronal differentiation, and assessing bladder nerve fiber density. In Pax3Sp-d/Sp-d fetal mice we observed delayed migration of Sox10+ NC-derived progenitors (NCPs), deficient pelvic ganglia neurogenesis, and reduced density of bladder wall innervation. We further combined NC-specific deletion of Pax3 with the constitutive Pax3Sp-d allele in an effort to generate viable Pax3 mutants to examine later stages of bladder innervation and postnatal bladder function. Neural crest specific deletion of a Pax3 flox allele, using a Sox10-cre driver, in combination with a constitutive Pax3Sp-d mutation produced postnatal viable offspring that exhibited altered bladder function as well as reduced bladder wall innervation and altered connectivity between accessory ganglia at the bladder neck. Combined, the results show that Pax3 plays critical roles within sacral NC that are essential for initiation of neurogenesis and differentiation of autonomic neurons within pelvic ganglia.

The influence of coccygeal dynamic patterns on ganglion impar block treatment results in chronic coccygodynia.

Objective Ganglion impar block (GIB) can be performed in patients with chronic coccygodynia who do not respond to conservative treatments. We investigated the effect of coccygeal dynamic patterns on the treatment outcome in patients with chronic coccygodynia treated with GIB. Materials and methods We retrospectively analyzed the data for patients diagnosed with chronic coccygodynia who underwent GIB only once by a transsacrococcygeal method under fluoroscopy guidance in our Pain Medicine Clinic. Patients were assessed with standard and dynamic coccyx radiographs and classified according to coccygeal mobility. Pain scores were assessed with a numerical rating scale (NRS) before and after the intervention (at 1 hour and 4, 12 and 24 weeks). A 50% or more reduction in the NRS score was accepted as significant pain relief. Results Of the 37 patients included in the study, 14 had normal coccyx (Group I) and 23 had immobile coccyx (Group II) based on the radiological evaluation. The NRS scores were significantly reduced in both groups on each follow-up visit but there was no significant difference between the two groups in terms of pre- and post-intervention NRS scores. Significant pain relief was achieved in 42.9% and 61.9% of patients in Group I and II at the last examination, respectively. Conclusion GIB administered by transsacrococcygeal method in patients with chronic coccygodynia is a safe and alternative treatment approach with reduced pain scores and low complication rates. In patients with chronic coccygodynia, having a normal or immobile coccyx does not appear to affect treatment outcomes.

What Is New in Neuromodulation for Overactive Bladder?

We reviewed the available studies on efficacy and safety of percutaneous tibial nerve stimulation (PTNS) and sacral nerve modulation (SNM) for overactive bladder (OAB) symptoms not responsive to conservative treatments. We limited our search to randomized trials, in English, with at least 20 adult patients, and 6 mo and 12 wk of follow-up for SNM and PTNS, respectively, published between January 1998 and December 2017. Therapeutic success ranges from 61% to 90% for SNM and from 54% to 79% for PTNS. Both techniques are effective and safe, with no life-threatening adverse effects. PTNS is a less invasive technique that gives good results in short time with fewer side effects. PATIENT SUMMARY: Sacral nerve modulation and percutaneous tibial nerve stimulation are effective and safe in patients with overactive bladder syndrome not responsive to standard medical therapy.

A systematic review of sacral nerve stimulation for faecal incontinence following ileal pouch anal anastomosis.

Faecal incontinence is a common complication of ileal pouch anal anastomosis (IPAA) and seems to worsen with time. The aim of this paper is to review the evidence of the use of sacral nerve stimulation (SNS) for patients with faecal incontinence after IPAA. A literature search was performed on PubMed and Cochrane databases for all relevant articles. All studies, which reported the outcome of SNS in patients with faecal incontinence after IPAA, were reviewed. Three papers were identified, including a case report, cohort study and retrospective study. The total number of patients was 12. The follow-up duration included 3 months, 6 months and 24 months. After peripheral nerve evaluation, definitive implantation was performed in 10 (83.3%) patients. All three studies reported positive outcomes, with CCF scores and incontinence episodes improving significantly. Preliminary results suggest good outcome after permanent SNS implant. Studies with larger sample sizes, well-defined patient characteristics and standardized outcome measures are required to fully investigate the effect of SNS in IPAA patients.

Use of Sacral Nerve Stimulation for the Treatment of Overlapping Constipation and Fecal Incontinence.

