With its effects upon the brain, heart, kidneys,
and extremities, vascular disease is the leading cause of morbidity
and mortality in the United States. It is no wonder that vascular
diseases are familiar to coders. We spend hundreds of hours
every year coding vascular conditions, diagnostic, and therapeutic
procedures. This month, we are reviewing some of the most common
cerebrovascular diseases, along with the procedures done to
diagnose and treat them. It is important to note here that,
because of the prevalence of vascular diseases and the need
for effective treatment, diagnostic and therapeutic methods
are constantly evolving. Coders should communicate regularly
with their vascular specialists to keep up with the latest changes.
When blood leaves the heart via the left ventricle, it enters
the aorta, the central artery in the body from which
all arteries branch. The aorta is generally divided into three
parts: the ascending aorta, the aortic arch,
and the descending aorta. The ascending aorta is the
shortest part with only two branches, the right and
left coronary arteries, which supply blood to the heart
muscle. As the aorta leaves the pericardial sac, it arches
dorsally and to the left, forming the aortic arch.
Three branches arise from the arch: the brachiocephalic
artery, the left common carotid artery, and the
left subclavian artery. These arteries supply blood to
the head, neck, and arms.
The brachiocephalic artery travels only a short distance
before it divides into the right subclavian artery
and the right common carotid artery. Together with
the left common carotid artery, which arises
directly from the aortic arch, the right common carotid artery
supplies most of the blood to the head and neck. The common
carotids travel up the neck alongside the trachea and then
divide again into the internal carotid artery
and the external carotid artery. At the point where
the common carotids divide (also called the bifurcation),
the vessels enlarge, forming what is called the carotid
sinus. This sinus has pressure receptors to aid in blood
pressure control. In the same area is a small oval carotid
body containing chemoreceptors which monitor changes in
oxygen, carbon dioxide, and pH levels in blood traveling to
the brain. The external carotid carries blood to most of the
head and neck except for the brain. The internal carotid artery
supplies the brain through its end branches, the anterior
and middle cerebral arteries.
The right and left vertebral arteries branch
off the subclavian artery, traveling upward and providing
another major blood supply to the brain. They pass up through
the transverse foramina of the cervical vertebrae. Once in
the cranial vault, they unite to form the basilar artery.
Acute organic conditions affecting the cerebrovascular system
include arteriosclerosis, occlusion, thrombosis, and hemorrhage.
Cerebrovascular disease is grouped into one of five categories
depending upon the patient’s presenting symptoms:
- Asymptomatic Disease:
An audible bruit may be heard in the neck as the only
manifestation of any underlying disease.
- Transient Neurologic or Visual
Deficit: Symptoms in this category depend
upon where an embolus is lodged, the size and composition
of the embolus, and the presence of collateral vessels.
- Acute Unstable Neurologic Deficit:
Patients have increasing transient ischemic attacks (TIAs),
stroke in evolution, or waxing and waning neurologic symptoms.
Urgent treatment is required.
- Completed Stroke:
Patients are still at risk for another stroke without
immediate intervention.
- Vertebrobasilar Disease:
Emboli or hypoperfusion of the vertebral and basilar
arteries which supply blood to the back of the brain can
cause drop attacks, clumsiness, or other sensory problems.
Arteriosclerosis and Atherosclerosis
Arteriosclerosis is a chronic, generalized condition
occurring in small arterioles as well as in large vessels.
During the aging process, fibrosis and some intimal thickening
develop, with weakening and disruption of the elasticity of
the walls of the great arteries (e.g., the aorta and its major
branches). The smooth muscle layer of the vessels atrophies
to a certain extent, and the lumen of the aorta or one of
its branches widens (ectasia) and may lead to aneurysm.
Atherosclerosis affects medium and large arteries
and is characterized by patchy intramural thickening that
encroaches on the arterial lumen, and in its most severe form
causes obstruction. The atherosclerotic plaque consists of
accumulated lipids and other cellular debris.
Plaque may grow slowly over years and produce severe stenosis
or total occlusion. With time, the plaque becomes calcified
and may undergo spontaneous rupture into the bloodstream.
The ruptured plaque stimulates thrombosis; the thrombi may
embolize, rapidly block the lumen, or gradually become incorporated
into the plaque, contributing to its bulk and occlusive properties.
