Lumbosacral nerve root avulsion

Value of Direct Decompression of Lumbosacral Roots in Sacral Fractures with Neurologic Deficit: Is It Mandatory?

Background

The value of direct decompression of neural structures to treat lumbosacral plexus injury associated with sacral fractures is still debatable. Direct decompression allows decompression of nerve roots by sacral laminectomy and removal of bone fragments in the spinal canal. In contrast, indirect decompression may offer similar neurological outcomes if good fracture reduction and correction of sacral kyphosis are achieved. In this comparative retrospective study, we analyzed differences between direct and indirect neurological decompression in terms of neurological recovery, complications, and functional outcome.

Methods

This study included 33 cases with spinopelvic dissociation with variable degrees of lumbosacral plexus injury. All cases were managed by spinopelvic fixation. Eighteen patients (group 1) had direct decompression of lumbosacral nerve roots while 15 patients (group 2) had indirect decompression.

Results

Initial sacral kyphosis, quality of fracture reduction, and postoperative residual kyphosis were the main factors that significantly affected functional and neurological outcome in both groups. The final neurological improvement was similar in both groups. No significant difference was observed between both groups in the residual Gibbons' score recorded in the last visit (p = 0.206). The final Majeed score also showed no significant difference between the two groups (p = 0.869).

Conclusions

Indirect decompression of sacral fractures showed similar final functional outcome and neurological recovery compared to direct decompression. Restoration of lumbosacropelvic stability and anatomic reduction seem to be the cornerstone for better functional outcome and neurological recovery rather than direct decompression of neural elements.

Bioinformatic analysis of circular RNA expression profiles in a rat lumbosacral spinal root avulsion model

Lumbosacral spinal root avulsion (LSRA) is a severe nerve injury that results in devastating dysfunction in the lower limb. Circular ribonucleic acids (circRNAs) have been reported to be implicated in a variety of diseases. However, the role of circRNAs in LSRA remains unclear. Here, we performed RNA sequencing (RNA-seq) to determine circRNA expression profiles in a rat LSRA model and further investigated their potential functions and the underlying mechanisms by bioinformatic analyses and in vitro experiments. In all, 1708 circRNAs were found to be differentially expressed in spinal cord tissues after LSRA (|fold change| ≥ 2 and p < 0.05), with 591 up-regulated 1117 down-regulated. Meanwhile, 2263 mRNAs were also indentified to be differentially expressed, of which 1471 were upregulated and 792 were downregulated. Eight randomly selected circRNAs and mRNA were successfully verified to be consistent the RNA-seq results by quantitative real-time polymerase chain reaction. Functional analyses based on gene ontology and Kyoto Encyclopedia of Genes and Genomes predicted the potential roles of differentially expressed circRNAs and mRNAs in LSRA, and circRNA/miRNA/mRNA interaction networks revealed that circRNA_7025, a down-regulated circRNA in LSRA, was targeted by two neuronal apoptosis-related miRNAs, rno-miR-1224 and rno-miR-326-5p. Further in vitro experiments revealed that circRNA_7025 protected against oxygen-glucose deprivation induced neuronal apoptosis via the circRNA_7025/miR-1224/miR-326-5p axis. In summary, our results revealed circRNA expression profiles and their potential functions in LSRA. These findings improve our understanding of the pathogenic mechanisms involved in LSRA and might enable us to identify new molecular targets for LSRA.

Identification of Potential Ferroptosis Key Genes in the Pathogenesis of Lumbosacral Spinal Root Avulsion by RNA Sequencing and Bioinformatics Analysis

Objective: Ferroptosis is a type of cell death involved in various human diseases, including nerve injury. However, the role of ferroptosis in lumbosacral spinal root avulsion (LSRA) remains unknown. This study aims to investigate whether ferroptosis is induced after LSRA and the key ferroptosis-related genes and their potential function in LSRA.

Methods: The biochemical and morphological changes of ferroptosis were determined by detection of iron accumulation and by transmission electron microscopy in a rat LSRA model. The transcriptional expression profile following LSRA was investigated by RNA sequencing and ferroptosis-related genes were downloaded from FerrDb and used to identify ferroptosis differentially expressed genes (DEGs). The differential expressions of ferroptosis DEGs were confirmed by qRT-PCR analysis. The potential functions of ferroptosis DEGs were revealed by DAVID 6.8 and WebGestalt. A protein–protein interaction (PPI) network and gene–miRNA interaction network were further constructed to identify key modules in ferroptosis DEGs, and the results were verified by qRT-PCR and western blot analysis.

