Contralateral C7 transfer to lower trunk via the prespinal route in the repair of brachial plexus injury: an experimental study in rats

Why It Is Necessary to Use the Entire Root rather than Partial Root When Doing Contralateral C7 Nerve Transfer: Cortical Plasticity Also Matters besides the Amount of Nerve Fibers

Previous studies suggested that the mode of donor transection is a critical factor affecting the efficacy of the contralateral C7 (CC7) nerve transfer. Nevertheless, the mechanism underlying this phenomenon remains elusive. The aim of this study was to investigate the relationship between the division modes of the CC7 nerve and cortical functional reorganization of Sprague-Dawley rats. We hypothesized that different methods of CC7 nerve transection might induce differences in cortical functional reorganization, thus resulting in differences in surgery efficacy. BDNF, TNF-α/IL-6, and miR-132/134 were selected as indicators of cortical functional reorganization. No significant differences in all these indicators were noted between the entire group and the entire root+posterior division group (P > 0.05). BDNF and miR-132/134 levels in the entire group and the entire root+posterior division group were significantly increased compared with their levels in the posterior group and the blank control group (P < 0.001). In all groups, BDNF, TNF-α/IL-6, and miR-132/134 levels in both hemispheres initially increased and subsequently decreased until week 40. In conclusion, this study provided the evidence of dynamic changes in BDNF, TNF-α/IL-6, and miR-132/134 in the cortex of rats after CC7 nerve transfer using different transecting modes, demonstrating that different CC7 nerve divisions might result in different surgical effects through modulation of cortical reorganization.

A novel mouse model of contralateral C7 transfer via the pretracheal route: A feasibility study

BACKGROUND

Contralateral seventh cervical nerve transfer (contralateral C7 transfer) is a novel treatment for patients with spastic paralysis, including stroke and traumatic brain injury. However, little is known on changes in plasticity that occur in the intact hemisphere after C7 transfer. An appropriate surgical model is required.

NEW METHOD

We described in detail the anatomy of the C7 in a mouse model. We designed a pretracheal route by excising the contralateral C6 lamina ventralis, and the largest nerve defect necessary for direct neurorrhaphy was compared with defect lengths in a prespinal route. To test feasibility, we performed in-vivo surgery and assessed nerve regeneration by immunofluorescence, histology, electrophysiology, and behavioral examinations.

RESULTS

Two types of branching were found in the anterior and posterior divisions of C7, both of which were significantly larger than the sural nerve. The length of the nerve defect was drastically reduced after contralateral C6 lamina ventralis excision. Direct tension-free neurorrhaphy was achieved in 66.7% of mice. The expression of neurofilament in the distal segment of the regenerated C7 increased. Histological examination revealed remyelination. Behavioral tests and electrophysiology tests showed functional recovery in a traumatic brain injury mouse.

COMPARISON WITH EXISTING METHODS

This is the first direct tension-free neurorrhaphy mouse model of contralateral C7 transfer which shortened the time of nerve regeneration; previous models have used nerve grafting.

CONCLUSIONS

This paper describes a simple, reproducible, and effective mouse model of contralateral C7 transfer for studying brain plasticity and exploring potential new therapies after unilateral cerebral injury.

Modified contralateral C7 nerve transfer: the possibility of permitting ulnar nerve recovery is confirmed by 10 cases of autopsy

