Survival after resection of malignant peripheral nerve sheath tumors: Introducing and validating a novel type-specific prognostic model.

Background: This study aimed to assess the performance of currently available risk calculators in a cohort of patients with malignant peripheral nerve sheath tumors (MPNST) and to create an MPNST-specific prognostic model including type-specific predictors for overall survival (OS). Methods: This is a retrospective multicenter cohort study of patients with MPNST from 11 secondary or tertiary centers in The Netherlands, Italy and the United States of America. All patients diagnosed with primary MPNST who underwent macroscopically complete surgical resection from 2000 to 2019 were included in this study. A multivariable Cox proportional hazard model for OS was estimated with prespecified predictors (age, grade, size, NF-1 status, triton status, depth, tumor location, and surgical margin). Model performance was assessed for the Sarculator and PERSARC calculators by examining discrimination (C-index) and calibration (calibration plots and observed-expected statistic; O/E-statistic). Internal-external cross-validation by different regions was performed to evaluate the generalizability of the model. Results: A total of 507 patients with primary MPNSTs were included from 11 centers in 7 regions. During follow-up (median 8.7 years), 211 patients died. The C-index was 0.60 (95% CI 0.53-0.67) for both Sarculator and PERSARC. The MPNST-specific model had a pooled C-index of 0.69 (95%CI 0.65-0.73) at validation, with adequate discrimination and calibration across regions. Conclusions: The MPNST-specific MONACO model can be used to predict 3-, 5-, and 10-year OS in patients with primary MPNST who underwent macroscopically complete surgical resection. Further validation may refine the model to inform patients and physicians on prognosis and support them in shared decision-making.

Complete encasement of the radial nerve by a giant lipoma: illustrative case.

BACKGROUND: Among the spectrum of adipose lesions associated with peripheral nerves, complete circumferential encasement of the nerve by the lesion is a very rare entity. The authors report the first case of a giant lipoma that completely and circumferentially encased the radial nerve. OBSERVATIONS: A 57-year-old woman presented with a large left-arm mass that she had noticed over a year following significant weight loss. She had hypersensitivity and dysesthesias in the left posterior arm but no weakness or other symptoms. Magnetic resonance imaging of the left upper limb demonstrated a large lipoma completely encasing the radial nerve, originating at the level of the spiral grove proximally and extending distally to the lateral epicondyle. The lesion was completely resected at surgery with total preservation of radial nerve function. LESSONS: Lipomas encasing peripheral nerves can be difficult to manage while preserving function. This case adds to the intriguing spectrum of adipose lesions associated with peripheral nerves. https://thejns.org/doi/10.3171/CASE24148.

Superficial Branch of the Radial Nerve Versus Sural Nerve Grafting After Traumatic Adult Brachial Plexus Injury.

The purpose of this study was to compare two sources of nerve graft for brachial plexus reconstruction: the denervated superficial branch of the radial nerve (SBRN) and the sural nerve. Ninety-seven patients who underwent brachial plexus reconstruction with denervated SBRN nerve (24 patients with 24 grafts) or with sural nerve grafting (73 patients with 83 nerve grafts) were included. The two groups were compared with respect to postoperative muscle reinnervation, disabilities of the arm, shoulder, and hand (DASH) scores. In the SBRN group, only four (17%) of the nerve grafts provided grade III or higher muscle function. In the sural nerve group, 31 (37%) of the nerve grafts provided grade III or higher muscle function. Smoking had a negative impact on muscle recovery. Denervated SBRN grafts are associated with inferior outcomes when compared with sural nerve grafts in the treatment of traumatic adult brachial plexus injuries. (Journal of Surgical Orthopaedic Advances 33(2):080-083, 2024).

Triceps-to-Biceps Tendon Transfer Technique for Restoration of Elbow Flexion in Adult Brachial Plexus Injury.

Restoration of elbow flexion is a priority in treating adult traumatic brachial plexus injuries. A tendon transfer is an ideal option for patients not candidates for reconstructive nerve surgery or free-functioning muscle transfer. For patients with a partial brachial plexus injury or a pan plexus injury with adequate recovered triceps function and loss of elbow flexion, a triceps-to-biceps tendon transfer is a nonmicrosurgical option to restore elbow flexion. The technique of triceps-to-biceps transfer in which the complete triceps tendon is transferred laterally, secured lateral to the radial tuberosity, and reinforced with suture to the biceps tendon is described.

