Advanced imaging of melorheostosis with emphasis on MRI

Objective. To describe the CT and MR imaging appearance of both osseous and extraosseous manifestations of melorheostosis. Design and patients. We retrospectively reviewed the CT (n=7) and/or MR ima ging findings (n=12) of 17 patients with characteristic radiographic findin gs of melorheostosis (undulating cortical hyperostosis with marked uptake o n radionuclide bone scintigraphy). Results. CT and MR imaging revealed cortical hyperostosis as high attenuati on and low signal intensity on all MR pulse sequences, respectively. Encroa chment on the marrow space was seen in all cases resulting from endosteal i nvolvement. Thirteen patients demonstrated 14 soft tissue masses with infil trative margins in 80% of cases and seven showed extensive mineralization o n CT or MR imaging (low intensity on all pulse sequences). Seven soft tissu e masses were predominantly nonmineralized with intermediate signal intensi ty on T1-weighted and intermediate to high signal on T2-weighted MR images corresponding to vascularized fibrous tissue with variable collagen content pathologically. Enhancement after intravenous gadolinium was seen in all p atients imaged with soft tissue masses (n=2). Two patients demonstrated mus cle atrophy resulting from nerve involvement. Conclusions. The osseous abnormalities in melorheostosis are identical on a dvanced imaging and radiographs. Mineralized or nonmineralized soft tissue masses should be recognized as another manifestation of this disease as opp osed to a more ominous finding, making biopsy unwarrranted.