Most patients referred to the neurology service are seen only once or twice. For these patients a diagnosis can be made at the first consultation and treatment and advice provided. This can be characterised as a ‘type A’ strategy, when you know what is wrong and what to do about it. However, often we do not know what it is and have no specific treatment—but we do know what to do next: usually what tests to do, and what part of the nervous system to image, what symptomatic treatment might help. This is a ‘type B strategy’. Having an appropriate array of type B strategies is essential for successful follow-up clinics. Hopefully, with the benefit of the investigations (often helped by the passage of time), you may get into a position to switch back to a ‘type A’ solution. CT perfusion scanning in acute stroke is a type B strategy (described on page 136 by Stevan Wing and Hugh Markus) that …