Stroke

Description

Alternative Names

Diagnosis

In people who experience transient ischemic attacks or small strokes, it is important to determine the source of these attacks in order to prevent a major stroke. A complete blood count, chest x-ray, and electrocardiogram are usually performed. Discouragingly, a 2001 study reported that over 30% of patients with TIA who called their primary care physician were neither evaluated nor sent to the hospital within the month after a first event.

Examining the Carotid Artery. The physician usually first examines the carotid artery to determine if it is severely narrowed. If it is, the patient is in danger of a major stroke. (The thickness of the carotid artery is also proving to be a valuable indicator for long-term risks for stroke, as well as heart disease and mortality rates in general.)

The physician may use a number of approaches to determine the thickness of the artery:

• An important clue to a blocked carotid artery is a bruit. This is a whooshing sound caused by blood flow turbulence in the narrowed artery. A physician may be able to hear a bruit using a stethoscope. Occasionally, even a patient can hear the sound. The presence of a bruit, however, is not necessarily a sign of an impending stroke, nor does the absence of a bruit indicate an unblocked artery.
• Carotid ultrasound is a very valuable tool for measuring the width of the artery. At this time, ultrasound is most useful in people between the ages of 40 and 60 years. It should be noted that severely blocked carotid arteries may distort some measurements, so other tests may be required to confirm the results.

Carotid duplex is an ultrasound procedure performed to assess blood flow through the carotid artery to the brain. High-frequency sound waves are directed from a hand-held transducer probe to the area. These waves "echo" off the arterial structures and produce a 2-dimensional image on a monitor, which will make obstructions or narrowing of the arteries visible.

• Measuring blood pressure to the eye may also be important in identifying problems in the carotid artery. If blood flow to the eye is reduced, then it is likely that the carotid artery is severely narrowed.

Imaging Techniques for TIAs. A number of imaging techniques may be useful for identifying small clots or other indicators of risk in the brain.

General Guidelines for Diagnosing a Major Stroke

Identifying a Stroke Quickly. To save a patient's life, a fast diagnosis of both the presence and type of stroke is critical. Health professionals have devised different tests to help emergency workers quickly identify a person with stroke even before they reach the hospital. For example, an assessment tool called the Face, Arm, Speech Test (FAST) is proving to be highly accurate. It involves watching for the following signs:

• Face: The face is not symmetrical. The mouth droops and the patient is unable to show teeth when smiling.
• Arm: The patient is unable to lift an arm above shoulder level.
• Speech: The patient has a hard time talking clearly and following simple instructions.

In one study, emergency workers who used this test accurately identified more people with stroke than either primary care or emergency room physicians.

Determining Ischemia Versus Hemorrhagic Stroke. Once a stroke has been determined, the next important step is to determine as quickly as possible whether it is hemorrhagic or ischemic. Clot-busting drug therapies can be life-saving for ischemic stroke patients, but they are effective only in the first three hours. In addition, they cause bleeding and can be lethal if the stroke is actually caused by a hemorrhage.

A computed tomography (CT) scan is essential for identifying or ruling out hemorrhagic strokes. The goal is to complete the CT examination and obtain and interpret the results within 45 minutes of arrival at the hospital. (The ultrasound technique, transcranial duplex sonography, may be sensitive enough to differentiate between hemorrhagic and ischemic strokes if CT scans are not available.)

Certain factors may also suggest a hemorrhagic rather than ischemic stroke. They include specific symptoms (e.g., coma, vomiting, and severe headache), taking anticoagulants, very high systolic blood pressure, or high blood sugar levels in nondiabetics. However, such findings are not conclusive, and a CT scan or MRI is always needed.

Ruling Out Other Disorders. In most cases of stroke, the diagnosis is evident although a number of conditions may cause similar symptoms. These include seizures; infections that cause mental confusion; syncope (fainting); hypoglycemia; and brain tumors.

