Internal Carotid Artery Aneurysm Mimicking a Pituitary Adenoma: A Case Report and Review of the Literature

Background/Objective: A thrombosed internal carotid artery (ICA) aneurysm mimicking a pituitary adenoma can be catastrophic if unrecognized. We report a unique case of the rare presentation of ICA aneurysms masquerading as pituitary adenomas, which can preserve pituitary function when treated early. Case Report: A 54-year-old man with type 2 diabetes, aortic valve replacement, and stroke presented with sudden onset severe headache and left eye pain. Left third nerve palsy was noted. Laboratory studies showed low thyroid-stimulating hormone, follicle-stimulating hormone, luteinizing hormone, testosterone, and insulin-like growth factor 1 levels and baseline, post–30-minute, and post–60-minute cortisol levels of 16, 17, and 14 μg/dL, respectively, after adrenocorticotropic hormone stimulation. Magnetic resonance imaging of the pituitary revealed a heterogeneously enhancing 2.0 × 2.1 × 2.1-cm sellar/suprasellar mass with peripheral enhancement abutting the left cavernous sinus. Given the acute third nerve palsy without visual defects and magnetic resonance imaging findings, other sources of sellar occupying etiology were suspected. Therefore, carotid cerebral angiography was performed and revealed a mostly thrombosed left ICA aneurysm projected into the sellar/suprasellar region. The patient underwent successful endovascular treatment with a resolution of the cranial nerve palsy and hormonal abnormalities at 3-month follow-up. Discussion: Our case demonstrates the importance of swift recognition of ICA aneurysms masquerading as pituitary adenomas. Early recognition and treatment may lead to the complete resolution of presenting symptoms and hormonal deficiencies. Conclusion: Clinicians should have a high index of suspicion for ICA aneurysm in the differential diagnosis for a sellar mass. Careful evaluation is essential because misdiagnosis may lead to catastrophic consequences.