Motor Examination of the Brachial Plexus.

Serial physical examination is often required in the evaluation of brachial plexus injuries. (Noland, 2019) A comprehensive evaluation that includes a thorough history, electrodiagnostic evaluation, and imaging studies, in addition to physical examination, can provide valuable information about the location of the lesion, prognosis for recovery, and whether surgical intervention is necessary. After brachial plexus reconstruction, physical examinations are also performed to document clinical improvement and identify any residual issues. The videos included in this clinical examination techniques section demonstrate the muscle strength examination testing for the brachial plexus and offer best practices for documentation.

High Resolution MRI Confirms Torsional Injury as Mechanism for Combined Ankle and Common Fibular (Peroneal) Nerve Injuries.

Common fibular nerve (CFN) injury due to ankle fracture is an underreported complication. The authors have proposed that torsional injury to the ankle can be translated along the interosseous membrane (IOM), producing tension on the CFN at the fibular neck. A 23-year-old woman presented to our clinic for left foot drop. Three months prior, the patient sustained a fall with left ankle inversion injury while running. She was diagnosed with a minor ankle fracture and placed in an orthopaedic boot. Unfortunately, her swelling worsened and one week later the patient was diagnosed with foot drop, which was further corroborated with EMG studies showing severe CFN injury localizing to the fibular neck. Because of the lack of recovery, she underwent decompression of the CFN. She experienced immediate symptomatic relief. High resolution imaging in this case supports our previous mechanism for indirect trauma to the ankle resulting in CFN injury. (Journal of Surgical Orthopaedic Advances 33(1):053-055, 2024).

Evaluating the Ability of Brachial Plexus-Injured Patients to Control an Externally Powered (Myoelectric) Hand Prosthesis.

BACKGROUND: Restoration of hand function after traumatic brachial plexus injury (BPI) remains a formidable challenge. Traditional methods such as nerve or free muscle transfers yield suboptimal results. Advancements in myoelectric prostheses, characterized by novel signal acquisition and improved material technology, show promise in restoring functional grasp. This study evaluated the ability of adults with a BPI injury to control an externally powered prosthetic hand using nonintuitive signals, simulating the restoration of grasp with a myoelectric prosthesis. It also assessed the effectiveness of a comprehensive multidisciplinary evaluation in guiding treatment decisions. METHODS: A multidisciplinary brachial plexus team assessed adults with compromised hand function due to BPI. The feasibility of amputation coupled with fitting of a myoelectric prosthesis for grasp reconstruction was evaluated. Participants' ability to control a virtual or model prosthetic hand using surface electromyography (EMG) as well as with contralateral shoulder motion-activated linear transducer signals was tested. The patient's input and injury type, along with the information from the prosthetic evaluation, were used to determine the reconstructive plan. The study also reviewed the number of participants opting for amputation and a myoelectric prosthetic hand for grasp restoration, and a follow-up survey was conducted to assess the impact of the initial evaluation on decision-making. RESULTS: Of 58 subjects evaluated, 47 (81%) had pan-plexus BPI and 42 (72%) received their initial assessment within 1 year post-injury. Forty-seven patients (81%) could control the virtual or model prosthetic hand using nonintuitive surface EMG signals, and all 58 could control it with contralateral uniscapular motion via a linear transducer and harness. Thirty patients (52%) chose and pursued amputation, and 20 (34%) actively used a myoelectric prosthesis for grasp. The initial evaluation was informative and beneficial for the majority of the patients, especially in demonstrating the functionality of the myoelectric prosthesis. CONCLUSIONS: The study indicates that adults with traumatic BPI can effectively operate a virtual or model myoelectric prosthesis using nonintuitive control signals. The simulation and multidisciplinary evaluation influenced informed treatment choices, with a high percentage of patients continuing to use the myoelectric prostheses post-amputation, highlighting its long-term acceptance and viability. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Precision oncology in neurofibromatosis type 1: quantification of differential sensitivity to selumetinib in plexiform neurofibromas using single-cell RNA sequencing.