Results: LSRA was followed by ferroptosis-specific changes, such as shrunken mitochondria and increased iron accumulation, that can be alleviated by ferroptosis inhibitor deferoxamine (DFO). A total of 2,446 DEGs and 46 ferroptosis DEGs were identified after LSRA, and over 90% of the ferroptosis DEGs were confirmed to be differentially expressed following LSRA, which can also be eliminated by DFO treatment. Functional analysis demonstrated significant enrichment of the ferroptosis DEGs in pathways related to the oxidative stress response, the HIF-1 signaling pathway, and the tumor necrosis factor signaling pathway. PPI network analysis demonstrated that a set of key modules in ferroptosis DEGs were related to the HIF-1 signaling pathway: Il6, Nos2, Stat3, Hif1a, Vegfa, Cdkn1a, and Rela. Construction of a gene–miRNA network predicted miRNAs targeting four key ferroptosis DEGs—Stat3, Hif1a, Vegfa, and Rela, and further western blot analysis confirmed their upregulation after LSRA, which can be alleviated by DFO pretreatment.

Conclusion: The data revealed the induction of ferroptosis in a rat LSRA model and identified possible regulatory roles for ferroptosis-related genes in the molecular mechanisms of LSRA, which provides new insights into the pathogenesis and helps to find new molecular targets for the treatment of LSRA.

Epitranscriptomic analysis of m6A methylome in rats after lumbosacral nerve root avulsion

Background: N⁶-methyladenosine (m⁶A) is the most prevalent modification in mRNAs but its role in lumbosacral nerve root avulsion (LSRA) remains elusive. Materials & methods: Mettl3 expression and global m⁶A level were detected by qPCR, western blot and immunostaining. Altered m⁶A-tagged transcript profiles were revealed by methylated RNA immunoprecipitation and RNA sequencing. Results: Mettl3 and global m⁶A level were upregulated in spinal cord tissues of LSRA rats. In all, 1087 m⁶A peaks were differentially modified by m⁶A, of which 654 were upregulated and 433 downregulated. Biological functions of these transcripts and the hypermethylated or hypomethylated transcripts were also identified. Conclusion: Our findings revealed a profound function of m⁶A modification in LSRA, which provides new insights into its pathogenesis.

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.

Anterior cornual motoneuron regression pattern after sacral plexus avulsion in rats

BACKGROUND

Sacral plexus avulsions lead to severe disability in patients and remain a thorny clinical problem due to the lack of anatomical, experimental and clinical studies. Attempts have been made to treat lumbosacral plexus injuries with such operations as direct anastomosis of the ends of injured sacral plexuses, and certain therapeutic effects were achieved. To further explore the degeneration pattern of anterior cornual motoneurons and determine the best time for treatment, we carried out this study.

METHODS

We randomly assigned 60 SD rats into six groups (group A-F), with ten rats per group. The A, B, C, D, E, F groups included animals that received operation for L4-L6 nerve root avulsion at 2, 4, 6, 8, 10 and 12 weeks respectively. We measured the apoptosis of motor neurons in the anterior corn through hematoxylin-eosin (HE) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, and found that after sacral plexus avulsions, motor neurons in the anterior horn of the spinal cord gradually reduced and the apoptosis index gradually increased as the time went by.

RESULTS

Survival rates of motoneurons at 2, 4, 6, 8, 10, and 12 weeks after avulsion were (92.1 ± 4.7)%, (83.6 ± 3.7)%, (43.6 ± 4.2)%, (32.1 ± 3.5)%, (18.4 ± 3.7)% and (12.1 ± 3.3)%, respectively. The difference was most significant at week 6.

CONCLUSION

Week 6 after injury is probably the deadline for surgical repair of sacral plexus avulsions.

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.

Cauda equina repair in the rat: part 1. Stimulus-evoked EMG for identifying spinal nerves innervating intrinsic tail muscles

