Transient ischemic attack
A transient ischemic
attack (TIA) is a transient episode
of neurologic dysfunction caused by ischemia (loss of
blood flow) – either focal
brain, spinal
cord or retinal –
without acuteinfarction (tissue
death). TIAs have the same underlying cause as strokes: a
disruption ofcerebral blood
flow (CBF), and are frequently referred to
as mini-strokes. TIAs and strokes cause the
same symptoms, such as contralateral paralysis
(opposite side of body from affected brain hemisphere) or sudden
weakness or numbness. A TIA may cause sudden dimming or loss of
vision (amaurosis
fugax), aphasia, slurred speech
(dysarthria) and
mental confusion. But unlike a stroke, the symptoms of a TIA can
resolve within a few minutes or 24 hours. Brain injury may still
occur in a TIA lasting only a few minutes. Having a TIA is a risk
factor for eventually having a stroke or a silent
stroke.[1][2] A
silent stroke or silent
cerebral infarct (SCI) differs from a TIA in that there
are no immediately observable symptoms. A SCI may still cause long
lasting neurological dysfunction affecting such areas
as mood,
personality and cognition. A SCI often occurs before or after a TIA
or major stroke.[3]
A
cerebral infarct that lasts
longer than 24 hours but fewer than 72 hours is called a reversible
ischemic neurologic deficit or RIND.
Symptoms vary widely from person to person, depending on the area
of the brain involved. The most frequent symptoms include temporary
loss of vision (typically amaurosis
fugax); difficulty speaking (aphasia); weakness on
one side of the body (hemiparesis); and
numbness or tingling (paresthesia),
usually on one side of the body. Impairment of consciousness is
very uncommon. There have been cases of temporary and
partial paralysis affecting
the face and tongue of the
afflicted. The symptoms of a TIA are short-lived and usually last a
few seconds to a few minutes and most symptoms disappear within 60
minutes. Some individuals may have a lingering feeling that
something odd happened to the body. Dizziness, lack of
coordination or poor balance are also symptoms related to TIA.
Symptoms vary in severity.
The
most common cause of a TIA is an embolus that
occludes an artery in the brain. This usually arises from a
dislodgedatherosclerotic
plaque in one of the carotid
arteries (i.e. two of the four major
arteries supplying the brain) or from a thrombus (i.e. a
blood clot) in the heart because of atrial
fibrillation. In a TIA, the blockage period is very short-lived
and hence there is no permanent damage.[4] The
cholesterol build-up is gradual and eventually narrows
the lumen. With
time, blood flow to that side of the brain is reduced and a stroke
may result. In other cases, cholesterol particles from the
atherosclerotic plaque may suddenly break off and enter the brain.
In some people, these fragments come off from the heart and go to the
brain. This often happens during a heart
attack or an infection of the valves.[5]
Other reasons include excessive narrowing of large vessels
resulting from an atherosclerotic plaque and increased blood
viscosity caused by some blood
diseases. TIA is related to other medical conditions such
as hypertension, heart
disease (especially atrial
fibrillation), migraine, cigarette
smoking, hypercholesterolemia,
and diabetes
mellitus.
TIA
will usually be diagnosed after a doctor performs a history and
a physical
exam. There are several radiological tests
that are done to evaluate patients who have had a TIA. This
includes a CT
scan or an MRI of the brain, ultrasound of
the neck, an echocardiogram of
the heart. In most cases, the source of atherosclerosis is
usually identified with an ultrasound.[7]
Other diagnoses may have symptoms similar to those of a TIA:
A
TIA may be prevented by changes in lifestyle; although most of
these recommendations have no solid empirical data, most medical
professionals believe them to be so.[8] These
include:
The
mainstay of treatment following acute recovery from a TIA should be
to diagnose and treat the underlying cause. It is not always
immediately possible to tell the difference between a CVA (stroke) and a
TIA. Most patients who are diagnosed at a hospital'semergency
department as having suffered from a TIA will be
discharged home and advised to contact their primary physician to
organize further investigations. A TIA can be considered as the
last warning. The reason for the condition should be immediately
examined by imaging of the brain. Occasionally, none of these tests
will determine the cause, but the symptoms show that the stroke did
occur.
The
initial treatment is aspirin, second line
is clopidogrel (PLAVIX),
third line is ticlopidine. If TIA
is recurrent after aspirin treatment, the combination
of aspirin and dipyridamole is
needed (Aggrenox).
An electrocardiogram (ECG)
may show atrial
fibrillation, a common cause of TIAs, or other arrhythmias that
may cause embolisation to
the brain. An echocardiogram is
useful in detecting thrombus within
the heart chambers. Such patients benefit from anticoagulation.
If
the TIA affects an area supplied by the carotid arteries,
an ultrasound (TCD) scan
may demonstrate carotid stenosis. For people
with a greater than 70% stenosis within the carotid artery, removal
of atherosclerotic plaque by surgery, specifically a carotid
endarterectomy, may be recommended. The blood vessel is opened
up and the plaque is removed. The carotid may be replaced with a
vessel retrieved from the lower leg or foot. The procedure is not
technically difficult but carries the potential complication of
inducing a stroke. A stroke can occur during surgery or after the
procedure. The chance of a stroke ranges from 1–4
percent.[9]
Some
patients may also be given modified-release dipyridamole or
clopidogrel.
The
use of anti-coagulant medications, heparin and warfarin, or
anti-platelet medications
such as aspirin may be
warranted. Antiplatelet
drugs prevent platelets from agglutinating or sticking to
each other, hence the term "blood thinner." Thinning the blood
helps to ensure that small particles do not form and travel to the
brain. These drugs require frequent monitoring. These drugs also
have side effects such as easy bruising and bleeding from mild
trauma.[10]
People diagnosed with a TIA are sometimes said to have had a
warning for an approaching stroke. If the time
period of blood supply impairment lasts more than a few minutes,
the nerve cells of that area of the brain die and cause permanent
neurologic damage. One third of the people with TIA later have
recurrent TIAs and one third have a stroke because of permanent
nerve cell loss. Other sources cite that 10% of TIAs will develop
stroke within 90 days, half of which will occur in the first two
days following the TIA.[citation
needed] The risk of a stroke occurring
after a TIA can be predicted using the ABCD²
score.
