Asymptomatic Progressive Multifocal Leukoencephalopathy Associated with Natalizumab: Diagnostic Precision with MR Imaging.

PURPOSE: To determine diagnostic precision with magnetic resonance (MR) imaging of the brain, the most predictive MR imaging features, and the added value of comparison with previous data for the diagnosis of asymptomatic progressive multifocal leukoencephalopathy (PML) associated with natalizumab (NTZ). MATERIALS AND METHODS: This retrospective study was approved by the institutional review board, and written informed consent was obtained. Eleven consecutive patients with multiple sclerosis (MS) who had received a definitive diagnosis of asymptomatic NTZ-associated PML (NTZ PML, 18 brain lesions) underwent 3-T MR imaging. The control group included 40 patients with MS but without PML who were treated with NTZ. Three readers independently performed blinded analysis of MR images. First, the readers were asked to detect NTZ PML lesions without comparing current images with previously obtained MR imaging data by evaluating MR images for the following features: U fiber and/or cortex involvement, lesion signal intensity and borders, and occurrence of punctate lesions. Second, they reassessed NTZ PML lesions with all the previous MR imaging data available. Diagnostic precision with MR imaging was assessed with and without comparison with previously obtained data. Logistic regression analyses were performed to identify the association of MR imaging features with NTZ PML. RESULTS: Overall interobserver agreement was good (κ = 0.76; 95% confidence interval [CI]: 0.71, 0.81). Hyperintensity on diffusion-weighted images and involvement of U fibers were the most predictive features (odds ratio, 33.7; 95% CI: 4.9, 229.7 [P < .0001] and odds ratio, 8.7; 95% CI: 1.2, 61.4 [P = .03], respectively), while punctate lesions were exclusively observed in patients with NTZ PML. Comparison with previous MR imaging data improved specificity of MR imaging for the detection of NTZ PML lesions (from 88% to 100%, P = .05). CONCLUSION: Recognition of the most predictive imaging features and comparison with previous MR imaging data may facilitate the detection of asymptomatic NTZ PML.

Prospective evaluation of free-breathing diffusion-weighted imaging for the detection of inflammatory bowel disease with MR enterography in childhood population.

OBJECTIVE: To evaluate prospectively the performance of diffusion-weighted imaging (DWI) for the detection of active lesions on MR enterography (MRE) in children with inflammatory bowel disease (IBD). METHODS: MRE of 48 children (mean age 13 years) with suspected or known IBD were blindly analysed by 2 independent readers for the presence of active lesions. Two sets of imaging including DWI and gadolinium-enhanced imaging (GEI) were reviewed. A reader consensus was obtained. The gold standard was histopathological findings. In patient-level analysis and segment-level analysis, sensitivity and specificity were calculated for DWI and GEI and compared using McNemar's test or logistic random-effects models. RESULTS: At least 1 active lesion was confirmed in 42 (87.5%) children. Sensitivity and specificity for the detection of at least one lesion were 88.1% (95% CI, 74.3-96.1) and 83.3% (95% CI, 35.9-99.6), respectively, for DWI and 66.7% (95% CI, 50.4-80.4) and 83.3% (95% CI, 35.9-99.6), respectively, for GEI. In segment-level analysis, sensitivity and specificity for the detection of specific segment lesions were 62.5% (95% CI, 48.1-75) and 97.1% (95% CI, 93.5-98.7), respectively, for DWI and 45.7% (95% CI, 30.8-61.3) and 98.2% (95% CI, 95.3-99.4), respectively, for GEI. The sensitivity of DWI was significantly better than that of GEI per patient (p = 0.004) and per segment (p = 0.028). CONCLUSION: DWI demonstrates better performance than GEI for the detection of active lesions in children with IBD. ADVANCES IN KNOWLEDGE: Examination with no intravenous injection-DWI can replace T1 weighted images when paediatric patients are screened with MRE for IBD. Examination performed in free breathing is better tolerated by children.