The spinal accessory nerve distal to the posterior triangle

Functional and morphological evaluation of the trapezius muscle after spinal accessory nerve transfer to brachial plexus nerves

INTRODUCTION

The main innervation of the trapezius muscle is provided by the spinal accessory nerve. Several studies describe the contributions of cervical plexus roots to the trapezius muscle innervation, either directly or through connections with the spinal accessory nerve. There is no adequate understanding of how the trapezius muscle is affected after using the spinal accessory nerve in nerve transfer procedures with the usual technique, preserving at least 1 branch for the upper trapezius.

METHODS

We evaluated 20 patients with sequelae of traumatic brachial plexus injury who underwent surgical procedures for brachial plexus repair or free muscle transfer, which included the spinal accessory nerve transfer technique and were followed for a minimum of 1 year. The three portions trapezius muscle were evaluated by physical examination, magnetic resonance imaging (analysis of fatty degeneration) and electromyography.

RESULTS

In all evaluation methods, the middle and lower portions of the trapezius muscle showed more significant morphological and/or functional impairment than the upper portion, in most cases. There was a statistically significant difference in all the complementary exams results, between the affected side (with sacrifice of the nerve) versus the normal side, in the middle and lower portions of the trapezius muscle.

CONCLUSIONS

Physical examination alone is not sufficient to determine the residual functionality of the trapezius muscle. Magnetic resonance imaging and electromyography are useful tools to assess both morphological involvement of the trapezius muscle and nerve conduction impairment of the trapezius muscle, respectively. The results suggest that the middle and lower portions of the trapezius muscle are affected by previous SAN transfer and should be considered with caution for further muscle transfer procedures.

Nerve Transfers to Restore Shoulder Function

The restoration of shoulder function after brachial plexus injury represents a significant challenge facing the peripheral nerve surgeons. This is owing to a combination of the complex biomechanics of the shoulder girdle, the multitude of muscles and nerves that could be potentially injured, and a limited number of donor options. In general, nerve transfer is favored over tendon transfer, because the biomechanics of the musculotendinous units are not altered. This article summarizes the surgical techniques and clinical results of nerve transfers for restoration of shoulder function.

Expanding what is known of the anatomy of the spinal accessory nerve

The spinal accessory nerve (SAN) is classically considered a motor nerve innervating the sternocleidomastoid and trapezius muscles. Its anatomical relevance derives from the high prevalence of lesions following head and neck surgeries. As expected, trapezius weakness and atrophy are the most common findings; however, it is also commonly accompanied by pain and other sensory deficits that have no clear explanation, suggesting other functions. We have recently seen two patients presenting with an unrecognized sign, that is, subclavicular/pectoral asymmetry secondary to the SAN lesion. Retrospectively, we reviewed other patients with similar findings in our case series and in the literature. We discuss the anatomical connections of the SAN with the superficial cervical plexus and propose an explanation for this finding. Of the 41 patients in our series, we identified this sign in all who had preoperative photographs. New insights on the anatomy and connections of the SAN may account for the diversity of symptoms and signs presented following an operative intervention as well as the variability of its severity.

Reconstruction of shoulder abduction by multiple nerve fascicle transfer through posterior approach

PURPOSE

To evaluate the feasibility and clinical efficacy of multiple nerve fascicle transfer through posterior approach for reconstruction of shoulder abduction in patients with C5 or upper brachial plexus injury.

METHODS

11 patients (aged between 17 and 56 years) with dysfunction of shoulder abduction post C5 or upper brachial plexus injury were recruited in this study. Among them, four out of 11 patients also had dysfunction of elbow flexion simultaneously. The duration from injury to the surgery ranged from 4 to 12 months, with an average of 6.7 months. The affected shoulder joints showed abduction, extension and elevation dysfunction, but the muscle strength of shoulder shrugging and elbow extension was graded to M4 or higher. Accessory nerve was transferred to the suprascapular nerve and triceps muscle was branched to the axillary nerve through posterior approach. Ulnar fascicle was transferred to the motor branches of biceps for the 4 patients involved with elbow flexion dysfunction.

