PURPOSE: To describe the MR findings for the three phases of eosinophilic granuloma, as defined by Mirra 'sconventional radiographic criteria. MATERIALS AND METHODS: Eighteen lesions in 14 patients with proveneosinophilic granuloma were retrospectively analyzed. Among this total, three vertebral lesions were excluded,and the remaining is were classified as early, middle, or late phase on the basis of Mirra's radiographiccriteria. For each phase, we compared MR findings with regard to signal intensity, homogeneity, contrastenhancement, perilesional marrow edema, and soft tissue change. For the three vertebral lesions excluded becausethe application of radiographic criteria was difficult, MR findings for paravertebral soft tissue reaction anddegree of cord compression were compared. RESULTS: Of the fifteen cases classified, eight were early phase, fivewere mid phase, and two were late phase. During each phase, all lesions except one, as seen on T1-weightedimages(T1W1), showed iso-signal intensity. On T2WI, all lesions showed high signal intensity. Contrast studydemonstrated marked contrast enhancement. Thus, no remarkable differences were found in the signal intensitydegree of contrast enhancement of each phase. With regard to heterogeneity, this was demonstrated in most earlyphase lesions, reflecting necrosis and hemorrhage of those lesions. Soft tissue swelling was more severe duringthe early phase than the mid or late phase, but marrow edema was similar in each of the three phase. One of threepatients with vertebra plana showed para-vertebral soft tissue swelling and cord compression, but this was notseen in the two other cases. CONCLUSION: For evalvating the extent of eosinophilic granuloma and its relationshipwith surrounding structures, MRI was superior to conventional radiography. During the early phase of the disease,lesions showed greater inhomogeneity and more aggressive soft tissue reaction than during the mid and late phase.The use of MRI for the evalvation of eosinophilic granuloma can help decide a therapeutic plan of action andfollow up evaluation.
Bone Marrow ; Edema ; Eosinophilic Granuloma* ; Eosinophils* ; Granuloma ; Hemorrhage ; Histiocytosis ; Humans ; Magnetic Resonance Imaging ; Necrosis ; Population Characteristics ; Radiography ; Retrospective Studies ; Spine