A young male presented with progressive right sided cranial nerve palsies was diagnosed as having a cavernous sinus syndrome. CT was done (Fig. 1) and showed a mass in the right cavernous sinus extending to the sphenoid sinus. Note that the mass contained some flecks of calcium and remodeled adjacent bones. At this point in time, the differential diagnosis included mainly a solid tumor (schwannoma, neurofibroma, meningioma, metastases [less like due to age and absence of primary tumor), lymphoma, and hemangioma). MR imaging with contrast was obtained and a coronal T1 image (Fig. 2) demonstrated that the mass enhanced homogeneously and avidly (there was also ventricular dilatation). Axial post Gd image (Fig. 3) showed similar findings with the anterior aspect of the lesion projecting into the region of the right spheno-ethmoidal recess. Posteriorly, the expanded the cavernous sinus and had a small region of no contrast enhancement. The differential diagnosis continued to be same.
Figures 1-3: Non contrast CT, coronal post Gd T1WI, and axial post Gd T1WI.
What is your diagnosis? What should you always consider when a lesion in a cavernous sinus is present?
The imaging studies were re-evaluated and due to the calcifications and the non-enhancing region the possibility of a partially thrombosed aneurysm of the ICA was considered. An angiogram was done (Fig. 4).
Fig 4. Nearly lateral 3D DSA view after injection of right ICA.
Giant aneurysms represent 5% of all intracranial ones; the prognosis is not good: mortality is 50-100% depending on location. The most common type is saccular and they can be further subdivided into those that have concentric layers of clot in their walls and those do not. In the first subtype, their growth is due to intramural re-bleeding and associated inflammation which also results in significant perilesional edema. When they bleed, SAH is generally small, near the aneurysm, and/or inside its walls. In the 2nd subtype, a small saccular aneurysm becomes giant and when it bleeds it results in diffuse SAH. Fusiform giant aneurysm are a second type and they are seen with dissections (like in the posterior circulation), infections, and disorders of the arterial walls (such as collagen-vascular ones). The 3rd typ- the rarest- are the serpentine ones. These represent re-canalized channels within the clot inside a giant thrombosed aneurysm and what is typical about them is that they have entry and exit points.
Aneurysms become “giant” when they reach > 25 mm in size. They are more common in middle age females. They generally produce symptoms by mass effect and tend to spontaneously clot more often than others (about 10%). Common sites: bifurcation of the ICA, intracavernous ICA, basilar artery (dome and then body), and MCA. Note that this patient also has a smaller aneurysm in the MCA bifurcation (Fig. 4). The patient underwent a test balloon occlusion of the right ICA successfully and awaits treatment.