MON-094 - Giant Pituitary Adenoma with Obstructive Hydrocephalus: A Rare Presentation and Management Challenge

Background: Giant pituitary adenomas (>4 cm) are uncommon, and obstructive hydrocephalus is an exceptionally rare complication that typically occurs only with marked suprasellar extension. Gonadotroph adenomas are the most common clinically nonfunctioning subtype and may remain silent until significant mass effect develops.

Case description: A 47-year-old man presented with recurrent episodes of transient loss of consciousness without seizure-like features and progressive bilateral visual decline over the preceding four months. He denied headache and reported no symptoms suggestive of hypopituitarism. CT and MRI revealed an extremely large 6.7 cm homogeneously enhancing sellar and suprasellar mass with optic chiasm compression. The mass caused third ventricle compression with obstructive hydrocephalus and encased both internal carotid and cerebral arteries. Preoperative evening cortisol was 9.1 µg/dL; ACTH stimulation and further endocrine testing were not performed at that time. He underwent semi-urgent right orbitozygomatic craniotomy with subtotal resection. Immunohistochemistry was positive for synaptophysin, CAM5.2, SF-1, GATA3, FSH, and LH, consistent with a gonadotroph adenoma (Ki-67 ≈ 3%). Postoperatively, the patient developed panhypopituitarism, including central hypothyroidism (TSH 1.86 mIU/L, free T4 0.56 ng/dL), adrenal insufficiency diagnosed clinically in the postoperative period, for which he was started on hydrocortisone (morning cortisol 5.6 µg/dL; ACTH stimulation test was not performed), and hypogonadotropic hypogonadism (total testosterone 71 ng/dL, LH 2.6 mIU/mL, FSH 8.1 mIU/mL). Growth hormone was < 0.05 ng/mL. He did not develop diabetes insipidus. The patient was seen for endocrinology follow-up at 2, 3, 4, and 6 months postoperatively and remains on dexamethasone, levothyroxine, and testosterone cypionate, with surveillance brain MRI planned at 6 months postoperatively. He has persistent right-sided vision loss and left temporal hemianopsia, but loss-of-consciousness episodes have not recurred.

Conclusion: This case highlights an uncommon presentation of a giant pituitary adenoma with obstructive hydrocephalus, manifesting primarily as recurrent transient loss of consciousness with progressive visual impairment in the absence of overt preoperative symptoms of adrenal insufficiency. Although long-term endocrine monitoring is essential after pituitary surgery, care delivery in this case was complicated by social determinants of health. Specific strategies for hormonal surveillance and imaging will be discussed with reference to current guidelines.

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