Root reconstruction for bladder reinnervation: an experimental study in rats

Anatomical Feasibility of Extradural Transferring S2 and S3 Ventral Roots to S1 Ventral Root for Restoring Neurogenic Bladder in Spinal Cord Injury

STUDY DESIGN

Anatomic study in six formalin-fixed cadavers.

OBJECTIVE

To determine the anatomical feasibility of transferring the S2 and S3 ventral roots (VRs) to S1 VR as a method for restoring bladder dysfunction in spinal cord injury.

SUMMARY OF BACKGROUND DATA

A large quantity of researches of neuroanastomosis methods have been used for treating the bladder dysfunction in spinal cord injury. However, some limitations retard the development of those studies.

METHODS

In this study, six formalin-fixed cadavers (four males, two females) were dissected. The feasibility of exposing the S1, S2, and S3 extradural nerve roots by the limited laminectomy, isolating the VR and dorsal roots from each extradural nerve root and transferring the S2,S3 VRs to the S1 VR were assessed. The pertinent distances and the nerve cross-sectional areas in each specimen were measured. The morphology of each nerve root was observed by hematoxylin-eosin staining.

RESULTS

The limited laminectomy was performed to expose the S1 to S3 extradural nerve roots. The VRs could be isolated from each extradural nerve root at the location of the dorsal root ganglion and the hematoxylin-eosin staining showed that there were some connective tissues separating the VRs from the corresponding dorsal root ganglion. The S2 and S3 VRs have sufficient lengths to be transferred to S1 VR without grafting. The mean cross-sectional area of the S1 VR was 2.60 ± 0.17 mm, and that was 1.02 ± 0.32 mm and 0.51 ± 0.21 mm of the S2 and S3 VRs, respectively.

CONCLUSION

This study demonstrated that use of the S2 and S3 VRs for extradural transfer to S1 VR for restoring bladder dysfunction is surgically feasible.

LEVEL OF EVIDENCE

5.

Novel method for restoration of anorectal function following spinal cord injury via nerve transfer in rats

OBJECTIVES

Nerve transfer has been developed to restore partial function after serious nerve injuries, for example, restoring bladder control after spinal cord injury (SCI). Our aim here was to establish a preclinical proof-of-concept model using nerve transfer for restoring anorectal function after SCI.

SETTING

We used laminectomy to model SCI, and bilateral spinal ventral and dorsal nerve root anastomosis to re-establish connectivity to the anorectal musculature.

METHODS

Multidisciplinary methods were used to assess the anatomical and functional integrity of the alternative spinal-to-anorectal nerve circuit. Adult rats were used to establish the model. Bilateral anterior and posterior L5 nerve roots were surgically matched with anterior and posterior of S1 nerve roots by microscopic anastomosis to establish an artificial rectal reflex arc with complete sensory and motor pathways. Twelve weeks later, we used retrograde nerve tracing and neurohistomorphological analysis to assess anatomical integrity of the new artificial rectal reflex arc. Anorectal manometry was used to assess the function of the new nerve circuit.

RESULTS

Retrograde tracing with recombinant attenuated pseudo rabies virus indicated that the new neural pathway was successfully established to the anorectal musculature after experimental SCI. Toluidine blue-stained sections of the anastomosis site revealed normal-appearing nerve fiber morphology and regeneration, and transmission electron microscopy revealed myelinated axons. Anorectal manometry revealed significant anorectal functional recovery.

CONCLUSION

These results suggest that our model is a feasible first step in developing an alternative reflex pathway after laminectomy at L4 to S2 and shows promise for effective restoration of anorectal function.

The feasibility study of extradural nerve anastomosis technique for canine bladder reinnervation after spinal cord injury

OBJECTIVE

Intradural nerve anastomosis for bladder innervation has been demonstrated to be useful. However, its clinical application remains limited because of the complex surgery, its complications and extensive bony destruction. The purpose of the current study was to demonstrate the feasibility of extradural spinal root anastomosis for bladder innervation in canines.

