Clinical Anatomy of the Sacral Nerve Roots and Its Relevance to Their Reconstruction After Sacrectomy

BACKGROUND AND OBJECTIVES

En bloc sacrectomy is associated with sacral root transection causing loss of urinary bladder, rectum, and sexual function. The aim of the study was to determine the position of the pudendal branches (sensorimotor) and pelvic splanchnic nerves (parasympathetic) on the sacral roots relative to the sacrum, and the minimal and maximal defects in the sacral roots that can be reconstructed by grafting after various types of sacrectomy.

METHODS

Five cadaveric pelves were dissected bilaterally. The lengths and widths of the S1-S4 roots and their branches were measured. Then, the minimal and maximal defects between the proximal and distal stumps of the sacrificed roots were measured following 3 models of sacrectomy (below S2, below S1, and total sacrectomy).

RESULTS

The mean distance of the splanchnic nerves from the S2 and S3 anterior sacral foramina was 17.7 ± 7.3 and 23.6 ± 11.1 mm, respectively, and the mean distance of the pudendal S2 and S3 branches was 36.8 ± 13.7 and 30.2 ± 10.8 mm, respectively. The mean widths of the S2 and S3 roots were 9.3 ± 1.9 and 5.4 ± 1.2 mm, respectively. The mean maximal defects in S2 and S3 roots after various types of sacrectomies were between 61.8 ± 16.3 and 100.7 ± 14.3 mm and between 62.7 ± 20.2 and 84.7 ± 25.1 mm, respectively. There were no statistically significant differences between sides or sexes for all obtained measurements.

CONCLUSION

The reconstruction of the S2-S3 roots is anatomically feasible after partial or total sacrectomies in which the resection of the soft tissue does not extend further than approximately 1.5 to 2 cm ventrally from the sacrum.

Peripheral nerve transfers for dysfunctions in central nervous system injuries: a systematic review

BACKGROUND

The review highlights recent advancements and innovative uses of nerve transfer surgery in treating dysfunctions caused by central nervous system (CNS) injuries, with a particular focus on spinal cord injury (SCI), stroke, traumatic brain injury, and cerebral palsy.

METHODS

A comprehensive literature search was conducted regarding nerve transfer for restoring sensorimotor functions and bladder control following injuries of spinal cord and brain, across PubMed and Web of Science from January 1920 to May 2023. Two independent reviewers undertook article selection, data extraction, and risk of bias assessment with several appraisal tools, including the Cochrane Risk of Bias Tool, the JBI Critical Appraisal Checklist, and SYRCLE's ROB tool. The study protocol has been registered and reported following PRISMA and AMSTAR guidelines.

RESULTS

Nine hundred six articles were retrieved, of which 35 studies were included (20 on SCI and 15 on brain injury), with 371 participants included in the surgery group and 192 in the control group. These articles were mostly low-risk, with methodological concerns in study types, highlighting the complexity and diversity. For SCI, the strength of target muscle increased by 3.13 of Medical Research Council grade, and the residual urine volume reduced by more than 100 ml in 15 of 20 patients. For unilateral brain injury, the Fugl-Myer motor assessment (FMA) improved 15.14-26 score in upper extremity compared to 2.35-26 in the control group. The overall reduction in Modified Ashworth score was 0.76-2 compared to 0-1 in the control group. Range of motion (ROM) increased 18.4-80° in elbow, 20.4-110° in wrist and 18.8-130° in forearm, while ROM changed -4.03°-20° in elbow, -2.08°-10° in wrist, -2.26°-20° in forearm in the control group. The improvement of FMA in lower extremity was 9 score compared to the presurgery.

CONCLUSION

Nerve transfer generally improves sensorimotor functions in paralyzed limbs and bladder control following CNS injury. The technique effectively creates a 'bypass' for signals and facilitates functional recovery by leveraging neural plasticity. It suggested a future of surgery, neurorehabilitation and robotic-assistants converge to improve outcomes for CNS.