RESULTS

Ten out of 11 cases were followed-up for 15-36 months. Neo-potential of deltoid and supraspinatus/infraspinatus was documented at 4-5 months post surgery. Shoulder abduction (and elbow flexion) was reanimated at 4-8 months post surgery. Significant improvement was observed at 15-36 months post surgery, shoulder abduction regained to 40-160° (mean: 92.5°), muscle strength of supraspinatus/infraspinatus and deltoid were graded to M3-M5 (mean: 4.0 and 4.1); 3 cases muscle strength of elbow flexion was graded from M4 to M5- (mean: 4.4) with 1 case loss. Shoulder shrugging of trapezius was graded to M5 in 5 cases, M5- in 2 cases, M4 in 2 cases and M3 in 1 case (mean: 4.5). All cases showed normal elbow extension and muscle strength of triceps (M5).

CONCLUSION

It is feasible to carry out multiple nerve fascicle transfers for early reconstruction of shoulder abduction by posterior approach. Patients who received this procedure achieved good functional recovery and their donor site morbidity/injury was minimal.

Posterior approach for accessory-suprascapular nerve transfer: an electrophysiological outcomes study

The aim of this study was to retrospectively investigate the electrophysiological results obtained after employing the posterior approach for spinal accessory nerve-suprascapular nerve (SAN-SSN) transfer, and to compare this with the traditional anterior approach. SAN-SSN transfer was performed in 74 patients with brachial plexus injury. The posterior approach was used in 35 patients and the anterior approach was used in 39 patients. Electrophysiological examination was conducted and analyzed postoperatively. There was no significant difference between approaches in the time it took for the infraspinatus to show low-incidence motor unit action potentials (MUAPs) and an incomplete interference pattern. In addition, the final ratio of patients that showed regeneration potential of the infraspinatus was not significantly different between the approaches. Furthermore, latency and wave amplitude showed a linear regression with post-operative time in the posterior approach group. In the posterior approach group, the final abduction of the shoulder was positively correlated with the amplitude. The posterior approach for SAN-SSN is an effective potential alternative technique that may be appropriate for some clinical situations.

Outcome following spinal accessory to suprascapular (spinoscapular) nerve transfer in infants with brachial plexus birth injuries

The purpose of this study is to evaluate the value of distal spinal accessory nerve (SAN) transfer to the suprascapular nerve (SSN) in children with brachial plexus birth injuries in order to better define the application and outcome of this transfer in these infants. Over a 3-year period, 34 infants with brachial plexus injuries underwent transfer of the SAN to the SSN as part of the primary surgical reconstruction. Twenty-five patients (direct repair, n = 20; interposition graft, n = 5) achieved a minimum follow-up of 24 months. Fourteen children underwent plexus reconstruction with SAN-to-SSN transfer at less than 9 months of age, and 11 underwent surgical reconstruction at the age of 9 months or older. Mean age at the time of nerve transfer was 11.6 months (range, 5-30 months). At latest follow-up, active shoulder external rotation was measured in the arm abducted position and confirmed by review of videos. The Gilbert and Miami shoulder classification scores were utilized to report shoulder-specific functional outcomes. The effects of patient age at the time of nerve transfer and the use of interpositional nerve graft were analyzed. Overall mean active external rotation measured 69.6°; mean Gilbert score was 4.1 and the mean Miami score was 7.1, corresponding to overall good shoulder functional outcomes. Similar clinical and shoulder-specific functional outcomes were obtained in patients undergoing early (<9 months of age, n = 14) and late (>9 months of age, n = 11) SAN-to-SSN transfer and primary plexus reconstruction. Nine patients (27%) were lost to follow-up and are not included in the analysis. Optimum results were achieved following direct transfer (n = 20). Results following the use of an interpositional graft (n = 5) were rated satisfactory. No patient required a secondary shoulder procedure during the study period. There were no postoperative complications. Distal SAN-to-SSN (spinoscapular) nerve transfer is a reliable option for shoulder reinnervation in infants with brachial plexus birth injuries. Direct transfer seems to be the optimum method. The age of the patient does not seem to significantly impact on outcome.