METHODS

Ten beagle dogs were used. The length of the extradural segment of the nerve root, upper nerve root outlet (the point at which it emerges from the spinal dura mater) to S2 (dS2), the S3 (dS3) nerve root outlet distance, and the diameters of the extradural spinal roots were measured. The numbers of nerve fibers from L6 to S3 ventral roots were calculated using immunohistochemical staining.

RESULTS

The extradural spinal roots could be divided into a ventral root (VR) and a dorsal root (DR) before the ganglionic enlargement of the dorsal root, and the extradural motor nerve roots situate ventrally to their corresponding sensory nerve roots. The extradural nerve root lengths of S1 and parts of L7 were longer than the corresponding dS2. The numbers of nerve and motor nerve fibers, and the diameters of extradural nerve roots, were gradually descending from L6 to S3.

CONCLUSION

The S1 VRs and parts of the L7 VRs can be extradurally anastomosed to the S2 nerves without tension. A nerve graft was needed for extradural anastomosis of L6 VRs and parts of L7 VRs to S2 VRs. This study demonstrated the feasibility of extradural spinal nerve anastomosis for treating neurogenic bladder in canines.

Extradural nerve anastomosis technique for bladder reinnervation in spinal cord injury: anatomical feasibility study in human cadavers

STUDY DESIGN

An anatomic study of extradural spinal root in 9 embalmed cadavers.

OBJECTIVE

To ascertain the anatomical parameters of the extradural spinal root and to demonstrate the feasibility of spinal root anastomoses without opening the spinal dura mater.

SUMMARY OF BACKGROUND DATA

Intradural anastomosis of the spinal root has made breakthrough progress in treating neurogenic bladder in spinal cord injury. However, because of the complex surgical procedures and extensive bony destruction, its clinical use is not widely promoted.

METHODS

Nine formalin-fixed cadavers were used. The distance between the nerve root outlet and ganglion center, the neighboring nerve root-outlet distance, and the gross anatomy of the extradural spinal root were measured with a surgical microscope. The number of nerve fibers from the T7 to S4 ventral roots (VRs) was calculated by immunohistochemical staining.

RESULTS

The longest and shortest lengths of the extradural spinal root were observed at the S4 and T7 levels, with average values of 33.29 and 6.06 mm, respectively. The longest distance between the adjacent nerve root outlets was observed at L1-L2 (mean, 29.16 mm), and shortest at S3-S4 (mean, 11.79 mm). After leaving the dural sac, the spinal root descends in the spinal canal until reaching the corresponding intervertebral foramina, and the motor nerve roots still lie ventrally to the sensory nerve roots. The largest and smallest numbers of nerve fibers were observed at the L3 and S4 levels (mean, 9169 and 1356, respectively).

CONCLUSION

The dorsal roots and VRs can both be successfully harvested and identified outside the dural sac. The S1 VR can be anastomosed to the S2 VR extradurally without nerve grafts. For extradural neuroanastomosis of the thoracic VRs to the S2 VR, a nerve graft is required. In addition, there are a sufficient number of nerve fibers for functional bladder recovery at the T7-T12 and S1 levels. This study supports the feasibility of extradural spinal root anastomosis as a modified surgical method for treating neurogenic bladder.

LEVEL OF EVIDENCE

N/A.

Neurostimulation for neurogenic bowel dysfunction

Background. Loss of normal bowel function caused by nerve injury, neurological disease or congenital defects of the nervous system is termed neurogenic bowel dysfunction (NBD). It usually includes combinations of fecal incontinence, constipation, abdominal pain and bloating. When standard treatment of NBD fails surgical procedures are often needed. Neurostimulation has also been investigated, but no consensus exists about efficacy or clinical use. Methods. A systematic literature search of NBD treated by sacral anterior root stimulation (SARS), sacral nerve stimulation (SNS), peripheral nerve stimulation, magnetic stimulation, and nerve re-routing was made in Pubmed, Embase, Scopus, and the Cochrane Library. Results. SARS improves bowel function in some patients with complete spinal cord injury (SCI). Nerve re-routing is claimed to facilitate defecation through mechanical stimulation of dermatomes in patients with complete or incomplete SCI or myelomeningocele. SNS can reduce NBD in selected patients with a variety of incomplete neurological lesions. Peripheral stimulation using electrical stimulation or magnetic stimulation may represent non-invasive alternatives. Conclusion. Numerous methods of neurostimulation to treat NBD have been investigated in pilot studies or retrospective studies. Therefore, larger controlled trials with well-defined inclusion criteria and endpoints are recommended before widespread clinical use of neurostimulation against NBD.

