Urgent CT is mandatory to look for evidence of haemorrhage. 

Itís also important to look for signs of stroke mimics (such as other space occupying lesions). 

Early subtle signs of ischaemia may also be present on early CT and these include changes such as sulcal effacement. 

Itís important to remember that if there are clear signs of ischaemic change, than the time of onset needs to be carefully re-checked, as the stroke may be older than initially thought.