Cauda equina injuries may produce severe leg and pelvic floor dysfunction, for which no effective treatments exist. We are developing a rat cauda equina injury model to allow nerve root identification and surgical repair. One possible difficulty in implementing any repair strategy after trauma in humans involves the correct identification of proximal and distal ends of nerve roots separated by the injury. Two series of studies were carried out. In Series 1, we electrically stimulated segmental contributors to the dorsal and ventral caudales nerves in order to characterize the recruitment patterns of muscles controlling rat tail movements. In Series 2, we attempted to identify individual nerve roots forming the cauda equina by both level of origin and function (i.e., dorsal or ventral), based solely upon the recruitment patterns in response to electrical stimulation. For Series 1 studies, electrical stimulation of the segmental contributors showed that all nerve roots-from the sixth lumbar to the first coccygeal-contributed to recruitment of muscles found at the base of the tail. Intrinsic tail muscles lying more distally in the tail showed a more root-specific pattern of innervation. For Series 2, the rate of successful identification of an unknown nerve root as being ventral was very high (>95%), and only somewhat lower (approximately 80%) for dorsal roots. Correctly identifying the level of origin of that root was more difficult, but for ventral roots this rate still exceeded 90%. Using the rat cauda equina model, we have shown that stimulus-evoked EMG can be used to identify ventral nerve roots innervating tail muscles with a high degree of accuracy. These findings support the feasibility of using this conceptual approach for identifying and repairing damaged human cauda equina nerve roots based on stimulus-evoked recruitment of muscles in the leg and pelvic floor.

Traumatic lumbosacral pseudomeningocele associated with spinal fracture

BACKGROUND CONTEXT

Traumatic pseudomeningocele and avulsion of lumbosacral nerve roots are rare in the absence of fractures of the pelvic ring or hip dislocation. Clear prognoses for the root avulsion or pseudomeningocele do not exist.

PURPOSE

To present a patient who developed a posttraumatic pseudomeningocele after lumbosacral injury.

STUDY DESIGN

Case report and review of the literature.

METHODS

A patient who sustained traumatic pseudomeningocele of the lumbar spine was treated nonsurgically and followed over a 2-year period.

RESULTS

Nerve root deficit largely recovered, although an asymptomatic pseudomeningocele persisted.

CONCLUSIONS

The radiographic diagnosis of lumbar root avulsion is not predictive, and recovery may be expected in some patients without operative intervention. Management of patients with lumbar nerve root avulsion and posttraumatic pseudomeningocele should be based on the size and clinical significance of the pseudomeningocele.

Minocycline protects motor but not autonomic neurons after cauda equina injury

Conus medullaris/cauda equina injuries typically result in loss of bladder, bowel, and sexual functions, partly as a consequence of autonomic and motor neuron death. To mimic these injuries, we previously developed a rodent lumbosacral ventral root avulsion (VRA) injury model, where both autonomic and motor neurons progressively die over several weeks. Here, we investigate whether minocycline, an antibiotic with putative neuroprotective effects, may rescue degenerating autonomic and motor neurons after VRA injury. Adult female rats underwent lumbosacral VRA injuries followed by a 2-week treatment with either minocycline or vehicle injected intraperitoneally. The sacral segment of the spinal cord was studied immunohistochemically using choline acetyltransferase (ChAT) and activated caspase-3 at 4 weeks post-operatively. Minocycline increased the survival of motoneurons but not preganglionic parasympathetic neurons (PPNs). Further investigations demonstrated that a larger proportion of motoneurons expressed activated caspase-3 compared to PPNs after VRA injury and indicated an association with minocycline's differential neuroprotective effect. Our findings suggest that minocycline may protect degenerating motoneurons and expand the therapeutic window of opportunity for surgical repair of proximal root lesions affecting spinal motoneurons.

Neurologic Injury Associated With Pelvic Trauma: Radiology and Electrodiagnosis Evaluation and Their Relationships to Pain and Gait Outcome

OBJECTIVES

To study the electrodiagnosis presentation of patients with lower-extremity nerve injury related to pelvic trauma, to assess gait outcome and correlation to injury type and electrodiagnosis, and to study the incidence of pain postinjury and the relationships between injury type and electrodiagnosis and pain type.

DESIGN

Retrospective review.

SETTING

Tertiary care university hospital.

PARTICIPANTS

Seventy-eight patients who present with lower-extremity nerve injury associated with pelvic trauma.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Electrodiagnostic results, the relationship between electrodiagnosis and fracture or injury type, and gait and pain outcomes.

RESULTS

The characteristic neurologic injury in patients with pelvic trauma was a lumbosacral plexus injury (71% of cases). Sciatic nerve injuries were more common in patients with isolated acetabular fractures (9/10 cases). Gait outcome was related to electrodiagnostic abnormality and severity. Long-term assisted gait was best predicted by absent peroneal conduction to the extensor digitorum brevis (P<.001) and absent motor unit potentials on anterior tibialis needle examination (P<.001). Neuropathic pain was seen in patients with any degree of gait abnormality. Orthopedic pain was more common in patients with an acetabular fracture (P<.025).

CONCLUSIONS

Lumbosacral plexus injury after pelvic trauma is a characteristic disorder with severe long-term implications regarding both pain and gait outcome.

