2. Blood supply to nerves system
The central nervous system, like any system of the body,
requires constant oxygenation and nourishment.
The brain has a particularly high oxygen demand at rest. it
represents one fifth of the body’s total oxygen consumption.
It is also very sensitive to oxygen deprivation, with ischemic
cell death resulting within minutes.
Arterial Supply to the Brain
There are two paired arteries which are responsible for the
blood supply to the brain; the vertebral arteries, and
the internal carotid arteries. These arteries arise in the
neck, and ascend to the cranium.
3.
4. CONT..
• Internal Carotid Arteries
• The internal carotid arteries (ICA) originate at the bifurcation
of the left and right common carotid arteries, at the level of
the fourth cervical vertebrae (C4).
• They move superiorly within the carotid sheath, and enter the
brain via the carotid canal of the temporal bone. They do not
supply any branches to the face or neck.
• Once in the cranial cavity, the internal carotids pass interiorly
through the cavernous sinus. Distal to the cavernous sinus,
each ICA gives rise to:
• Anterior choroidal artery – supplies structures in the brain
important for motor control and vision.
• Anterior cerebral artery – supplies part of the cerebrum.
• The internal carotids then continue as the middle cerebral
artery, which supplies the lateral portions of the cerebrum.
5. CONT..
• Vertebral Arteries
• The right and left vertebral arteries arise from
the subclavian arteries, medial to the anterior scalene
muscle. They then ascend the posterior aspect of the
neck, through holes in the transverse processes of the
cervical vertebrae, known as foramen transversarium.
• The vertebral arteries enter the cranial cavity via
the foramen magnum. Within the cranial vault, some
branches are given off:
• Meningeal branch – supplies the falx cerebelli, a sheet
of dura mater.
• Anterior and posterior spinal arteries – supplies the
spinal cord, spanning its entire length.
• Posterior inferior cerebellar artery – supplies the
cerebellum.
6. CONT…
Regional Blood Supply to the Cerebrum
There are three cerebral arteries; anterior, middle and posterior. They
each supply a different portion of the cerebrum.
The anterior cerebral arteries supply the anteromedial portion of the
cerebrum. The middle cerebral arteries are situated laterally, supplying
the majority of the lateral part of the brain. The posterior cerebral
arteries supply both the medial and lateral parts of
the posterior cerebrum.
7. Cerebrovascular accident (CVA)
• The brain is particularly sensitive to oxygen starvation. A stroke is an acute
development of a neurological deficit, due to a disturbance in the blood supply
of the brain.
• There are four main causes of a cerebrovascular accident:
• Thrombosis – obstruction of a blood vessel by a locally forming clot.
• Embolism – obstruction of a blood vessel by an embolus formed elsewhere.
• Hypoperfusion – lack of blood supply to the brain, due to systemically low
blood pressure (e.g shock).
• Hemorrhage – an accumulation of blood within the cranial cavity.
• Out of these four, the most common cause is embolism. In many patients,
the atherosclerotic embolus arises from the vessels of the neck.
• Intracerebral Aneurysms
• An aneurysm is a dilation of an artery, which is greater than 50% of the normal
diameter. They are most likely to occur to occur in the vessels contributing to
the Circle of Willis. They are particularly dangerous – producing
few symptoms until they rupture. Upon rupture, blood typically accumulates in
the subarachnoid space – with a subsequent increase in intracranial pressure.
8. Cerebrovascular accident (CVA)
• Cerebrovascular accident
(CVA) is the medical term
for a stroke. A stroke is
when blood flow to a part of
your brain is stopped either
by a blockage or the rupture
of a blood vessel. There are
two main types of
cerebrovascular accident, or
stroke: an ischemic stroke is
caused by a blockage;
a hemorrhagic stroke is
caused by the rupture of a
blood vessel. Both types of
stroke deprive part of the
brain of blood and oxygen,
causing brain cells to die.
9. Ischemic stroke
• An ischemic stroke is the
most common and occurs
when a blood clot blocks a
blood vessel and prevents
blood and oxygen from
getting to a part of the
brain. There are two ways
that this can happen. One
way is an embolic stroke,
which occurs when a clot
forms somewhere else in
your body and gets lodged
in a blood vessel in the
brain. The other way is a
thrombotic stroke, which
occurs when the clot forms
in a blood vessel within the
brain.
10. Hemorrhagic stroke
• A hemorrhagic stroke occurs when a blood vessel
ruptures, or hemorrhages, and then prevents blood
from getting to part of the brain. The hemorrhage
may occur in any blood vessel in the brain, or it
may occur in the membrane surrounding the
brain.
