Nerve Imaging in the Wrist.

Neuropathic symptoms involving the wrist are a common clinical presentation that can be due to a variety of causes. Imaging plays a key role in differentiating distal nerve lesions in the wrist from more proximal nerve abnormalities such as a cervical radiculopathy or brachial plexopathy. Imaging complements electrodiagnostic testing by helping define the specific lesion site and by providing anatomical information to guide surgical planning. This article reviews nerve anatomy, normal and abnormal findings on ultrasonography and magnetic resonance imaging, and common and uncommon causes of neuropathy.

CLINICAL AND NEUROPHYSIOLOGICAL PARALLELS OF THE BRACHIAL PLEXOPATHY IN THE STRUCTURE OF NEUROGENIC THORACIC OUTLET SYNDROME.

OBJECTIVE: The aim: Was assessment of the neurophysiological data and features of clinical picture in patients with neurogenic thoracic outlet syndrome (TOS). PATIENTS AND METHODS: Materials and methods: 103 patients with upper extremity pain and/or paresthesia or hypotrophy, or a combination of these symptoms were examined. The examination algorithm included: cervical spine radiography, cervical spine and brachial plexuses magnetic resonance imaging (MRI), upper extremity soft tissues and vessels ultrasonic examination, stimulation electroneuromiography with F-waves registration. RESULTS: Results: Neurogenic TOS was diagnosed in 29 patients. A significant relationship between the following complaints and neurophysiological parameters was observed: pain, numbness during physical activity and decreased medial anrebrachial cutaneous nerve response amplitude by ≥25% compared to the contralateral side; hypothenar hypotrophy and decrease of ulnar nerve motor/sensory response amplitude; the 4-5th fingers hypoesthesia and decrease of ulnar nerve sensory response amplitude. CONCLUSION: Conclusions: Medial antebrachial cutaneous nerve amplitudes asymmetry indices of ≥25% or lack of response may be considered to be a marker of true neurogenic TOS.

Local Riluzole Release from a Thermosensitive Hydrogel Rescues Injured Motoneurons through Nerve Root Stumps in a Brachial Plexus Injury Rat Model.

The C5-C6 nerve roots are usually spared from avulsion after brachial plexus injury (BPI) and can thus be used as donors for nerve repair. A BPI rat model with C5-C6 nerve root stumps has been established in our previous work. The aim of this study was to test whether riluzole loaded into a thermosensitive hydrogel could applied locally in the nerve root stumps of this BPI rat model, thus increasing the reparative effect of the nerve root stumps. Nile red (a hydrophobic dye) was used as a substitute for riluzole since riluzole itself does not emit light. Nile red, loaded into a thermosensitive hydrogel, was added to the nerve root stumps of the BPI rat model. Additionally, eighteen rats, with operation on right brachial plexus, were evenly divided into three groups: control (Con), thermosensitive hydrogel (Gel) and thermosensitive hydrogel loaded with riluzole (Gel + Ri) groups. Direct nerve repair was performed after local riluzole release for two weeks. Functional and electrophysiological evaluations and histological assessments were used to evaluate the reparative effect 8 weeks after nerve repair. Nile red was slowly released from the thermosensitive hydrogel and retrograde transport through the nerve root stumps to the motoneurons, according to immunofluorescence. Discernible functional recovery began earlier in the Gel + Ri group. The compound muscle action potential, ChAT-expressing motoneurons, positivity for neurofilaments and S100, diameter of regenerating axons, myelin sheath thickness and density of myelinated fibers were markedly increased in the Gel + Ri group compared with the Con and Gel groups. Our results indicate that the local administration of riluzole could undergo retrograde transportation through C5-C6 nerve root stumps, thereby promoting neuroprotection and increasing nerve regeneration.

Examination of the human motor endplate after brachial plexus injury with two-photon microscopy.

INTRODUCTION: After traumatic nerve injury, neuromuscular junction remodeling plays a key role in determining functional outcomes. Immunohistochemical analyses of denervated muscle biopsies may provide valuable prognostic data regarding clinical outcomes to supplement electrodiagnostic studies. METHODS: We performed biopsies on nonfunctioning deltoid muscles in two patients after gunshot wounds and visualized the neuromuscular junctions using two-photon microscopy with immunohistochemistry. RESULTS: Although the nerves in both patients showed evidence of acute Wallerian degeneration, some of the motor endplates were intact but exhibited significantly decreased surface area and volume. Both patients exhibited substantial recovery of motor function over several weeks postinjury. DISCUSSION: Two-photon microscopic assessment of neuromuscular junction integrity and motor endplate morphometry in muscle biopsies provided evidence of partial sparing of muscle innervation. This finding supported the clinical judgment that eventual recovery would occur. With further study, this technique may help to guide operative decisionmaking after traumatic nerve injuries.

