Philipp Bäumer

Ulnar Neuropathy at the Elbow: MR Neurography—Nerve T2 Signal Increase and Caliber

PURPOSE To assess nerve T2 signal and caliber as diagnostic signs at magnetic resonance (MR) neurography in ulnar neuropathy at the elbow (UNE). MATERIALS AND METHODS This prospective study was approved by the institutional review board, and written informed consent was obtained from all participants. Twenty patients with UNE were graded by using clinical criteria and nerve conduction studies as mild (n = 12) and severe (n = 8) and were compared with 20 healthy control subjects. All subjects underwent ulnar nerve MR neurography (in-plane resolution of 0.4 × 0.4 mm) covering the elbow region, including T2-weighted imaging with fat suppression (turbo inversion-recovery magnitude sequence: repetition time msec/echo time msec/inversion time msec, 6, 120/66/180) and T1-weighted turbo spin-echo imaging (843/16). Nerve T2 signal increase, measured by using T2-weighted contrast-to-noise ratios across the cubital tunnel, and nerve caliber, determined by using T1-weighted pixelwise measurement of cross-sectional nerve area, were evaluated as diagnostic signs. Qualitative assessment by using visual grading was performed additionally. RESULTS Diagnostic performance, as determined with area under the receiver operating characteristic curve (AUC), was excellent for nerve T2 signal to discriminate UNE from a normal finding (AUC = 0.94; 95% confidence interval [CI]: 0.87, 1.00) and was excellent for nerve caliber to discriminate severe from mild UNE (AUC = 0.95; 95% CI: 0.85, 1.00). Qualitative assessment demonstrated sensitivity of 83% and specificity of 85% for MR neurography of UNE. CONCLUSION Nerve T2 signal increase seems to be an accurate sign to determine the presence of UNE. Nerve caliber enlargement discriminates severe from mild UNE. UNE may be diagnosed with high accuracy by means of quantitative or qualitative evaluation of these signs.

Anterior interosseous nerve syndrome Fascicular motor lesions of median nerve trunk

Objective: We sought to determine lesion sites and spatial lesion patterns in spontaneous anterior interosseous nerve syndrome (AINS) with high-resolution magnetic resonance neurography (MRN). Methods: In 20 patients with AINS and 20 age- and sex-matched controls, MRN of median nerve fascicles was performed at 3T with large longitudinal anatomical coverage (upper arm/elbow/forearm): 135 contiguous axial slices (T2-weighted: echo time/repetition time 52/7,020 ms, time of acquisition: 15 minutes 48 seconds, in-plane resolution: 0.25 × 0.25 mm). Lesion classification was performed by visual inspection and by quantitative analysis of normalized T2 signal after segmentation of median nerve voxels. Results: In all patients and no controls, T2 lesions of individual fascicles were observed within upper arm median nerve trunk and strictly followed a somatotopic/internal topography: affected were those motor fascicles that will form the anterior interosseous nerve further distally while other fascicles were spared. Predominant lesion focus was at a mean distance of 14.6 ± 5.4 cm proximal to the humeroradial joint. Discriminative power of quantitative T2 signal analysis and of qualitative lesion rating was high, with 100% sensitivity and 100% specificity (p < 0.0001). Fascicular T2 lesion patterns were rated as multifocal (n = 17), monofocal (n = 2), or indeterminate (n = 1) by 2 independent observers with strong agreement (kappa = 0.83). Conclusion: It has been difficult to prove the existence of fascicular/partial nerve lesions in spontaneous neuropathies using clinical and electrophysiologic findings. With MRN, fascicular lesions with strict somatotopic organization were observed in upper arm median nerve trunks of patients with AINS. Our data strongly support that AINS in the majority of cases is not a surgically treatable entrapment neuropathy but a multifocal mononeuropathy selectively involving, within the main trunk of the median nerve, the motor fascicles that continue distally to form the anterior interosseous nerve.

Relevance of T2 signal changes in the assessment of progression of glioblastoma according to the Response Assessment in Neurooncology criteria