BACKGROUND Fecal incontinence and constipation are common gastrointestinal complaints, but rarely occur concurrently. Management of these seemingly paradoxical processes is challenging, as treatment of one symptom may exacerbate the other. CASE REPORT A 51-year-old female with lifelong neurogenic bladder secondary to spina bifida occulta presented with progressive symptoms of daily urge fecal incontinence as well as hard bowel movements associated with straining and a sensation of incomplete evacuation requiring manual disimpaction. Pelvic floor testing showed poor ability to squeeze the anal sphincter, which indicated sphincter weakness as a major contributor to her fecal incontinence symptoms. Additionally, on defecography she was unable to widen her posterior anorectal angle or relax the anal sphincter during defecation consistent with dyssynergic defecation. A sacral nerve stimulator was placed for management of her fecal incontinence. Interestingly, her constipation also dramatically improved with sacral neuromodulation. CONCLUSIONS This unique case highlights the emerging role of sacral nerve stimulation in the treatment of complex pelvic floor dysfunction with improvement in symptoms beyond fecal incontinence in a patient with dyssynergic-type constipation.

Shaping the Output of Lumbar Flexor Motoneurons by Sacral Neuronal Networks.

The ability to improve motor function in spinal cord injury patients by reactivating spinal central pattern generators (CPGs) requires the elucidation of neurons and pathways involved in activation and modulation of spinal networks in accessible experimental models. Previously we reported on adrenoceptor-dependent sacral control of lumbar flexor motoneuron firing in newborn rats. The current work focuses on clarification of the circuitry and connectivity involved in this unique modulation and its potential use. Using surgical manipulations of the spinal gray and white matter, electrophysiological recordings, and confocal microscopy mapping, we found that methoxamine (METH) activation of sacral networks within the ventral aspect of S2 segments was sufficient to produce alternating rhythmic bursting (0.15-1 Hz) in lumbar flexor motoneurons. This lumbar rhythm depended on continuity of the ventral funiculus (VF) along the S2-L2 segments. Interrupting the VF abolished the rhythm and replaced it by slow unstable bursting. Calcium imaging of S1-S2 neurons, back-labeled via the VF, revealed that ∼40% responded to METH, mostly by rhythmic firing. All uncrossed projecting METH responders and ∼70% of crossed projecting METH responders fired with the concurrent ipsilateral motor output, while the rest (∼30%) fired with the contralateral motor output. We suggest that METH-activated sacral CPGs excite ventral clusters of sacral VF neurons to deliver the ascending drive required for direct rhythmic activation of lumbar flexor motoneurons. The capacity of noradrenergic-activated sacral CPGs to modulate the activity of lumbar networks via sacral VF neurons provides a novel way to recruit rostral lumbar motoneurons and modulate the output required to execute various motor behaviors. SIGNIFICANCE STATEMENT: Spinal central pattern generators (CPGs) produce the rhythmic output required for coordinating stepping and stabilizing the body axis during movements. Electrical stimulation and exogenous drugs can reactivate the spinal CPGs and improve the motor function in the absence of descending supraspinal control. Since the body-stabilizing sacral networks can activate and modulate the limb-moving lumbar circuitry, it is important to clarify the functional organization of sacral and lumbar networks and their linking pathways. Here we decipher the ascending circuitry linking adrenoceptor-activated sacral CPGs and lumbar flexor motoneurons, thereby providing novel insights into mechanisms by which sacral circuitry recruits lumbar flexors, and enhances the motor output during lumbar afferent-induced locomotor rhythms. Moreover, our findings might help to improve drug/electrical stimulation-based therapy to accelerate locomotor-based rehabilitation.

Sacral nerve stimulation for faecal incontinence: medium-term follow-up from a single institution.

BACKGROUND: Most studies on sacral nerve stimulation (SNS) are either single-centre with small numbers of patients or multi-centre studies. We present the medium-term follow-up results from a single centre for 127 patients undergoing SNS. METHODS: Consecutive patients treated with SNS for faecal incontinence had preoperative baseline St Mark's continence scores, faecal incontinence quality of life (FIQL) measures and anorectal physiology studies. Follow-up was a postal questionnaire concerning continence, FIQL, patient-perceived change in bowel control (-5 to +5 where 0 is no change), overall satisfaction (0-10 visual analogue scale) and use of medications. RESULTS: A total of 166 patients underwent temporary nerve stimulation testing, of which 112 progressed to a permanent implantable pulse generator (IPG). Fifteen received an IPG without the testing phase, hence 127 patients in total. Fourteen had the IPG removed, four were deceased, leaving 109 for assessment; 91 (83%) responded to the survey. Mean follow-up was 2.7 years (range: 2 months-8.5 years). Mean baseline St Mark's continence score was 14.4, and mean follow-up score was 10.3 (P < 0.01). FIQL improved in all domains (P < 0.001). Patient-reported improved bowel control mean score was +3.2 (95% CI: 2.9, 3.55). Median satisfaction score was 8.0 (range: 0-10). Complications included 17 lead dislodgements, seven superficial infections, five infections requiring surgery and five repositioning of a rotated IPG. Thirty-two patients used loperamide and 34 used fibre supplements. CONCLUSION: In this observational study, limited by the absence of a placebo control group, SNS significantly improved continence and quality of life, and patient satisfaction was high.

