Phrenic Nerve Transfer to Musculocutaneous Nerve: An Anatomical and Histological Study

BACKGROUND

To restore elbow flexor muscle function in case of traumatic brachial plexus avulsion, the phrenic nerve transfer to the musculocutaneous nerve has become part of clinical practice. The nerve transfer can be done by means of video-assisted thoracic surgery without nerve graft or via supraclavicular approach in combination with an autograft. This study focuses on a detailed microscopic and macroscopic examination of the phrenic nerve. It will allow a better interpretation of existing clinical results and, thus, serve as a basis for future clinical studies.

MATERIAL AND METHODS

An anatomical study was conducted on 28 body donors of Caucasian origin (female n = 14, male n = 14). A sliding caliper and measuring tape were used to measure the diameter and length of the nerves. Sudan black staining was performed on 15 µm thick cryostat sections mounted on glass slides and the number of axons was determined by the ImageJ counting tool. In 23 individuals, the phrenic nerve could be examined on both sides. In 5 individuals, however, only one side was examined. Thus, a total of 51 nerves were examined.

RESULTS

The mean length of the left phrenic nerves (33 cm (29-38 cm)) was significantly longer compared to the mean length of the right phrenic nerves (30 cm (24-33 cm)) (p < 0.001). Accessory phrenic nerves were present in 9 of 51 (18%) phrenic nerves. The mean number of phrenic nerves axons at the level of the first intercostal space in body donors with a right accessory phrenic nerve was significantly greater compared to the mean number of phrenic nerves axons at the same level in body donors without a right accessory phrenic nerve (3145 (range, 2688-3877) vs. 2278 (range, 1558-3276)), p = 0.034. A negative correlation was registered between age and the nerve number of axons in left (0.742, p < 0.001) and right (-0.273, p = 0.197) phrenic nerves. The mean distance from the upper edge of the ventral ramus of the fourth cervical spinal nerve to the point of entrance of the musculocutaneous nerve between the two parts of the coracobrachialis muscle was 19 cm (range, 15-24 cm) for the right and 20 cm (range, 15-25 cm) for the left arm.

CONCLUSIONS

If an accessory phrenic nerve is available, it presumably should be spared. Thus, in that case, a supraclavicular approach in combination with a nerve graft would probably be of advantage.

Neurotization of musculocutaneous nerve with intercostal nerve versus phrenic nerve – A retrospective comparative study

Background:

Brachial plexus injuries are common after both blunt and penetrating traumas resulting in upper limb weakness. The nerve transfer to the affected nerve distal to the injury site is a good option where proximal stump of the nerve is unhealthy or absent which has shown early recovery and better results. Commonly used procedures to restore elbow flexion are ipsilateral phrenic or ipsilateral intercostal nerves (ICNs) in global plexus injuries. The use of both intercostal and phrenic nerves for elbow flexion is well described and there is no definite consensus on the superiority of one on another.

Methods:

All patients presented in the outpatient department of LNH and MC from January 2014 to December 2017 with pan plexus or upper plexus injury with no signs of improvement for at least 3 months were included in the study. After 3 months of conservative trial; surgery offered to patients.

Results:

A total of 25 patients (n = 25) were operated from January 2015 to December 2017. Patients were followed to record Medical Research Council (MRC) grades at 3, 6, 9, 12, and 18 months. The patients achieved at least MRC Grade 3; 70% at 12 months follow-up to 80% at 18 months in the phrenic nerve transfer group. While in the ICN transfer group, it is 86% and 100% at 12 and 18 months postoperative, respectively.

Conclusion:

Our study has shown better results with ICN transfers to musculocutaneous nerve, recorded on MRC grading system.

Transfer of Soleus Muscular Branch of Tibial Nerve to Deep Fibular Nerve to Repair Foot Drop After Common Peroneal Nerve Injury: A Retrospective Study

Objective

Common peroneal nerve (CPN) injury that leads to foot drop is difficult to manage and treat. We present a new strategy for management of foot drop after CPN injury. The soleus muscular branch of the tibial nerve is directly transferred to the deep fibular nerve, providing partial restoration of motor function.

Methods

We retrospectively reviewed eight patients treated for CPN injury between 2017 and 2019. The soleus muscular branch of the tibial nerve was transferred to the deep fibular nerve to repair foot drop. Electrophysiology was conducted, and motor function was assessed. Motor function was evaluated by measuring leg muscle strength during ankle dorsiflexion using the British Medical Research Council (BMRC) grading system and electromyography (EMG).