Contralateral C7 nerve transfer surgery is one of the most important surgical techniques for treating total brachial plexus nerve injury. In the traditional contralateral C7 nerve transfer surgery, the whole ulnar nerve on the paralyzed side is harvested for transfer, which completely sacrifices its potential of recovery. In the present, novel study, we report on the anatomical feasibility of a modified contralateral C7 nerve transfer surgery. Ten fresh cadavers (4 males and 6 females) provided by the Department of Anatomy, Histology, and Embryology at the Medical College of Fudan University, China were used in modified contralateral C7 nerve transfer surgery. In this surgical model, only the dorsal and superficial branches of the ulnar nerve and the medial antebrachial cutaneous nerve on the paralyzed side (left) were harvested for grafting the contralateral (right) C7 nerve and the recipient nerves. Both the median nerve and deep branch of the ulnar nerve on the paralyzed (left) side were recipient nerves. To verify the feasibility of this surgery, the distances between each pair of coaptating nerve ends were measured by a vernier caliper. The results validated that starting point of the deep branch of ulnar nerve and the starting point of the medial antebrachial cutaneous nerve at the elbow were close to each other and could be readily anastomosed. We investigated whether the fiber number of donor and recipient nerves matched one another. The axons were counted in sections of nerve segments distal and proximal to the coaptation sites after silver impregnation. Averaged axon number of the ulnar nerve at the upper arm level was approximately equal to the sum of the median nerve and proximal end of medial antebrachial cutaneous nerve (left: 0.94:1; right: 0.93:1). In conclusion, the contralateral C7 nerve could be transferred to the median nerve but also to the deep branch of the ulnar nerve via grafts of the ulnar nerve without deep branch and the medial antebrachial cutaneous nerve. The advantage over traditional surgery was that the recovery potential of the deep branch of ulnar nerve was preserved. The study was approved by the Ethics Committee of Fudan University (approval number: 2015-064) in July, 2015.

Overexpression of Neuregulin-1 (NRG-1) Gene Contributes to Surgical Repair of Brachial Plexus Injury After Contralateral C7 Nerve Root Transfer in Rats

Background

Surgeons usually transfer the contralateral C7 to the median nerve on the injured side via a nerve graft to recover sensation and movement in a paralyzed hand. The purpose of our study was to determine whether NRG-1 affects the recovery of nerve function in brachial plexus injury after contralateral C7 nerve root transfer in a rat model.

Material/Methods

An injury model of left brachial plexus and contralateral C7 nerve root transfer was established. Four weeks after the operation, NRG-1 expression was examined by reverse transcription quantitative polymerase chain reaction and Western blot analysis. The diameter rate differences of the healthy limb and affected limb were estimated. The postoperative mass of the left latissimus dorsi, triceps, extensor carpi radialis brevis, and musculus extensor digitorum were examined. The number of nerve fibers and typical area of the affected side were assessed. Postoperative left motor nerve conduction velocity (MNCV) and motor nerve action potential (MNAP) were tested by use of a biological information recording and collecting system.

Results

Eukaryotic expression plasmid of pcDNA4/myc/A-NRG-1 was successfully constructed, and NRG-1 was overexpressed. Compared with the model group, the NRG-1 group had a lower rate of differences of the limbs; higher mass of left latissimus dorsi, triceps, extensor carpi radialis brevis, and musculus extensor digitorum; more nerve fibers and larger typical area in the affected side, left MNCV, and MNAP; and wider CSA of the left triceps.

Conclusions

These results demonstrated that NRG-1 can promote recovery of nerve function in brachial plexus injury after contralateral C7 nerve root transfer in rats.

Retropharyngeal Contralateral C7 Nerve Transfer to the Lower Trunk for Brachial Plexus Birth Injury: Technique and Results

PURPOSE

Brachial plexus birth injuries with multiple nerve root avulsions present a particularly difficult reconstructive challenge because of the limited availability of donor nerves. The contralateral C7 has been described for brachial plexus reconstruction in adults but has not been well-studied in the pediatric population. We present our technique and results for retropharyngeal contralateral C7 nerve transfer to the lower trunk for brachial plexus birth injury.

METHODS

We performed a retrospective review. Any child aged less than 2 years was included. Charts were analyzed for patient demographic data, operative variables, functional outcomes, complications, and length of follow-up.

RESULTS

We had a total of 5 patients. Average nerve graft length was 3 cm. All patients had return of hand sensation to the ulnar nerve distribution as evidenced by a pinch test, unprompted use of the recipient limb without mirror movement, and an Active Movement Scale (AMS) of at least 2/7 for finger and thumb flexion; one patient had an AMS of 7/7 for finger and thumb flexion. Only one patient had return of ulnar intrinsic hand function with an AMS of 3/7. Two patients had temporary triceps weakness in the donor limb and one had clinically insignificant temporary phrenic nerve paresis. No complications were related to the retropharyngeal nerve dissection in any patient. Average follow-up was 3.3 years.

