For Doctors in a Hurry
- Clinicians often struggle to choose between high-resolution ultrasound and magnetic resonance neurography for evaluating suspected upper extremity peripheral neuropathies.
- The researchers analyzed 800 patients to identify clinical predictors for when one imaging modality provides superior diagnostic information over the other.
- Magnetic resonance neurography offered additional diagnostic value in 94.9 percent of cases where one modality was superior to the other.
- The authors concluded that proximal lesions, multi-regional involvement, and multi-nerve pathology strongly favor the use of magnetic resonance neurography.
- Clinicians should prioritize high-resolution ultrasound when patients have metal implants that might otherwise cause significant artifacts on magnetic resonance imaging.
Optimizing Imaging Selection in Upper Extremity Neuropathies
Diagnosing peripheral neuropathies of the upper limb remains a significant clinical challenge due to the overlapping presentations of entrapment syndromes, inflammatory plexopathies, and systemic polyneuropathies [1, 2]. While nerve conduction studies serve as the primary diagnostic tool, they frequently lack the structural detail necessary to identify specific etiologies or precise anatomical locations of nerve compromise [3, 4]. High-resolution ultrasound and magnetic resonance neurography (an imaging technique optimized for visualizing peripheral nerves using specialized sequences to suppress fat and vessel signals) have emerged as vital adjuncts, offering the ability to visualize nerve cross-sectional area (the measurement of a nerve's thickness in a transverse plane) and signal changes that correlate with axonal distortion or edema [5, 6]. In a recent exploratory subanalysis of 800 patients, researchers found that magnetic resonance neurography provided additional diagnostic value in 94.9% of cases where one modality surpassed the other, particularly when identifying proximal nerve lesions (odds ratio 5.72, 95% confidence interval: 3.42 to 9.56) or multi-nerve involvement (odds ratio 1.65, 95% confidence interval: 1.03 to 2.63) [7]. Conversely, high-resolution ultrasound proved most beneficial when magnetic resonance imaging was limited by metal artifacts [7]. These findings provide a clinical rationale for choosing imaging based on the suspected lesion site and the presence of multi-regional pathology to improve diagnostic accuracy in routine practice.
Quantifying the Diagnostic Yield of Advanced Nerve Imaging
The researchers conducted a retrospective exploratory subanalysis nested within a larger prospective, observational, single-center study to evaluate the utility of advanced imaging in peripheral nerve assessment. This investigation focused on a substantial cohort of 800 patients who were referred for both high-resolution nerve ultrasound and magnetic resonance neurography between November 2015 and February 2022. Every patient in this group presented with suspected upper extremity neuropathy, a clinical scenario where identifying the exact site and nature of nerve pathology is often difficult using physical examination or electrodiagnostic testing alone. For the clinician, this study addresses the common dilemma of which advanced imaging tool to order when initial electrophysiology is inconclusive or requires anatomical correlation.
Predictors Favoring Magnetic Resonance Neurography
To identify which clinical factors predicted the superiority of one imaging modality over the other, the researchers employed a robust statistical framework. They utilized uni- and multivariable logistic regression (statistical methods used to determine the relationship between a dependent variable and one or more independent variables) alongside a classification regression tree (CART) model (a machine learning algorithm that partitions data into subsets based on the most significant predictors to create a decision-making flowchart). Within the subset of 275 patients where a diagnostic difference was observed, magnetic resonance neurography provided additional diagnostic value in 261 cases, accounting for 94.9% of those instances. This suggests that when high-resolution nerve ultrasound and magnetic resonance neurography yield discordant results, the latter is significantly more likely to provide the definitive clinical information needed for diagnosis. Proximal nerve lesion location emerged as a primary predictor for the additional diagnostic utility of this modality. For patients with proximal-only nerve lesions, the odds ratio for magnetic resonance neurography providing additional value was 5.72 (95% CI: 3.42 to 9.56). The diagnostic advantage remained strong for combined proximal-peripheral lesions, which demonstrated an odds ratio of 4.59 (95% CI: 2.31 to 9.09). These data points underscore the utility of magnetic resonance neurography in visualizing deep-seated structures, such as the brachial plexus or nerve roots, where the depth and overlying bony structures often limit the acoustic window available for ultrasound. Beyond lesion depth, the complexity and extent of the neuropathy also influenced imaging yield. The researchers found that multi-anatomical region-involvement was a significant predictor of additional diagnostic value for magnetic resonance neurography, with an odds ratio of 1.81 (95% CI: 1.14 to 2.87). Similarly, multi-nerve involvement favored the use of magnetic resonance neurography, yielding an odds ratio of 1.65 (95% CI: 1.03 to 2.63). For clinicians, these findings suggest that when a patient presents with symptoms suggesting a diffuse or multi-focal process rather than a localized entrapment, magnetic resonance neurography may offer a more comprehensive assessment of the peripheral nervous system by capturing a wider field of view in a single examination.