Anatomy, Imaging, and Pathologic Conditions of the Brachial Plexus.

The brachial plexus is an intricate anatomic structure with an important function: providing innervation to the upper extremity, shoulder, and upper chest. Owing to its complex form and longitudinal course, the brachial plexus can be challenging to conceptualize in three dimensions, which complicates evaluations in standard orthogonal imaging planes. The components of the brachial plexus can be determined by using key anatomic landmarks. Applying this anatomic knowledge, a radiologist should then be able to identify pathologic appearances of the brachial plexus by using imaging modalities such as MRI, CT, and US. Brachial plexopathies can be divided into two broad categories that are based on disease origin: traumatic and nontraumatic. In the traumatic plexopathy group, there are distinct imaging findings and management methods for pre- versus postganglionic injuries. For nontraumatic plexopathies, having access to an accurate patient history is often crucial. Knowledge of the timing of radiation therapy is critical to diagnosing post-radiation therapy brachial plexopathy. In acute brachial neuritis, antecedent stressors occur within a specific time frame. Primary and secondary tumors of the brachial plexus are not uncommon, with the most common primary tumors being peripheral nerve sheath tumors. Direct extension and metastasis from primary malignancies such as breast and lung cancer can occur. Although diagnosing a brachial plexus anomaly is potentially perplexing, it can be straightforward if it is based on foundational knowledge of anatomy, imaging findings, and pathologic features. ©RSNA, 2020.

Backpack palsy and other brachial plexus neuropathies in the military population.

Brachial plexus neuropathy is often seen in the military population, especially due to pressure (backpack palsy, BPP) or idiopathic (neuralgic amyotrophy, NA). We aimed to gain insight in the disease characteristics of soldiers with brachial plexus neuropathies in the Dutch military population and to compare disease characteristics between patients with BPP and NA. In this retrospective chart review study we aimed to include all patients with brachial plexus neuropathy, who presented in the Joint Military Hospital between 1 January, 2011 and 31 December, 2016. We calculated the incidence of NA and BPP and Chi-square tests or Student t tests were performed for differences in patient characteristics between NA and BPP. We included 127 patients, 63 with BPP, 45 with NA, 10 with traumatic brachial plexus neuropathy, and 9 with other plexopathy. The incidence of brachial plexus neuropathy was 50/100 000 person years overall, 25/100 000 person years for BPP, and 18/100 000 person years for NA. Patients in the BPP group differed from the NA with regard to pain (BPP 41% vs NA 93%, P = .000), atrophy (13% BPP vs 29% NA, P = .049), and sensory symptoms (83% BPP vs 44% NA, P = .000). In the BPP group 90% had incomplete recovery and in the NA group 78%. Our study showed a high incidence of BPP and NA in the military population and suggests recovery is not so benevolent as previously thought. Future research is necessary to improve insight and outcome of military patients with brachial plexus neuropathies.

Characteristics of metastatic brachial plexopathy in patients with breast cancer.

PURPOSE: Brachial plexopathy in cancer patients is a rare but significant complication that causes pain and disability of the upper extremities. Clinical features of breast cancer patients with metastatic brachial plexopathy (MBP) have not been studied. We aimed to investigate the characteristics of MBP in breast cancer patients. METHODS: We retrospectively reviewed medical records of patients with breast cancer with MBP who visited Asan Medical Center from 2000 to 2016; we enrolled 44 patients. We comprehensively reviewed the characteristics, range of metastatic lymph nodes, initial symptoms, location, and severity of brachial plexus injury by electrodiagnostic study, radiologic findings, and associated complications. RESULTS: The mean age of patients with MBP was 51.9 ± 9.3 years; 25% were diagnosed with stage IV breast cancer at initial diagnosis. Weakness was the most common initial symptom of MBP (52.3%). Most patients showed limitation of shoulder range of motion and pain; 66% of patients exhibited malignant lymphedema. Forty-one patients were evaluated by electromyography; upper nerve trunk involvement (22.0%) was more frequent than lower nerve trunk involvement (9.8%). Nineteen patients underwent brachial plexus MRI, and supraclavicular area (SCA) metastasis was most frequent (57.9%). Sixteen patients were examined by both brachial plexus MRI and electromyography; patients with SCA metastasis exhibited significantly more frequent malignant lymphedema (p = 0.019) and upper nerve trunk involvement (p = 0.035), compared with patients with non-SCA metastasis. CONCLUSIONS: Our study revealed clinical features of MBP in breast cancer patients. Additional diagnostic evaluation focused on metastasis or aggravated metastatic tumor is needed when breast cancer patients are diagnosed with brachial plexopathy.

