MRI classification of cavernous malformations and correlation with pathology

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.

Axial CT of the brain showing a type 1a cavernous malformation: This image was obtained at the time of acute onset of headache. An acute hematoma is present in the right temporal lobe.
 
T2-weighted MRI of a type 1a cavernoma:
 

 

T1-weighted MRI of a type 1a cavernoma: This scan, taken 6 days after symptoms of a fresh hemorrhage, shows a hyperintense focus of hematoma.
 
Contrast-enhanced T1-weighted MRI of a type 1a cavernoma: Contrast-enhanced T1-weighted MRI of a type 1a cavernoma
 

 

 

  • 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.

 

Axial CT scan of a type 1b cavernous malformation: Shown is the brain at the acute onset of headache. An acute hematoma is present in the posterior pons.
 
T2-weighted axial MRI of a type 1b cavernous hematoma: The scan shows a hyperintense focus of hematoma surrounded by a hypointense rim.

T1-weighted MRI of a type 1b cavernous hematoma: The scan shows a hyperintense focus of hematoma.
 
T1-weighted MRI of a type 1b cavernous hematoma: There is obvious enhancement.

 

  • 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.

Axial CT scan of a type II cavernous malformation: The scan shows a heterogeneous, hyperdense lesion in the left pons of a 13-year-old boy who presented with progressive left-handed weakness.
 
Posteroanterior view of the skull (reconstruction from CT scan) showing a type II cavernous malformation:: The image shows a fleckless collection of calcification corresponding to the hyperdense focus seen on CT.

T1-weighted axial MRI of a type II cavernous malformation: The scan shows a reticular mixed signal core.
 
Contrast-enhanced T1-weighted axial MRI of a type II cavernous malformation: Contrast-enhanced T1-weighted axial MRI of a type II cavernous malformation

T2-weighted MRI of a type II cavernous malformation: Shown is the reticular mixed signal core of the lesion surrounded by a hypointense rim.
 
GRE axial MRI of a type II cavernous malformation: Shown is the blooming artifact of the focus.

 

  • 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.

GRE axial MRI of a type III cavernous malformation: The scan shows two foci in the white matter of the left frontal lobe and in the subcortical region of the left parietal lobe, respectively, in a 15-year-old boy with multiple cavernomas. Both foci show blooming artifact.
 
T1-weighted axial MRI of a type III cavernous malformation: The lesions show as hypointense foci.

T2-weighted axial MRI of a type III cavernous malformation: The lesions are also hypointense foci on T2-weighted imaging.

 

  • 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).