PURPOSE: Selumetinib is an FDA-approved targeted therapy for plexiform neurofibromas in neurofibromatosis type 1(NF1) with durable response rates seen in most, but not all patients. In this proof-of-concept study, we demonstrate single-cell RNA sequencing(scRNAseq) as a technique for quantifying drug response to selumetinib at the single cell level. METHODS: scRNAseq data from neurofibroma biopsies was obtained from a public genomics repository. Schwann cell populations were identified through standard clustering techniques and single-cell selumetinib sensitivity was quantified on a scale of 0(resistant) to 1(sensitive) based on the expression pattern of a 500 gene selumetinib sensitivity signature from the BeyondCell sensitivity library. RESULTS: A total of seven plexiform neurofibromas were included in our final analysis. The median absolute number of Schwann cells across samples was 658 cells (IQR: 1,029 cells, Q1-Q3: 135 cells to 1,163 cells). There was a statistically significant difference in selumetinib sensitivity profiles across samples (p < 0.001). The tumor with the highest median selumetinib sensitivity score had a median selumetinib sensitivity score of 0.64(IQR: 0.14, Q1-Q3: 0.59-0.70, n = 112 cells) and the tumor with the lowest median selumetinib sensitivity score had a median score of 0.37 (IQR: 0.21, Q1-Q3: 0.27-0.48, n = 1,034 cells). CONCLUSIONS: scRNAseq of plexiform neurofibroma biopsies reveals differential susceptibilities to selumetinib on a single cell level. These findings may explain the partial responses seen in clinical trials of selumetinib for NF1 and demonstrate the value of collecting scRNAseq data for future NF1 trials.

Neuromuscular choristoma-associated desmoid-type fibromatosis of the brachial plexus: Additional evidence to support a nerve-driven mechanism.

BACKGROUND: We have recently described circumferential nerve involvement of neuromuscular choristoma associated with desmoid-type fibromatosis (NMC-DTF) in cases involving the sciatic nerve, supporting a nerve-derived mechanism for the DTF. We wondered whether a similar growth pattern occurs in cases involving the brachial plexus (BP). METHODS: We reviewed all available magnetic resonance (MR) imaging in patients diagnosed at our institution with NMC or NMC-DTF of the BP. We also performed a literature search of patients with NMC or NMC-DTF of the BP. RESULTS: In our clinical records, four patients with NMC of the BP were identified, and three developed NMC-DTF. All three patients had MR imaging evidence of circumferential encasement of the BP. In the literature, we identified 15 cases of NMC of the BP, of which 12 had identified NMC-DTF. Four published cases included MR images, and only two were of sufficient quality for review. The single provided image in both cases demonstrated a similar pattern of circumferential encasement of the BP by the NMC-DTF. One additional case report was published without MR images but described circumferential involvement in the surgical findings. One unpublished case of NMC-DTF of the BP from an international radiology meeting also had this circumferential pattern pattern on MRI. CONCLUSIONS: The MRI findings of circumferential nerve involvement in patients with NMC-DTF of the BP are similar to our previously reported data in patients with NMC-DTF of the sciatic nerve, providing further imaging-based support of a nerve-driven mechanism. Clinical implications are presented based on the proposed pathogenetic mechanism.

Injury and Biological Factors Impact Shoulder Function following Autogenous Grafting of Spinal Nerves for Pan-Brachial Plexus Reconstruction.

BACKGROUND: Shoulder function following spinal nerve grafting in pan-brachial plexus injuries(Pan-BPI) is not well described. The purpose of this study was twofold: 1)to evaluate shoulder abduction(ABD) and external rotation(ER) after grafting of viable spinal nerves to the suprascapular nerve(SSN), axillary nerve(AxN), or posterior division of the upper trunk(PDUT); and 2)to determine patient characteristics, injury severity/characteristics, and nerve graft factors that influenced outcomes. METHODS: 362 Pan-BPI reconstruction patients from a single institution were reviewed for those who underwent spinal nerve grafting for shoulder reanimation between 2001 and 2018. Patient demographics, injury severity scores(ISS), graft characteristics, strength, range of motion for shoulder ABD and ER, and patient-reported outcomes were recorded. Patients were divided into three groups based on the recovery of shoulder function: no return, ABD only, and ABD and ER. RESULTS: 110 patients underwent spinal nerve grafting, with 41 meeting inclusion criteria. 17(41.5%) had no return of shoulder function, 14(34.1%) had ABD alone, and 10(24.4%) had ABD and ER. Patients with recovery of both ABD and ER were significantly younger(18.6±5.56), had lower BMI(22.4±4.0), and lower ISS(10.5±6.24, p=0.003). Multivariable analysis found that with increasing age(OR:0.786, 95%CI:0.576,0.941) and ISS(OR:0.820, 95%CI:0.606-0.979), odds for return of ABD and ER significantly decreased. CONCLUSIONS: In Pan-BPI, 24.4% of patients demonstrated return of both ABD and ER following spinal nerve grafting to SSN and either AxN or PDUT. Age, BMI, and ISS were associated with poorer recovery of shoulder function. Careful patient selection and consideration of age, BMI, and ISS may improve outcomes of spinal nerve grafting for shoulder reanimation. LEVEL OF EVIDENCE: III.

