Utility of High-Resolution 3 T MR Neurography in Peripheral Nerve Pathologies

Abstract

Background and objectives: Magnetic resonance neurography (MRN) allows for the direct visualization of nerves, which can be instrumental in diagnosing, characterizing, and localizing peripheral nerve disorders. We planned to conduct a study on the patients of peripheral nerve injuries who were referred for MRN and to compare the findings of MRN to those of nerve conduction studies (NCS) on various focal nerve disorders.

Methods: This prospective study was conducted over 1½ years, involving 58 subjects with clinically diagnosed focal peripheral nerve pathologies who were referred for MRN to the Department of Radiodiagnosis and Imaging. The range of focal peripheral nerve pathologies detected using MRN was correlated and compared to NCS and/or electromyography results, as well as to surgical and/or histopathological results, wherever available. The Chi-squared (χ²) test and Fisher's exact test were used to evaluate the association between MRN and NCS outcomes.

Results: The study identified a broad spectrum of peripheral nerve pathologies. Out of 58 subjects, abnormalities were found in 52 (89.6%) subjects, whereas six patients (10.3%) did not show any significant abnormalities. Fifty patients (86.3%) showed abnormalities on both MRN and NCS, while five patients (8.6%) did not show any abnormalities on either MRN or NCS. Two patients (3.4%) showed abnormalities on MRN but had normal NCS results, and in one case (1.7%), MRN was normal but NCS showed an abnormality. Out of the 58 MRN examinations, 25 were found to have brachial plexus involvement.

Conclusion: MRN is a highly sensitive tool for evaluating peripheral nerve pathologies. Its correlation with NCS and intraoperative findings further supports its clinical utility. The 3 T MRN should be considered a key imaging modality in the diagnostic process for peripheral nerve pathologies. In addition, it serves as a valuable guide for planning therapeutic interventions and assessing prognosis in various patient subsets.

Keywords: MRN (magnetic resonance neurography); NCS-EMG (nerve conduction studies–electromyography); brachial plexus; peripheral nerve pathologies.

Figure 1

(a) A 55-year-old male with occupational machine injury to the left arm had weakness of extensors of forearm, and hand along with sensory symptoms. 3D T2 SPACE image reveals a fusiform neuroma of the radial nerve in the radial groove (yellow arrow). (b) Intraoperative image shows neuroma of the transected radial nerve in the mid arm (black arrow). (c) A 32-year-old male with glass cut injury of the left forearm, had diagnosis of median nerve injury. On MRN, 3D T2 SPACE MIP image shows proximal (white arrow) and distal (orange arrow) neuromas involving the median nerve in the forearm with adjacent hematoma (asterisk). (d) Intraoperative image confirms MRN findings with short segment non-visualisation of median nerve in the distal forearm with evidence of proximal and distal neuromas (black arrows) and adjacent hematoma. 3D: three-dimensional, MRN: magnetic resonance neurography, SPACE: Sampling Perfection with Application optimized Contrasts using different flip angle Evolution, MIP: Maximum intensity projection

Figure 2

Brachial plexus pathologies are demonstrated. (a) Coronal STIR and (b) coronal DW MIP images show a well-circumscribed STIR heterogeneously hyperintense lesion (blue arrows) in the left supraclavicular region, which was inseparable from the upper trunk of the left brachial plexus and was suggestive of nerve sheath tumor. (c) Coronal DWI MIP and (d) coronal STIR MRN images of a young female reveal diffusely thickened and hyperintense C5 and C6 nerve roots (yellow arrows), left upper trunk (purple arrows), lateral as well as posterior cords (green arrows), and she was diagnosed with plexiform neurofibroma. (e) Coronal STIR and (f) sagittal STIR images of MR brachial plexus of a 4-year-old male with brachial plexus injury show avulsion of anterior and posterior rootlets of C8 nerve root on the right side with pseudo-meningocele formation (white arrows), which was consistent with preganglionic nerve injury. DWI: diffusion-weighted imaging, MR: magnetic resonance, MRN: magnetic resonance neurography, STIR: Short Tau Inversion Recovery magnetic resonance image

Figure 3

(a) A 23-year-old male who had swelling on the medial aspect of the left arm (yellow arrow) suggestive of left ulnar nerve palsy underwent MRN. (b) 3D T2 fat-saturated image shows diffuse thickening and hyperintense signal involving C8 and T1 nerve roots (purple arrows), the inferior trunk (red arrow), anterior cord of the inferior trunk (white arrow), and medial cord (green arrow), extending to involve the ulnar nerve (blue arrow). (c) Coronal PD fat-saturated MIP image showing diffusely thickened and hyperintense ulnar nerve (curved white arrow) near cubital tunnel with hyperintense collection (*) communicating with the ulnar nerve. (d) Axial T1 fat-saturated post-contrast image showing thick peripheral enhancement of thickened nerve (curved red arrow) with adjacent peripherally enhancing collection (orange arrow), confirmed on HPE as leprosy. 3D: three-dimensional, MRN: magnetic resonance neurography, PD: proton density, HPE: Histopathological examination