Giant aneurysm of the left internal carotid artery

This 79 year old female presented with a two year history of diplopia. Taking into account the coexistence of a chronic torticollis, the diagnosis of a left IV nerve palsy due to functional overload resulting in decompensation was made. Her IV nerve palsy was successfully treated with corrective lenses for a short time.
She returned complaining of recurrent diplopia and progressive left hemifacial pain. Neurological examination detected both a IV and a VI nerve palsy on the left side.
CT examination was performed at this point, in order to rule out parasellar mass lesion. Instead, it was highly suggestive of a giant saccular aneurysm of the carotid siphon. Subsequent MRI-MRA examination confirmed this diagnosis and also demonstrated partial thrombosis of the aneurysm.
Conventional catheter based angiography was considered in order to determine whether endovascular treatment was feasible. Unfortunately, the patient suddenly died of intractable subarachnoid hemorrhage.

Giant cerebral aneurysm, 1.5 T
Fig.1 Sagittal T1-weighted spin-echo images of the left parasellar region. A large, rounded inhomogeneous lesion is detected. The internal carotid artery siphon appears to be displaced superiorly and posteriorly by the mass effect.
Fig.2 Coronal proton density-weighted fast spin-echo images of the sellar region. The lesion exhibits markedly heterogeneous signal intensity, somewhat similar to the laminated (staged) appearance of the thrombus in another previously seen partially thrombosed giant aneurysm (compare with Giant aneurysm: patient case). No residual channel is identified on these images.
Fig.3 Coronal T2-weighted fast spin-echo images of the sellar region. Similar observations as in Fig.2.
Fig.4 Coronal T2-weighted gradient-echo images of the sellar region. Typical magnetic susceptibility artifacts around the sphenoidal sinus. Moreover, the laminated appearance of the aneurysmal sac, including low intensity layers of hemosiderin, is even more apparent.
Fig.5 Coronal non-enhanced (left) and Gadolinium-enhanced T1-weighted images of the sellar region. The enhancing area within the left parasellar lesion suggests a residual patent lumen within the aneurysm. This together with the enhancing wall, clearly delineate the intraaneurysmal thrombus.
Fig.6 Transverse non-enhanced (left) and Gadolinium-enhanced T1-weighted images of the sellar region. Same observations as in Fig.5.
Fig.7 Sagittal survey Gadolinium-enhanced 2D PC MR angiogram (slice thickness: 30 mm, Venc: 35 cm/s). Rapid, positive diagnosis of the giant internal carotid artery aneurysm is established.
Fig.8 Transverse source images from a multislab 3D TOF MRA acquisition data set. The patent lumen of the aneurysm exhibits flow-related enhancement, while the thrombosed portion is practically isointense with the adjacent parenchyma. Note that the internal carotid artery (exhibiting higher signal intensity) is always behind or above the aneurysm.
Fig.9 Sagittal, coronal and transverse targeted MIP reconstructions from the multislab 3D TOF MRA acquisition data set. Only the patent lumen is seen.
Fig.10 Sagittal and coronal targeted MIP reconstructions from a Gadolinium-enhanced 3D TOF MRA acquisition data set. Both the patent lumen and the thrombosed portion are visible, the latter only very faintly (T1 contamination?, enhancement?).
Fig.11 Sagittal averaged modulus (left) and corresponding magnitude of complex differences (right) type source images from a 3D PC MRA acquisition. Upon analyzing the magnitude of complex differences images, the inflow pathway (yellow arrow) appears to be located at the summit of the aneurysmal sac and intraaneurysmal flow (blue arrows) exhibits a rather regular, circular pattern on these images.

Video 1: sagittal thick slice 3D Phase Contrast MRA acquisition with retrospective cardiac gating. Turbulent intraaneurysmal flow pattern in a partially thombosed giant saccular aneurysm at the internal carotid artery siphon.

Video 2: coronal thick slice 3D Phase Contrast MRA acquisition with retrospective cardiac gating. Turbulent intraaneurysmal flow pattern in a partially thombosed giant saccular aneurysm at the internal carotid artery siphon.

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