The paraneurium and the tumefactive appearance of peripheral nerve neurolymphomatosis: illustrative case.

BACKGROUND: Peripheral neurolymphomatosis (NL) is an often-misdiagnosed condition characterized by lymphomatous infiltration within the peripheral nerves. Its rarity and complexity frequently result in delayed diagnosis and suboptimal patient outcomes. This study aims to elucidate the role of the paraneurium (circumneurium) in NL, emphasizing its diagnostic and therapeutic significance. OBSERVATIONS: A 72-year-old man presented with lesions on his right lower eyelid. Initial diagnostics were inconclusive until an excisional biopsy confirmed extranodal marginal zone lymphoma. Following a complete metabolic response to rituximab treatment, the patient relapsed 14 months later with progressive lymphoma and bilateral sciatic nerve involvement, as confirmed by positron emission tomography-computed tomography and magnetic resonance imaging. LESSONS: This paper underscores the critical role of the paraneurium in NL, enhancing understanding of its pathophysiology. Integrating advanced imaging techniques have proved essential in accurately identifying neurolymphomatous involvement within the paraneurium. This study paves the way for more effective management strategies in NL and similar conditions, focusing on improving patient care and outcomes.

The 2-by-2 Inch "Key Window" in the Upper Extremity: An Anatomical Appraisal of the Accessibility and Proximity of the Major Nerves and Vessels.

BACKGROUND: The brachial plexus is a network of nerves located between the neck and axilla, which receives input from C5-T1. Distally, the nerves and blood vessels that supply the arm and forearm form a medial neurovascular bundle. The purpose of this study was to illustrate that a peripheral nerve dissection via a 2 × 2 inch window would allow for identification and isolation of the major nerves and blood vessels that supply the arm and forearm. METHODS: A right side formalin-fixed latex-injected cadaveric arm was transected at the proximal part of the axillary fold and included the scapular attachments. Step-by-step anatomical dissection was carried out and documented with three-dimensional digital imaging. RESULTS: A 2 × 2 inch window centered 2 inches distal to the axillary fold on the medial surface of the arm enabled access to the major neurovascular structures of the arm and forearm: the median nerve, ulnar nerve, medial antebrachial cutaneous nerve, radial nerve and triceps motor branches, musculocutaneous nerve and its biceps and brachialis branches and lateral antebrachial cutaneous nerve, basilic vein and brachial artery and vein, and profunda brachii artery. CONCLUSIONS: Our study demonstrates that the majority of the neurovascular supply in the arm and forearm can be accessed through a 2 × 2 inch area in the medial arm. Although this "key window" may not be entirely utilized in the operative setting, our comprehensive didactic description of peripheral nerve dissection in the cadaver laboratory can help in safer identification of complex anatomy encountered during surgical procedures.

Validation of the Root Analysis Score for C5 Viability in Patients With Pan-Brachial Plexus Injury.

