Stroke Diagnosis and Evaluation
A stroke occurs when blood vessels carrying oxygen to the brain
burst or become blocked, damaging the brain cells' ability to control
sensation, movement, or function, and eventually causing the nerve
cells to die.
The ability to pinpoint quickly the precise location of a stroke and
determine the extent of damage is critical in making treatment
decisions during a stroke emergency. For instance, the doctor must be
able to quickly determine whether the stroke is ischemic (arising from
a blocked blood vessel) or hemorrhagic (bleeding caused by bursting of
a blood vessel) before the appropriate therapy can begin.
State-of-the-art brain diagnostic devices
The Stanford Stroke Center is one of the few places in the country
that has more than a dozen state-of-the-art brain diagnostic devices
available to obtain in-depth information about a patient's status.
These highly sensitive tools are of critical importance in
diagnosing abnormalities that place you at high risk for stroke, such
as a blocked blood vessel or the presence of an aneurysm or AVM.
Diagnostic tests
To obtain complete diagnostic information, several of the following
diagnostic tests may be performed during an evaluation for stroke or
stroke risk.
-
Computerized
tomography (CT) scan
This is generally the first diagnostic test done after a
patient with a suspected stroke arrives in the emergency room. It is
used to quickly distinguish between ischemic and hemorrhagic
strokes. The test involves the use of low-dose X-rays to visualize
the brain.
-
Magnetic
resonance imaging (MRI)
MRI is an advanced diagnostic tool that provides a high level
of anatomic detail for precisely locating the stroke and determining
the extent of damage. Due to its high level of sensitivity, MRI is
especially useful when the stroke involves small blood
vessels.
The technology involves use of a strong
magnetic field, and is performed in a special room free of metallic
equipment. Recently, there have been great advances in the early
detection of stroke using diffusion (DWI) and perfusion (PWI)
weighted imaging. These methods allow early and more accurate
detection of acute stroke, improving our ability to treat patients
with cerebrovascular problems. Stanford has been a leader in the
development of this technique.
-
Magnetic
resonance angiography (MRA)
MRA is a noninvasive technology for imaging the cerebral
blood vessels, and yields valuable information regarding blood
supply to the brain. The use of intravenous contrast agents has
provided great improvements in accurately viewing the cerebral blood
vessels. Many such techniques have been pioneered by researchers at
Stanford.
-
Transcranial
doppler (TCD)
TCD a new, noninvasive ultrasound procedure that allows the
assessment of blood flow through the cerebral vessels via a small
probe placed against the skull. TCD is a portable test that can be
performed frequently at the patient's bedside to follow the progress
of medical treatment for stroke.
-
Carotid
duplex scanning
This is a noninvasive study to
diagnose blockage in the carotid arteries. This technology involves
recording sound waves that reflect the velocity of blood flow.
-
Cerebral
angiography (angiogram)
This method requires injection of a contrast dye through a
major artery (usually the femoral artery in the thigh) for
evaluation of blood flow to the brain. This procedure is completed
in Stanford's Cath/Angio lab. The procedure time is approximately
two to three hours; bed rest for six hours is required after the
procedure.
-
Transesophageal echocardiography
This involves placing a flexible tube in the esophagus (tube
to stomach) to directly image the heart and assess its function and
structures.
-
Ultrasound
An ultrasound is a diagnostic test that uses high frequency
waves of sound to help examine the movement, size and shape of blood
vessels.