Cadaveric study to assess the feasibility of S1 neurectomy and contralateral S1 transfer for spastic hemiparesis

Purpose

Acquired brain injury causing spasticity, pain and loss of function is a major cause of disability and lower quality of life. Sacral 1 (S1) neurectomy claims promising outcomes in spastic hemiparesis. This cadaveric study was conducted to study the surgical anatomy, surgical approach and feasibility of S1 neurectomy and contralateral S1 (cS1) transfer.

Methods

This study was conducted over a period of 10 months and 10 cadavers (age 18-60 years, 7 male and 3 female) were included in the study. 2 cadavers underwent endoscopic S1 neurectomy and 8 cadavers underwent open S1 neurectomy. Mean S1 root length and diameter were recorded using Schirmer tear strips and Vernier calliper. Feasibility of transfer was also assessed by measuring the length of donor nerve and distance between distal ends to proximal end of recipient nerve.

Results

Mean thickness of right S1 root was 4.02 ± 1.5 mm and left S1 was 3.89 ± 1.18 mm. Mean length of right S1 root was 24.9 ± 4.56 mm and left S1 was 23.6 ± 2.86 mm. Endoscopically dissected length of S1 was much less as compared to open technique.

Conclusion

S1 neurectomy is simple procedure to reduce spasticity in lower limb without any permanent deficit. It can be done by open as well as with endoscopic approach while for contralateral S1 transfer open approach need to be used.

Injection of N‑butyl Cyanoacrylate Through a Dual-Lumen Balloon for Embolization of High-flow Intranidal Fistulas in Brain Arteriovenous Malformations: Technical Note

PURPOSE

N-butyl cyanoacrylate (NBCA) glue is a valuable liquid embolic agent for the endovascular treatment of brain arteriovenous malformations (BAVM). The use of NBCA carries a risk of embolic agent reflux and distal migration with ensuing possibility of venous drainage compromise. The aim of this technical note is to describe a single center case series of high-flow intranidal fistulas embolized though a dual lumen balloon under local flow-arrest conditions.

METHODS

This article presents a retrospective description of a case series including five NBCA injections through a dual lumen balloon performed by a single operator in three patients with BAVM. Demographic, clinical, imaging and procedure-related data are reported.

RESULTS

The three patients presented with ruptured BAVMs. Of the patients, one underwent proximal flow-related ruptured aneurysm coiling before planned BAVM embolization. In the three patients, staged BAVM embolization as a first line treatment was decided. Preliminary embolization of high-flow BAVM fistulas by NBCA using a dual lumen balloon under local flow-arrest conditions was performed and five separate injections were carried out without any complications. No balloon entrapment or rupture was observed.

CONCLUSION

High-flow BAVM fistulas can be treated with NBCA embolization using a dual lumen balloon under local flow-arrest conditions.

Contralateral peripheral neurotization for a hemiplegic hindlimb after central neurological injury

