Pituitary tumors are the commonest type of intracranial tumors with a prevalence of 5–20% according to autopsy studies. In contrast, intracranial aneurysms are rare. Failure to make the correct diagnosis can lead to catastrophic consequences.
A 69 year old previously healthy female presented with progressive intermittent headache for 3 years. There was no diurnal pattern of symptoms, associated vomiting or visual disturbance. She was clinically euthyroid and denied galactorrhea, postural dizziness or limb weakness. On examination visual fields were normal and she had no papilledema or other focal neurological deficits. Thyroid profile was suggestive of secondary hypothyroidism [TSH 1.2 mIU/L (0.4–4.0), free T4 0.6 ng/dL (0.9–1.7) and free T3 3.5 pmol/L (3.5–6.5)]. Perimetry showed a right homonymous inferior quadrantanopia. Further investigation showed low cortisol levels (4.03 μg/dL) and markedly raised prolactin level of 1634 mU/L (< 400 mU/L). Thyroxin and hydrocortisone replacement therapy were commenced. An MRI scan of the head was performed and a mass lesion in the sellar region was found, which was reported as a pituitary macroadenoma. Patient was referred for neurosurgery. On re-evaluation by the neurosurgeon, doubt was cast on the nature of the tumor due to the multilayered and ‘halo’ like appearance of the lesion on MRI. A CT angiogram was performed and a large aneurysm measuring 19.9 mm × 21.5 mm was discovered arising from the cavernous portion of the left internal carotid artery. The patient eventually underwent endosaccular coiling and stenting and made an uncomplicated recovery without recurrence of symptoms during follow-up.
Attempt of trans-sphenoidal surgery for a pituitary tumor would have had catastrophic consequences in this patient. The rare possibility of an intra-cavernous carotid aneurysm should always be kept in mind in evaluating a patient with a mass lesion suggestive of a pituitary tumor.