Diffusion-weighted MR imaging in chronic non-bacterial osteitis: Proof-of-concept of the apparent diffusion coefficient as an outcome measure.

BACKGROUND: The apparent diffusion coefficient (ADC), as determined by whole-body diffusion-weighted MRI, may be useful as an outcome measure for monitoring response to treatment in chronic non-bacterial osteitis. PURPOSE: To test and demonstrate the feasibility of ADC-measurement methods for use as outcome measure in chronic non-bacterial osteitis. MATERIALS AND METHODS: Using data from a randomized pilot study, feasibility of change-score ADC between baseline and second MRI (ΔADC12) and third MRI (ΔADC13) as outcome measure was assessed in three settings: "whole-lesion," "single-slice per lesion," and "index-lesion per patient". Bone marrow edema lesions were depicted on short tau inversion recovery sequence at baseline and copied to ADC maps at the three time-points. Correlations between the three settings were measured as were analysis of variances. Discriminant validity was assessed as inter- and intra-observer reproducibility and smallest detectable change. RESULTS: 12 subjects were enrolled, and MRI was performed at baseline and weeks 12 and 36. Pearson correlation was high (r > 0.86; p ≤ 0.01) for ΔADC between single-slice-whole-lesion and whole-lesion-index-lesion and tended to be significant for single-slice-index-lesion settings (p = 0.06). For ΔADC12 and ΔADC13, Bland-Altman plots showed small differences (0.02, 0.03) and narrow 95% limits-of-agreement (-0.13-0.09, -0.07-0.05 µm2/s) between whole-lesion and single-slice ROI settings. Inter-observer reproducibility measured by intra-class correlation coefficient was poor-to-fair (range: 0.09-0.31), whereas intra-observer reproducibility was good-to-excellent (range: 0.67-0.90). Smallest detectable changes were between 0.21-0.28 µm2/s. CONCLUSION: ADC change-score as outcome measure was feasible, and the single-slice per lesion ROI setting performed almost equally to whole-lesion setting resulting in reduced assessment time.

[Pompe disease is a differential diagnosis in case of reduced physical capacity and abnormal muscular fatigue].

Late-onset Pompe disease is an inherited metabolic myopathy with low activity of alpha glucosidase and variable clinical symptoms. In this case report we describe a woman with long standing muscular fatigue and malaise with the diagnosis initially established by pathologic findings in the muscle biopsy. Enzyme replacement therapy is now a treatment option, and a prompt diagnosis is therefore relevant. This disease should be considered in patients with unexplained fatigue and reduced physical capacity, especially in case of concurrent elevated levels of creatine kinase and liver enzymes.