Sacral nerve stimulation allows for decreased antegrade continence enema use in children with severe constipation.

BACKGROUND: Sacral nerve stimulation (SNS) can be beneficial for children with constipation, but no studies have focused on children with constipation severe enough to require antegrade continence enemas (ACEs). Our objective was to evaluate the efficacy of SNS in children with constipation treated with ACE. METHODS: Using a prospective patient registry, we identified patients <21years old who were receiving ACE prior to SNS placement. We compared ACE/laxative usage, PedsQL Gastrointestinal Symptom Scale (GSS), Fecal Incontinence Quality of Life Scale (FIQL), Fecal Incontinence Severity Index (FISI), and Vancouver Dysfunctional Elimination Syndrome Score (DES) at baseline and progressive follow-up time intervals. RESULTS: Twenty-two patients (55% male, median 12years) were included. Median ACE frequency decreased from 7 per week at baseline to 1 per week at 12months (p<0.0001). Ten children (45%) had their cecostomy/appendicostomy closed. Laxative use, GSS, FIQL, and DES did not change. FISI improved over the first 12months with statistical significance reached only at 6months (p=0.02). Six (27%) children experienced complications after SNS that required further surgery. CONCLUSIONS: In children with severe constipation dependent on ACE, SNS led to a steady decrease in ACE usage with nearly half of patients receiving cecostomy/appendicostomy closure within 2years. LEVEL OF EVIDENCE: IV.

Surface anatomical landmarks for the location of posterior sacral foramina in sacral nerve stimulation.

BACKGROUND: Sacral nerve stimulation is a common treatment for various pelvic floor disorders. It consists of the percutaneous introduction of electrodes through the posterior sacral foramina for therapeutic stimulation of the target sacral spinal nerve. The aim of our study was to determine the surface anatomical landmarks of the sacrum to facilitate identification of the posterior sacral foramina. METHODS: This study was conducted on 20 human cadavers. The cadavers were placed in a prone position, and all the soft tissues of the sacral region were removed to allow exposure of the osseous structures. Different measurements were taken in relation to the posterior sacral foramina, the posterior superior iliac spine (PSIS) and the median sacral crest (MSC). A median coefficient of variation (CV) was determined. RESULTS: The diameter of the second sacral foramen showed the greatest variability. The distances between each individual foramen and the MSC had an acceptable variability (CV < 20%). In contrast, the distance between foramina had a high variability. The distance between PSIS and the second posterior sacral foramen was also found to have an acceptable variability (CV < 20%). However, the angle formed by an horizontal line between PSIS and a line between PSIS and S2 foramina had high variability. CONCLUSIONS: We found that the distance between sacral foramina and MSC is relatively constant while the distance between foramina and the relations between foramina and PSIS is highly variable. Detailed knowledge of the anatomy may facilitate electrode placement and is complementary to the regular use of fluoroscopy.

Topography and landmarks for the nerve supply to the levator ani and its relevance to pelvic floor pathologies.

The aim of this study was to explore the anatomical variations of the nerve to the levator ani (LA) and to relate these findings to LA dysfunction. One hundred fixed human female cadavers were dissected using transabdominal, gluteal, and perineal approaches, resulting in two hundred dissections of the sacral plexus. The pudendal nerve and the sacral nerve roots were traced from their origin at the sacral foramina to their termination. All nerves contributing to the innervation of the LA were considered to be the nerve to the LA. Based on the spinal nerve components, the nerve to the LA was classified into the following categories: 50% (n = 100) originated from S4 and S5 (type I); 19% (n = 38) originated from S5 (type II); 16% (n = 32) originated from S4 (type III); 11% (n = 22) originated from S3 and S4 (type IV); 4% (n = 8) originated from S3, S4, and S5 (type V). Two patterns of nerve termination were observed. In 42% of specimens, the nerve to the LA penetrated the coccygeus muscle and assumed an external position along the inferior surface of the LA muscle. In the remaining 58% of specimens, the nerve crossed the superior surface of the coccygeus muscle and continued along the superior surface of the iliococcygeus muscle. Damage to the nerve to LA has been associated with various pathologies. In order to minimize injuries during surgical procedures, a thorough understanding of the course and variations of the nerve to the LA is extremely important.

