WHAT IS STROKE?
- 1WHAT IS THE MEANING OF STROKE?
- A stroke involves the abrupt onset of focal neurologic deficit that lasts at least 24 hours and is presumed to be of vascular origin. Stroke can be either ischemic or hemorrhagic. Transient ischemic attacks (TIAs) are focal ischemic neurologic deficits lasting less than 24 hours and usually less than 30 minutes.
- 2WHAT ARE THE CAUSES OF STROKE?
- Ischemic strokes (87% of all strokes) are due either to local thrombus formation or emboli occluding a cerebral artery. Cerebral atherosclerosis is a cause in most cases, but 30% are of unknown aetiology. Emboli arise either from intra- or extracranial arteries. Twenty per cent of ischemic strokes arise from the heart.
- Carotid atherosclerotic plaques may rupture, resulting in collagen exposure, platelet aggregation, and thrombus formation. The clot may cause local occlusion or dislodge and travel distally, eventually occluding a cerebral vessel.
- In cardiogenic embolism, stasis of blood flow in the atria or ventricles leads to the formation of local clots that can dislodge and travel through the aorta to the cerebral circulation.
- Thrombus formation and embolism result in arterial occlusion, decreasing cerebral blood flow and causing ischemia and ultimately infarction distal to the occlusion.
- Hemorrhagic strokes (13% of strokes) include subarachnoid haemorrhage (SAH) and intracerebral haemorrhage. SAH may result from trauma or rupture of an intracranial aneurysm or arteriovenous malformation (AVM). Intracerebral haemorrhage occurs when a ruptured blood vessel within the brain causes a hematoma.
- Blood in the brain parenchyma causes mechanical compression of vulnerable tissue and subsequent activation of inflammation and neurotoxins.
- 3WHAT ARE THE SIGNS AND SYMPTOMS OF STROKE?
- Patients may be unable to provide a reliable history because of neurologic deficits. Family members or other witnesses may need to provide this information.
- Symptoms include unilateral weakness, inability to speak, loss of vision, vertigo, or falling. Ischemic stroke is not usually painful, but headache may occur in hemorrhagic stroke.
- Neurologic deficits on physical examination depend on the brain area involved. Hemi- or monoparesis and hemisensory deficits are common. Patients with posterior circulation involvement may have vertigo and diplopia. Anterior circulation strokes commonly result in aphasia. Patients may experience dysarthria, visual field defects, and altered levels of consciousness.