BACKGROUND According to the Response Assessment in Neurooncology (RANO) criteria, significant nonenhancing signal increase in T2-weighted images qualifies for progression in high-grade glioma (T2-progress), even if there is no change in the contrast-enhancing tumor portion. The purpose of this retrospective study was to assess the frequency of isolated T2-progress and its predictive value on subsequent T1-progress, as determined by a T2 signal increase of 15% or 25%, respectively. The frequency of T2-progress was correlated with antiangiogenic therapy. PATIENTS AND METHODS MRI follow-up examinations (n = 777) of 144 patients with histologically proven glioblastoma were assessed for contrast-enhanced T1 and T2-weighted images. Examinations were classified as T1-progress, T2-progress with 15% or 25% T2-signal increase, stable disease, or partial or complete response. RESULTS Thirty-five examinations revealed exclusive T2-progress using the 15% criterion, and only 2 examinations qualified for the 25% criterion; 61.8% of the scans presenting T2-progress and 31.5% of the scans presenting stable disease revealed T1-progress in the next follow-up examination. The χ(2) test showed a highly significant correlation (P < .001) between T2-progress, with the 15% criterion and subsequent T1-progress. No correlation between antiangiogenic therapy and T2-progress was shown. CONCLUSION Tumor progression, as determined by both contrast-enhanced T1 and T2 sequences is more frequently diagnosed than when considering only contrast-enhanced T1 sequences. Definition of T2-progress by a 15% T2-signal increase criterion is superior to a 25% criterion. The missing correlation of T2-progress and antiangiogenic therapy supports the hypothesis of T2-progress as part of the natural course of the tumor disease.

Pseudoprogression in patients with glioblastoma: clinical relevance despite low incidence

BACKGROUND According to the Response Assessment in Neuro-Oncology criteria, new enhancement within the radiation field on contrast enhanced T1-weighted images within 12 weeks after completion of radiotherapy should not qualify for progressive disease, since up to 50% of these cases may be pseudoprogression (PsP). To validate this concept, we assessed incidence and overall survival (OS) of patients with suspected and confirmed PsP dependent on different time intervals and definitions of PsP. METHODS Patients with newly diagnosed glioblastoma and an enhancement increase of at least 25% after completion of standard radiochemotherapy at month 1, 4, 7, or 10 were eligible. Based on the development of the enhancement in follow-up examinations, patients were categorized as either PsP (subgrouped as complete resolution/decrease >50% and decrease <50%/stable) or true progression. RESULTS Out of 548 patients, 79 fulfilled the inclusion criteria. Of these 79 patients, 9 (11.4%) showed PsP (6/45 patients at 1 month, 2/17 at 4 months, 1/9 at 7 months, and 0/8 at 10 months). Complete resolution of the enhancement was found in 1, decrease >50% in 3, decrease <50% in 2, and stable enhancement in 3 patients with PsP. Patients with PsP showed a significantly longer OS (P < .012). No difference in OS was found among PsP subgroups. CONCLUSIONS This series challenges the current concept of PsP. Even though we could confirm a prolonged OS of patients with PsP, the incidence of PsP was lower than reported previously and extended beyond 12 weeks.

Proximal Neuropathic Lesions in Distal Symmetric Diabetic Polyneuropathy Findings of high-resolution magnetic resonance neurography

OBJECTIVE This study investigated high-resolution magnetic resonance neurography (MRN) in distal symmetric diabetic polyneuropathy (dPNP). RESEARCH DESIGN AND METHODS MRN comprised high-resolution transaxial imaging of peripheral nerves of the lower limbs in 20 patients with type 2 diabetes (10 with dPNP, type 2/dPNP[+], and 10 without dPNP, type 2/dPNP[−]), seven patients with type 1 diabetes (two with dPNP, type 1/dPNP[+], five without dPNP, type 1/dPNP[−]), and 10 nondiabetic control subjects. Intraneural T2 lesions, as the main diagnostic criterion of MRN, were detected visually by two independent observers and quantitatively by analysis of T2 contrast ratios. RESULTS Multifocal fascicular, symmetric intraneural T2 lesions occurred in the proximal trunks of sciatic nerves in four patients (three with type 2/dPNP[+] and one with type 1/dPNP[+]) but not in control subjects (type 2/dPNP[−], type 1/dPNP[−], nondiabetic control subjects), which was confirmed by quantitative analysis. Clinical severity was higher in patients with T2 lesions (neuropathy deficit score: 10 vs. 7.8; P = 0.05). CONCLUSIONS For the first time, proximal neuropathic lesions of dPNP are reported in vivo. This supports that accumulation of proximal, multifocal fascicular injury may be important in disease progression.