OBJECTIVE Contralateral peripheral neurotization surgery has been successfully applied to rescue motor function of the hemiplegic upper extremity in patients with central neurological injury (CNI). It may contribute to strengthened neural pathways between the contralesional cortex and paretic limbs. However, the effect of this surgery in the lower extremities remains unknown. In the present study the authors explored the effectiveness and safety of contralateral peripheral neurotization in treating a hemiplegic lower extremity following CNI in adult rats. METHODS Controlled cortical impact (CCI) was performed on the hindlimb motor cortex of 36 adult Sprague-Dawley rats to create severe unilateral traumatic brain injury models. These CCI rats were randomly divided into 3 groups. At 1 month post-CCI, the experimental group (Group 1, 12 rats) underwent contralateral L-6 to L-6 transfer, 1 control group (Group 2, 12 rats) underwent bilateral L-6 nerve transection, and another control group (Group 3, 12 rats) underwent an L-6 laminectomy without injuring the L-6 nerves. Bilateral L-6 nerve transection rats without CCI (Group 4, 12 rats) and naïve rats (Group 5, 12 rats) were used as 2 additional control groups. Beam and ladder rung walking tests and CatWalk gait analysis were performed in each rat at baseline and at 0.5, 1, 2, 4, 6, 8, and 10 months to detect the skilled walking functions and gait parameters of both hindlimbs. Histological and electromyography studies were used at the final followup to verify establishment of the traumatic brain injury model and regeneration of the L6-L6 neural pathway. RESULTS In behavioral tests, comparable motor injury in the paretic hindlimbs was observed after CCI in Groups 1-3. Group 1 started to show significantly lower slip and error rates in the beam and ladder rung walking tests than Groups 2 and 3 at 6 months post-CCI (p < 0.05). In the CatWalk analysis, Group 1 also showed a higher mean intensity and swing speed after 8 months post-CCI and a longer stride length after 6 months post-CCI than Groups 2 and 3 (p < 0.05). Transection of L-6 resulted in transient skilled walking impairment in the intact hindlimbs in Groups 1 and 2 (compared with Group 3) and in the bilateral hindlimbs in Group 4 (compared with Group 5). All recovered to baseline level within 2 months. Histological study of the rat brains verified comparable injured volumes among Groups 1-3 at final examinations, and electromyography and toluidine blue staining indicated successful regeneration of the L6-L6 neural pathways in Group 1. CONCLUSIONS Contralateral L-6 neurotization could be a promising and safe surgical approach for improving motor recovery of the hemiplegic hindlimb after unilateral CNI in adult rats. Further investigations are needed before extrapolating the present conclusions to humans.

Hindlimb spasticity after unilateral motor cortex lesion in rats is reduced by contralateral nerve root transfer

Transfer of nerve root from normal side to the spastic side could reduce unilateral motor cortex lesion-induced contralateral hindlimb spasticity in rats.

Lower extremity spasticity is a common sequela among patients with acquired brain injury. The optimum treatment remains controversial. The aim of our study was to test the feasibility and effectiveness of contralateral nerve root transfer in reducing post stroke spasticity of the affected hindlimb muscles in rats. In our study, we for the first time created a novel animal hindlimb spastic hemiplegia model in rats with photothrombotic lesion of unilateral motor cortex and we established a novel surgical procedure in reducing motor cortex lesion-induced hindlimb spastic hemiplegia in rats. Thirty six rats were randomized into three groups. In group A, rats received sham operation. In group B, rats underwent unilateral hindlimb motor cortex lesion. In group C, rats underwent unilateral hindlimb cortex lesion followed by contralateral L4 ventral root transfer to L5 ventral root of the affected side. Footprint analysis, Hoffmann reflex (H-reflex), cholera toxin subunit B (CTB) retrograde tracing of gastrocnemius muscle (GM) motoneurons and immunofluorescent staining of vesicle glutamate transporter 1 (VGLUT1) on CTB-labelled motoneurons were used to assess spasticity of the affected hindlimb. Sixteen weeks postoperatively, toe spread and stride length recovered significantly in group C compared with group B (P<0.001). H_max (H-wave maximum amplitude)/M_max (M-wave maximum amplitude) ratio of gastrocnemius and plantaris muscles (PMs) significantly reduced in group C (P<0.01). Average VGLUT1 positive boutons per CTB-labelled motoneurons significantly reduced in group C (P<0.001). We demonstrated for the first time that contralateral L4 ventral root transfer to L5 ventral root of the affected side was effective in relieving unilateral motor cortex lesion-induced hindlimb spasticity in rats. Our data indicated that this could be an alternative treatment for unilateral lower extremity spasticity after brain injury. Therefore, contralateral neurotization may exert a potential therapeutic candidate to improve the function of lower extremity in patients with spastic hemiplegia.

