Endocrine fellow Harbor-UCLA/COH duarte, California, United States
Introduction : Prolactinomas comprise 40% of all pituitary tumors. Dopamine agonists are the treatment of choice in most prolactinomas. The recommended starting dose of cabergoline as suggested by some colleagues was 0.5 mg/day in patients with visual field deficits with close in-patient monitoring and 0.25-0.5 mg /week in non-emergent situations. However, starting on higher doses of dopamine agonists could lead to rapid shrinkage of tumor resulting in iatrogenic herniation of brain.
Case(s) Description : A 37-year-old woman initially presented to the hospital with complaints of galactorrhea, headaches, mild loss of peripheral vision and abnormal uterine bleeding. Initial labs were suggestive of high prolactin levels of 3291 ng/ml, with normal thyroid stimulating hormone and morning cortisol levels and suppressed Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) < 3 mIU/ml. Magnetic Resonance Imaging (MRI) of the sella and pituitary with and without contrastrevealed an intra-sellar mass with supra-sellar extension invading the right cavernous sinus and encasing the carotid artery compressing and uplifting of the central and left aspect of the optic chiasm most consistent with macroadenoma of size 21 mm Anterior Posterior (AP) x 32 mm Transverse (TR) x 33 mm Cranio Caudal (CC). Patient was started on cabergoline 1 mg twice a week. Prolactin levels were repeated 6 months after treatment initiation and levels were down to 3 ng/ml. Repeat MRI of the sella and pituitary with and without contrast 8 months after initial MRI showed significant decrease in the size and extent of the mass with resolution of the mass effect on the optic chiasm and inferior frontal lobes. With residual mass measuring 5 mm AP x 2.3 mm TR x 5 mm CC. As patient was complaining of loss of peripheral vision, MRI was performed which revealed herniation of inferior medial frontal lobes and the floor of the third ventricle into the sella with mass effect and displacement of the pituitary gland. There was splaying of the optic chiasm by herniation. The native pituitary gland appears unremarkable without abnormal signal or enhancement to suggest a pituitary tumor. Patient was referred to Neurosurgery and eventually underwent cranioplasty and chiasmopexy.
Discussion : Our case is one of the rare presentations of treatment related adverse effects of prolactinoma and sheds light on the importance of starting the lowest possible dose of dopamine agonist therapy to prevent iatrogenic adverse events from rapid tumor shrinkage. The mechanism of herniation is unclear. Frequent follow-up and patient education of this potential side effect in managing this patient population must be emphasized.