The morphologic change of the elbow with flexion contracture in upper obstetric brachial plexus palsy.

BACKGROUND: Contracture of the elbow after obstetric brachial plexus palsy (OBPP) is well known; however, details of the 3-dimensional (3D) morphologic changes in the elbow joint in OBPP have not been clarified. This study aimed to clarify the 3D morphologic changes in the elbow joint by focusing on the distal humerus with flexion contracture in upper OBPP. We tested the hypothesis that the shape of the distal humerus with flexion contracture in upper OBPP is hypoplastic in the trochlea, capitellum, and olecranon fossa. METHODS: We retrospectively studied 20 patients with elbow flexion contracture and residual OBPP. The approximate radius of the distal humerus, the shortest distance between the olecranon and coronoid fossa, and the size of the olecranon fossa were measured and compared between the affected and normal sides using 3D bone models to assess the distal humerus morphology. RESULTS: The average radius of the distal humerus was smaller on the affected side than on the normal side. Furthermore, the average distance between the olecranon and coronoid fossa was greater and the average size of the olecranon fossa was smaller on the affected side than on the normal side. The size of the distal humerus was significantly smaller and the olecranon fossa was significantly shallower on the affected side. CONCLUSIONS: Consistent with our original hypothesis, the distal humerus with flexion contracture in upper OBPP was hypoplastic. The shallow olecranon fossa might prevent full extension of the elbow even though soft tissue contracture release is performed. We recommend evaluation of the morphology of the olecranon fossa to determine the treatment plan for elbow flexion contracture with OBPP.

Current status of magnetic resonance neurography in evaluating patients with brachial plexopathy.

Magnetic resonance neurography (MRN) is recognized as the imaging modality of choice in the evaluation of patients with brachial plexopathy. It adds vital information to the results of the clinical evaluation and electrodiagnostic tests and facilitates patient management. Its indications include both trauma and non-traumatic forms of plexopathy such as inflammatory, neoplastic and compressive. This article will familiarize readers with the routine MRN protocol in clinical practice and discuss the utility of the different sequences. The timing of the scan is important, especially with reference to trauma and this has been discussed. Both the advantages and limitations of MRN have been elaborated upon.

Ultrasound of the Brachial Plexus.

Examination of the brachial plexus with ultrasound is efficient because it allows many parts of the brachial plexus as well as the surrounding soft tissues to be assessed with high spatial resolution. The key to performing good ultrasound of the brachial plexus is being familiar with the anatomy and the common variants. That makes it possible to concentrate solely on the ultrasound appearances free of simultaneously wondering about the anatomy. Ultrasound of the brachial plexus is particularly good for assessing nerve sheath tumor, perineural fibrosis, metastases, some inflammatory neuropathies, neuralgic amyotrophy, and posttraumatic sequalae. It is limited in the assessment of thoracic outlet syndrome and in the acute/subacute trauma setting. This review addresses the anatomy, ultrasound technique, as well as pathology of the brachial plexus from the cervical foramina to the axilla.

Development of a Device-Assisted Nerve-Regeneration Procedure in Disruptive Lesions of the Brachial Plexus.

BACKGROUND: We describe the development of a new surgical procedure to be used in the treatment of disruptive brachial plexus (BP) lesions. It is centered on an artificial device designed to assist nerve regeneration by providing a confined and protected environment. Nerve fibers can repair inside the device, while the adverse massive scar-tissue formation is limited to the outside of the device. METHODS: Steps in the development of the procedure were (1) definition of the rationale, (2) design of the device, (3) choice of an in vivo translational model, (4)refinement of the surgical procedure, and (5) performance of an in vivo pilot study as a proof of concept. An interdisciplinary team from several laboratories was involved in this work over a period of 6 years. RESULTS: Results showed the absence of significant scar tissue in the regenerate and the presence of myelinated fibers aligned proximodistally between the stumps. This surgical approach can be seen not only as a definitive treatment but also as an early examination and stabilization before some different surgery will be later performed. It may also be used as additional protection for traditional surgery like end-to-end coaptation. CONCLUSIONS: We conclude that the availability of a suitable device-assisted early treatment, even if not to be considered definitive, could help in addressing the BP lesions at an earlier stage and this may improve the final outcome. Our evidence justifies further experimentation on this approach.

