A 24-year-old male is admitted with a head injury. Approximately one hour ago he was hit on the lateral aspect of his head by a high velocity cricket ball. A collateral history reveals that he lost consciousness immediately after the impact. Paramedics on the scene noted his Glasgow coma score of 15. On examination he has Glasgow coma score of 13 (M5, V4, E4) on arrival in the department. He has anterograde and retrograde amnesia to events. You arrange an urgent CT scan.
Which clinical sign would be most concerning in this patient?
Decreased pulse pressure