A 25-year-old motorcyclist is brought to the Emergency Department after a road traffic collision. He was not wearing a helmet. His GCS is 7 (E2, V2, M3). His pupils are unequal, with the right pupil being 6mm and unreactive, and the left pupil 3mm and reactive. He has a left hemiparesis. What is the most likely diagnosis causing the pupillary changes and hemiparesis?