Pre- and post embolization evaluation of a right occipital cortical AVM
This 33 year old male presented with sudden onset of headache and left hemianopsia.
MRI revealed an intracerebral hemorrhage in the right occipital lobe. He recovered fully and refused further evaluation.
One year later he returned for re-evaluation. As an initial diagnostic imaging modality, combined MRI-MRA examination was performed revealing a right occipital AVM. No diagnostic catheter based cerebral angiography was performed.
Endovascular treatment was recommended. Total devascularization of the lesion was achieved at the first embolization session.
Occipital cortical-subcortical AVM, 1.5 T
Examination 1 (initial evaluation)
Fig.1 Sagittal T1-weighted spin-echo images. Abnormal signal void vascular structures are seen in the occipital region, suggesting a cortical AVM.
Fig.2 Transverse proton density and T2-weighted fast spin-echo images. Same observations as on Fig.1.
Fig.3 Transverse source images from a 3D TOF MRA acquisition (with 512 matrix, MOTSA and magnetization transfer). The nidus of the lesion is clearly identified. The curvilinear low signal intensity structure, adjacent to the nidus, probably corresponds to intracellular hemosiderin deposits originating from the previous intracerebral hemorrhage.
Fig.4 Transverse targeted MIP reconstruction from the 3D TOF MRA (with MOTSA and magnetization transfer) acquisition data set (TR: 43 ms, TE: 6.6 ms, flip angle: 20 degrees, matrix: 512, Nex: 1, Tac: 6 min 12 sec). The right occipital AVM is well visualized. The arterial feeders arise from the calcarine branch of the posterior cerebral artery. The draining vein leads to the superior sagittal sinus (the latter not being visualized, due to the saturating effect of the off-resonance magnetization transfer technique outside the acquisition volume).
Fig.5 Sagittal Gadolinium-enhanced survey 2D PC MR angiogram (TR: 14 ms, TE: 6.8 ms, flip angle: 20 degrees, Nex: 16, matrix: 256, Venc: 60 cm/s, Tac: 1 min 25 sec). Besides the visualization of the nidus, this image clearly shows additional blood supply to the AVM from the pericallosal branch of the right anterior cerebral artery. The single draining vein is also well appreciated in this projection.
Fig.6 Transverse averaged modulus (left) and magnitude of complex differences (right) type source images from a Gadolinium-enhanced 3D PC MRA acquisition (TR: 16 ms, TE: 7.5 ms, flip angle: 20 degrees, Nex: 1, matrix 256, Venc: 60 cm/s, Tac: 6 min 1 sec). The sulcal topography of the nidus is well appreciated on the anatomical images (left).
Fig.7 Transverse targeted MIP reconstruction from the Gadolinium-enhanced 3D PC MRA acquisition data set. Due to the lower spatial resolution (matrix: 256) of this technique, this image provides slightly inferior vessel definition compared to Fig.4, however, the right occipital AVM is well demonstrated.
Examination 2 (endovascular treatment)
Fig.8 Pre-embolization evaluation. DSA images (lateral views) after selective injection of the right internal carotid artery. An embryonic right posterior communicating artery provides direct blood supply to the ipsilateral posterior cerebral artery (above), the calcarine branch of which is one of the main feeders of the AVM. Additional blood supply is provided by the pericallosal branch of the anterior cerebral artery, as predicted by the MRA examination. The single draining vein leads to the superior sagittal sinus (below).
Fig.9 Embolization (step 1). DSA images (lateral views) after superselective catheterization of the calcarine branch of the left posterior cerebral artery (above) and during the injection of the cyanoacrylate embolic agent (below).
Fig.10 Immediate post-embolization verification. DSA images (lateral views) after selective injection of the right internal carotid artery. A residual nidus is identified on these images.
Fig.11 Embolization (step 2). DSA images (lateral views) after superselective catheterization of the pericallosal branch of the left anterior cerebral artery (above) and during injection of the cyanoacrylate embolic agent (below).
Fig.12 Immediate post-embolization verification. DSA images (lateral views) after selective injection of the right internal carotid artery. Total disappearance of the AVM.
Examination 3 (post-treatment follow-up)
Fig.13 Sagittal T1-weighted spin-echo images. The high-signal intensity areas within the nidus of the AVM correspond to post-embolization thrombosis.
Fig.14 Transverse proton density (left) and T2-weighted (right) fast spin-echo images. The signal void of the nidus has disappeared. However, an area of slightly increased signal intensity is detected in the occipital subcortical white matter.
Fig.15 Transverse turbo FLAIR (left) and corresponding T2-weighted fast spin-echo (right) images, for comparison. The abnormal signal intensity area is significantly more apparent on the FLAIR images. These intraparenchymal lesions proved to be reversible and were not seen at a later follow-up.
Fig.16 Transverse source images from a 3D TOF MRA acquisition (with 512 matrix, MOTSA and magnetization transfer). The intravascular signal within the nidus of the lesion has disappeared. The curvilinear low signal intensity structure (arrow), corresponding to intracellular hemosiderin deposits originating from the previous intracerebral hemorrhage is unchanged (compare with Fig.3 of Exam 1). Other low signal intensity components within the nidus are consistent with the intravascular embolic agent, whereas the punctate high signal intensity structures represent thrombosis.
Fig.17 Transverse targeted MIP reconstruction from the 3D TOF MRA (with MOTSA and magnetization transfer) acquisition data set (TR: 43 ms, TE: 6.6 ms, flip angle: 20 degrees, matrix: 512, Nex: 1, Tac: 6 min 12 sec). In agreement with the immediate post-embolization angiographic verification, total elimination of the right occipital AVM is confirmed
Fig.18 Transverse targeted MIP reconstructions from the pre- and postembolization 3D TOF MRA (with MOTSA and magnetization transfer) acquisition data sets, for comparison.
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