Results

In 10–15 months postoperatively, EMG revealed newly appearing electrical potentials in the tibialis anterior, extensor hallucis longus, and extensor toe longus muscle (N = 7). Two patients achieved BMRC grade of M4 for ankle dorsiflexion, 2 patients achieved M3, 1 patient achieved M2, and 2 patients achieved M1. Four patients showed good functional recovery after surgery and could walk and participate in activities without ankle-foot orthotics.

Conclusion

Surgical transfer of the soleus muscular branch of the tibial nerve to the deep fibular nerve after CPN injury provides variable improvements in ankle dorsiflexion strength. Despite variable strength gains, 50% of patients achieved BMRC M3 or greater motor recovery, which enabled them to walk without assistive devices.

The Terminal Anatomy of Phrenic Nerve: a Deeper Look at Diaphragm Innervation Patterns

BACKGROUND

Traumatic brachial plexus injuries are devastating lesions and neurotization is an usually elected surgical therapy. The phrenic nerve has been harvested as motor fibers donor in brachial plexus neurotization, showing great results in terms of motor reinnervation. Unfortunately, these interventions lack solid evidence regarding long-term safety and possible late respiratory function sequelae, raising crescent concerns after the COVID-19 pandemic onset and possibly resulting in reduced propensity to use this technique. The study of the distal anatomy of the phrenic nerves may lead to a better understanding of their branching patterns, and thus the proposition of surgical approaches that better preserve patient respiratory function.

METHODS

Twenty-one phrenic nerves in ten formalized cadavers were scrutinized. Pre-diaphragmatic branching patterns were inspected through analysis of the distance between the piercing site of the nerve at the diaphragm and the cardiac structures, number of divisions, and length from the point where the main trunk emits its branches to the diaphragm.

RESULTS

The main trunk of the right phrenic nerve reaches the diaphragm near the inferior vena cava and branches into three major divisions. The left phrenic nerve reaches the diaphragm in variable locations near the heart, branching into two to five main trunks. Moreover, we noticed a specimen presenting two ipsilateral parallel phrenic nerves.

CONCLUSION

The right phrenic nerve presented greater consistency concerning insertion site, terminal branching point distance to this muscle, and number of rami than the left phrenic nerve.

Long-Term Outcome of Phrenic Nerve Transfer in Brachial Plexus Avulsion Injuries

INTRODUCTION

In brachial plexus injuries, useful recovery of arm function has been documented in most patients after phrenic nerve transfer after variable follow-up durations, but there is not much information about long-term functional outcomes. In addition, there is still some concern that respiratory complications might become manifest with aging. The aim of this study was to report the outcome of phrenic nerve transfer after a minimum follow-up of 5 years.

PATIENTS AND METHODS

Twenty-six patients were reviewed and evaluated clinically. Age at surgery averaged 25.2 years and follow-up averaged 9.15 years.

RESULTS

Shoulder abduction and external rotation achieved by transfer of phrenic to axillary nerve (or posterior division of upper trunk), combined with spinal accessory to suprascapular nerve transfer, were better than that achieved by transfer of phrenic to suprascapular nerve, combined with grafting the posterior division of upper trunk from C5, 52.3 and 45.5 degrees versus 47.5 and 39.4 degrees, respectively. There was no difference in abduction when the phrenic nerve was transferred directly to the posterior division of upper trunk or to the axillary nerve using nerve graft. Elbow flexion (≥M3 MRC) was achieved in 5 (83.3%) of 6 cases. Elbow extension M4 MRC or greater was achieved in 4 (66.6%) of 6 cases. All patients, including those who exceeded the age of 45 years and those who had concomitant intercostal nerve transfer, continued to have no respiratory symptoms.

CONCLUSIONS

The long-term follow-up confirms the safety and effectiveness and of phrenic nerve transfer for functional restoration of shoulder and elbow functions in brachial plexus avulsion injuries.

Anatomical feasibility of peripheral nerve transfer to reestablish external anal sphincter control - cadaveric study

PURPOSE

Motor deficits affecting anal sphincter control can severely impair quality of life. Peripheral nerve transfer has been proposed as an option to reestablish anal sphincter motor function. We assessed, in human cadavers, the anatomical feasibility of nerve transfer from a motor branch of the tibialis portion of the sciatic nerve to two distinct points on pudendal nerve (PN), through transgluteal access, as a potential approach to reestablish anal sphincter function.

METHODS

We dissected 24 formalinized specimens of the gluteal region and posterior proximal third of the thigh. We characterized the motor fascicle (donor nerve) from the sciatic nerve to the long head of the biceps femoris muscle and the PN (recipient nerve), and measured nerve lengths required for direct coaptation from the donor nerve to the recipient in both the gluteal region (proximal) and perineal cavity (distal).