Accessory nerve: anatomy and surgical identification

The XIth cranial nerve or accessory nerve provides the motor supply to the sternocleidomastoid and trapezius muscles. It is frequently encountered during neck surgery, and as such is at risk of iatrogenic injury, resulting in the ‘shoulder syndrome’. Historically, the nerve was sacrificed on oncological grounds during radical neck dissection. However, the basis for sacrifice is unfounded in the majority of cases, and accessory nerve sparing selective neck dissection has equal oncological efficacy. The path of the nerve in the neck is very variable, and there is not a wholly reliable landmark for its identification. However, there are a number of methods described in the literature to guide the surgeon in its identification. This paper provides a systematic review of all the methods available for identification of the accessory nerve, and comments on the reliability of each. In doing so, the detailed anatomy of the accessory nerve is also described.

Identification of the spinal accessory nerve within the surgical field during primary exploration of the brachial plexus in infants with obstetric palsy

This report describes our technique for identifying the spinal accessory nerve during primary exploration of the brachial plexus in infants with obstetric palsy.

Patient outcome after surgical management of an accessory nerve injury

OBJECTIVE

This study assessed patient outcome following surgical reconstruction of the accessory nerve after an iatrogenic injury.

STUDY DESIGN

A retrospective chart review of 8 patients was performed.

RESULTS

There were 3 men and 5 women in the study, and the mean time between injury and nerve graft/repair surgery was 5 months. Four injuries were sustained during a lymph node biopsy. Electromyography revealed a complete accessory nerve injury in all cases. In 6 cases, a nerve graft was required (mean length, 3.6 cm), and in 2 cases, a direct nerve repair was possible. The trapezius muscle was successfully reinnervated in all cases. In total, full shoulder abduction was achieved in 6 cases; in the remaining 2 cases, the patients achieved shoulder abduction to 90 degrees.

CONCLUSION

Functional deficit after accessory nerve injury is significant. Nerve graft/repair reconstruction reliably yields a satisfactory result, providing good scapular rotation and thus good shoulder function.

Bilateral elbow flexion reconstruction with functioning free muscle transfer for obstetric brachial plexus palsy

A child suffered a bilateral obstetric brachial plexus palsy involving the C5 and C6 nerve roots. Abduction of the shoulder joints had recovered by 1 year, but elbow flexion did not recover on either side. Free gracilis muscle transfers were performed on both sides, at an interval of 6 months, to achieve elbow flexion. The spinal accessory nerve was used as the donor nerve.

Surgical approach to the spinal accessory nerve for brachial plexus reconstruction

An easy, safe, and less invasive surgical approach to the spinal accessory nerve for brachial plexus reconstruction is described. The technique avoids a longitudinal unsightly scar over the neck and preserves the branches innervating the upper part of the trapezius.

Surgical anatomy of spinal accessory nerve: is trapezius functional deficit inevitable after division of the nerve?

The course of spinal accessory nerve in the posterior triangle, the innervation of the sternocleidomastoid and trapezius muscles and the contributions from the cervical plexus were studied in 20 cadaveric dissections. The nerve was most vulnerable to iatrogenic injuries after leaving the sternocleidomastoid. Direct innervation of trapezius by cervical plexus branches was noted in five dissections, whereas connections between the cervical plexus and the spinal accessory nerve were observed in 19 dissections. These were usually under the sternocleidomastoid (proximal to the level of division of the nerve in nerve transfer procedures). Although the contribution from the cervical plexus to trapezius innervation is considered minimal, trapezius function can be protected in neurotization procedures by transecting the spinal accessory nerve distal to its branches to the upper position of trapezius.