CONCLUSIONS

The retropharyngeal contralateral C7 nerve transfer is a safe way to supply extra axons to the severely injured arm in brachial plexus birth injuries with no permanent donor limb deficits. Early functional recovery in these patients, with regard to hand function and sensation, is promising.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic V.

Phrenic and intercostal nerves with rhythmic discharge can promote early nerve regeneration after brachial plexus repair in rats

Exogenous discharge can positively promote nerve repair. We, therefore, hypothesized that endogenous discharges may have similar effects. The phrenic nerve and intercostal nerve, controlled by the respiratory center, can emit regular nerve impulses; therefore these endogenous automatically discharging nerves might promote nerve regeneration. Action potential discharge patterns were examined in the diaphragm, external intercostal and latissimus dorsi muscles of rats. The phrenic and intercostal nerves showed rhythmic clusters of discharge, which were consistent with breathing frequency. From the first to the third intercostal nerves, spontaneous discharge amplitude was gradually increased. There was no obvious rhythmic discharge in the thoracodorsal nerve. Four animal groups were performed in rats as the musculocutaneous nerve cut and repaired was bland control. The other three groups were followed by a side-to-side anastomosis with the phrenic nerve, intercostal nerve and thoracodorsal nerve. Compound muscle action potentials in the biceps muscle innervated by the musculocutaneous nerve were recorded with electrodes. The tetanic forces of ipsilateral and contralateral biceps muscles were detected by a force displacement transducer. Wet muscle weight recovery rate was measured and pathological changes were observed using hematoxylin-eosin staining. The number of nerve fibers was observed using toluidine blue staining and changes in nerve ultrastructure were observed using transmission electron microscopy. The compound muscle action potential amplitude was significantly higher at 1 month after surgery in phrenic and intercostal nerve groups compared with the thoracodorsal nerve and blank control groups. The recovery rate of tetanic tension and wet weight of the right biceps were significantly lower at 2 months after surgery in the phrenic nerve, intercostal nerve, and thoracodorsal nerve groups compared with the negative control group. The number of myelinated axons distal to the coaptation site of the musculocutaneous nerve at 1 month after surgery was significantly higher in phrenic and intercostal nerve groups than in thoracodorsal nerve and negative control groups. These results indicate that endogenous autonomic discharge from phrenic and intercostal nerves can promote nerve regeneration in early stages after brachial plexus injury.

Total brachial plexus injury: contralateral C7 root transfer to the lower trunk versus the median nerve

Contralateral C7 (cC7) root transfer to the healthy side is the main method for the treatment of brachial plexus root injury. A relatively new modification of this method involves cC7 root transfer to the lower trunk via the prespinal route. In the current study, we examined the effectiveness of this method using electrophysiological and histological analyses. To this end, we used a rat model of total brachial plexus injury, and cC7 root transfer was performed to either the lower trunk via the prespinal route or the median nerve via a subcutaneous tunnel to repair the injury. At 4, 8 and 12 weeks, the grasping test was used to measure the changes in grasp strength of the injured forepaw. Electrophysiological changes were examined in the flexor digitorum superficialis muscle. The change in the wet weight of the forearm flexor was also measured. Atrophy of the flexor digitorum superficialis muscle was assessed by hematoxylin-eosin staining. Toluidine blue staining was used to count the number of myelinated nerve fibers in the injured nerves. Compared with the traditional method, cC7 root transfer to the lower trunk via the prespinal route increased grasp strength of the injured forepaw, increased the compound muscle action potential maximum amplitude, shortened latency, substantially restored tetanic contraction of the forearm flexor muscles, increased the wet weight of the muscle, reduced atrophy of the flexor digitorum superficialis muscle, and increased the number of myelinated nerve fibers. These findings demonstrate that for finger flexion functional recovery in rats with total brachial plexus injury, transfer of the cC7 root to the lower trunk via the prespinal route is more effective than transfer to the median nerve via subcutaneous tunnel.

Is it necessary to use the entire root as a donor when transferring contralateral C7 nerve to repair median nerve?

