Question category: Neurology
A 72 year old male presents to his GP with severe right sided facial pain affecting his cheek. They occur intermittently and he can have several within an hour. They affect the upper part of the face, are very sudden and last a few seconds or so. It is aggravated by the cold. He has no PMH. On examination there is reduced sensation in the right cheek and forehead and loss of corneal reflex. What is the most likely diagnosis?