Carotid Artery Occlusive
Disease
Atherosclerotic carotid artery disease is the leading cause
of stroke. Treatment is aimed at prevention of this complication.
"Mini-Strokes" or TIAs don't always precede a permanent
stroke, and severe blockage (>70%) is usually treated surgically,
even if there have been no symptoms.
Transient Ischemic Attacks
Transient ischemic attacks (TIAs) are one of the earliest
signs of cerebrovascular disease. These episodes may last
only seconds or as long as 24 hours. Some of the neurologic
deficits during a TIA are identical to those seen with stroke,
but they are of short duration with no lingering effects.
Symptoms may include temporary paralysis of a limb, inability
to speak or garbled speech, or changes in vision. Amaurosis
fugax (temporary blindness of one eye) is a term commonly
seen in a description of presenting symptoms in TIA patients.
The etiology of a TIA is temporary obstruction of a cerebral
vessel by a small particle of atheromatous debris or a blood
clot usually embolized from plaque in the carotid artery.
Stroke in Evolution and
Completed Stroke
A stroke in evolution is a growing infarction of brain tissue
with neurologic symptoms that increase over a period of 24
to 48 hours. A completed stroke is an infarction of brain
tissue manifested by neurologic deficits of varying degrees.
Stroke is responsible for nearly 150,000 U.S. deaths each
year and ranks as the third leading killer in the United States.
A stroke (or cerebrovascular accident) occurs when
a vessel which supplies blood to the brain is blocked by an
intraluminal blood clot (cerebral thrombosis) or when
it ruptures (cerebral hemorrhage). Flow of blood to
the brain is reduced, causing the area of affected brain tissue
to degenerate and die. The area of tissue breakdown is called
an infarct or infarction. A cerebral hemorrhage
is a much more serious type of stroke because the blood escapes
into brain tissue under high pressure, thus causing more extensive
damage.
Stroke may also be caused by disease in any of the precerebral
arteries arising from the aorta to supply the brain. As
mentioned above, one common site is at the origin of the internal
carotid artery in the neck, where atheromatous plaques may
narrow the lumen and reduce blood flow. These plaques may
also become ulcerated, and thrombi may form on the roughened
surfaces. Bits of debris or thrombus may break off and travel
to the brain where they block smaller cerebral arteries. Once
a thrombus breaks off and travels through the vascular system
it is called an embolus. Sometimes the internal carotid
artery becomes completely blocked by a thrombus before it
breaks apart, leading to a large cerebral infarction.
Subclavian Steal Syndrome
Subclavian steal is another condition that causes reduction
in the amount of blood reaching the brain. As noted above,
the vertebral arteries feed the back of the brain, and branch
off the subclavian artery. In subclavian steal, blockage of
the subclavian artery occurs proximal to the vertebral artery
branch. This blockage causes reversal of blood flow through
the vertebral artery as the subclavian artery steals blood
that normally flows up to the brain.
Cerebral Aneurysm
An aneurysm is a localized dilation of an artery due to weakness
of the arterial wall. Aneurysms may occur in any of the arteries
that supply the brain. Occasionally an aneurysm occurs in
the large cerebral arteries at the base of the brain. The
most common type is a congenital cerebral aneurysm. Over time,
the weakness of the artery causes a bubble or saclike protrusion
of the artery through the defect. Though the weakness is present
from birth, the aneurysm does not usually develop until adulthood.
Cerebral aneurysms larger than 2.5 cm in diameter are termed
giant. Their incidence is around 5% of all intracranial aneurysms.
The peak age of occurrence is 60 years. The danger, as with
any aneurysm, is that the aneurysm sac will rupture and cause
tissue damage. When this happens in the brain, the results
can be fatal.
Some of the following tests are used to diagnose not only
cerebrovascular disease, but vascular lesions of other circulatory
sites as well. A review of the results of these tests in the
medical record is important for correct code assignment.
- Cerebral Angiogram/Cerebral Arteriogram:
This test tracks cerebral blood flow by injecting radiopaque
dye into the carotid and vertebral arteries. The course
of the dye is followed by serial x-rays.
- Digital Subtraction Angiography
(DSA): DSA is also an x-ray study of the
carotid artery. It is similar to arteriography except that
less dye is used.
- Magnetic Resonance Angiography
(MRA): This is one of the newest imaging techniques.