PURPOSE: Pan-brachial plexus injury patients present a reconstructive challenge. The root analysis score, developed from parsimonious multivariable modeling of 311 pan-brachial plexus injury patients, determines the probability of having a viable C5 nerve based on four categories: positive C5 Tinel test, intact C5 nerve on computed tomography myelogram, lack of hemidiaphragmatic elevation, and absence of midcervical paraspinal fibrillations. METHODS: Root analysis scores were calculated for a separate cohort of patients with pan-brachial plexus injuries. Scores were validated by the presence or absence of a graftable C5 root, based on supraclavicular exploration and intraoperative electrophysiologic testing. Receiver operating characteristic curve, accuracy, and concordance statistic of the scores were calculated. Patients were divided into three root analysis score cohorts: less than 50 (low), 50-75 (average), and 75-100 points (high) based on dividing the score into quartiles and combining the lowest two. The probability, sensitivity, and specificity of each cohort having an available C5 nerve were based on the intraoperative assessment. RESULTS: Eighty patients (mean age, 33.1 years; 15 women and 65 men) were included. Thirty-one patients (39%) had a viable C5 nerve. The root analysis calculator had an overall accuracy of 82.5%, a receiver operating characteristic of 0.87, and a concordance statistic of 0.87, demonstrating high overall predictive value; 6.5% of patients with a score of less than 50 (94% sensitivity and 43% specificity), 16.1% of patients with a score of 50-75 (94% sensitivity and 67% specificity), and 77.4% of patients with a score of 75-100 (77% sensitivity and 90% specificity) had a graftable C5 nerve. CONCLUSIONS: The root analysis score demonstrated high accuracy and predictive power for a viable C5 nerve. In patients with a score of less than 50, the necessity of supraclavicular root exploration should balance patient factors, presentation timing, and concomitant injuries. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnosis II.

Abnormal Brachial Plexus Differentiation from Routine Magnetic Resonance Imaging: An AI-based Approach.

Automatic abnormality identification of brachial plexus (BP) from normal magnetic resonance imaging to localize and identify a neurologic injury in clinical practice (MRI) is still a novel topic in brachial plexopathy. This study developed and evaluated an approach to differentiate abnormal BP with artificial intelligence (AI) over three commonly used MRI sequences, i.e. T1, FLUID sensitive and post-gadolinium sequences. A BP dataset was collected by radiological experts and a semi-supervised artificial intelligence method was used to segment the BP (based on nnU-net). Hereafter, a radiomics method was utilized to extract 107 shape and texture features from these ROIs. From various machine learning methods, we selected six widely recognized classifiers for training our Brachial plexus (BP) models and assessing their efficacy. To optimize these models, we introduced a dynamic feature selection approach aimed at discarding redundant and less informative features. Our experimental findings demonstrated that, in the context of identifying abnormal BP cases, shape features displayed heightened sensitivity compared to texture features. Notably, both the Logistic classifier and Bagging classifier outperformed other methods in our study. These evaluations illuminated the exceptional performance of our model trained on FLUID-sensitive sequences, which notably exceeded the results of both T1 and post-gadolinium sequences. Crucially, our analysis highlighted that both its classification accuracies and AUC score (area under the curve of receiver operating characteristics) over FLUID-sensitive sequence exceeded 90%. This outcome served as a robust experimental validation, affirming the substantial potential and strong feasibility of integrating AI into clinical practice.

Alfred Washington Adson: Perspectives on Intracranial Neurosurgery and the Responsibilities of the Neurosurgeon.

In a period when the budding field of neurosurgery was believed to have little promise, Dr Alfred Washington Adson founded and led the first neurosurgical department at Mayo Clinic. He was not without reservations-surgical intervention for neurological conditions was rarely pursued because of poor outcomes and high complication rates, and Dr Adson acknowledged his early concerns about the future of neurosurgery in his memoirs. However, his education, mentorship, his training, and his first neurosurgical cases helped to shape the impact he ultimately had on the field and his legacy as a neurosurgeon. Dr Adson trained with several renowned Mayo general surgeons, notably his mentor Dr Emil Beckman, whose desire for operative precision shaped Dr Adson's drive to develop his own skills as a surgeon. Two years into his residency, he became the youngest staff surgeon and was tasked with managing the neurosurgical cases at Mayo. The five neurosurgical cases overseen by Dr Adson in the next year illuminated the opportunity for neurosurgery to drastically improve the lives of patients. Dr Adson, given the option of continuing as either a general surgeon or a neurosurgeon, ultimately chose to pursue neurosurgery. This article seeks to provide a historical perspective on the neurosurgeon Dr Alfred Washington Adson using primary and secondary accounts from the Mayo archives, highlighting his contributions to the early understanding of intracranial pathology and how his early experiences as a trainee developed into a personal passion for self-improvement, education, and advocacy for health care in America.

