MRN is widely being accepted for nerve imaging, as it exhibits high diagnostic performance while inspecting brachial plexus injuries and helps in conducting further analysis of the cause, the site, and the nature of the injury [12]. In our study, we found minimal differences between the clinical examination findings and the MRN findings, and good agreement between electromyography, nerve conduction, and the MRN finding, with a sensitivity of 94.44% and a specificity of 100% (kappa 0.773, P¼ 0.016). Another study by Fisher et al. [13] compared ED with MRN and showed that the ED tests were concordant with the MRN findings in 31 (66.0%) of 47 cases. MRN imaging preceded the ED tests in 21 (44.7%) of 47 cases. Another study by Smith et al. [14] showed that there was a greater correlation between the MRN and physical examination findings (kappa 0.6715, coefficient of correlation 0.7110, P < 0.001) than between the EMG and the physical examination findings (kappa 0.5748, coefficient of correlation 0.5883, P¼ 0.0012). Contrary to our results, Du et al. [15] showed that when MRN was compared with EMG/NCS, MRN was found to give the same information in 29 patients (32%), additional diagnostic information in 41 (45%), less in 15 (17%), and a different diagnosis in 6 (7%). They explained that MRN provided less diagnostic information when no abnormality was shown, or the area of abnormality was not included in the scan (for example, if the brachial plexus was scanned when the lesion was in the distal ulnar nerve). This difference in the findings and correlation between the ED studies and MRN may be attributed to their use of a 3 Tesla MRI machine, while our study used a 1.5 Tesla machine.
In our study, we found that the electrophysiological tests were negative in 4 cases (10%) and positive in 36 (90%) confirming the MRN diagnosis. Our MRN findings regarding the level of detected lesions involved as a proportion of cases were as follows: root 80%, trunks in 70% (mainly the middle trunk), cord affection 40%, involved middle and posterior cord in 25%, lateral cord in 50% and terminal branches affection in 10% of cases. The MRN study of brachial plexuses by Upadhyaya et al., however, revealed the percentage of lesions per case: roots in 88%, trunks in 80%, and cords in 88%. This implies a high incidence of injury in both the proximal and distal plexuses. Yoshida et al. [16] also showed that the nerve root affection was founded in most patients. The distribution of nerve root signal abnormalities and foraminal stenosis showed a significant correlation.
Our study has been claimed that the cause of brachial plexopathy was per number of cases: preganglionic nerve root avulsion (30%), mild perineural edema surrounding C6/7 nerve roots (20%), lower brachial trunk high signal (10%), pseudo meningocele (20%), and with increased shoulder muscle T2 signal intensity with muscle atrophy in 10% of cases.
Upadhyaya et al.’s [17] MRN findings suggested root avulsion in 11 patients (44%) with 31 avulsed roots. The percentage of avulsed roots at C5, C6, C7, C8, and T1 levels was 12.9, 29.0, 32.2, 19.3, and 6.4, respectively. In agreement with Gad et al. [12], Vargas et al. [1], and Somashekar et al. [18], most of pervious MRN studies used the traditional MR sequences (T1WI, T2WI, and STAIR). We used new advanced sequences (3 D FIASTA, FIASTA FATSAT), and these sequences did not extend the time of examination by more than 6 min and added significant value as they clarified the neural details from the nearby vessels and improved the visualization of the nerve along the entire pathways. We are hoping to add it to the MRN protocol for examining nerve pathways.
As a result of good agreement between the ED studies and the MRN, we recommended this MRN protocol be used in selective cases such as those with no detectable cause for brachial plexopathy. This could include postoperative patients or suspected tumor invasions that need further localization and determination of the nature of the lesion.
Our study had many limitations since the variations of the types of pathology causing brachial plexopathy result in a small sample size for each group affecting the degree of confidence of the statistical analysis. Histopathological evaluation and nerve biopsy are not common, and all cases should have an ED tests before the MRN examination as it would influence the MRN interpretation. More extensive prospective studies to establish the efficacy of the MRN and to explain the nature of these interesting radiological findings are warranted.
MRN significantly impacts the diagnostic and therapeutic management of patients with brachial plexopathy. It can consequently help the medical team select treatment (conservative or surgical), decide the most appropriate time to operate, and select the surgical technique. It also reduces operative time and thus allows for a better prognosis for these patients.
In most cases, MRN and ED results were agreed, and the combined anatomical and functional information obtained were complementary. MRN is a non-invasive imaging, and it represents a good alternative way for diagnosis in patients who cannot tolerate EMG. The actual utility of MRN will need to be determined.