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.

Micturition reflex arc reconstruction including sensory and motor nerves after spinal cord injury: urodynamic and electrophysiological responses

OBJECTIVE

To evaluate artificial reflex arcs for micturition using urodynamics and electrophysiological recordings.

DESIGN

Sixteen beagles were equally and randomly divided into two groups.

METHODS

In group A, anastomosis of the proximal end of the left L7 ventral root (VR) and distal end of the left S2 VR was performed, as well as anastomosis of the L7 dorsal root (DR) and S2 DR to reconstruct the sensory and the motor function of the bladder. In group B the proximal end of the left L7 VR and the distal end of the left S2 VR were anastomosed, while the left L7 DR was kept intact to reconstruct the motor function of the bladder. Outcome measures included electrophysiological testing and the urodynamic measures. In addition, we also monitored urinary infection rates.

RESULTS

Stimulation to the left S2 DR in groups A and B both elevated the bladder pressure before and after the spinal lower motor neuron lesion. Single stimulation of the two groups both elicited evoked action potentials. Urinary infections occurred in group A (three occurrences) and in group B (eight occurrences) during the 3 months after the spinal lower motor neuron lesion.

CONCLUSION

Data showed that both reconstructive methods could induce bladder micturition and evoked action potentials. However, in group A the micturition response was better and the urinary infection rates were lower after the spinal lower motor neuron lesion. Thus, the artificial physiological reflex arc reconstruction method used in group A, with sensory input above the lesion, might provide a better alternative in clinical practice.

Reconstructed bladder innervation above the level of spinal cord injury to produce urination by abdomen-to-bladder reflex contractions

Neurogenic bladder dysfunction following spinal cord injury is a major medical and social problem for which there is no ideal treatment strategy. This paper describes the authors' attempts to establish bladder reinnervation, by establishing an abdomen-to-bladder reflex pathway, in a patient with an injury to the conus medullaris.

Reinnervation of atonic bladder after conus medullaris injury using a modified nerve crossover technique in canines

BACKGROUND

Neurogenic bladder represents a major cause of morbidity in patients with spinal cord injuries (SCI). Herein, we evaluated a novel reconstructive surgical technique designed to restore afferent and efferent nerve function in atonic bladder caused by conus medullaris injury.

MATERIALS AND METHODS

A new reflex pathway was established by extradural transfer of the left L5 ventral root (VR) to the left S2 VR root together with extradural postganglionic spinal nerve transfer of the L5 dorsal root (DR) to the S2 DR with a nerve graft in a canine model. The corresponding nerves on the right side were kept intact and served as a control. After the new reflex pathway was reestablished, the early function of the reflex arc was evaluated by electrophysiologic study, intravesical pressure, and histologic examination.

RESULTS

Action potential (AP) curves were recorded with single focal stimulation of the left S2 DR before and after the spinal cord was destroyed horizontally between the L6 and S3 levels. Bladder contraction was successfully initiated by trains of stimuli targeting the left L5-S2 DR anastomosis. Achievable bladder pressures and the amplitude of bladder smooth muscle complex action potentials were unchanged before and after induced paraplegia and were comparable to those of the control. Prominent axonal sprouting was observed in the distal region of the nerve graft.

CONCLUSION

Both afferent and efferent nerve pathways in the atonic bladder were reconstructed by suprasacral motor-to-motor and sensory-to-sensory extradural nerve transfer in canines. Taken together, these findings suggest a new potential clinical approach for restoring bladder function in individuals with paraplegia.