RESULTS

We identified three anatomical variations of the donor nerve as well as three distinct branching patterns of the recipient nerve from the piriformis muscle to the pudendal canal region. Donor nerve lengths (proximal and distal) were satisfactory for direct coaptation in all cases.

CONCLUSIONS

Transfer of a motor fascicle of the sciatic nerve to the PN is anatomically feasible without nerve grafts. Donor nerve length was sufficient and donor nerve functionally compatible (motor). Anatomical variations in the PN could also be accommodated.

Comparison Between Supraclavicular Versus Video-Assisted Intrathoracic Phrenic Nerve Section for Transfer in Patients With Traumatic Brachial Plexus Injuries: Case Series

BACKGROUND

The phrenic nerve has been extensively reported to be a very powerful source of transferable axons in brachial plexus injuries. The most used technique used is supraclavicular sectioning of this nerve. More recently, video-assisted thoracoscopic techniques have been reported as a good alternative, since harvesting a longer phrenic nerve avoids the need of an interposed graft.

OBJECTIVE

To compare grafting vs phrenic nerve transfer via thoracoscopy with respect to mean elbow strength at final follow-up.

METHODS

A retrospective analysis was conducted among patients who underwent phrenic nerve transfer for elbow flexion at 2 centers from 2008 to 2017. All data analysis was performed in order to determine statistical significance among the analyzed variables.

RESULTS

A total of 32 patients underwent supraclavicular phrenic nerve transfer, while 28 underwent phrenic nerve transfer via video-assisted thoracoscopy. Demographic characteristics were similar in both groups. A statistically significant difference in elbow flexion strength recovery was observed, favoring the supraclavicular phrenic nerve section group against the intrathoracic group (P = .036). A moderate though nonsignificant difference was observed favoring the same group in mean elbow flexion strength. Also, statistical differences included patient age (P = .01) and earlier time from trauma to surgery (P = .069).

CONCLUSION

Comparing supraclavicular sectioning of the nerve vs video-assisted, intrathoracic nerve sectioning to restore elbow flexion showed that the former yielded statistically better results than the latter, in terms of the percentage of patients who achieve at least level 3 MRC strength at final follow-up. Furthermore, larger scale prospective studies assessing the long-term effects of phrenic nerve transfers remain necessary.

Intercostal to musculocutaneous nerve transfer in patients with complete traumatic brachial plexus injuries: case series

BACKGROUND

To recover biceps strength in patients with complete brachial plexus injuries, the intercostal nerve can be transferred to the musculocutaneous nerve. The surgical results are very controversial, and most of the studies with good outcomes and large samples were carried out in Asiatic countries. The objective of the study was to evaluate biceps strength after intercostal nerve transfer in patients undergoing this procedure in a Western country hospital.

METHODS

We retrospectively analyzed 39 patients from 2011 to 2016 with traumatic brachial plexus injuries receiving intercostal to musculocutaneous nerve transfer in a rehabilitation hospital. The biceps strength was graded using the British Medical Research Council (BMRC) scale. The variables reported and analyzed were age, the time between trauma and surgery, surgeon experience, body mass index, nerve receptor (biceps motor branch or musculocutaneous nerve), and the number of intercostal nerves transferred. Statistical tests, with a significance level of 5%, were used.

RESULTS

Biceps strength recovery was graded ≥M3 in 19 patients (48.8%) and M4 in 15 patients (38.5%). There was no statistical association between biceps strength and the variables. The most frequent complication was a pleural rupture.

CONCLUSIONS

Intercostal to musculocutaneous nerve transfer is a safe procedure. Still, biceps strength after surgery was ≥M3 in only 48.8% of the patients. Other donor nerve options should be considered, e.g., the phrenic or spinal accessory nerves.

Experimental Study of Nerve Transfer to Restore Diaphragm Function

BACKGROUND

Diaphragmatic paralysis after phrenic nerve injury is an infrequent but serious condition. The destruction of respiratory function after unilateral phrenic nerve injury has been the subject of many investigations.

METHODS

In this study, we used a rat model of complete paralysis of the unilateral diaphragm to observe changes in pulmonary function.

RESULTS

We found in young rats with complete paralysis of the unilateral diaphragm, the vital capacity and total lung capacity show compensation after 4 weeks, and contralateral phrenic nerve transfer can enhance pulmonary function. However, in the aged rats, respiratory function parameters do not show compensation until 16 weeks after injury.

CONCLUSIONS

These findings suggest that contralateral phrenic nerve end-to-side anastomosis is a promising therapeutic strategy. In general, our results suggest that this surgical method may hold great potential to be a secure, feasible, and effective technique to rescue diaphragmatic function.