MR Neurography in Ulnar Neuropathy as Surrogate Parameter for the Presence of Disseminated Neuropathy

Abstract

PurposePatients with ulnar neuropathy of unclear etiology occasionally present with lesion extension from elbow to upper arm level on MRI. This study investigated whether MRI thereby distinguishes multifocal neuropathy from focal-compressive neuropathy at the elbow.MethodsThis prospective study was approved by the institutional ethics committee and written informed consent was obtained from all participants. 122 patients with ulnar mononeuropathy of undetermined localization and etiology by clinical and electrophysiological examination were assessed by MRI at upper arm and elbow level using T2-weighted fat-saturated sequences at 3T. Twenty-one patients were identified with proximal ulnar nerve lesions and evaluated for findings suggestive of disseminated neuropathy (i) subclinical lesions in other nerves, (ii) unfavorable outcome after previous decompressive elbow surgery, and (iii) subsequent diagnosis of inflammatory or other disseminated neuropathy. Two groups served as controls for quantitative analysis of nerve-to-muscle signal intensity ratios: 20 subjects with typical focal ulnar neuropathy at the elbow and 20 healthy subjects.ResultsIn the group of 21 patients with proximal ulnar nerve lesion extension, T2-w ulnar nerve signal was significantly (p<0.001) higher at upper arm level than in both control groups. A cut-off value of 1.92 for maximum nerve-to-muscle signal intensity ratio was found to be sensitive (86%) and specific (100%) to discriminate this group. Ten patients (48%) exhibited additional T2-w lesions in the median and/or radial nerve. Another ten (48%) had previously undergone elbow surgery without satisfying outcome. Clinical follow-up was available in 15 (71%) and revealed definitive diagnoses of multifocal neuropathy of various etiologies in four patients. In another eight, diagnoses could not yet be considered definitive but were consistent with multifocal neuropathy.ConclusionProximal ulnar nerve T2 lesions at upper arm level are detected by MRI and indicate the presence of a non-focal disseminated neuropathy instead of a focal compressive neuropathy.

Diffusion Tensor Imaging Adds Diagnostic Accuracy in Magnetic Resonance Neurography

“…In addition, neuropathy of the upper extremity can have severe debilitating effects that account for the high morbidity of the disease. 7,34 Diagnosis remains a challenge and is mainly based on clinical and electrophysiological signs, the latter being particularly difficult to be performed and evaluated at proximal extremity sites. We hypothesized that MRN and specifically DTI could be an additional diagnostic tool.…”

“…3 In imaging studies, T2-weighted (T2-w) imaging is currently the criterion standard for lesion detection and allows the assessment of spatial distribution and severity with good sensitivity and specificity. 2,3,7 Recent developments of MRN include more sophisticated "functional" imaging methods that allow the assessment, for example, of the blood-nerve barrier and nerve perfusion imaging in vivo. 11 Diffusion tensor imaging (DTI) offers another innovative approach to probe the cellular pathophysiology of disease and microstructural alterations on fiber level.…”

Clinical impact of magnetic resonance neurography in patients with brachial plexus neuropathies

“…18 Diagnostic accuracy of MRN has been widely reported in literature. 8,[19][20][21] However, studies demonstrating the impact on clinical management and patient outcomes are limited. Andreisek et al 22 found moderate to major impact in the evaluation of the majority of upper extremity neuropathies (84%) with MRI.…”

MR Neurography: Diagnostic Imaging in the PNS

“…Even in 2006, Andreisek et al [27] found that the sensitivity and specificity of MR signs in CTS are low, and stated PNS disorders [16][17][18][19][20][21]. To achieve high structural resolution and visualization of nerve fascicles, high magnetic field strength of 3 T and fat-saturated 2D T2w sequences with an in-plane resolution of 0.1-0.4 × 0.1-0.4 mm and a slice thickness of 2-3.5 mm are required [21].…”

“…We will focus on findings of MRN in the most frequent entrapment neuropathies as examples for focal nerve lesions, and on distally-symmetric level as surrogate parameter for disseminated neuropathies [19].…”