Thoracic outlet syndrome in 3T MR neurography—fibrous bands causing discernible lesions of the lower brachial plexus

ObjectivesTo investigate whether targeted magnetic resonance neurography (MRN) of the brachial plexus can visualise fibrous bands compressing the brachial plexus and directly detect injury in plexus nerve fascicles.MethodsHigh-resolution MRN was employed in 30 patients with clinical suspicion of either true neurogenic thoracic outlet syndrome (TOS) or non-specific TOS. The protocol for the brachial plexus included a SPACE (3D turbo spin echo with variable flip angle) STIR (short tau inversion recovery), a sagittal-oblique T2-weighted (T2W) SPAIR (spectral adiabatic inversion recovery) and a 3D PDW (proton density weighted) SPACE. Images were evaluated for anatomical anomalies compressing the brachial plexus and for abnormal T2W signal within plexus elements. Patients with abnormal MR imaging findings underwent surgical exploration.ResultsSeven out of 30 patients were identified with unambiguous morphological correlates of TOS. These were verified by surgical exploration. Correlates included fibrous bands (n = 5) and pseudarthrosis or synostosis of ribs (n = 2). Increased T2W signal was detected within compressed plexus portion (C8 spinal nerve, inferior trunk, or medial cord) and confirmed the diagnosis.ConclusionsThe clinical suspicion of TOS can be diagnostically confirmed by MRN. Entrapment of plexus structures by subtle anatomical anomalies such as fibrous bands can be visualised and relevant compression can be confirmed by increased T2W signal of compromised plexus elements.Key Points• MR neurography (MRN) can aid the diagnosis of thoracic outlet syndrome (TOS).• Identifiable causes of TOS in MRN include fibrous bands and bony anomalies.• Increased T2W signal within brachial plexus elements indicate relevant nerve compression.• High positive predictive value allows confident and targeted indication for surgery.

Peripheral Neuropathy: Detection with Diffusion-Tensor Imaging

PURPOSE To investigate the ability of diffusion-tensor imaging (DTI) and T2 to help detect the mildest nerve lesion conceivable, that is, subclinical ulnar neuropathy at the elbow. MATERIALS AND METHODS This prospective study was approved by the institutional ethics board. Written informed consent was obtained from all participants. Magnetic resonance neurography was performed at 3.0 T by using proton density- and T2-weighted relaxometry and DTI on elbows in 30 healthy subjects without clinical evidence of neuropathy. Quantitative analysis of ulnar nerve T2 and fractional anisotropy (FA) was performed, and T2 and FA values were correlated to electrical nerve conduction velocities (NCVs) with Pearson correlation analysis. Additional qualitative assessment of T2-weighted and FA images was performed by two readers, and sensitivity and specificity were calculated. RESULTS Ten of the 30 subjects (33%) had NCV slowing across the elbow segment. Compared with subjects without NCV slowing, subjects with slowing had decreased FA values (0.51 ± 0.09 vs 0.41 ± 0.07, respectively; P = .006) and increased T2 values (64.2 msec ± 10.9 vs 76.2 msec ± 13.7, respectively; P = .01) in the proximal ulnar sulcus. FA values showed a significant correlation (P = .01) with NCV slowing over the sulcus as an electrophysiologic indicator of myelin sheath damage. Qualitative assessment of FA maps and T2-weighted images helped identify subjects with conduction slowing with a sensitivity of 80% and 55%, respectively, and a specificity of 83% and 63%. CONCLUSION FA maps can accurately depict even mild peripheral neuropathy and perform better than the current standard of reference, T2-weighted images. DTI may therefore add diagnostic value as a highly sensitive technique for the detection of peripheral neuropathy.

Diffusion Tensor Imaging Adds Diagnostic Accuracy in Magnetic Resonance Neurography.

ObjectiveThe aim of this study was to determine whether quantitative diffusion tensor imaging (DTI) adds diagnostic accuracy in magnetic resonance neurography. Materials and MethodsThis prospective study was approved by the institutional review board. We enrolled 16 patients with peripheral polyneuropathy of various etiologies involving the upper arm and 30 healthy controls. Magnetic resonance neurography was performed at 3 T using transverse T2-weighted (T2-w) turbo spin echo and spin echo planar imaging diffusion-weighted sequences. T2-weighted normalized signal (nT2), fractional anisotropy (FA), apparent diffusion coefficient (ADC), radial diffusivity (RD), and axial diffusivity (AD) of the median, ulnar, and radial nerves were quantified after manual segmentation. Diagnostic performance of each separate parameter and combinations of parameters was assessed using the area under the receiver operating characteristic curve (AUC). Bootstrap validation was used to adjust for potential overfitting. ResultsAverage nT2, ADC, RD, and AD values of the median, ulnar, and radial nerve were significantly increased in neuropathy patients compared with that in healthy controls (nT2, 1.49 ± 0.05 vs 1.05 ± 0.05; ADC, 1.4 × 10−3 ± 2.8 × 10−5 mm2/s vs 1.1 × 10−3 ± 1.3 × 10−5 mm2/s; RD, 9.5 × 10−4 ± 2.9 × 10−5 mm2/s vs 7.2 × 10−4 ± 1.3 × 10−5 mm2/s; AD, 2.3 × 10−3 ± 3.7 × 10−5 mm2/s vs 2.0 × 10−3 ± 2.2 × 10−5 mm2/s; P < 0.001 for all comparisons). Fractional anisotropy values were significantly decreased in patients (0.51 ± 0.01 vs 0.59 ± 0.01; P < 0.001). T2-weighted normalized signal and DTI parameters had comparable diagnostic accuracy (adjusted AUC: T2-w, 0.92; FA, 0.88; ADC, 0.89; AD, 0.84; RD, 0.86). Combining DTI parameters significantly improved the diagnostic accuracy over single-parameter analysis. In addition, the combination of nT2 with DTI parameters yielded excellent adjusted AUCs up to 0.97 (nT2 + FA). ConclusionsDiffusion tensor imaging has high diagnostic accuracy in peripheral neuropathy. Combining DTI with T2 can outperform T2-w imaging alone and provides added value in magnetic resonance neurography.