Clinical study of reconstructed bladder innervation below the level of spinal cord injury to produce urination by Achilles tendon–to-bladder reflex contractions

Object

Neurogenic bladder dysfunction following spinal cord injury (SCI) is a major medical and social problem for which there is no ideal treatment strategy. In the present study, the authors analyze the effectiveness of neurogenic bladder reinnervation in patients with SCIs by using Achilles tendon reflexes below the paraplegic level.

Methods

Spinal root anastomoses were performed in 12 paraplegic patients with hyperreflexic neurogenic bladder and detrusor external sphincter dyssynergia (DESD) caused by complete suprasacral SCI, in an attempt to reinnervate the bladder. The surgery anastomosed the unilateral proximal end of the S-1 ventral root and the distal end of the S-2 and/or S-3 ventral roots to build the Achilles tendon–to-bladder reflex, while the S-1 dorsal root was kept intact as the trigger for micturition after axonal regeneration. All patients underwent urodynamic evaluation before surgery and at follow-up.

Results

The mean follow-up duration was 3 years. Of the 12 patients, 9 (75%) regained satisfactory bladder control within 6 to 12 months after ventral root microanastomosis. In these 9 patients, urodynamic studies revealed a change from detrusor hyperreflexia with DESD and high detrusor pressure to almost normal storage and synergic voiding without DESD. The average bladder capacity increased from 258 ± 33 ml to 350 ± 49 ml, residual urine decreased from 214 ± 36 ml to 45 ± 11 ml, and urinary infections were not observed. Patients with impaired renal function experienced a full recovery. Three patients failed to show any improvement after the operation.

Conclusions

These results suggest the effectiveness of bladder innervation below the level of SCI to produce urination by Achilles tendon–to-bladder reflex contractions, and might therefore provide a new clinical approach to reconstructing spasmodic bladder urination function.

Reconstruction of reflex pathways to the atonic bladder after conus medullaris injury: preliminary clinical results

Neurogenic bladder dysfunction following spinal cord injury is a major medical and social problem for which there is no ideal treatment strategy. In this study, spinal root anastomoses were performed in 10 paraplegic patients with traumatic lesions of the conus medullaris, in an attempt to reinnervate the paralyzed bladder. For the operation, the functional T11 ventral root (VR) above the lesion was transected and anastomosed to the S2 ventral roots unilaterally through a nerve graft. The T11 dorsal root was left intact as the trigger for micturition after axonal regeneration. All patients underwent urodynamic evaluation before surgery and at follow-up. The mean follow-up duration was 2 years. Of the 10 patients, 7 (70%) regained satisfactory bladder control within 18-24 months after VR microanastomosis. In these seven patients, the average bladder capacity decreased from 508 +/- 83 (mean +/- SD) to 370 +/- 59 ml, residual urine decreased from 477 +/- 98 to 35 +/- 11 ml, and urinary infections were not observed. Patients with impaired renal function experienced a full recovery. Three patients failed to show any improvement after the operation. These results suggest that a restitutive process occurs in the bladder following reinnervation from new T11 VR connections to the bladder nerves. Spinal cord lesions that may benefit from such a nerve crossover surgery are those located at the conus, whereby a functional suprasacral nerve can be connected to the sacral roots to bypass the injury in an attempt to restore central connections to the bladder.

Reconstructed bladder innervation below the level of spinal cord injury: the knee-tendon to bladder artificial reflex arc

BACKGROUND/OBJECTIVE

To study the effectiveness of knee-tendon to bladder artificial reflex arc in dogs.

METHODS

In 6 beagles, the proximal end of the right L5 anterior motor root and the distal end of the right S2 anterior root were anastomosed to build a knee-tendon to bladder reflex, whereas the right L5 posterior sensory root was kept intact. Action potential (AP) curves and electromyograms (EMGs) of the detrusor muscle, the intravesical pressure, horseradish peroxidase (HRP)-labeled neurons, and the passing rates of myelinic nerve fibers were calculated to evaluate its feasibility.

