Biology of Disease

in most cases, by high blood pressure, but it can also be a consequence of

certain hereditary conditions. The clinical picture includes stroke, heart

attack, sudden abdominal pain, nerve damage and an inability to move a limb.

Treatment in intensive care is required. Drugs are given to reduce the heart

rate and lower the blood pressure. Thereafter a decision needs to be taken

as to whether to carry out surgery to replace the portion of damaged blood

vessel with a synthetic graft. Untreated, about 75% of patients die within two

weeks, but following treatment several years of life are possible in the majority

of cases even though the death rate from surgery is 15% or more.

Stroke

If the blood supply to the brain is disrupted for any length of time the brain

cells can be permanently damaged or die due to the lack of oxygen and this

is called a cerebrovascular accident (CVA) or stroke (Figure 14.17). Brain cells

are also damaged if bleeding into the brain occurs. Therefore strokes can be

either ischemic or hemorrhagic. In ischemic stroke the blood supply to part

of the brain is cut off either because of atherosclerosis or a clot blocking a

blood vessel. In hemorrhagic stroke, a blood vessel bursts, preventing normal

flow of blood and allowing it to leak into an area of the brain and destroy it.

In the developed world, strokes are the most common cause of disabling

neurological damage resulting, typically, in a loss of speech and/or loss of motor

function on one side of the body. High blood pressure and atherosclerosis

are the major risk factors. The incidence is falling because the importance

of controlling high blood pressure and dealing with inappropriate blood

cholesterol levels has been recognized. Clinicians can usually diagnose a stroke

from the clinical history of events and a physical examination. Computerized

tomography scans and MRI (Chapter 18) are used for differential diagnoses.

Many people who have had a stroke recover some or all of their normal

functions but others may be mentally and physically devastated, unable to

speak or move normally. About 20% of people who have had a stroke die

in hospital and the older the patient the greater the risk of this happening.

Since each area of the brain is served by specific blood vessels, the area

where the cerebrovascular accident occurs decides which part of the body

becomes disabled. The loss of function is greatest just after the stroke and

some function may return subsequently. This is because although some brain

cells die, others may recover and take over a given function at least partially.

The immediate treatment is to give oxygen to try to prevent further damage.

Anticoagulants may be given if the stroke is ischemic but these are of little use

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Figure14.17 Photomicrographs showing (A)

normal brain tissue with the nuclei of numerous

neurones prominent. (B) Brain tissue following

an ischemic stroke. The area of damaged

(infarcted) tissue is enclosed. Note the surviving

blood vessels (SBV).

A) B)

SBV

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