Imaging Tests Used for Stroke and Risk Factors for Stroke

Computed Tomography. A computed tomography (CT) scan is the standard imaging test for the brain. It is performed as early as possible. It is essential in ruling out hemorrhagic stroke and can accurately diagnose about 95% of hemorrhagic strokes. The full evidence of an ischemic stroke will usually not show up on a CT scan for hours to days. A CT scan, however, may be useful in identifying early signs of injury from ischemic strokes that could effect the decision to use thrombolytics (clot-busting drugs). High-speed CT scans (called helical or spiral CTs) that quickly identify ischemic strokes and the location of the blockage are now available in many centers.

Magnetic Resonance Imaging (MRI). A standard magnetic resonance imaging (MRI) scan is able to evaluate the blood vessels and the brain's circulation and determine injuries from ischemic strokes. It is not very useful in the first hours of a stroke, however, since it tends to show abnormalities that may not be significant. Advanced MRI techniques, such as diffusion- or perfusion-weighted MRIs, may be sensitive enough to identify injured areas within minutes of symptoms. MRIs cannot be used by patients with pacemakers, any metal implants, or who are claustrophobic.

Ultrasound. Ultrasound may be used in different circumstances. This imaging technique is painless and noninvasive.

• Carotid ultrasound (also called Doppler or duplex sonography) is used to determine blockage in the carotid arteries that could lead to or be causing a stroke.
• Transcranial duplex sonography is used to identify blockage in large arteries in stroke patients and to monitor the effects of thrombolytic therapy.

Cerebral Angiography. Cerebral angiography is an invasive procedure that may be used for patients with TIAs who require surgery. It can also detect aneurysms and be used to monitor thrombolytic therapy. It requires the insertion of a catheter into the groin, which is then threaded up through the arteries to the base of the carotid artery. At this point a dye is injected and x-rays, CTs, or MRI scans are used to determine the location and extent of the narrowing, or stenosis, of the artery. It should be noted that in people with TIAs the risk of stroke itself increases using this technique, particularly in elderly people with diabetes.

Other Techniques. Other imaging tests, including positron-emission tomography (PET) and single photon-emission computed tomography (SPECT), may further refine the physician's knowledge of the injuries caused by the stroke.

Heart Evaluation

Electrocardiogram (ECG). A heart evaluation using an electrocardiogram (ECG) is important in any patient with a stroke or suspected stroke. An ECG records the electrical current in the heart muscle.

Echocardiogram. An echocardiogram uses ultrasound to view the chambers and valves of the heart. It is generally useful for stroke patients to identify blood clots or risk factors for blood clots that can travel to the brain and cause stroke. There two are types:

• Transthoracic echocardiograms (TTE) view the heart through the chest. It is noninvasive and is the standard approach.
• Transesophageal echocardiogram (TEE) examines the heart using an ultrasound tube that the patient literally swallows and is passed down the throat. It is uncomfortable and requires sedation. It is typically used to obtain more accurate images of the heart if a TTE has suggested abnormalities, such as atrial fibrillation or patent foramen ovale (PFO).

Other Tests

Blood Tests. A number of blood tests may be helpful for predicting the risk for a stroke as well determining the severity and complications of an existing stroke. Some of these are investigatory.

• Specific blood tests are important to determine clotting times, to check electrolytes (potassium, calcium, sodium), and to measure factors indicating liver or kidney problems.
• Blood sugar (glucose) levels are measured. Hyperglycemia (elevated levels) may indicate a worse outcome for some strokes (although not hemorrhagic or lacunar strokes). Hypoglycemia (low levels) is a common complication of diabetes treatments and its symptoms may mimic those of a stroke.
• Blood tests showing high levels the amino acid glutamate indicate a severe stroke.

Examination of Spinal Fluid. If the CT scan is negative, but the physician still suspects a subarachnoid hemorrhagic stroke, a spinal tap may be indicated. Spinal fluid containing significant amounts of blood will usually confirm a hemorrhagic stroke.