The bone marrow is one of the largest organs in the body and is visible in every magnetic resonance (MR) imaging study. It is composed of a combination of hematopoietic red marrow and fatty yellow marrow, and its composition changes throughout life in response to normal maturation (red to yellow conversion) and stress (yellow to red reconversion). MR imaging is highly sensitive for detection of altered marrow signal intensity, and the T1-weighted spin-echo sequence provides the most robust contrast between yellow marrow and disease. Heterogeneous red marrow and red marrow hyperplasia can mimic marrow disease, but should be distinguished from neoplastic replacement (leukemia, lymphoma, primary bone sarcomas, hematogenous metastases) and expected posttreatment changes (radiation therapy, chemotherapy, colony-stimulating factor, bone marrow transplant). Nonneoplastic edema-like processes can also alter marrow signal intensity, including trauma, infection, inflammation (chronic recurrent multifocal osteomyelitis, juvenile inflammatory arthritis), altered biomechanics, and chronic regional pain syndrome. Unfortunately, MR imaging findings are often nonspecific and overlap among many of these vastly different causes. Therefore, a definitive diagnosis is reliant on a combination of imaging findings, clinical evaluation, laboratory assessment, and occasionally tissue analysis. RSNA, 2016.
Among children with medulloblastoma, surveillance scanning is of little clinical value. Scanning detected a minority of recurrences, and no patient who had a recurrence survived.
Sinus histiocytosis with massive lymphadenopathy was first described in 1969 by Rosai and Dorfman. The typical clinical characteristics of this disease include painless cervical lymphadenopathy, fever, and weight loss. The condition can present with an extranodal mass in about 25% of patients, and isolated masses without lymph node involvement occur rarely. The authors describe a 5-year-old boy with cavernous sinus syndrome due to an isolated extranodal form of sinus histiocytosis with massive lymphadenopathy in the temporal fossa. Several cases of this disease involving the central nervous system are reviewed. The histopathological and magnetic resonance imaging characteristics are discussed.
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