Oberlin's procedure in children with obstetric brachial plexus palsy.

PURPOSE: Most cases of obstetric brachial plexus palsy (OBPP) involve C5 and C6 nerve roots (Erb's palsy). In those cases, re-establishing the elbow flexion is the primary goal of surgery. The partial transfer of the ulnar nerve to the musculocutaneous nerve (Oberlin's procedure) is widely used in adults, but incipient in children. The purpose of this study is to describe the results obtained with such procedure as regards the improvement of the elbow flexion and donor nerve morbidity. METHOD: Thirteen children aged 9 to 15 months underwent Oberlin's procedure. They were assessed preoperatively and 1 year postoperatively using the active movement scale and also according to the functionality of the affected limb. All of them were evaluated because of the possibility of movement loss resulting from the donor nerve. We used the non-parametric, statistic Wilcoxon signed rank test (α = 0,05) method. RESULTS: There was a significant improvement in the active elbow flexion between pre- and postoperative periods. Eleven children presented functional improvement. All of them maintained negative cookie test 1 year after the surgery. We did not observe any loss related to the donor nerve in terms of wrist flexion. CONCLUSION: The results suggest that Oberlin's procedure can be an effective and safe alternative to treat elbow flexion in Erb's palsy.

The current role of diagnostic imaging in the preoperative workup for refractory neonatal brachial plexus palsy.

INTRODUCTION: Despite recent improvements in perinatal care, the incidence of neonatal brachial plexus palsy (NBPP) remains relatively common. CT myelography is currently considered to be the optimal imaging modality for evaluating nerve root integrity. Recent improvements in MRI techniques have made it an attractive alternative to evaluate nerve root avulsions (preganglionic injuries). AIM: We demonstrate the utility of MRI for the evaluation of normal and avulsed spinal nerve roots. We also show the utility of ultrasound in providing useful preoperative evaluation of the postganglionic brachial plexus in patients with NBPP.

A New Animal Model of Brachial Plexus Neuralgia Produced by Injection of Cobra Venom into the Lower Trunk in the Rat.

BACKGROUND: To establish a new animal model for the study of neuropathic pain developed by administration of cobra venom to the brachial plexus (BP) lower trunk. METHODS: Fifty-eight adult male Sprague-Dawley rats were randomly divided into 5 groups. Under pentobarbital sodium anesthesia, cobra venom was injected into the lower trunk or sham operation was performed in the animals. On postoperative day 1 and day 12, pregabalin was administered intragastricly at 30 mg/kg in two groups. Mechanical withdrawal thresholds (MWT) were tested with von Frey filaments. Video recordings were used to analyze the spontaneous behaviors. Meanwhile, our model was confirmed by observing ultrastructural alterations of the BP and cervical cord (C8-T1) via electron microscope examination. RESULTS: In comparison to the blank and sham-operated group, cobra venom-treated rats showed a profound decrease in the MWT, exploratory and increase in grooming behaviors (P<0.05). The changes were long-lasting (up to 60 days), in both ipsilateral and contralateral paws. Furthermore, it was observed under microscopic examination that the myelin sheath was demyelinated in the BP and cervical cord (C8-T1) after injection of cobra venom to the lower trunk. Pregabalin group rats showed changes in MWT and spontaneous behaviors after pregabalin treatment at postoperative day 1 (P>0.05), compared with the control and sham-operated groups. In pregabalin test POD12 group, the decreased MWT and the increased grooming behavior were improved at 20 days after operation. However, pregabalin had no effect on exploratory activity. Results indicate that pregabalin effectively attenuates mechanical hyperalgesia in acute period. CONCLUSIONS: The cobra venom model can be used as a model to induce neuropathic pain and to enable study of the mechanism and treatment.

Long-term outcome of accessory nerve to suprascapular nerve transfer in obstetric brachial plexus lesion: functional, morphological, and electrophysiological results.