11. Symptoms of a cerebrovascular
accident
• The quicker you can get a diagnosis and treatment for a stroke, the
better your prognosis will be. For this reason, it’s important to
understand and recognize the symptoms of a stroke.
Stroke symptoms include:
difficulty walking
dizziness
loss of balance and coordination
difficulty speaking or understanding others who are speaking
numbness or paralysis in the face, leg, or arm, most likely on just
one side of the body
blurred or darkened vision
a sudden headache, especially when accompanied by nausea,
vomiting, or dizziness
12. CONT..
• The symptoms of a stroke can vary depending on the
individual and where in the brain it has happened.
Symptoms usually appear suddenly, even if they’re not
very severe, and they may become worse over time.
• Remembering the acronym “FAST” helps people
recognize the most common symptoms of stroke:
• Face: Does one side of the face droop?
• Arm: If a person holds both arms out, does one drift
downward?
• Speech: Is their speech abnormal or slurred?
• Time: It’s time to call 1122 and get to the hospital if
any of these symptoms are present.
13. DIAGNOSTIC CRITERIA
• Blood tests: Your healthcare provider may want to test your blood for
clotting time, blood sugar levels, or infection. These can all affect the
likelihood and progression of a stroke.
• Angiogram: An angiogram, which involves adding a dye to your blood
and taking an X-ray of your head, can help your doctor find the
blocked or hemorrhaged blood vessel.
• Carotid ultrasound: This test uses sound waves to create images of the
blood vessels in your neck. This test can help your provider determine
if there’s abnormal blood flow toward your brain.
• CT scan: A CT scan is often performed soon after symptoms of a
stroke develop. The test can help your provider find the problem area
or other problems that might be associated with stroke.
• MRI scan: An MRI can provide a more detailed picture of the brain
compared to CT scan. It’s more sensitive than a CT scan in being able
to detect a stroke.
14. Treatment for a cerebrovascular
accident
• Treatment for stroke depends on the type of stroke you’ve had. The
goal of treatment for ischemic stroke, for instance, is to restore the
blood flow. Treatments for hemorrhagic stroke are aimed at
controlling the bleeding.
• Ischemic stroke treatment
• To treat an ischemic stroke, you may be given a clot-dissolving drug
or a blood thinner. You may also be given aspirin to prevent a
second stroke. Emergency treatment for this type of stroke may
include injecting medicine into the brain or removing a blockage
with a procedure.
• Hemorrhagic stroke treatment
• For a hemorrhagic stroke, you may be given a drug that lowers the
pressure in your brain caused by the bleeding. If the bleeding is
severe, you may need surgery to remove excess blood. It’s also
possible that you will need surgery to repair the ruptured blood
vessel.
15. Long-term outlook for a cerebrovascular
accident
• There’s a recovery period after having any kind of stroke.
The length of recovery varies depending on how severe the
stroke was. You may need to participate in rehabilitation
because of the stroke’s effects on your health, particularly
any disabilities it may cause. This can include speech
therapy or occupational therapy, or work with a
psychiatrist, neurologist, or other healthcare professional.
16. Prevention of a cerebrovascular
accident
• There are many risk factors for having a stroke,
including diabetes, atrial fibrillation,
and hypertension (high blood pressure).
• Correspondingly, there are many measures you can take to
help prevent stroke. Preventive measures for stroke are
similar to the actions that you would take to help prevent
heart disease. Here are a few ways to reduce your risk:
• Maintain normal blood pressure.
• Limit saturated fat and cholesterol intake.
• Refrain from smoking, and drink alcohol in moderation.
• Control diabetes.
• Maintain a healthy weight.
• Get regular exercise.
• Eat a diet rich in vegetables and fruits.
17. Transient ischemic attack (TIA)
• A transient ischemic attack (TIA) is a temporary period of
symptoms similar to those of a stroke. A TIA usually lasts
only a few minutes and doesn't cause permanent damage.
• Often called a ministroke, a TIA may be a warning. About 1
in 3 people who has a TIA will eventually have a stroke,
with about half occurring within a year after the TIA.
• A TIA can serve as both a warning of a future stroke and an
opportunity to prevent it
18. Symptoms
• Weakness, numbness or paralysis in the face, arm or
leg, typically on one side of the body
• Slurred or garbled speech or difficulty understanding
others
• Blindness in one or both eyes or double vision
• Vertigo or loss of balance or coordination