MR imaging of myositis ossificans: Variable patterns at different stages

Abstract

Five patients with a palpable mass at presentation underwent magnetic resonance (MR) imaging. The final diagnosis was myositis ossificans (MO). MR imaging features, particularly after injection of gadopentetate dimeglumine, mimicked those of an inflammatory mass or neoplasm. The lesions were excised in three patients, and the images were correlated with histologic findings. Three different appearances were noted on MR images, corresponding to the stages of maturation of MO. Two cases involved early-stage lesions, and T1-weighted MR images showed a mass with homogeneous intermediate signal intensity. Both lesions showed rim enhancement after contrast agent injection and high signal intensity on T2-weighted images. Pathologic specimens demonstrated stroma with masses of spindle cells in which osteoid production was interspersed. The enhanced rim of the lesion mimicked the expected MR appearance of an abscess or necrotic tumor. Areas of enhancement in adjacent muscle were also seen on postcontrast T1-weighted images. Intermediate-stage MO was present in one case; there was evidence of a thin rim of calcification on plain radiographs and fatty changes in the lesion on T1-weighted images, corresponding with histologic findings. One case of a mature lesion showed a considerable degree of peripheral calcification both on MR images and at histology. MR imaging is nonspecific in the diagnosis of early-stage MO.

Magnetic resonance signal alterations in the acute onset of heterotopic ossification in patients with spinal cord injury

“…Early-stage lesions of myositis ossificans have been reported to display extensive muscle edema [23] with areas similar to our nonenhancing regions with a focal hyperintense signal [24][25][26] on T2-weighted images, rim enhancement [23,24] and a zonal architecture resembling our observations [26,27]. Adjacent bone marrow edema and joint effusion have also been described [23].…”

Myositis Ossificans of the Temporal Muscle as a Primary Scalp Tumor-Case Report-

“…In the early stage, the lesion is usually isointense on T 1 -weighted and hyperintense on T 2 -weighted images. 6,7) The signal intensity may change depending on the blood products. Surrounding edema and heterogeneous enhancement are also seen.…”

“…6,7) The initial management of myositis ossificans depends on the stage of development. 1,7) Myositis ossificans circumscripta is usually treated conservatively.…”

MR Imaging of Muscle Trauma: Anatomy, Biomechanics, Pathophysiology, and Imaging Appearance

“…Immature lesions may be intensely edematous and poorly defined, resembling an aggressive neoplasm, or may have a thick enhancing rim, mimicking an abscess (79). Intermediate lesions exhibit a predominantly cellular core of active fibroblasts, resembling nodular fasciitis (80), before developing betterdefined margins and faint marginal calcifications, typically 2-4 weeks after injury.…”

“…Intermediate lesions exhibit a predominantly cellular core of active fibroblasts, resembling nodular fasciitis (80), before developing betterdefined margins and faint marginal calcifications, typically 2-4 weeks after injury. Such early calcifications are difficult to appreciate at MR imaging and are best demonstrated at CT (79).…”