MRI is excellent in the subacute phase in demonstrating lesions which can influence their clinical evolution and prognosis of the patient. In the acute phase some information about extracranial carotid-vertebral arteries can be obtained by ultrasounds. Angiography is commonly not necessary unless an acute endovascular treatment is indicated for instance a dramatic epistaxis. As far as concerns the stroke we have to distinguish between the hemorrhagic and the ischemic-one. A particular form of hemorrhagic stroke is subarachnoid hemorrhage.
Cerebral aneurysms are in general responsible for it.
In the acute phase CT is the best method for the evaluation of the hemorrhagic stroke. MR is superior in the subacute-chronic phase. Cerebral angiography is not needed in hypertensive haemorrhage, but should be performed in the majority of other cases, in particular if we suspect a vascular malformation. Ischemia is the most frequent cause of stroke. It is due to a critical local diminished blood flow to brain parenchyma.