Quantitative magnetic resonance (MR) neurography for evaluation of peripheral nerves and plexus injuries

Abstract

Traumatic conditions of peripheral nerves and plexus have been classically evaluated by morphological imaging techniques and electrophysiological tests. New magnetic resonance imaging (MRI) studies based on 3D fat-suppressed techniques are providing high accuracy for peripheral nerve injury evaluation from a qualitative point of view. However, these techniques do not provide quantitative information. Diffusion weighted imaging (DWI) and diffusion tensor imaging (DTI) are functional MRI techniques that are able to evaluate and quantify the movement of water molecules within different biological structures. These techniques have been successfully applied in other anatomical areas, especially in the assessment of central nervous system, and now are being imported, with promising results for peripheral nerve and plexus evaluation. DWI and DTI allow performing a qualitative and quantitative peripheral nerve analysis, providing valuable pathophysiological information about functional integrity of these structures.In the field of trauma and peripheral nerve or plexus injury, several derived parameters from DWI and DTI studies such as apparent diffusion coefficient (ADC) or fractional anisotropy (FA) among others, can be used as potential biomarkers of neural damage providing information about fiber organization, axonal flow or myelin integrity. A proper knowledge of physical basis of these techniques and their limitations is important for an optimal interpretation of the imaging findings and derived data. In this paper, a comprehensive review of the potential applications of DWI and DTI neurographic studies is performed with a focus on traumatic conditions, including main nerve entrapment syndromes in both peripheral nerves and brachial or lumbar plexus.

Use of collision tests to identify physiological differences between the median and ulnar nerves

“…Increased signal intensity on fluid‐sensitive MRI images is most commonly seen in the ulnar nerve, being present in up to 60% of healthy persons. Nerve diameters in MRI images are also different in different nerves around the elbow . Because of the limitation of the advanced MRI techniques and the lack of standardization for obtaining more reproducible results, differentiation of small changes between nerves is as difficult as it is in electrophysiological studies.…”

Peripheral Nerves: Not Only Cross-sectional Area in the Era of Radiomics

“…Moreover, diffusion tensor imaging and nerve signal were used extensively to assess the inner texture of peripheral nerves on MRI. 13,[32][33][34][35][36][37] In addition, MRI allowed the evaluation of the fascicular ratio (FR), that is, the ratio between fascicles and non-fascicular tissue. A study compared the FR changes on MRI between patients with peripheral neuropathies and healthy controls, 24,25 and reported that the FR was significantly increased in patients compared with controls (FR: 76.7 AE 15.1 versus 56 AE 12.3; p < 0.0001 for the semiautomatic interface; and FR: 66.3 AE 17.5 versus 47.8 AE 18.4; p < 0.0001 for the automatic interface).…”

Current Concept in the Management of Brachial Plexus Birth Palsy

“…Different MRI sequences can give excellent imaging of intra-spinal as well as extra-spinal imaging of plexus. MRI can also give a clue about nerve edema, scarring and neuroma formation [14,26].…”

“…Van der Juis reported that excessive release of muscle from insertion leads to external rotation contracture and anterior shoulder instability. A subset of patients in their series required secondary internal rotation osteotomy [26,63].…”