RESULTS

AP curves and EMG detected in all 6 dogs were similar to those of the control. Six and 18 months after surgery, the means for bladder contraction induced by percussion of the right knee-tendon were 38 +/- 27% and 62 +/- 5% that of the normal control, respectively. The mean duration times induced by percussion of the right knee-tendon at 6 and 18 months after surgery were 51 +/- 37% and 84 +/- 12% that of the normal control, respectively. HRP retrograde tracing and neurohistologic observation indicated the feasibility of the artificial reflex arc.

CONCLUSIONS

Our data showed the effectiveness of bladder innervation below the level of spinal cord injury producing urination by knee-tendon to bladder reflex contractions, and therefore, might provide a new clinical approach for restoring bladder function in individuals with paraplegia.

Optimal timing of operation for repairing atonic bladder after medullary cone injury: an experimental study in rats

OBJECTIVE

To determine optimal timing of operation for repairing atonic bladder after medullary cone injury in rats.

MATERIALS AND METHODS

I n all, 56 adult female Sprague-Dawley rats were equally randomized into seven groups: normal control group, and 4w, 6w, 8w, 10w, 12w and 16w groups after medullary cone injury, assigned as groups A-G. The model was established by sharp transaction of spinal cord at the level of L(4/5) vertebral body. Bladder weight, cross-sectional area and ultrastructure of the detrusor muscle and its neuromuscular junction (NMJ), fibrotic change, and alpha-smooth muscle antibody (alpha-SMA) expression in the detrusor muscle were examined individually.

RESULTS

Bladder weight in groups E-G was significantly increased than that in group A (P<0.05). And cross-sectional area of detrusor muscle fiber in groups E-G was significantly smaller than that in group A (P<0.05). Transmission electronic microscopy showed that the number of synaptic vesicles, mitochondria and other organelles in NMJ decreased markedly in group E. In groups F and G, NMJ further degenerated with synaptic vesicles and organelles decreased or even disappeared. Masson's stain showed that the proportion of connective tissue in the detrusor muscle of groups E-G was significantly different from that of group A (P<0.05). alpha-SMA expression in the detrusor muscle decreased with the lapse of time.

CONCLUSIONS

The 10th week after rat medullary cone injury can be regarded as the time node when the detrusor muscle and NMJ undergo changes, and therefore surgical nerve repair should be performed before this.

Selection of the sacral nerve posterior roots to establish skin-CNS-bladder reflex pathway: an experimental study in rats

The purpose of this study was to explore the innervations of different sacral nerve posterior roots to bladder, and to provide evidence for further study of skin-CNS-bladder reflex pathway in the spinal cord injury patient. Spinal cord injury was produced in 10 rats. The bilateral spinal posterior roots of S1-S4 were electrically stimulated, and the bladder plexus action, bladder smooth muscle complex action potential, and intravesical pressure were examined and measured. The results showed that all the sacral nerve posterior roots were involved in innervations of bladder in rats. Among them, the S2 sacral nerve is the dominant nerve in innervations of bladder, followed by S1, S3, and S4 sacral nerve posterior roots. This study has provided valuable information for selection of sacral nerve posterior root for further study of the artificial bladder reflex arc for improving the micturition function in spinal cord injury patients.

Reinnervation for neurogenic bladder: historic review and introduction of a somatic-autonomic reflex pathway procedure for patients with spinal cord injury or spina bifida

Neurogenic bladder caused by SCI or spina bifida is a major problem. Research in restoring functional micturition has mainly focused on electrical stimulation for many decades with good progress, but it is still not the definitive solution for majority of the SCI patients. An alternative approach has been to investigate restoring innervation to the lower urinary tract after spinal SCI. Different animal and clinical studies were reviewed historically in this article, focused on mainly cross over nerve surgery for reinnervation of the bladder. An artificial somatic-autonomic reflex pathway procedure and its mechanisms were introduced. Clinical application and the satisfactory results of the new procedure were reviewed in details in restoring voluntary bladder control in patients with SCI or spina bifida.