Retinotopic organization of the primary visual cortex before and after pharmacological treatment for a large prolactinoma with compression of the optic chiasm

Abstract Patients suffering from pituitary macroadenomas - pituitary tumors larger than 10mm - often have visual deficits, typically bilateral hemianopsia, because of chiasmal compression. Treatment of macroadenomas is usually successful, and thus such patients provide a unique opportunity for studying neuroplasticity in the human visual system and its consequences for vision. This case study focuses on patient BS, a 48-year-old man, who had a large prolactinoma, a common pituitary tumor, and, as a consequence, a severe visual field loss. We used functional magnetic resonance imaging (fMRI) to map the retinotopic organization of primary visual cortex (V1) of patient BS before and after successful treatment of his prolactinoma with cabergoline over the course of 13 months. In addition, we used the same fMRI protocol to examine the organization of V1 in a healthy age- and gender-matched control participant with normal vision. Humphrey's perimetry was used to assess the integrity of the visual fields, before and after the completion of treatment for patient BS, and over two successive scans in the healthy control. The Humphrey field exam revealed significant visual improvement after treatment and this recovery was accompanied by substantial changes in V1 activation. Before the start of treatment, the amount of cortical tissue in V1 which was activated by the retinotopic stimuli was only 21% that of the healthy control participant. After treatment, the amount of activation normalized to approximately 90% of that of the control participant. The organization of retinotopic representations in V1 also normalized after treatment. These results illustrate that the visual system is capable of repair following conservative medical treatment, opening the door for assessing the effects of compression on different components of the optic nerve and tract. Meeting abstract presented at VSS 2015.