Disturbances of the symphysis pubis in rheumatoid arthritis: report of two cases

We present two rheumatoid arthritis (RA) patients suffering from disturbances of the symphysis pubis. Radiography revealed one with pelvic ring disruption with symphysis pubis diastasis, and the other with osteolysis at both pubic rami and disruption of the superior aspect of the symphysis pubis. Both cases had received long-term corticosteroid therapy, including pulse therapy. We recommend reducing the corticosteroid dose to prevent disturbances of the symphysis pubis especially in RA patients on long-term steroid therapy.

Rho-kinase inhibition enhances axonal plasticity and attenuates cold hyperalgesia after dorsal rhizotomy

Dorsal rhizotomy results in primary deafferentation of the dorsal horn with concomitant sprouting of spared intraspinal monoaminergic axons. Because descending monoaminergic systems are thought to mitigate nociceptive transmission from the periphery and because dorsal rhizotomy can result in neuropathic pain, we sought to determine whether the rhizotomy-induced sprouting response could be further augmented. Because myelin-derived molecules mask endogenous plasticity of CNS axons and because myelin-inhibitory signaling occurs through the Rho-GTPase pathway, we inhibited Rho-pathway signaling after cervical dorsal rhizotomy in rats. An increase in the density of serotonergic- and tyrosine hydroxylase-positive fibers was seen in the dorsal horn 1 week after septuple rhizotomy, and axon density continued to increase for at least 1 month. One week after septuple rhizotomy, administration of intrathecal Y-27632, an antagonist of Rho-kinase (ROCK), increased the density of both fiber types over vehicle-treated controls. To examine behavioral effects of both cervical rhizotomy and ROCK inhibition, we examined responses to evoked pain: mechanical and thermal allodynia and cold hyperalgesia in the forepaw were examined after single, double, and quadruple rhizotomies of dorsal roots of the brachial plexus. The most notable behavioral outcome was the development of cold hyperalgesia in the affected forepaw after rhizotomies of the C7 and C8 dorsal roots. Application of Y-27632 both attenuated cold hyperalgesia and induced monoaminergic plasticity after C7/8 rhizotomy. Thus, inhibition of Rho-pathway signaling both promoted the sprouting of intact supraspinal monoaminergic fibers and alleviated pain after dorsal rhizotomy.

Autonomic and motor neuron death is progressive and parallel in a lumbosacral ventral root avulsion model of cauda equina injury

Injuries to the cauda equina of the spinal cord result in autonomic and motor neuron dysfunction. We developed a rodent lumbosacral ventral root avulsion injury model of cauda equina injury to investigate the lesion effect in the spinal cord. We studied the retrograde effects of a unilateral L5-S2 ventral root avulsion on efferent preganglionic parasympathetic neurons (PPNs) and pelvic motoneurons in the L6 and S1 segments at 1, 2, 4, and 6 weeks postoperatively in the adult male rat. We used Fluoro-Gold-prelabeling techniques, immunohistochemistry, and quantitative stereologic analysis to show an injury-induced progressive and parallel death of PPNs and motoneurons. At 6 weeks after injury, only 22% of PPNs and 16% of motoneurons remained. Furthermore, of the neurons that survived at 6 weeks, the soma volume was reduced by 25% in PPNs and 50% in motoneurons. Choline acetyltransferase (ChAT) protein was expressed in only 30% of PPNs, but 80% of motoneurons remaining at 1 week postoperatively, suggesting early differential effects between these two neuronal types. However, all remaining PPNs and motoneurons were ChAT positive at 4 weeks postoperatively. Nuclear condensation and cleaved caspase-3 were detected in axotomized PPNs and motoneurons, suggesting apoptosis as a contributing mechanism of the neural death. We conclude that lumbosacral ventral root avulsions progressively deplete autonomic and motor neurons. The findings suggest that early neuroprotection will be an important consideration in future attempts of treating acute cauda equina injuries.

Post-traumatic lumbar nerve root avulsion

Lumbar nerve root avulsion is a rarely seen clinical entity that may complicate major trauma. The majority of previously reported cases have associated pelvic or lumbar vertebral fractures. Two cases of traumatic pseudomeningoceles at the lumbar level with associated avulsions of the lumbar nerve roots are presented. Both patients were involved in high velocity motor vehicle accidents. Case 1 had associated pelvic fractures but no spinal fractures and, interestingly, case 2 had no fractures of the spine or pelvis. The value of MRI in making the diagnosis is demonstrated.