PURPOSE: An accessory to suprascapular nerve (XIN-SSN) transfer is considered in patients with obstetric brachial plexus lesion who fail to recover active shoulder external rotation. The aim of this study was to evaluate the quality of extraplexal suprascapular nerve neurotization and to perform a detailed analysis of the infraspinatus muscle (IM) and shoulder external rotation. METHODS: A XIN-SSN transfer was performed in 14 patients between 2000 and 2007. Patients had been operated at the age of 3.7 ± 2.8 years. Follow-up examinations were conducted up to 8.5 ± 2.5 years. Magnetic resonance imaging was performed to investigate muscle trophism. Fatty muscle degeneration of the IM was classified according to the Goutallier classification. We conducted nerve conduction velocity studies of the suprascapular nerve and needle electromyography of the IM to assess pathologic spontaneous activity and interference patterns. Active glenohumeral shoulder external rotation and global shoulder function were evaluated using the Mallet score. RESULTS: Postoperatively, growth of the IM increased equally on the affected and unaffected sides, although significant differences of muscle thickness persisted over time. There was only grade 1 or 2 fatty degeneration pre- and postoperatively. Electromyography of the IM revealed a full interference pattern in all except one patient, and there was no pathological spontaneous activity. Glenohumeral external rotation as well as global shoulder function increased significantly. CONCLUSION: Our results indicate that the anastomosis after XIN-SSN transfer is functional and that successful reinnervation of the infraspinatus muscle may enable true glenohumeral active external rotation.

Time-specific microRNA changes during spinal motoneuron degeneration in adult rats following unilateral brachial plexus root avulsion: ipsilateral vs. contralateral changes.

BACKGROUND: Spinal root avulsion induces multiple pathophysiological events consisting of altered levels of specific genes and proteins related to inflammation, apoptosis, and oxidative stress, which collectively result in the death of the affected motoneurons. Recent studies have demonstrated that the gene changes involved in spinal cord injury can be regulated by microRNAs, which are a class of short non-coding RNA molecules that repress target mRNAs post-transcriptionally. With consideration for the time course of the avulsion-induced gene expression patterns within dying motoneurons, we employed microarray analysis to determine whether and how microRNAs are involved in the changes of gene expression induced by pathophysiological events in spinal cord motoneurons. RESULTS: The expression of a total of 3,361 miRNAs in the spinal cord of adult rats was identified. Unilateral root-avulsion resulted in significant alterations in miRNA expression. In the ipsilateral half compared to the contralateral half of the spinal cord, on the 3rd day after the injury, 55 miRNAs were upregulated, and 24 were downregulated, and on the 14th day after the injury, 36 miRNAs were upregulated, and 23 were downregulated. The upregulation of miR-146b-5p and miR-31a-3p and the downregulation of miR-324-3p and miR-484 were observed. Eleven of the miRNAs, including miR-21-5p, demonstrated a sustained increase; however, only miR-466c-3p presented a sustained decrease 3 and 14 days after the injury. More interestingly, 4 of the miRNAs, including miR-18a, were upregulated on the 3rd day but were downregulated on the 14th day after injury.Some of these miRNAs target inflammatory-response genes in the early stage of injury, and others target neurotransmitter transport genes in the intermediate stages of injury. The altered miRNA expression pattern suggests that the MAPK and calcium signaling pathways are consistently involved in the injury response. CONCLUSIONS: This analysis may facilitate the understanding of the time-specific altered expression of a large set of microRNAs in the spinal cord after brachial root avulsion.

Sensorimotor cortical changes assessed with resting-state fMRI following total brachial plexus root avulsion.

OBJECTIVE: Peripheral nerve injury can induce immediate and long-standing remodelling of the brain cortex, which may affect outcomes of nerve repair. This study examined changes of corresponding cortical representations in patients with brachial plexus injuries. METHODS: Resting-state fMRI was acquired for 13 adult patients with total brachial plexus root avulsion, three of whom underwent second scans 7 or 8 months later. The time of examination ranged from 1 to 16 months after injuries. Nine healthy adults were enrolled as control. Seed-based functional connectivity was performed for all subjects. RESULTS: For nine patients whose first fMRI was performed from 1 to 4 months after brachial plexus injuries, images showed that their cortical maps of sensorimotor areas corresponding to the hand and arm in the hemisphere contralateral to the injured side had much weaker correlation with the supplementary motor area (SMA) than those ipsilateral to the injured side. Symmetrical maps of bilateral cortical sensorimotor areas corresponding to the hand and arm were observed in other four cases with fMRI tested from 7 to 16 months after injuries. For three of the nine patients with asymmetrical cortical representations, second scans indicated symmetric results or even stronger correlation with SMA in the cerebral cortex contralateral to the injured side. CONCLUSIONS: Total brachial plexus root avulsion causes cortical representations of the brachial plexus to undergo a change from an inactive to an active state. This implies that peripheral deafferentation after brachial plexus injuries will induce corresponding cortical representations to be occupied by adjacent non-deafferented cortical territories.