Double-lumen balloon for Onyx® embolization via extracranial arteries in transverse sigmoid dural arteriovenous fistulas: initial experience

Transverse-sigmoid dural arteriovenous fistulas (TS DAVFs) can be challenging to treat by endovascular means. Indeed, a total cure of the fistula can only be achieved when complete occlusion of the fistulous point(s) is obtained by penetration of the embolic agent. However, in some cases, especially for transosseous branches from extracranial arteries like the occipital artery (OcA) or the superficial temporal artery (STA), such penetration is usually poor, leading to major proximal reflux and incomplete fistula obliteration. We present three cases of embolization in two patients with TS DAVF through the OcA and/or the STA with Onyx® using a double-lumen balloon (Microvention, Tustin, CA, USA). This technique allows the penetration of the embolic agent in the transosseous branches by forming a counter-pressure with the inflated balloon. This technique may be useful to achieve complete occlusion of TS DAVFs by endovascular means.

Sleeve bridging of the rhesus monkey ulnar nerve with muscular branches of the pronator teres: multiple amplification of axonal regeneration

Multiple-bud regeneration, i.e., multiple amplification, has been shown to exist in peripheral nerve regeneration. Multiple buds grow towards the distal nerve stump during proximal nerve fiber regeneration. Our previous studies have verified the limit and validity of multiple amplification of peripheral nerve regeneration using small gap sleeve bridging of small donor nerves to repair large receptor nerves in rodents. The present study sought to observe multiple amplification of myelinated nerve fiber regeneration in the primate peripheral nerve. Rhesus monkey models of distal ulnar nerve defects were established and repaired using muscular branches of the right forearm pronator teres. Proximal muscular branches of the pronator teres were sutured into the distal ulnar nerve using the small gap sleeve bridging method. At 6 months after suture, two-finger flexion and mild wrist flexion were restored in the ulnar-sided injured limbs of rhesus monkey. Neurophysiological examination showed that motor nerve conduction velocity reached 22.63 ± 6.34 m/s on the affected side of rhesus monkey. Osmium tetroxide staining demonstrated that the number of myelinated nerve fibers was 1,657 ± 652 in the branches of pronator teres of donor, and 2,661 ± 843 in the repaired ulnar nerve. The rate of multiple amplification of regenerating myelinated nerve fibers was 1.61. These data showed that when muscular branches of the pronator teres were used to repair ulnar nerve in primates, effective regeneration was observed in regenerating nerve fibers, and functions of the injured ulnar nerve were restored to a certain extent. Moreover, multiple amplification was subsequently detected in ulnar nerve axons.

Zhang, Yang D, Chen A. The effect of severing a normal S1 nerve root to use for reconstruction of an avulsed contralateral lumbosacral plexus

The aim of this study was to evaluate the feasibility of using the intact S1 nerve root as a donor nerve to repair an avulsion of the contralateral lumbosacral plexus. Two cohorts of patients were recruited. In cohort 1, the L4–S4 nerve roots of 15 patients with a unilateral fracture of the sacrum and sacral nerve injury were stimulated during surgery to establish the precise functional distribution of the S1 nerve root and its proportional contribution to individual muscles. In cohort 2, the contralateral uninjured S1 nerve root of six patients with a unilateral lumbosacral plexus avulsion was transected extradurally and used with a 25 cm segment of the common peroneal nerve from the injured leg to reconstruct the avulsed plexus.

The results from cohort 1 showed that the innervation of S1 in each muscle can be compensated for by L4, L5, S2 and S3. Numbness in the toes and a reduction in strength were found after surgery in cohort 2, but these symptoms gradually disappeared and strength recovered. The results of electrophysiological studies of the donor limb were generally normal.

Severing the S1 nerve root does not appear to damage the healthy limb as far as clinical assessment and electrophysiological testing can determine. Consequently, the S1 nerve can be considered to be a suitable donor nerve for reconstruction of an avulsed contralateral lumbosacral plexus.

