TEMPORAL LOBE HERNIATION AND CHIASMOPATHY DURING DOPAMINE AGONIST THERAPY FOR PROLACTINOMA

Dopamine agonists (DA) are first line treatment for prolactinomas. Optic chiasm herniation can rarely occur during therapy, while brain herniation is very uncommon.

A 34 yo woman presented with headaches and vision changes. Prolactin (PRL) was 4300 ng/mL. MRI showed a 4.5 cm pituitary adenoma with chiasm compression. After 3 months, PRL decreased to 201 ng/mL while patient was taking CAB 0.75 mg twice a week. MRI showed ~30% tumor reduction with medial temporal lobe herniation and encephalocele. CAB was stopped and she underwent surgical debulking and encephalocele repair. Histopathology confirmed prolactin tumor. CAB 0.75 mg twice a week was resumed.A 50 yo man had incidental detection of a sellar mass after trauma. MRI showed 3.6 cm tumor with minimal contact of right optic nerve, and PRL 3,318 ng/ml. He received CAB 0.5mg twice a week with PRL improvement to 26 ng/mL after 1 month. After 2 months ophthalmology exam showed new left superotemporal depression. PRL was 68 ng/mL and MRI showed 35% mass reduction and new inferior displacement tethering of the chiasm. CAB dose was decreased to 0.25 mg twice a week.

Our cases illustrate that rapid biochemical and radiographic response to DA therapy in large prolactinomas warrants close clinical and neuro-ophthalmologic follow-up. We recommend repeating the MRI 3 months after initiation of DA therapy or sooner in case of new mass effect manifestations. Decision regarding DA dose reduction or chiasmopexy for visual field deficits needs to be multi-disciplinary and on a case-to-case basis.