Academic Promotions in Medicine: An Appraisal of Fairness.

OBJECTIVE: To investigate whether the process of conferring academic rank or components of the promotion packet contribute to the lack of parity in academic advancement for women and individuals underrepresented in medicine (URMs). PATIENTS AND METHODS: We retrospectively reviewed prospective promotion applications to the position of associate professor or professor at Mayo Clinic from January 2, 2015, through July 1, 2019. Individuals with doctorate degrees who applied for either rank were included in the study. Data collected included demographic characteristics, curriculum vitae at time of application, committee score sheets, and deferral and approval decisions. Deferral rates for women compared with men and for URMs compared with non-URMs was the primary outcome. RESULTS: Of 462 people who applied for associate professor, 10% (n=46) were deferred. Those promoted had worked longer at Mayo Clinic (median, 6 years vs 2 years; P=.01), had more mentees (median, 6 vs 4; P=.02), authored more publications (median [interquartile range (IQR)], 39 [32-52] vs 30 [24-35]; P<.001), and were more likely to be on a National Institutes of Health or institutional grant (P<.05). Of the 320 people who applied for professor, 8.8% (n=28) were deferred. Those promoted had authored more publications (median [IQR], 77 [60-99] vs 56 [44-66]; P<.001) and were less likely to hold an elected office to a professional society (22.6% vs 39.3%; P=.05). There was no significant association between deferral status and sex (P>.4) or race/ethnicity (P>.9) for either rank. CONCLUSION: The process for academic advancement for professorships does not contribute to the gap in promotion rates for women and URMs.

Core outcomes in nerve surgery: development of a core outcome set for brachial plexus and upper extremity nerve injuries.

OBJECTIVE: When considering traumatic brachial plexus and upper extremity nerve injuries, iatrogenic nerve injuries, and nontraumatic nerve injuries, brachial plexus and upper extremity nerve injuries are commonly encountered in clinical practice. Despite this, data synthesis and comparison of available studies are difficult. This is at least in part due to the lack of standardization in reporting and a lack of a core outcome set (COS). Thus, there is a need for a COS for adult brachial plexus and upper extremity nerve injuries (COS-BPUE). The objective of this study was to develop a COS-BPUE using a modified Delphi approach. METHODS: A 5-stage approach was used to develop the COS-BPUE: 1) consortium development, 2) literature review to identify potential outcome measures, 3) Delphi survey to develop consensus on outcomes for inclusion, 4) Delphi survey to develop definitions, and 5) consensus meeting to finalize the COS and definitions. The study followed the Core Outcome Set-STAndards for Development (COS-STAD) recommendations. RESULTS: The Core Outcomes in Nerve Surgery (COINS) Consortium comprised 23 participants, all neurological surgeons, representing 13 countries. The final COS-BPUE consisted of 36 data points/outcomes covering demographic, diagnostic, patient-reported outcome, motor/sensory outcome, and complication domains. Appropriate instruments, methods of testing, and definitions were set. The consensus minimum duration of follow-up was 24 months, with the consensus optimal time points for assessment being preoperatively and 3, 6, 12, and 24 months postoperatively. CONCLUSIONS: The COINS Consortium developed a consensus COS and provided definitions, methods of implementation, and time points for assessment. The COS-BPUE should serve as a minimum set of data that should be collected in all future neurosurgical studies on adult brachial plexus and upper extremity nerve injuries. Incorporation of this COS should help improve consistency in reporting, data synthesis, and comparability, and should minimize outcome reporting bias.

The failed adult traumatic brachial plexus reconstruction.

Traumatic adult brachial plexus injuries typically cause immediate loss of upper limb function. Timely multidisciplinary treatment in specialized centres often results in a useful helper arm. Both the patient and the surgical team can benefit from an open discussion to set realistic expectations. Surgical reconstruction is customized for each patient, considering their injury factors and functional objectives. Optimizing pain control, adherence to procedure indications and using meticulous surgical techniques help minimize the risk of failing to meet the patient's goals. The need for potential alternative treatment(s) if the desired result is not achieved should be detailed before the initial reconstruction. This review discusses late treatment options, including tendon transfers, joint fusions, free functioning muscle transfers and prosthetics, for managing the failed primary reconstruction of the traumatic adult brachial plexus.