Introduction

Aneurysms of the CCA account for between 3 and 5% of all intracranial aneurysms [1]. Because they are located in extradural space, the clinical manifestation is different from other intradural aneurysms. However, they can grow large in size, and can present with pressure symptoms due to mass effect on cranial nerves, such as ophthalmoplegia and facial pain [2]. Spontaneous intramural thrombosis of giant intracranial aneurysms occurs in between 13 and 20% of cases [3]. We describe an unusual pediatric case of a huge cavernous sinus mass mimicking a cystic neoplasm with peripheral rim enhancement on MRI, where the surgery and subsequent histopathological investigation revealed that this mass was a completely thrombosed giant aneurysm of the CCA. We also searched the literature on thrombosed CCA aneurysms that mimic intracranial neoplasms.

Case report

A 2-year-old boy with no previous medical history was admitted to us with progressive oculomotor palsy and seizure for 3 months. The symptoms began insidiously and were not associated with a history suggestive of subarachnoid hemorrhage. A clinical examination revealed left ptosis, oculomotor paresis, and left relative afferent pupillary defect. The patient was evaluated with gadolinium-enhanced MRI that showed a huge cystic lesion adjacent to the left ICA with peripheral rim enhancement on T1-weighted and hypointensity on T2-weighted images that was suspicious for a neoplastic process (Fig. 1). Differential diagnosis included intra-axial tumors such as glioma or ganglioglioma, dermoid cyst, epidermoid cyst, vestibular schwannoma, and ependymoma. Then, we performed MR angiography, which showed a giant left cavernous sinus mass measuring 2.7 × 2.9 × 4 cm and the occlusion of the left ICA, with no filling past the petrous segment (Fig. 2). CTA also verified the findings of the MRA with a lack of flow through the left ICA from the skull base to the suparclinoid segment (Fig. 3). Head CT scan also showed the direct erosion of the cavernous sinus wall and erosion into the sella turcica by the growing mass. His left middle cerebral artery (MCA) and anterior cerebral artery (ACA) were supplied through a patent Willis circuit via a left posterior communicating artery (PCoA) and a patent anterior communicating artery. Reconstitution of flow at the supraclinoid segment with filling of the left MCA, ACA, and PCoA was seen. Based on the T1W MRI overlayed to the TOF-MRI, a vascular origin of the lesion was considered more likely (Fig. 4). Therefore, we performed a subsequent craniotomy for resection of the lesion using a left pterional craniotomy. The lesion exposed was found to be a large completely thrombosed aneurysm originating from the CCA. After cutting the wall of the aneurysm, thrombectomy, aneurysm wall resection, and reconstruction were performed (Fig. 5).

Fig. 1
figure 1

The gadolinium-enhanced MRI demonstrated a crescent-shaped hyperintensity of the lesion wall with no intraluminal filling of mass on T1-weighted frame and heterogeneous signal intensity on T2-weighted images concerning the neoplastic process

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Fig. 2
figure 2

MR Angiogram shows a large neoplasm with the absent flow in the left ICA

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Fig. 3
figure 3

CT angiogram shows a lack of flow through the left ICA from the skull base to the suparclinoid segment

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Fig. 4
figure 4

T1W MRI images were registered to the TOF-MRI images by using 3D anatomical landmarks and image fusion was done

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Fig. 5
figure 5

Intraoperative photographs displaying a huge thrombosed aneurysm. Meticulous dissection and cutting of the aneurysm wall were performed

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Hystopathologic examination confirmed the diagnosis of thrombosed aneurysm, which revealed hemosiderin deposits, calcifications, and inflammatory infiltrates within the remnants of the vessel wall. The patient showed no new neurological deficits postoperatively was put on aspirin 50 mg daily for stroke prevention and was discharged a week later after admission. At his 1-month follow-up, he was doing well; his ophthalmoparesis and ptosis had improved.

Discussion

Pediatric cerebral aneurysms occur at a frequency between 0.17 and 6.8% among all patients treated for intracranial aneurysms, where the percentage of pediatric cerebral aneurysms that are giant (diameter ≥ 25 mm) range from 14 to 54% [4]. Complete intraluminal thrombosis occurs especially in large and giant cerebral aneurysms in 13–20% of cases [5]. However, there are few reports where completely thrombosed CCA aneurysms have imitated neoplasms based on initial presentation and imaging [6, 7], while no cases have been reported among the pediatric population. They also treated their patient with open surgery and removal of intramural clot via an aneurysmotomy [8].

Most of the patients with large CCA aneurysms presented with symptoms of ophthalmoparesis, facial pain, or hyposthesia due to the mass effect. In our patient, the medial extension of the mass caused the oculomotor paresis, while the seizure activity is probably because of the lateral extension and compression of the insular cortex by an enlarging lesion.

CT angiography provided reliable and informative data regarding the thrombosed aneurysm, the extent of ICA thrombosis, and the distal blood flow provided by collateral circulation through the circle of Willis comparable to DSA with high sensitivity and specificity [9]. Preoperatively, a DSA is always helpful and must be included in the preoperative workup to visualize the parent vessel of the giant intracranial aneurysm and plan the operation. But in the case of a completely thrombosed aneurysm, DSA could be negative [10]. The accepted methods of treatment for giant cavernous aneurysms are occlusion of the ICA, with or without bypass, depending on the cross-flow, as well as results of balloon test occlusion [11]. Endovascular interventions for both the feeding vessel and the aneurysm itself are also done with good results and less morbidity than an extensive open procedure [12]. We also believe there is a role for conservative management in patients who are not acutely and severely symptomatic and fail balloon test occlusion [13]. Further clinical and imagiological follow-up is needed once recanalization of thrombosed lesions, although rare [14], cannot be anticipated [15]. Some authors advocate performing control angiographic studies at 3, 6, and 12 months and subsequently with yearly intervals until at least 3-year follow-up, due to the risk of recurrence and rehemorrhage [16].

Conclusions

In this case report, we describe a pediatric case of a completely thrombosed giant CCA aneurysm with ipsilateral internal carotid artery (ICA) occlusion, which imitates an intra-axial cystic lesion on MRI. We also searched the literature on thrombosed CCA aneurysms that mimic intracranial neoplasms.