Five different types of lesions can be identified by MRI of individuals with cavernous malformations (20, 70).
- Type Ia: “Overt” subacute focus of hemorrhage extending outside the lesion capsule of hemosiderin-stained gliotic brain. T1-weighted images show a hyperintense focus of hematoma. T2-weighted images have a hyper- or hypointense core with a surrounding hypointense rim. There is subacute hemorrhage in the lesion. Focal edema may be present.
- Type Ib: Subacute focus of hematoma surrounded by a rim of hemosiderin-stained macrophage and gliotic brain. The T1-weighted image shows a hypointense focus of hematoma, while the T2-weighted image shows a hyper- or hypointense focus of hematoma surrounded by a hypointense rim.
- Type II: Loculated area of hematoma and thrombosis of varying ages surrounded by gliotic, hemosiderin-stained brain. In large lesions, areas of calcification may be seen. The T1-weighted MRI demonstrates a lesion with a reticulated mixed signal core. The T2-weighted image shows a reticulated mixed signal core surrounded by a hypointense rim.
- Type III: Chronic resolved hemorrhage with residual hemosiderin staining in and around the cavernous malformation. The T1-weighted MRI shows a lesion that is iso- or hypointense and the T2-weighted MRI demonstrates a lesion that is hypointense with a hypointense rim that magnifies the size of lesion. The GRE image of the lesion shows it to be hypointense with greater magnification than the T2-weighted image.
- Type IV: Two lesions designated as type IV have been described in the literature. (20, 70) Pathological examination documented them to be telangiectasias. They were poorly seen or not visualized at all on T1-weighted and T2-weighted MRIs. GRE MRIs show punctate hypointense lesions (20, 70).
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