Accurate segmental motor innervation of human lower-extremity skeletal muscles

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.

Impact of Preoperative Motor Status for the Positive Predictive Value of Transcranial Motor-Evoked Potentials Alerts in Thoracic Spine Surgery: A Prospective Multicenter Study by the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research

STUDY DESIGN

Prospective multicenter study.

OBJECTIVE

To investigate the validity of transcranial motor-evoked potentials (Tc-MEP) in thoracic spine surgery and evaluate the impact of specific factors associated with positive predictive value (PPV).

METHODS

One thousand hundred and fifty-six cases of thoracic spine surgeries were examined by comparing patient backgrounds, disease type, preoperative motor status, and Tc-MEP alert timing. Tc-MEP alerts were defined as an amplitude decrease of more than 70% from the baseline waveform. Factors were compared according to preoperative motor status and the result of Tc-MEP alerts. Factors that showed significant differences were identified by univariate and multivariate analysis.

RESULTS

Overall sensitivity was 91.9% and specificity was 88.4%. The PPV was significantly higher in the preoperative motor deficits group than in the preoperative no-motor deficits group for both high-risk (60.3% vs 38.3%) and non-high-risk surgery groups (35.1% vs 12.8%). In multivariate logistic analysis, the significant factors associated with true positive were surgical maneuvers related to ossification of the posterior longitudinal ligament (odds ratio = 11.88; 95% CI: 3.17-44.55), resection of intradural intramedullary spinal cord tumor (odds ratio = 8.83; 95% CI: 2.89-27), preoperative motor deficit (odds ratio = 3.46; 95% CI: 1.64-7.3) and resection of intradural extramedullary spinal cord tumor (odds ratio = 3.0; 95% CI: 1.16-7.8). The significant factor associated with false positive was non-attributable alerts (odds ratio = .28; 95% CI: .09-.85).

CONCLUSION

Surgeons are strongly encouraged to use Tc-MEP in patients with preoperative motor deficits, regardless of whether they are undergoing high-risk spine surgery or not. Knowledge of PPV characteristics will greatly assist in effective Tc-MEP enforcement and minimize neurological complications with appropriate interventions.

Correlation Between Atrophy of the Gluteus Medius Muscle and Symptoms of Lumbar Spinal Stenosis

OBJECTIVE

Lower muscular weakness and gait disturbance are typical lumbar spinal stenosis (LSS) symptoms. Gait initiation and standing balance function are dependent on hip muscle groups, particularly gluteus medius (GMed). However, alterations to GMed in patients with LSS have not been studied. Therefore, we evaluated the impact of LSS on GMed in this study.

METHODS

This study included 96 participants divided into the LSS and non-LSS groups. A total of 48 patients with LSS and unilateral buttock pain underwent T2-weighted magnetic resonance imaging of GMed, and 48 age- and sex-matched controls formed the control group. Differences between the cross-sectional areas (CSAs) on both sides of GMed were compared between the 2 groups. Additionally, correlations among patient characteristics, clinical evaluation, and radiological measurement data with a decrease in the CSA of GMed were assessed in the LSS group.

RESULTS

A significant difference was observed in the bilateral discrepancy of the GMed CSA between the LSS and non-LSS groups. For patients with LSS with unilateral buttock pain, 81% had reduced CSA of GMed. Regression analysis revealed that buttock pain was an independent factor related to GMed atrophy.

CONCLUSIONS

The degree of GMed atrophy is related to symptoms of LSS. Spine surgeons should be aware of the risk of GMed atrophy in patients with LSS with unilateral buttock pain.

Correlation Between Neurologic Impairment Grade and Ambulation Status in the Adult Spina Bifida Population

OBJECTIVE

The aim of the study was to identify which neurologic impairment scales correlate with ambulation status in adults with spina bifida.

DESIGN

A retrospective chart review was performed on patients seen at the University of Pittsburgh Medical Center Adult Spina Bifida Clinic. Findings were graded using several neurologic impairment scales: two versions of the National Spina Bifida Patient Registry classification, the International Standards for Neurological Classification of Spinal Cord Injury motor level, and the Broughton Neurologic Impairment Scale. Ambulation ability was ranked using the Hoffer classification system.

RESULTS

Data collected from 409 patient records showed significant correlations between Hoffer ambulation status and all neurologic impairment scales evaluated. The strongest correlation was noted with the Broughton classification (rs = -0.771, P < 0.001). High correlations were also noted with both versions of the National Spina Bifida Patient Registry: strength 3/5 or greater (rs = -0.763, P < 0.001), and strength 1/5 or greater (rs = -0.716, P < 0.001). For the International Standards for Neurological Classification of Spinal Cord Injury motor level, only a moderate correlation was observed (rs = -0.565, P < 0.001).

CONCLUSIONS

Multiple grading scales can be used to measure motor function in adult spina bifida patients. Although the Broughton classification seems to be the most highly correlated with ambulation status, the less complex National Spina Bifida Patient Registry scale is also highly correlated and may be easier to administer in busy clinic settings.

TO CLAIM CME CREDITS

Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME CME OBJECTIVES: Upon completion of this article, the reader should be able to: (1) Explain the clinical significance of identifying ambulation status and maximizing ambulation potential in adults with spina bifida; (2) Describe each of the neurologic grading scales examined in this study, identifying potential shortcomings in applying them to the adult spina bifida population; and (3) Administer the National Spina Bifida Patient Registry (NSBPR) impairment scale motor assessment in a standard adult spina bifida outpatient clinic visit.