Differentiation of glioblastoma and primary CNS lymphomas using susceptibility weighted imaging

INTRODUCTION Reliable differentiation between glioblastoma and primary CNS lymphoma (PCNSL) using conventional MR imaging is challenging, since both entities may show similar appearance on structural MR imaging. Here we analyzed if the appearance of intratumoural susceptibility signals (ITSS) on susceptibility weighted imaging (SWI) may differentiate between both entities. METHODS AND MATERIALS SWI and contrast enhanced T1-weighted images were acquired from 15 patients with newly diagnosed PCNSL (14 B-cell PCNSL, 1 T-cell PCNSL) and 117 patients with newly diagnosed glioblastoma with a 3 Tesla MR. Additional phase images were available in 8 patients with PCNSL and 88 patients with glioblastoma. Appearance of ITSS was assessed by two readers on SWI and the size of the enhancing lesions on contrast enhanced T1-weighted images were measured. Furthermore it was assessed if ITSS displayed more clearly on SWI or on phase images. RESULTS ITSS were detected in 106 (reader 1) and 109 (reader 2) glioblastoma, respectively. Both readers identified ITSS within the T-cell PCNSL while both readers did not identify any ITSS within the 14 Bcell PCNSL. Interrarter variability as determined by Cohen κ was excellent for glioblastoma (κ=0.938) and for PCNSL (κ=1). The medium size of the enhancing lesion of the glioblastoma that did not harbour ITSS was significantly smaller than the size of the glioblastoma exhibiting ITSS (p<0.008). All identified ITSS displayed more clearly on SWI than on phase images. CONCLUSION Presence of ITSS differentiates reliably between glioblastoma and B-cell PCNSL and provides a fast bases for the clinical decision without causing any postprocessing work.

Magic Angle Effect: A Relevant Artifact in MR Neurography at 3T?

BACKGROUND AND PURPOSE: MRN is an emerging diagnostic method for disorders of peripheral nerves. However, it is unclear whether the influence of the MA on intraneural T2 signal is severe enough to provoke false-positive findings. MATERIALS AND METHODS: Twenty-five healthy subjects underwent MRN of the sciatic nerve of the proximal thigh at 3T. The T2app was calculated from a DE-TSE sequence (TR = 3000 ms, TE1 = 12 ms, TE2 = 69 ms) at 7 angles of the sciatic nerve relative to B0 = 0°, 30°, 35°, 40°, 45°, 50°, and 55°. Precise angle adjustments were performed with a dedicated in-bore positioning aid. Qualitative evaluation of intraneural T2-weighted contrast between this group of healthy subjects and 14 patients with neuropathic lesions was performed by comparing CNRs of a TIRM sequence (TR = 5000 ms, TE = 76 ms, TI = 180 ms). RESULTS: In healthy subjects, the prolongation of T2app from 0° to 55° was from 74.5 ± 13.4 to 104.0 ± 16.9 ms (P < .001). The increase in T2app relative to baseline (0°) was 9.6% (30°), 18.4% (35°), 25% (40°), 27.6% (45°), and 37% (55°). Intraneural CNR increased by 1.98 ± 0.69 at 40° and 2.93 ± 0.46 at 55°. Nevertheless, the mean CNR of healthy subjects was substantially lower than that in patients at 40° (P < .0001) and even at the position of maximum MA (55°: 20.6 ± 5.11 versus 52.6 ± 7.12, P < .0001). CONCLUSIONS: Neuropathic lesions are clearly distinguishable from an artificial increase of intraneural T2 by the MA. Even at a maximum MA (55°), the false-positive determination of a neuropathic lesion is unlikely.