An 84-year-old lady with hypertension, bladder cancer, and chronic kidney disease, presented with a 3-day history of diplopia on looking to the right, abnormal eye movements, right-sided peri-orbital headache, and diarrhoea. Clinical examination revealed right-sided sixth cranial nerve palsy with normal pupillary light reaction, visual acuity, and visual fields. There were no other neurological deficits. The patient did not have features of hypercortisolism, GH excess, or adrenal insufficiency.
CT brain demonstrated 39×18×15 mm lesion involving the pituitary fossa, with bony erosion of the right cavernous sinus and to a lesser degree the left cavernous sinus, sphenoid sinus and posterior sella turcica. MRI pituitary without contrast (due to impaired renal function), revealed a heterogeneous signal in the pituitary fossa adjacent to the right internal carotid artery (ICA). Pituitary function tests were normal (LH 18.5 (NR 3.08.0 IU/l), FSH (NR 4.07.0 IU/l), 48.5, and prolactin 219 (NR <400 mIU/l)). The patient had acute on chronic kidney injury (Cr 178 μmol/l). The working diagnosis was non-functioning pituitary macroadenoma causing sixth cranial nerve palsy. After renal function improved with i.v. fluids, contrast MRI pituitary was done. This revealed a homogenously enhancing lesion of the pituitary fossa extending into the sella and suprasellar cistern. CT angiography confirmed a large right ICA aneurysm compressing and displacing the pituitary gland to the left. Owing to operative mortality risk of 50%, and annual aneurysm rupture risk of 8%, the patient was managed conservatively.
Although aneurysms of the ICA involving the pituitary fossa are rare, they need to be excluded before pituitary surgical referral. This case also highlights the importance of performing a contrast pituitary MRI to reliably establish the diagnosis of a pituitary lesion.