[Circumscribed myositis ossificans: bone changes detected by MRI]. / Myosite ossifiante circonscrite: remaniements osseux décelés en IRM.

The authors report a case of ossificans myositis, in which MRI showed inflammatory changes of the adjacent bone. T1 weighted fat saturation sequence with gadolinium injection showed enhancement of medullary and cortical bone. This potentially mistaking pattern must be known, to avoid misdiagnosing with malignant osseous tumor, specially before achievement of the characteristic pattern of zonal maturation and its calcified rim.

[Dental-radicular cysts invading the maxillary sinus]. / Kystes radiculodentaires à expression sinusienne.

The authors report three cases of radicular cyst developing into the maxillary sinus which was partially or completely obscured. Looking for a thin rim of cortical bone should be undertaken in case of opacity of maxillary sinus. This rim correspond to the floor of the sinus, which is lifted up by the cyst. If the attenuation value of the intrasinusal process is near of that of water, the diagnosis of radicular cyst invading the maxillary sinus is very likely and may indicate intraoral surgical approach.

[Rhabdomyolysis and truncular sciatica. 2 cases studied by MRI]. / Rhabdomyolyse et sciatique tronculaire. Deux cas étudiés en IRM.

We report two cases of acute rhabdomyolysis in pelvic girdle muscles with sciatic palsy secondary to compression of the sciatic nerve trunk, with clinical and MRI correlation. The diagnosis of rhabdomyolysis is based on clinical and biological data, but diagnosis of compression complications secondary to swelling of the muscles, especially the compression of nerve trunk, is done by imaging. T2 weighted images give a definite anatomical evaluation. They show enlarged high signal intensity muscles and anatomic relationship with the sciatic nerve from its emergence out of pelvis, giving a good correlation between rhabdomyolysis and the compressed nervous trunk. It helps for planning a possible surgical fasciotomy. However, MRI provides only morphological informations, but not differentiates edema from necrosis in involved muscles.

[Myxoid liposarcoma. MRI imaging]. / Liposarcome myxoïde. Aspects en IRM.

PURPOSE: Myxoid liposarcoma is the most common type of liposarcoma (approximately 40 to 50% of all liposarcomas). The main tissue component is a myxoid matrix present primarily in extracellular compartments; proliferating lipoblasts account for less 10% of the tumor: MRI appearances are not typical for lipomatous tumor. Nevertheless histological features may permit understanding MRI findings and identifying patients with myxoid liposarcoma. MATERIALS AND METHODS: Clinical history and radiologic images of 7 patients with histologically verified myxoid liposarcoma were retrospectively studied. In all patients the tumor presented in a lower extremity as a painless, slowly growing mass. MR images were available for review in all cases (T1- and T2-weighted images); in addition fat-suppression before and after gadolinium enhancement were assessed with T1-weighted sequences. RESULTS: MRI examination revealed an "encapsulated" tumor, non infiltrating and septated. On T1-weighted sequences all the lesions show lacy, amorphous and linear foci of high signal within a low signal of the tumor due to the predominance of a myxoid matrix. The high sensitivity of MRI demonstrates the presence of small areas of high signal and fat-suppression technique is valuable for characterizing soft-tissue tumors: suppression of high signal intensity on fat-saturated T1-weighted images indicates the presence of fatty tissue components. CONCLUSION: Clinical correlation with MRI appearances on T1-weighted sequences (in addition to fat-suppression technique) may suggest the possibility of myxoid liposarcoma.