Cerebrovascular disease

Cerebrovascular disease
Cerebral angiogram of a carotid-cavernous fistula
Classification and external resources
ICD-10	I60-I69

A cerebrovascular disease 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.^[1] Most commonly this is a stroke or mini-stroke and sometimes can be a hemorrhagic stroke.^[1] Any of these can result in vascular dementia.^[2]

Hypertension (high blood pressure) 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 (narrow, deformed).^[3]

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.^[4]

A stroke usually presents with an abrupt onset of a neurologic deficit, attributable to a focal vascular lesion.^[5] The neurologic symptoms manifest within seconds because neurons lack glycogen, so energy failure is rapid.^[6]

Types of stroke

• Ischemic stroke,the most common is caused by a blockage of a blood vessel in the brain, usually caused by thrombosis or emboli from a proximal arterial source or the heart, that leads to the brain being starved of oxygen.^[7] The neurologic signs and symptoms must last longer than 24 hours or the brain infarction is demonstrated, mainly by imaging techniques.^[8]
• Transient ischemic attack (TIA) also called a mini-stroke. 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.^[9] In order to diagnose this entity all neurologic signs and symptoms must have been resolved within 24 hrs without evidence of brain infarction on brain imaging.^[10]
• Subarachnoid haemorrhage where blood leaks out of blood vessels directly into or around the brain.^[1] 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.^[11]

Causes

Causes of cerebrovascular disease can be divided into: atherosclerosis, embolism, aneurysms, low flow states, and other rare causes.^[12] Major modifiable risk factors include:^[13]

Pathophysiology

Once a reduction in blood flow occurs, that lasts seconds the brain tissue suffers ischemia.^[14][15] If the interruption of blood flow is not restored in minutes, the tissue suffers infarction followed by tissue death.^[16] When the low cerebral blood flow persists for a longer duration, this may develop into an infarction in the border zones (areas of poor blood flow between the major cerebral artery distributions). In more severe instances, global hypoxia-ischemia causes widespread brain injury leading to a severe cognitive sequelae called hypoxic-ischemic encephalopathy.^[17]

Strokes can also result from embolisms, furthermore, embolisms block small arteries, causing damage to occur.^[4] Spontaneous rupture of a blood vessel in the brain causes a hemorrhagic stroke.^[18] 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 ( connective tissue disorders, polycystic kidney disease, and arteriovenous malformations).^[19]

Brain infarct

The carotid arteries cover the majority of the cerebrum. The common carotid artery divides into the internal and the external carotid 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.^[20] 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 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 <25 ml/100g tissue/min, remain usable for more time (hours).^[21]

An ischemic cascade occurs where an energetic molecular problem arises. ATP consumption continues in spite of insufficient production, this causes total levels of adenosine triphosphate to decrease and lactate acidosis to become established (ionic homeostasis in neurons is lost). The downstream mechanisms of the ischemic cascade thus begins. Ion pumps no longer transport Ca²⁺ out of cell, this triggers release of glutamate, which in turn allows calcium into cell walls. In the end the apoptosis pathway is initiated and cell death occurs.^[22]

Evaluation

Diagnosis of cerebrovascular disease is done by (among other diagnoses):^[23]

• clinical history
• physical exam
• neurological examination.

It is important to differentiate the symptoms caused by a stroke from those caused by syncope (fainting) which is also a reduction in cerebral blood flow, almost always generalized, but they are usually caused by systemic hypotension of various origins: cardiac arrhythmias, myocardial infarction, hemorrhagic shock, among others.^[24]

Treatment

Treatment for cerebrovascular disease includes medication, lifestyle changes and surgery.^[4]

Examples of medications are:

• antiplatelets (aspirin, clopidogrel)
• blood thinners (heparin, warfarin)
• antihypertensives (ACE inhibitors, beta blockers)
• anti-diabetic medications.

Surgical procedures include:

• endovascular surgery and vascular surgery (for future stroke prevention).

Epidemiology

Disability-adjusted life year for cerebrovascular disease per 100,000 inhabitants in 2004.^[25]

  less than 250

  250–425

  425–600

  600–775

  775–950

  950–1125

  1125–1300

  1300–1475

  1475–1650

  1650–1825

  1825–2000

  more than 2000

Worldwide, it is estimated there are 31 million stroke survivors, though about 6 million deaths were due to cerebrovascular disease (2nd most common cause of death in the world and 6th most common cause of disability).^[26]

Cerebrovascular disease primarily occurs with advanced age; the risk for developing it goes up significantly after 65 years of age. CVD tends to occur earlier than Alzheimer's Disease (which is rare before the age of 80). In some countries such as Japan, CVD is more common than AD.

In 2012 6.4 million US individuals (adults) had a stroke, which corresponds to 2.7% in the U.S. With approximately 129,000 deaths in 2013 (U.S.)^[27]

Geographically, a "stroke belt" in the US has long been known, similar to the "diabetes belt"which includes all of Mississippi and parts of Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, and West Virginia.^[28]

References

Further reading

• Chan, Pak H. (2002-03-28). Cerebrovascular Disease: 22nd Princeton Conference. Cambridge University Press. ISBN 9781139439657. 
• Mark, Steven D.; Wang, Wen; Fraumeni, Joseph F.; Li, Jun-Yao; Taylor, Philip R.; Wang, Guo-Qing; Guo, Wande; Dawsey, Sanford M.; Li, Bing (1996-04-01). "Lowered Risks of Hypertension and Cerebrovascular Disease after Vitamin/Mineral Supplementation The Linxian Nutrition Intervention Trial". American Journal of Epidemiology. 143 (7): 658–664. doi:10.1093/oxfordjournals.aje.a008798. ISSN 0002-9262. PMID 8651227. 
• Ning, MingMing; Lopez, Mary; Cao, Jing; Buonanno, Ferdinando S.; Lo, Eng H. (2012-12-01). "Application of proteomics to cerebrovascular disease". Electrophoresis. 33 (24). doi:10.1002/elps.201200481. ISSN 0173-0835. PMC 3712851. PMID 23161401. 

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