Quantitative MR neurography of brachial plexus lesions based on diffusivity measurements

Abstract

ObjectivesNew magnetic resonance imaging (MRI) based on 3D fat-suppressed techniques provide high accuracy for evaluation of brachial plexus and peripheral nerve lesions from a qualitative point of view. However, this qualitative evaluation often demonstrates overlapping features among different pathologies (Pullman et al., 2013). Diffusion weighted imaging (DWI) and diffusion tensor imaging (DTI) are functional MRI techniques that have been successfully applied in the imaging of central nervous system lesions, and now are being imported, with promising results for peripheral nerve and plexus evaluation. Several derived parameters from DWI and DTI studies such as apparent diffusion coefficient (ADC) or fractional anisotropy (FA), can be used as potential biomarkers of neural damage by providing information about axonal flow, fiber organization or myelin integrity (Andreou et al., 2015). In this study we assess the role of DW and DT based quantitative measures in characterization of traumatic and non traumatic lesions of brachial plexus and peripheral nerve and its influence on therapeutic management and outcome. Methods34 patients with features ofbrachialplexopathy and peripheral neuropathy were included in the study. MR neurography examinations included conventional MR sequences and unidirectional DW-MRN with background suppression (DWIBS) and DTI. The images were independently reviewed by two radiologists and the findings were recorded at different levels of thebrachial plexus: ganglia, roots, trunks, divisions and cords. Mean ADC and FA values were determined within each lesion and within contra lateral homologous unaffected segment of the plexus. The Mann-Whitney Test was used to calculate the differences in ADC&FA values between diseased and normal sides and the One way ANOVA test between diseased segments of different pathologies with p-values <0.05 being considered statistically significant. Resultspatients were classified according to etiologic causes into four categories: traumatic, compressive degenerative disk, radiation induced plexitis and neoplastic nerve compression or invasion. T2 high signal intensity and swelling of the affected nerve, muscular denervation and complication such as pseudo meningeocele and neuroma were the major findings in qualitatitve sequences. A statistically significant difference in ADC and FA values were found between diseased and normal sides as well as across the traumatic and non traumatic groups and between benign compressive and malignant infiltrative etiologies. ConclusionThe resulted values of newly designed quantitative protocols give us functional and numerical marker by which the diagnosis and differentiation of different pathologies of peripheral nerves and brachial plexus will be more suitable.