It is more accurate than ultrasound and avoids the risks
associated with x-rays and dye injection. An MRA is a type
of magnetic resonance image that uses special software to
create an image of the arteries in the brain. The shifts
in the magnetic field where blood flows through vessels
allows three-dimensional "mapping" of arteries
and veins. Although the results of this test are not as
accurate as a traditional contrast arteriogram, MRAs do
not require the injection of contrast dye and therefore
involve less risk for the patient.
- Doppler Ultrasound Imaging:
This is a highly versatile, noninvasive test in which sound
waves are bounced off soft tissue. Ultrasound gives anatomic
and physiologic information regarding the location and severity
of blockages in arteries and veins. Similar to radar, scanners
can detect the turbulent, high velocity flow patterns common
around serious arterial narrowing. The degree of stenosis
is usually expressed as a percentage of the normal diameter
of the vessel opening.
- Plethysmography: This
method of detecting vessel blockages senses the quantity
and quality of arterial blood flow into an extremity. Coupled
with the measurement of segmental blood pressures (four
to six separate measurements in each extremity), plethysmography
accurately predicts the location and significance of arterial
disease.
- Oculoplethysmography (OPG):
This procedure measures the pulsation of the arteries in
the back of the eye. It is used as an indirect check for
blockages in the carotid arteries.
- Spiral Computed Tomography:
With sophisticated changes to a decades-old technology,
SPECT can produce 3-dimensional views of the arterial and
venous systems. This technology is not often needed, but
provides important information when it is used.
- Transcutaneous Oximetry:
Since the skin is the last part of an extremity to receive
blood, the amount of oxygen reaching the surface of the
skin is an important clue to the perfusion of the underlying
bone and muscle. When needed, small sensors are placed on
the extremity to measure the actual oxygen content of the
skin.
- Laser Doppler Flowmetry:
A laser-beam and tiny air bladder measure the blood
pressure in the skin capillaries. Like transcutaneous oximetry,
this test is not often needed, but is used to predict if
a wound can heal without major surgery, or if only a vascular
reconstruction will provide sufficient blood and oxygen.
- Angioscopy: A
fiberoptic catheter is passed directly into the artery to
visualize the blockage or damage or to assess the success
of a repair. This is sometimes used as a substitute to a
contrast arteriogram for patients allergic to contrast dyes.
- Carotid Endarterectomy:
A surgical excision of the arteriosclerotic lining of
the carotid artery increases the caliber of the lumen and
improve blood flow through the vessel. This procedure is
often accompanied by a carotid artery bypass graft. The
graft may be either synthetic, e.g., polytetrafluoroethylene
(PTFE), or autologous, with vessel harvested from either
the saphenous or jugular vein.
- Percutaneous Balloon Angioplasty
and Stenting: This is a relatively new
procedure for carotid artery disease, though balloon angioplasty
has been done for coronary arteries for some time. In this
procedure, a balloon-tipped catheter is maneuvered to the
site of carotid artery obstruction, and then the plaque
causing the obstruction is pushed to the sides of the artery
as the balloon is expanded. Sometimes a cage or wire stent
is then inserted into the carotid to support the work done
by the balloon and maintain vessel patency.
- Aneurysm Clipping and Occlusion:
Aneurysms are difficult to treat and are attacked in several
ways. This method involves applying a stainless steel clip
to the neck of the aneurysm to effectively seal it off from
its blood supply. Once this is done, the aneurysm is usually
deflated by the surgeon. A postoperative angiogram is done
to verify obliteration of the aneurysm. All modern aneurysm
surgery is performed with the aid of the operating microscope
and micro-instrumentation.
- Endovascular Aneurysm Coil Occlusion:
This procedure is often done following an incomplete
clipping of an aneurysm when residual aneurysm remains.
The surgeon inserts a coil within the vessel to complete
the obliteration of the aneurysm.
Now that you have a basic understanding of the cerebrovascular
system’s structure and various pathologies, try your
hand at coding the operative procedure on our Procedure
Practice page. Assign the ICD-9-CM diagnosis
code and the appropriate ICD-9-CM and CPT-4 codes for the
surgical procedure. Our suggestions appear on our Coding
Recommendations page.
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Major
Arteries of the Head and Neck
Diseases
of the Cerebrovascular System
Diagnostic
and Therapeutic Procedures
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