Value of enhancement technique in 3D-T2-STIR images of the brachial plexus.

OBJECTIVE: Imaging the brachial plexus is a challenge because of its complicated structure. The purpose of this study is to improve the diagnostic ability for brachial plexus via 3-dimensional T2-weighted short inversion time inversion recovery (3D-T2-STIR) technique with contrast agent administration. METHODS: Thirty patients with brachial plexopathies were recruited. The STIR sequences without and with contrast agent administration were performed on each subject. The grade of the diagnostic ability and the contrast ratio were assessed. RESULTS: After contrast agent administration, signals of the adjacent vessels were suppressed because of reduced T1 relaxation time similar to that of fat tissues. The outlines of nerves would be prominent with respect to surrounding tissues. Both diagnostic ability and contrast ratio were improved on 3D-T2-STIR with contrast agent administration. CONCLUSIONS: The maximum-intensity projection image of 3D-T2-STIR technique with contrast agent was superior to that without. It might be a better way to evaluate anatomies and pathologies of the brachial plexus. These advantages would improve the understanding and neurosurgical planning for brachial plexopathies in the future.

The role of muscle imbalance in the pathogenesis of shoulder contracture after neonatal brachial plexus palsy: a study in a rat model.

BACKGROUND: An internal rotation contracture of the shoulder is common after neonatal brachial plexus injuries due to subscapularis shortening and atrophy. It has been explained by 2 theories: muscle denervation and muscle imbalance between the internal and external rotators of the shoulder. The goal of this study was to test the hypothesis that muscle imbalance alone could cause subscapularis changes and shoulder contracture. MATERIALS AND METHODS: We performed selective neurectomy of the suprascapular nerve in 15 newborn rats to denervate only the supraspinatus and the infraspinatus muscles, leaving the subscapularis muscle intact. After 4 weeks, passive shoulder external rotation was measured and a 7.2-T magnetic resonance imaging scan of the shoulders was used to determine changes in the infraspinatus and subscapularis muscles. The subscapularis muscle was weighed to determine the degree of mass loss. An additional group of 10 newborn rats was evaluated to determine the sectional muscle fiber size and muscle area of fibrosis by use of images from type I collagen immunostaining. RESULTS: There was a significant decrease in passive shoulder external rotation, with a mean loss of 66°; in the thickness of the denervated infraspinatus, with a mean loss of 40%; and in the thickness and weight of the non-denervated subscapularis, with mean losses of 28% and 25%, respectively. No differences were found in subscapularis muscle fiber size and area of fibrosis between shoulders after suprascapular nerve injury. CONCLUSIONS: Our study supports the theory that shoulder muscle imbalance is a cause of shoulder contracture in patients with neonatal brachial plexus palsy.

Modified pathological classification of brachial plexus root injury and its MR imaging characteristics.

The authors described a modified pathological classification (PC) of brachial plexus injury (BPI) and its magnetic resonance (MR) imaging characteristics. The reliability and diagnostic accuracy of MR imaging for detecting nerve injury was discussed. Between 2006 and 2010, 86 patients with BPI were managed surgically in our department. Their preoperative MR images and surgical findings were analyzed retrospectively. The PC of BPI was classified into five types: (I) nerve root injury in continuity (including Sunderland grade I-IV injury); (II) postganglionic spinal nerve rupture with or without proximal stump; (III) preganglionic root injury (visible); (IV) preganglionic nerve root injury and postganglionic spinal nerves injury; (V) preganglionic root injury (invisible). The main MR imaging characteristics of BPI included traumatic meningocele, displacement of spinal cord, the absence of nerve root, "Black line" sign, nerve root/trunk injury in continuity, and thickening and edema of nerve root. The accuracy of MR imaging for detecting C5, C6, C7, C8, and T1 nerve roots injury were 93.3, 95.2, 92.3, 84, and 74.4%, respectively. The modified PC provides a detailed description of nerve root injury in BPI, and MR imaging technique is a reliable method for detecting nerve root injury.