Cerebrovascular disease or Stroke or cerebrovascular accident is a vascular
disease of the cerebral circulation. Arteries supplying oxygen to the brain
are affected resulting in one of a number of cerebrovascular diseases. Most
commonly this is a stroke or mini-stroke and sometimes can be a hemorrhagic
stroke. Any of these can result in vascular dementia.
Hypertension is the most important contributing cause because it damages
the blood vessel lining exposing collagen where platelets aggregate to
initiate a repair. If maintained hypertension can change the structure of
blood vessels. Blood pressure affects blood flow in
narrowed vessels causing ischemic stroke, a rise in blood pressure can
cause tearing of vessels leading to intracranial hemorrhage.
A stroke usually presents with an abrupt onset of a neurologic deficit,
attributable to a focal vascular lesion. The neurologic symptoms manifest within
seconds because neurons lack glycogen, so energy failure is rapid.
Subtypes of Stroke Transient ischemic attack. This is a
condition in which the blood flow is quickly restored and the brain tissue
can fully recover and the symptoms are only transient, leaving no sequelae. In
order to diagnose this entity all neurologic signs and symptoms must have
been resolved within 24 h without evidence of brain infarction on brain
imaging. Ischemic stroke,the most common, usually
caused by thrombosis of the cerebral vessels themselves or by emboli from a
proximal arterial source or the heart, that completely blocks a brain blood
vessel. The neurologic signs and symptoms must last longer than 24 hours
or the brain infarction is demonstrated, mainly by imaging techniques.
Subarachnoid haemorrhage where blood leaks out of blood vessels directly into
or around the brain. The neurologic symptoms are produced by the blood mass
effect on neural structures, from the toxic effects of blood on the brain
tissue, or by the increasing of intracranial pressure.
Causes Causes of cerebrovascular disease can be
divided into: atherosclerosis, embolism, aneurysms, low flow states, and other
rare causes. Major modifiable risk factors include:
hypertension smoking
obesity diabetes.
Pathophysiology Once there is a reduction in blood flow
that lasts seconds the brain tissue suffers ischemia. If the interruption of
blood flow is not restored in minutes, the tissue suffers infarction followed
by tissue death. When the low cerebral blood flow persists for a longer
duration, then overcomes an infarction in the border zones. In more severe
instances, global hypoxia-ischemia causes widespread brain injury leading
to a severe cognitive sequelae called hypoxic-ischemic encephalopathy.
Strokes can also result from embolisms,furthermore, embolism blocks
small arteries causing damage to occur. Spontaneous rupture of a blood vessel in
the brain causes a hemorrhagic stroke. Another form of cerebrovascular disease
includes aneurysms.Cerebral aneurysms can be genetic in nature, due to a wall
deformity of the artery. Such aneurysms are common in individuals with genetic
diseases. The carotid arteries cover the majority
of the cerebrum. The common carotid artery divides into the internal and the
external cartoid arteries. The internal carotid artery becomes the anterior
cerebral artery and the middle central artery. The ACA transmits blood to the
frontal parietal. From the basilar artery are two posterior cerebral
arteries. Branches of the basilar and PCA supply the occipital lobe, brain
stem, and the cerebellum. Ischemia is the loss of blood flow to the focal
region of the brain.This produces heterogeneous areas of ischemia at the
affected vascular region, furthermore blood flow is limited to a residual
flow.Regions with blood flow of less than than 10 mL/100 g of tissue/min are
core regions( cells here die within minutes of a stroke).The ischemic
penumbra with a blood flow of