If a partial contralateral C₇ nerve is transferred to a recipient injured nerve, results are not satisfactory. However, if an entire contralateral C₇ nerve is used to repair two nerves, both recipient nerves show good recovery. These findings seem contradictory, as the above two methods use the same donor nerve, only the cutting method of the contralateral C₇ nerve is different. To verify whether this can actually result in different repair effects, we divided rats with right total brachial plexus injury into three groups. In the entire root group, the entire contralateral C₇ root was transected and transferred to the median nerve of the affected limb. In the posterior division group, only the posterior division of the contralateral C₇ root was transected and transferred to the median nerve. In the entire root + posterior division group, the entire contralateral C₇ root was transected but only the posterior division was transferred to the median nerve. After neurectomy, the median nerve was repaired on the affected side in the three groups. At 8, 12, and 16 weeks postoperatively, electrophysiological examination showed that maximum amplitude, latency, muscle tetanic contraction force, and muscle fiber cross-sectional area of the flexor digitorum superficialis muscle were significantly better in the entire root and entire root + posterior division groups than in the posterior division group. No significant difference was found between the entire root and entire root + posterior division groups. Counts of myelinated axons in the median nerve were greater in the entire root group than in the entire root + posterior division group, which were greater than the posterior division group. We conclude that for the same recipient nerve, harvesting of the entire contralateral C₇ root achieved significantly better recovery than partial harvesting, even if only part of the entire root was used for transfer. This result indicates that the entire root should be used as a donor when transferring contralateral C₇ nerve.

Proximal versus Distal Nerve Transfer for Biceps Reinnervation-A Comparative Study in a Rat's Brachial Plexus Injury Model

BACKGROUND

The exact role of proximal and distal nerve transfers in reconstruction strategies of brachial plexus injury remains controversial. We compared proximal with distal nerve reconstruction strategies in a rat model of brachial plexus injury.

METHODS

In rats, the C6 spinal nerve with a nerve graft (proximal nerve transfer model, n = 30, group A) and 50% of ulnar nerve (distal nerve transfer model, n = 30, group B) were used as the donor nerves. The targets were the musculocutaneous nerve and the biceps muscle. Outcomes were recorded at 4, 8, 12, and 16 weeks postoperatively. Outcome parameters included grooming test, biceps muscle weight, compound muscle action potentials, tetanic contraction force, and axonal morphology of the donor and target nerves.

RESULTS

The axonal morphology of the 2 donor nerves revealed no significant difference. Time interval analysis in the proximal nerve transfer group showed peak axon counts at 12 weeks and a trend of improvement in all functional and physiologic parameters across all time points with statistically significant differences for grooming test, biceps compound action potentials, tetanic muscle contraction force, and muscle weight at 16 weeks. In contrast, in the distal nerve transfer group, the only statistically significant difference was observed between the 4 and 8 week time points, followed by a plateau from 8 to 16 weeks.

CONCLUSIONS

Outcomes of proximal nerve transfers are ultimately superior to distal nerve transfers in our experimental model. Possible explanations for the superior results include a reduced need for cortical adaptation and higher proportions of motor units in the proximal nerve transfers.

Robot-assisted C7 nerve root transfer from the contralateral healthy side: A preliminary cadaver study

Patients with cerebral palsy and spastic hemiplegia may have extremely poor upper extremity function. Unfortunately, many current therapies and treatments for patients with spastic hemiplegia offer very limited improvements. One innovative technique for treating these patients is the use a contralateral C7 nerve root transfer to neurotize the C7 nerve root in the affected limb. This may result not only in less spasticity in the affected limb, but also improved control and motor function vis-a-vis the new connection to the normal cerebral hemisphere. However, contralateral C7 transfers can require large incisions and long nerve grafts. The aim of this study was to test the feasibility of a contralateral C7 nerve root transfer procedure with the use of a prevertebral minimally invasive robot-assisted technique. In a cadaver, both sides of the C7 root were dissected. The right recipient C7 root was resected as proximally as possible, while the left donor C7 root was resected as distally as possible. With the use of the da Vinci (®) SI surgical robot (Intuitive Surgical ™, Sunnyvale, CA, USA), we were able to eliminate the large incision and use a much shorter nerve graft when performing contralateral C7 nerve transfer.

