ABSTRACT
Neuroimaging serves several purposes in acute stroke. Gradient echo sequences further aid the distinction between infarction and haemorrhage, although in general terms, this requires greater skill and experience than with Computed tomography (CT) scanning. A non-contrast enhanced CT (NCCT) brain scan will provide enough diagnostic information in many patients. A NCCT scan is also a sensitive and specific test for subarachnoid haemorrhage where congealed blood is seen as hyper intensity within the subarachnoid space. The diagnostic utility of CT scanning can be enhanced by the use of intravenous contrast agents that allow blood within blood vessels to be visualized and the passage of contrast through the brain to be monitored. MRI provides greater information than CT imaging in the context of acute stroke. Perfusion-weighted MRI is similar in principle to CT perfusion. Transcranial Doppler can be used to measure cerebral vasomotor reactivity, which is the compensatory dilatatory capacity of cerebral resistance vessels in response to increased arterial carbon dioxide concentration.
