MON-078 CSF Rhinorrhea Complicating a Medically Managed Macroprolactinoma

Abstract Disclosure: V.K. Babu: None. D. Sheely: None. Introduction: Prolactinomas represent the most common type of hormone secreting pituitary tumors. CSF rhinorrhea (CSF-R) is an uncommon but serious complication that occurs in about 6% of patients medically treated for a macroprolactinoma. Macroprolactinomas tend to cause osseous erosion. The development of CSF-R requires both osseous and dural destruction. We present a case of CSF-R following treatment of a macroprolactinoma with cabergoline. Case presentation: An 82-year-old man underwent brain imaging following a ground-level fall. MRI brain revealed a 21.5 x 21 x 25 mm contrast enhancing sellar mass with pituitary compression, extension into the right sphenoid sinus down to the sphenoid floor, with sellar floor erosion. This prompted a referral to neurosurgery and endocrinology. Upon questioning, his pituitary review of systems, including galactorrhea and headaches, were negative. He denied visual complaints. He denied family history of pituitary, pancreas, and/or parathyroid/calcium disorders. His physical exam was unremarkable. Labs showed prolactin 2308 ng/mL, TSH 1.43mIU/mL, ACTH 31 ng/L, FSH 8.6 mIU/mL, LH 2.5 mIU/mL, total testosterone 34 ng/dL, IGF-1 Z-score 0.5. He was diagnosed with a macroprolactinoma and started on cabergoline at 0.25mg 2x/week and was titrated up to 0.5mg 2x/week. His prolactin gradually normalized with a level of 18.5 ng/mL at the one-year mark. His free T4, AM cortisol, and IGF-1 z-score were normal but hypogonadotropic hypogonadism persisted. On his subsequent visit, he complained of clear discharge from the right nostril which worsened on leaning forward. MRI brain showed "reduction of the size and necrotic changes within the pituitary tumor… similar erosion of the sellar floor with interval fluid layering within the sphenoid sinus." He was then diagnosed with CSF-R and referred to ENT. Discussion: In Suliman et al's cohort of 114 patients with macroprolactinomas, the two main factors predictive of CSF-R development (n=7) were male gender and dopamine agonist resistance. In a retrospective analysis of 30 medically treated patients with macroprolactinomas, four developed CSF-R, all of whom demonstrated sphenoid sinus invasion. This was corroborated by Milton et al, where they recommended screening with HRCT of the sinuses in patients with large and/or locally invasive macroprolactinomas noted on MRI. Interestingly, the rate of tumor shrinkage and change in tumor size have not been associated with development of CSF-R. Patients with risk factors should be counselled regarding the clinical features and management of CSF-R. The mainstay of treatment is surgical repair. Presentation: Monday, July 14, 2025