The Specific Utility of High-Resolution Ultrasound
While magnetic resonance neurography demonstrated a broader diagnostic reach in this cohort, high-resolution nerve ultrasound remained the superior modality in a specific subset of patients. Out of the 275 cases where one imaging method provided additional diagnostic information over the other, high-resolution nerve ultrasound provided additional diagnostic value in 14 cases, which represents 5.1% of that subgroup. This finding indicates that while ultrasound may not be the primary driver of new diagnostic information in complex or proximal cases, it retains a critical role in the clinical workup of peripheral neuropathies when specific technical barriers interfere with magnetic resonance imaging. The primary clinical scenario where high-resolution nerve ultrasound proved more effective than magnetic resonance neurography was in the presence of metal artifacts (distortions in magnetic resonance images caused by metallic implants such as surgical plates, screws, or joint replacements). These artifacts can obscure the signal from adjacent neural structures, rendering magnetic resonance neurography non-diagnostic or less precise in the immediate vicinity of the hardware. The researchers found that high-resolution nerve ultrasound added diagnostic value primarily when magnetic resonance neurography was limited by these metal artifacts. For the practicing clinician, this suggests that ultrasound should be the preferred initial imaging choice or a necessary secondary study for patients with suspected neuropathies located near orthopedic hardware, where the acoustic properties of ultrasound allow for nerve visualization that is not compromised by the magnetic susceptibility of the metal.
References
1. Mangi MD, Zadow S, Lim W. Nerve entrapment syndromes of the upper limb: a pictorial review. Insights into Imaging. 2022. doi:10.1186/s13244-022-01305-5
2. Jones MR, Prabhakar A, Viswanath O, et al. Thoracic Outlet Syndrome: A Comprehensive Review of Pathophysiology, Diagnosis, and Treatment. Pain and Therapy. 2019. doi:10.1007/s40122-019-0124-2
3. Tozza S, Cassano E, Erra C, Muto M, Habetswallner F, Manganelli F. Role of Imaging in Chronic Inflammatory Demyelinating Polyneuropathy: A Systematic Review. European Journal of Neurology. 2025. doi:10.1111/ene.70226
4. Drăghici NC, Văcăraș V, Bolchis R, et al. Diagnostic Approach to Lower Limb Entrapment Neuropathies: A Narrative Literature Review. Diagnostics. 2023. doi:10.3390/diagnostics13213385
5. Boers N, Hahn B, Eligh AM, Jongen IC, Rinkel WD, Coert J. Peripheral nerve enlargement in patients with diabetic sensorimotor polyneuropathy: A systematic review and meta-analysis. Diabetes Research and Clinical Practice. 2026. doi:10.1016/j.diabres.2026.113226
6. Rojoa D, Raheman F, Rassam J, Wade RG. Meta-analysis of the normal diffusion tensor imaging values of the median nerve and how they change in carpal tunnel syndrome. Scientific Reports. 2021. doi:10.1038/s41598-021-00353-z
7. Brunnée M, Foesleitner O, Kirchner M, et al. High-resolution ultrasound vs. MR neurography in upper extremity neuropathies: exploratory analysis of perceived additional diagnostic value in routine clinical practice.. European radiology. 2026. doi:10.1007/s00330-026-12545-0