Effects of sacral nerve stimulation on postpartum urinary retention-related changes in rat bladder.

OBJECTIVE: To examine the effect of sacral nerve stimulation (SNS) on the urodynamic function and molecular structure of bladders in rats following acute urinary retention (AUR) after parturition. MATERIAL AND METHODS: Thirty primiparous rats were divided into three groups: postpartum, postpartum+AUR, and postpartum+AUR+SNS. AUR was achieved by clamping the distal urethra of a rat for 60 minutes. The postpartum+AUR+SNS group received electrical stimulation 60 minutes daily for 3 days after AUR. In addition to cystometric studies and external urethral sphincter electromyography, the expression of caveolins and nerve growth factor (NGF) and caveolae number in bladder muscle were analyzed. RESULTS: The postpartum+AUR group has significantly greater residual volume than the postpartum group, but the residual volume decreased significantly after SNS treatment. The postpartum+AUR group had significantly lower peak voiding pressure, a longer bursting period and lower amplitude of electromyograms of external urethral sphincter activity than the postpartum and postpartum+AUR+SNS groups. The postpartum+AUR rats had higher NGF expression, lower caveolin-1 expression, and fewer caveolae in bladder muscle compared with the postpartum rats. Conversely, the caveolin-1 expression and caveolae number increased, and the NGF expression decreased after SNS treatment. CONCLUSION: Bladder dysfunction after parturition in a rat model caused by AUR may be restored to the non-AUR structural and functional level after SNS treatment.

Comparison of Short Term Outcomes of Sacral Nerve Stimulation and Intradetrusor Injection of OnabotulinumtoxinA (Botox) in Women With Refractory Overactive Bladder.

OBJECTIVES: The aim of the study was to compare the short-term outcomes of sacral nerve stimulation (SNS) and intradetrusor injection of OnabotulinumtoxinA (Botox) for overactive bladder (OAB) symptoms refractory to behavioral modifications and pharmacologic therapy. METHODS: This is a retrospective cohort study evaluating the outcomes of SNS and Botox procedures that were performed for refractory OAB symptoms at a tertiary care referral center. The primary outcome was "failure" of treatment that was defined as less than 50% improvement from the baseline symptoms at 6 months. RESULTS: Sixty-five SNS and 63 Botox procedures met the inclusion criteria. Women undergoing Botox were more likely to report failure 6 months after the intervention as compared with those undergoing SNS (20 [31.8%] vs 7 [10.8%], P = 0.003; unadjusted odds ratio = 3.85, confidence interval = 1.5-9.93; adjusted odds ratio = 4.47, confidence interval = 1.69-14.4). However, there was no difference in the proportion of women who were started on antimuscarinic medications for persistent urgency urinary incontinence after both procedures (12 [18.5%] women in SNS group and 17 [27%] women in the Botox group, P = 0.249). The most common complication of the SNS procedure was wound related (8 [12.3%]), whereas the most common complication of the Botox procedure was urinary tract infection (31 [49.2%]). CONCLUSIONS: The SNS resulted in lower failure rates at 6 months when performed for refractory OAB symptoms as compared with the Botox procedure. However, further studies are needed to evaluate the long-term cost-effectiveness of both procedures.

Pain Relief due to Transsacrococcygeal Ganglion Impar Block in Chronic Coccygodynia: A Pilot Study.

OBJECTIVE: Coccygodynia is a distressing condition that presents with pain around the coccyx. Impar (Walther) ganglion is a sympathetic ganglion located at the end of lumbosacral sympathetic chain. The objective of this study is to share our results and follow up of 34 ganglion impar blocks in 22 patients. DESIGN: Retrospective pilot study. SETTING: Interventional Pain Clinic in the Department of Physical Medicine and Rehabilitation in a university hospital. SUBJECTS: Twenty-two patients with coccygodynia who did not respond to conservative treatment and then presented to interventional pain clinic of a PM&R department in a university hospital METHODS: Pain was evaluated via 10-cm visual analog scale (VAS). VAS values were obtained before, 1 hour and 3 weeks after injection and during this study was conducted. RESULTS: For achieving at least 50% relief of pain, the success rate of a first injection was 82%, but accounted for three technical failures. In patients with a successful outcome, relief lasted for a median duration of 6 months. Relief was reinstated for a median period of 17 months by a second injection in nine patients who presented for repeat treatment. No relief was achieved in two of these patients when they presented for a third treatment. CONCLUSIONS: Ganglion impar block appears to be effective in patients who have coccygodynia resistant to conservative therapy, with high success rates and prolonged duration of effect. Controlled studies are required to reveal the mechanism of this effect.