Cite this article: Bone Joint J 2015; 97-B:358–65.

Unaffected contralateral S1 transfer for the treatment of lumbosacral plexus avulsion

INTRODUCTION

This study describes a new surgical strategy for lumbosacral plexus avulsion by transfer of the unaffected contralateral S1 nerve root.

METHODS

A surgical reconstruction of the sacral nerve was performed on a 10-year-old boy with left lumbosacral plexus avulsion. The unaffected S1 nerve root (right side) is severed extradurally for transfer. A 25-cm long nerve graft from the common peroneal nerve of the affected side was used as donor nerve. One end of the nerve graft was anastomosed to the proximal stump of the right-sided extradural S1 nerve. The distal end of the nerve graft was divided into two fascicles and anastomosed to the left-sided inferior gluteal nerve and the branch of the sciatic nerve innervating the left-sided hamstrings.

RESULTS

According to motor score of the British Medical Research Council (MRC) system, the strength of glutei and hamstrings improved to the level of M3 1.5 years after surgery.

CONCLUSIONS

The extradural S1 nerve root in the unaffected side can be considered as a suitable donor nerve for transfer in patients with root avulsion of the lumbar or sacral nerve plexus.

Contralateral L-6 nerve root transfer to repair lumbosacral plexus root avulsion: experimental study in rhesus monkeys

Object

Nerve transfer is used for brachial plexus injuries but has rarely been applied to repairs in the lower extremities. The aim of this study was to evaluate the feasibility and effectiveness of using the contralateral L-6 nerve root to repair lumbosacral plexus root avulsions.

Methods

Eighteen rhesus monkeys were randomized into 3 groups. In the experimental group, the left L4–7 and S-1 nerve roots were avulsed and the right L-6 nerve root was transferred to the left inferior gluteal nerve and the sciatic nerve branch innervating the hamstrings. In the control group, the left L4–7 and S-1 nerve roots were avulsed and nerve transfer was not performed. In the sham operation group, the animals underwent a procedure that did not involve nerve avulsion and nerve transfer. Functional outcomes were measured by electrophysiological study, muscle mass investigation, and histological study.

Results

The mean amplitudes of the compound muscle action potentials from the gluteus maximus and biceps femoris in the experimental group were higher than those in the control group but lower than those in the sham group (p < 0.05). The muscle mass and myofiber cross-sectional area of these muscles were heavier and larger than those in the control group (p < 0.05). The number of myelinated nerve fibers of the inferior gluteal nerve and the branch of the sciatic nerve innervating the hamstrings in the control group was significantly smaller than the number in the experimental and sham groups (p < 0.01).

Conclusions

In this animal model, the contralateral L-6 (analogous to S-1 in humans) nerve root can be used to repair lumbosacral plexus root avulsion.

Transfer of normal S1 nerve root to reinnervate atonic bladder due to conus medullaris injury

INTRODUCTION

Neurogenic bladder dysfunction after spinal cord injury (SCI) is a major medical and social problem. In this study we assessed the effectiveness of neurogenic bladder reinnervation in patients with SCI using a normal S1 nerve root.

METHODS

Nine patients with bladder dysfunction caused by injury to the low conus medullaris (S2-S5) underwent a novel surgical procedure in which the unilateral proximal end of the S1 ventral root (VR) was anastomosed to the distal end of the S2 and S3 VRs.

RESULTS

Seven patients regained satisfactory bladder control within 8-12 months after VR microanastomosis. The average residual urine volume decreased from 186.0 ± 35.0 ml to 43.0 ± 10.0 ml, and no urinary infections occurred.

CONCLUSIONS

These results suggest the effectiveness of bladder innervation by S1 nerve transfer, which could provide a new approach for the reconstruction of atonic bladder function caused by low conus medullaris injuries.