Common presentations of intracranial aneurysms are subarachnoid haemorrhage, cerebral ischaemia or pseudotumoral syndromes .
However, intracavernous aneurysms are well known to present with ophthalmoplegia due to compression of third, fourth and sixth cranial nerves as they traverse the cavernous sinus, as well as visual field defects due to chiasmal compression [9, 10]. According to a study in Canada  involving 57 patients with giant cavernous carotid aneurysms (> 25 mm), the most common presenting symptoms were diplopia (89%), retro-orbital pain (61%), headache (19%), diminished or blurred vision (14%), and photophobia (4%). While 93% of these patients had had partial or complete ophthalmoplegia trigeminal nerve involvement had been found in 37% of patients. Other clinical signs included ptosis, decreased visual acuity, proptosis, and visual field defects.
Rarely, an intracavernous aneurysm can present as hypothalamo-pituitary axis dysfunction when it extends into the sellar region [8, 12]. Such aneurysms extending into sellar region account for 1–2% of all intracranial aneurysms . However hypopituitarism is very rare as the presenting feature of such tumours and evidence in medical literature is limited to case reports . Review of literature on over 4000 patients with hypopituitarism over four decades concluded that intrasellar aneurysm was the underlying aetiology only in 0.17% of those cases .
Intracavernous sinus aneurysms are thought to have a benign course . However, rare but serious complications include meningeal haemorrhage (1.4%), intracavernous fistula (8%) and rarely endocrinological manifestations  which warrant surgical treatment. Neurosurgical approach to an intracavernous aneurysm is deemed hazardous and endovascular therapeutic options remain the method of choice .
Differentiation between pituitary adenoma and an aneurysm is vital as these two have different management options and mistakenly attempting trans-sphenoidal resection of an aneurysm could have disastrous consequences. Halo appearance produced by the two dural layers encasing the cavernous portion of carotid artery should raise the suspicion of this diagnosis. Filling defects within the mass represent thrombosis. In contrast, a pituitary tumour would appear isointense to grey matter on T1 and T2 weighted MR imaging and would enhance with gadolinium contrast. Large tumours may show heterogeneity and erosion of clinoid processes. Probable higher risk of having an intracranial aneurysm along with the pituitary tumour should also be borne in mind. Infact several authors have reported on subarachnoid haemorrhage during transphenoidal surgery for pituitary adenomas, due to accidental damage to previously undetected intracranial aneurysms [15,16,17]. Some authors recommend routine preoperative carotid artery angiography in all patients with pituitary macroadenomas before trans-sphenoidal surgery .
In summary, this case report illustrates the rare possibility of misidentifying an intracavernous carotid aneurysm as a pituitary tumour. Therefore we emphasize the need of very careful evaluation of the MRI scan before proceeding to pituitary surgery, particularly observing for indirect evidence of an aneurysm such as multi layered halo like appearance, presence of intralesional filling defects and whenever a doubt exists, to perform angiogram to confirm the presence of an aneurysm.