[Effect of the anterior aspect of sacral nerve root tunnel on iliosacral screw placement on the standard lateral image of sacrum].

OBJECTIVE: To introduce the location and course of S1, S2 sacral nerve root tunnel and to clarify the significance of the anterior aspect of sacral nerve root tunnel on placement of iliosacral screw on the standard lateral sacral view. METHODS: Firstly the data of 2.0 mm slice pelvic axial CT images were imported into Mimics 10.0, and the sacrum, innominate bones, and sacral nerve root tunnels were reconstructed into 3D views respectively, which were rotated to the standard lateral sacral views, pelvic outlet and inlet views. Then the location and course of the S1, S2 sacral nerve root tunnel on each view were observed. RESULTS: The sacral nerve root tunnel started from the cranial end and anterior aspect of the vertebral canal of the same segment and ended up to the anterior sacral foramen with a direction from cranial-posterior-medial to caudal-anterior-lateral. The tunnel had a lower density than the iliac cortex and greater sciatic notch on the pelvic X-rays,especially on the standard sacral lateral view, on which it showed up as a disrupted are line and required more careful recognition. CONCLUSION: It can prevent the iliosacral screw from penetrating the sacral nerve root tunnel and vertebral canal when recognizing the anterior aspect of sacral nerve root tunnel and choosing it as the caudal-posterior boundary of the "safe zone" on the standard lateral sacral view.

Similarities and differences in cervical and thoracolumbar multisegmental motor responses and the combined use for testing spinal circuitries.

STUDY DESIGN: Experimental study. OBJECTIVE: To determine similarities and differences of C7 and T11-12 multisegmental motor responses (MMR) studies for the upper limbs (UL) and lower limbs (LL). SETTINGS: Neuroscience Lab, TWU (School of Physical Therapy, TX, USA). METHODS: C7 and T11-12 percutaneous electrical stimulations were applied while recording muscle action potentials from ULs and LLs. RESULTS: The procedure of cervical MMR (CMMR) was easier in application than thoracolumbar MMR (TMMR), requiring less current intensities but cause more "jolts" in the trapezius/shoulder complex, due to close proximity of the stimulation electrodes. CMMR evoked large amplitude motor responses in the millivolts range in (UL) muscles, but smaller amplitude signal in (LL) muscles (in microvolts). TMMR evoked large amplitude motor responses in both UL and LL (in millivolts). The MMR amplitude was generally larger in the UL as compared to the LL, in the distal limb muscles more than in the proximal limb muscles. CMMR and TMMR for the UL were comparable in amplitude, latencies and action potential shapes. Signal latencies were longer for distal limb muscles as compared to proximal limb muscles and were slightly longer for LL as compared to UL muscles. MMR signals were either biphasic or triphasic in shape. CONCLUSION: CMMR and TMMR have similarities and differences in the methods and recording signal that must be considered during its clinical applications. Comparing the signal of the UL muscles with CMMR and TMMR could be a useful test for the integrity of the ascending and descending spinal pathways in patients with spinal cord injuries and diseases.

The anatomy of the sacrococcygeal cornual region and its clinical relevance.

There has been no systematic study of the anatomy of the region between the sacral and coccygeal cornua. Reference texts describe an intercornual ligament connecting these structures. The aim of this study was to investigate the anatomy of this region, which may be relevant to unexplained cases of coccygeal pain (coccydynia) and local nerve blocks. The bony anatomy of the sacrococcygeal (SC) cornual region was analyzed in 33 CT scans obtained from supine adults of mostly European origin with no known SC pathology, 7 µCT scans of cadaver SC specimens, and 105 Asian Indian adult skeletons. A further five cadaver SC specimens were examined histologically. SC cornual fusion was seen in 45% of CT/µCT scans (mean age 67 years, 20 males) and in 20% of adult skeletons (78 males); there was no association with age or sex. In the absence of SC fusion, the mean intersacrococcygeal cornual gap was 7.1 ± 2.4 mm; this was bridged by an intercornual ligament composed of parallel vertical collagen fibers reinforced by elastin fibers on its anterior surface. Small nerve branches were observed adjacent to the ventral aspect of the intercornual ligament and, in one case, traversing the ligament. Ipsilateral sacral and coccygeal cornua are therefore normally bridged by an intercornual ligament that is probably innervated. The cornua are fused on one or both sides in 20-45% of adults. These findings may have implications for some cases of coccydynia and for anesthetists performing local nerve blocks.