Strokes otherwise called Cardiovascular Accidents (CVA)
are the sudden impairment of cerebral circulation in one
or more blood vessels.  Stroke in one hemisphere of the
brain causes deficits on the opposing side, while stroke
that damages cranial nerves affects structures on the
same side (Path physiology made incredibly easy, 2006).
The highest incidence of stroke occurs among people over
65 years old and 2.5 times higher in blacks than whites.
Depending on the severity of the damage and the type of
strokes the symptoms vary. In order to treat the
symptoms appropriately, identification of the types of
stroke is critical. 

Overall risk factors are: Arterial Hypertension;
elevated systolic and diastolic hypertension,; smoking
increases the risks by 50%; diabetes increases the risks
of ischemic strokes 2.5 to 3.5 times; insulin resistance
is an independent  risk factor for ischemic strokes;
obesity and sedentary lifestyle; history of transient
ischemic attack (TIA); hyperlipidemia; increase alcohol
intake; use of hormonal contraceptive; Atrial
fibrillation is associated with a 5 fold increase in
ischemic stroke; and chlamydia pneumoniae can cause
increase risk of stroke by injury to epithelium. 

Types of strokes:

Ischemic stroke:  This is the most common type
accounting for 88% of all strokes. It occurs when an
artery to the brain is blocked. If the artery is blocked
for more than a few minutes, brain cells may die. It’s
most commonly caused by atherosclerotic changes in the
vessels in the head and neck. If the arteries become too
narrow blood cells can collect there and form clots.
These blood clots can either stay put and block the
vessel or they can dislodge and become trapped in
arteries closer to the brain. Another cause of ischemic
strokes is blood clots in the heart as a result of an
irregular heart rate (e.g. atrial fibrillation), heart
attack or abnormalities in the heart valves. Some less
frequent causes include use of street drugs, traumatic
injury to the vessels in the head and neck or
abnormalities of blood clotting. Ischemic strokes can be
further sub-divided into two types – thrombotic and
embolic. Thrombolic strokes occur when cerebral arteries
become blocked by a clot.  An embolic stroke is also a
blockage of a cerebral artery but the difference is that
that the clot was formed elsewhere in the body. The most
common place embolic strokes are formed is in the heart.
Conditions associated with embolic stroke are atrial
fibrillation, MI, endocarditis, Rheumatic heart disease,
valvular prosthesis, atrial septal defect, and disorders
of the aorta.  Less common causes are air, fat and
tumors. 

Intracerebral hemorrhage: This type of stroke occurs
when a damaged blood vessel within the brain bursts with
subsequent bleeding into the brain. It usually occurs in
selected areas of the brain e.g. basal ganglia,
cerebellum, brainstem or cortex. Brain cells are damaged
by the build up in pressure due to the blood leakage.
The most common reason for this type of stroke is
hypertension untreated. Other less common reasons
include trauma, infections, and malformations of the
vessels in the brain and clotting deficiencies.
Hemorrhagic strokes are the 3rd most common cause of CVA
and account for 10 -15% in whites and 30% in blacks and
Asians. Risk Factors for Hemorrhagic strokes are:
1.Hypertension cerebral 2. Previous infarct. 3. Coronary
artery disease 4. Diabetes. Hemorrhages are described as
massive, (several centimeters in diameter) small (1-2
cms.) slit or petticheal (pinhead).

Subarachnoid hemorrhage: This type of stroke occurs when
a blood vessel outside the brain ruptures. The
subarachnoid space (between the brain and skull) fills
with blood and causes intense pressure. Often the person
describes the ensuing headache as the worst headache
they have ever had in their life. It may also be
accompanied by neck pain, nausea and vomiting. It’s most
often caused by cerebral aneurysms – small swellings in
the arteries of the brain. These aneurysms are prone to
weakness and eventual rupture. It can occur at any age.
Head trauma and Arteriovenous malformation are common
causes.

http://www.strokecenter.org/pat/stroke_types.htm


Pathophsiology : An incredibly easy  pocket guide (2006.
Philadelphia: Lippincott William- Wilkins