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Endovascular therapy using flow diversion for giant internal carotid artery pseudoaneurysm arising in the setting of an invasive pituitary macroadenoma.

This report illustrates the unusual occurrence of a pseudoaneurysm arising in the setting of a skull base mass and describes the first reported use of endovascular flow diversion therapy in such a setting. A 63-year-old man with occasional headaches during the preceding month presented with the acute onset of severe left retroorbital headache and oculomotor nerve palsy. Computed tomography (CT) and CT angiogram revealed a destructive skull base mass with an associated giant probable pseudoaneurysm of the cavernous segment of the left internal carotid artery. The patient underwent endoscopic transsphenoidal biopsy with a subsequent diagnosis of prolactinoma. Endovascular therapy utilizing two Pipeline[TM] flow diversion embolization devices was performed with subsequent resolution of the patient's headache and improvement in his cranial nerve deficits/cavernous sinus syndrome.

Aneurysms coincident with invasive skull base masses are unusual. An association between pituitary neoplasms and intracranial aneurysms has been documented. The acute development of a cavernous sinus syndrome with associated cranial nerve deficits in conjunction with an aneurysm entirely encased within a neoplastic lesion supports the diagnosis of an acutely enlarging pseudoaneurysm, and we describe the first reported use of endovascular flow diversion therapy in such a setting. This case illustrates a diagnostic pitfall with the potential for grave implications in patient outcome if an associated vascular lesion is not appreciated at the time an intracranial mass is diagnosed.

CASE PRESENTATION

A 63-year-old man with minor headaches in the preceding month presented to the emergency department following the acute onset of severe left retroorbital headache, ptosis, mydriasis, ophthalmoplegia, and diplopia. Noncontrast head computed tomography (CT) (Figure 1a) revealed a large destructive central skull base mass. Subsequently pre-and postgadolinium brain magnetic resonance imaging (MRI) (Figure 1b, 1c) delineated the margins and character of the skull base mass, which was centered in the clivus and extended to encase the left greater than right cavernous segments of the internal carotid arteries (ICAs) with partial destruction of the petrous carotid canals. A hypointense T2 signal was identified with heterogeneous enhancement following gadolinium administration. A suspicious large flow void within the region of the cavernous segment of the left ICA was confirmed to reflect a probable pseudoaneurysm on postgadolinium imaging and subsequent CT and catheter angiography (Figure 2), which revealed additional dysplastic irregular lobular projections arising from the pseudoaneurysm sac. The patient underwent an endoscopic transsphenoidal biopsy of the lesion. Histopathologic findings showed a pituitary adenoma, and subsequent laboratory testing showed serum prolactin levels to be 14191.5 ng/mL (normal range 2.1-17.7), compatible with the diagnosis of a prolactinoma.

The patient was loaded with aspirin and clopidogrel for 1 day and subsequently underwent endovascular therapy utilizing two overlapping Pipeline[TM] flow diversion embolization devices (Medtronic, Minneapolis, MN) measuring 4.25 X 30 mm and 4.5 X 16 mm (Figure 3), extending to the supraclinoid ICA. This resulted in an immediate and marked decrease in contrast flow within the pseudoaneurysm sac and contrast stasis. Cabergoline medical therapy was initiated to treat his prolactinoma.

The patient's headache resolved, and he was discharged in good condition 5 days following endovascular therapy. The patient continued to experience ptosis, mydriasis, and mild diplopia at the time of discharge, although he did experience an improvement in his ophthalmoplegia. On follow-up catheter angiography, the pseudoaneurysm was markedly decreased in size with only trace filling of a subcentimeter residual pseudoaneurysm sac. The patient's cranial nerve palsies also greatly improved during the 6 months following discharge, and he has continued to do well.

DISCUSSION

The incidence of intracranial aneurysms arising in association with pituitary adenomas is greater than the incidence of aneurysms arising in the general population (0.5%-7.4%) (1), as well as the incidence of aneurysms coexistent with intracranial masses of nonpituitary origin. The pathogenesis of this increased incidence is uncertain. Proposed etiologies include increased blood flow through vessels supplying the tumor, hormonal effects, and direct neoplastic infiltration (1). The concept of increased tumoral blood flow via internal carotid branch vessels is supported by the fact that the greatest proportion of adenoma-associated aneurysms arise from the ICA (50%) (1). A hormonal influence on the incidence of aneurysm formation is supported by the fact that the greatest incidence of adenoma-associated aneurysms occurs in the context of acromegaly (50%) (1), with associated increased insulin-like growth factor--1 potentially playing a role in the formation of intracranial aneurysms, as well as the more diffuse vasculopathic changes that can be seen in these patients, to include widespread cerebrovascular dolichoectasia (2). The contribution of tumor infiltration is supported by the statistically significant increase in aneurysm incidence in the setting of cavernous sinus invasion (3), as well as a case reported by Mangiardi et al that described a macroadenoma invading the walls of a giant cavernous carotid aneurysm on a postmortem examination (4). In our case, the fact that the entire pseudoaneurysm was encased within the mass that had invaded the cavernous sinus may provide additional support for the theory of direct neoplastic infiltration, particularly the clinical evidence of acute pseudoaneurysm enlargement supporting an underlying loss of integrity of the vessel wall.

The utility of flow diversion devices has been realized in treating giant aneurysms not amenable to traditional coiling, as well as in therapy of pseudoaneurysms arising secondary to trauma or iatrogenic causes. Vascular remodeling following flow diversion embolization is an established phenomenon that also occurs in pseudoaneurysms with an associated decrease in sac size and is particularly desirable in cases of symptomatic mass effect. Improvement in associated cranial nerve palsies is variable, although the degree of improvement likely relates to the duration and degree of compression.

(1.) Choi HS, Kim MS, Jung YJ, Kim OL. Incidental superior hypophygeal artery aneurysm embedded within pituitary adenoma. J Korean Neurosurg Soc 2013;54(3):250-252.

(2.) Weir B. Pituitary tumors and aneurysms: case report and review of the literature. Neurosurgery 1992;30 (4) : 585-591.

(3.) Oh MC, Kim EH, Kim SH. Coexistence of intracranial aneurysm in 800 patients with surgically confirmed pituitary adenoma. Neurosurg 2012;116(5):942-947.

(4.) Mangiardi JR, Aleksic SN, Lifshitz M, Pinto R, Budzilovic GN, Pearson J. Coincidental pituitary adenoma and cerebral aneurysm with pathological findings. Surg Neurol 1983;19 (1) : 38-41.

Amin F. Saad, MD, Almas Syed, MD, Keyan B. Marashi, MD, Brian D. O'Rourke, MD, Joseph H. Hise, MD, Michael J. Opatowsky, MD, MBA, and Kennith F. Layton, MD, MS

From the Departments of Diagnostic and Neurointerventional Radiology, Baylor University Medical Center at Dallas. Dr. Saad is now with Stanford University, and Dr. Marashi is now with University of Utah, Salt Lake City.

Corresponding author: Amin F. Saad, MD, Department of Radiology, Neuroradiology Division, Stanford University, 300 Pasteur Drive, MC 5105, Stanford, CA 94305 (e-mail: aminsaadmd@gmail.com).
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Author:Saad, Amin F.; Syed, Almas; Marashi, Keyan B.; O'Rourke, Brian D.; Hise, Joseph H.; Opatowsky, Micha
Publication:Baylor University Medical Center Proceedings
Article Type:Clinical report
Date:Jan 1, 2017
Words:1115
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