LEVEL

Advanced ACCREDITATION: The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Muscle responses to radicular stimulation during lumbo-sacral dorsal rhizotomy for spastic diplegia: Insights to myotome innervation

OBJECTIVE

Most of knowledge on muscle radicular innervation was from explorations in root/spinal cord pathologies. Direct and individual access to each of the lumbar-sacral -ventral and dorsal- nerve roots during dorsal rhizotomy for spastic diplegia allows precise study of the corresponding muscle innervation. Authors report the lumbo-sacral segmental myotomal organization obtained from recordings of muscle responses to root stimulation in a 20-children prospective series.

METHODS

Seven key-muscles in each lower limb and anal sphincter were Electromyography (EMG)-recorded and clinically observed by physiotherapist during L2-to-S2 dorsal rhizotomy. Ventral roots (VR), for topographical mapping, and dorsal roots (DR), for segmental excitability testing, were stimulated, just above threshold for eliciting muscular response.

RESULTS

In 70% of the muscles studied, VR innervation was pluri-radicular, from 2-to-4 roots, with 1 or 2 roots being dominant at each level. Overlapping was important. Muscle responses to DR stimulation were 1.75 times more extended compared to VR stimulation. Inter-individual variability was important.

CONCLUSIONS

Accuracy of root identification and stimulation with the used method brings some more precise information to radicular functional anatomy.

SIGNIFICANCE

Those neurophysiological findings plead for performing Intra-Operative Neuromonitoring when dealing with surgery in the lumbar-sacral roots.

Relationship Between Cauda Equina Conduction Time and Type of Neurogenic Intermittent Claudication due to Lumbar Spinal Stenosis

INTRODUCTION

This study investigated whether the prolongation of the cauda equina conduction time (CECT) was related to the type of neurogenic intermittent claudication due to lumbar spinal stenosis.

METHODS

In total, 149 patients who underwent surgery due to lumbar spinal stenosis with neurogenic intermittent claudication were classified into three groups as follows: cauda equina-type(n = 67), radicular-type(n = 29), and mixed-type(n = 53). Cauda equina conduction time was measured by placing disc electrodes on the abductor hallucis muscle, electrically stimulating the tibial nerve of the ankle and recording the compound muscle action potentials and F-waves. Motor evoked potentials from the abductor hallucis muscle were measured after magnetically stimulating the lumbosacral spine. Cauda equina conduction time was calculated from the latencies of compound muscle action potentials, F-waves, and motor evoked potentials. The measurement of the dural sac cross-sectional area were assessed using computed tomography myelography or MRI.

RESULTS

The values of CECT were as follows: cauda equina-type, 5.6 ± 1.1 ms; mixed-type, 5.1 ± 0.9 ms; and radicular-type, 4.0 ± 0.9 ms. The values of dural sac cross-sectional area were as follows: cauda equina-type, 42.8 ± 18.7 mm; mixed-type, 49.6 ± 20.9 mm; and radicular-type, 75.3 ± 19.1 mm. In the cauda equina-type and mixed-type patients, CECT was significantly prolonged and there were negative correlations between CECT and dural sac cross-sectional area.

CONCLUSIONS

Cauda equina conduction time differed according to the type of lumbar spinal stenosis. The prolongation of CECT may be caused by the demyelination of the CE. Cauda equina conduction time may be a useful measure for evaluating the dysfunction of the CE rather than radiculopathy for patients with lumbar spinal stenosis.

Quantitative measurements of hip abduction strength in lumbar surgery patients

BACKGROUND

We sought to evaluate the hip abduction strength in patients before and after lumbar surgery.

MATERIALS AND METHODS

Eighty-four patients (51 males and 33 females) undergoing surgery for lumbar disc herniation or lumbar canal stenosis were selected. Mean age was 64.7 ± 13.8 years. Seven patients (8.3%) had surgery at multiple levels, including L2-L3 (group A), 27 (32.1%) patients had surgery at multiple levels including L3-L4 (group B), 32 (38.1%) patients had surgery at the L4-L5 level only (group C), and 18 (21.4%) patients had surgery at the L5-S1 level only (group D). Hip abduction strength was measured in the 84 patients preoperatively and in 49 patients postoperatively.

RESULTS

In all patients, preoperative mean hip abduction strength on the symptomatic side and the asymptomatic side was 71.4 ± 34.5 N and 90.7 ± 36.5 N, respectively (p = 0.0008). In groups A and B, there were no significant differences between the mean hip abduction strength on the symptomatic and contralateral side. In group C, those on the symptomatic and contralateral side were 68.0 ± 33.5 N and 89.3 ± 34.8 N, respectively (p = 0.0181). In group D, those on the symptomatic and contralateral side were 74.3 ± 42.4 N and 101.7 ± 44.7 N, respectively (p = 0.0314). In the 49 patients of all groups that could be measured postoperatively, there were no significant differences between the mean hip abduction strength on both sides.

CONCLUSIONS

It was confirmed that the gluteus medius, which was main hip abductor, was mainly innervated by L5 and its mean strength significantly improved postoperatively. The possibility of improvement of hip abduction strength, especially with unchanged tibialis anterior strength, could be very useful for operative decisions.