Relevant Anatomic and Morphological Measurements of the Rat Spine: Considerations for Rodent Models of Human Spine Trauma

STUDY DESIGN

Basic science study measuring anatomical features of the cervical and lumbar spine in rat with normalized comparison with the human.

OBJECTIVE

The goal of this study is to comprehensively compare the rat and human cervical and lumbar spines to investigate whether the rat is an appropriate model for spine biomechanics investigations.

SUMMARY OF BACKGROUND DATA

Animal models have been used for a long time to investigate the effects of trauma, degenerative changes, and mechanical loading on the structure and function of the spine. Comparative studies have reported some mechanical properties and/or anatomical dimensions of the spine to be similar between various species. However, those studies are largely limited to the lumbar spine, and a comprehensive comparison of the rat and human spines is lacking.

METHODS

Spines were harvested from male Holtzman rats (n = 5) and were scanned using micro- computed tomography and digitally rendered in 3 dimensions to quantify the spinal bony anatomy, including the lateral width and anteroposterior depth of the vertebra, vertebral body, and spinal canal, as well as the vertebral body and intervertebral disc heights. Normalized measurements of the vertebra, vertebral body, and spinal canal of the rat were computed and compared with corresponding measurements from the literature for the human in the cervical and lumbar spinal regions.

RESULTS

The vertebral dimensions of the rat spine vary more between spinal levels than in humans. Rat vertebrae are more slender than human vertebrae, but the width-to-depth axial aspect ratios are very similar in both species in both the cervical and lumbar regions, especially for the spinal canal.

CONCLUSION

The similar spinal morphology in the axial plane between rats and humans supports using the rat spine as an appropriate surrogate for modeling axial and shear loading of the human spine.

Novel isolated cecal pouch model for endoscopic observation in rats

AIM: To create a new rat model for drug administration, cell transplantation, and endoscopic examination for the treatment of intestinal diseases.

METHODS: F344/NJc l-rnu/rnu rats (10-wk-old males, 350-400 g) were used in this study. The rats were anesthetized via 2% isoflurane inhalation. The rat’s cecum was isolated from the intestines, and a pouch was created. The remainder of the intestines was rejoined to create an anastomosis. The “side-to-side” anastomosis (SSA) technique initially involves the creation of a 2-cm longitudinal incision into each intestinal wall. To create an anastomosis along the ileal and colonic walls, both intestines were cut, and a continuous suture procedure was performed that included all layers of both intestines. The serous membrane was sutured along the edge and on the anterior wall of the anastomosis. The “end-to-end” anastomosis (EEA) technique was compared with the SSA technique. In the EEA technique, the frontal surfaces of both cut intestinal lumens were joined together by continuous sutures. Additional sutures were made at the serosa. After the anastomotic intestine was successfully constructed, the two intestinal lumens that were cut at the isolated cecum were managed. In addition, one luminal side of the pouch remained open to create an artificial anus on the dorsum as a passage for the residual substances in the pouch. Finally, small animal endoscopy was used to observe the inside of the pouch.

RESULTS: In this animal model, mucus and feces are excreted through the reconstructed passage. Accordingly, the cecal pouch mucosa was not obstructed or contaminated by feces, thus facilitating observations of the luminal surface of the intestine. The endoscopic observation of the cecal pouch provided clear visualization given the absence of feces. The membrane surface of the cecum was clearly observed. Two methods of creating an anastomotic intestine, the “SSA” and “EEA” techniques, were compared with regard to animal survival rate, complication rate, and operation time. The SSA technique resulted in a significantly increased survival rate and a lower incidence of complications in rat models compared with the EEA technique. The complications of stenosis and leakage resulted in death in the EEA technique. Thus, the EEA technique exhibited a lower survival rate compared with the SSA technique. However, the SSA technique required a significantly longer operation time compared with the EEA technique.

CONCLUSION: Our new rat model is potentially useful for the development of a novel treatment for intestinal diseases.