
Stroke diagnosis is a complex process that requires a range of diagnostic studies to identify the type of stroke and determine the most appropriate treatment approach. The first step in stroke diagnosis involves recognising the signs and symptoms, which can vary depending on the affected region of the brain. Common symptoms include facial droop, arm weakness, speech disturbances, and sudden onset of severe headache. To confirm the diagnosis, brain and neurovascular imaging is essential. Non-contrast computed tomography (CT) is often the initial imaging choice due to its speed and wide availability, allowing the detection of haemorrhagic strokes with high accuracy. However, CT may not be sensitive enough for small or posterior fossa strokes. Magnetic resonance imaging (MRI) offers greater resolution and is more effective in detecting acute ischemic strokes and transient ischemic attacks. Further diagnostic tests, such as blood tests and angiography, are also performed to identify underlying causes, rule out stroke mimics, and determine treatment eligibility.
What You'll Learn
- Neuroimaging: CT or MRI scans are used to rule out other conditions and determine the type of stroke
- Blood tests: These help to identify stroke mimics and detect critical comorbidities
- Clotting time: PT and PTT tests check how quickly blood clots, indicating potential bleeding problems
- Carotid ultrasound: This test uses sound waves to detect fatty deposits blocking blood flow to the brain
- Echocardiogram: An imaging test to detect clots in the heart that may have travelled to the brain
Neuroimaging: CT or MRI scans are used to rule out other conditions and determine the type of stroke
Neuroimaging is a critical aspect of stroke diagnosis, helping to differentiate between ischemic and hemorrhagic strokes, as well as ruling out other conditions. CT scans and MRI scans are the two primary neuroimaging techniques used.
Computed Tomography (CT) scans use X-rays to capture images of the brain. They are often the first test performed for stroke patients as they can detect bleeding in the brain, damage to brain cells, and other problems that might cause stroke-like symptoms. CT scans are also used to detect bleeding in subarachnoid hemorrhage, with high sensitivity in the first 12 hours after the onset of symptoms. However, their sensitivity decreases over time as the blood is cleared, dropping to around 50% after a week.
Magnetic Resonance Imaging (MRI) employs strong magnets and radio waves to create detailed images of the brain. MRI has better resolution than CT scans and can detect acute ischemic strokes more effectively. It can also identify bleeding and blood flow problems and rule out problems like tumors that might mimic stroke symptoms. MRI is particularly useful for patients presenting with acute vestibular syndrome or suspected posterior infarction. However, MRI scanners are less available and more expensive than CT scanners, and they may not be suitable for individuals with certain implanted devices or claustrophobia.
The choice between CT and MRI depends on factors such as availability, eligibility for acute stroke interventions, and the presence of patient contraindications. If a patient is within the time window for acute stroke treatment, and an MRI can be performed as quickly as a CT scan, it is the preferred option. However, if there is a delay in obtaining an MRI, a CT scan is recommended to ensure prompt treatment.
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Blood tests: These help to identify stroke mimics and detect critical comorbidities
Blood tests are a crucial step in diagnosing stroke patients and can help identify stroke mimics and detect critical comorbidities. They are often used in conjunction with brain imaging techniques and a detailed patient history to make an accurate diagnosis. Here are some common blood tests used in stroke diagnosis:
Complete Blood Count (CBC)
A CBC test measures the levels of platelets and red and white blood cells in the patient's blood. Abnormal levels of these blood components can suggest conditions such as leukemia, anemia, or infections, which may be associated with stroke. Additionally, very low platelet levels can indicate a bleeding disorder that could lead to a hemorrhagic stroke.
Blood Lipid Test
Blood lipid tests measure the levels of good (HDL) and bad (LDL) cholesterol. High levels of bad cholesterol are a major risk factor for stroke as they can lead to plaque buildup in the artery walls.
Markers-of-Inflammation Tests
These tests, including erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) tests, look for markers of inflammation, which could indicate a bacterial, fungal, or viral infection or a rheumatological condition. Inflammatory markers may also be present in vasculitis or endocarditis.
Blood Chemistry Tests
Blood chemistry tests assess the levels of substances like glucose, electrolytes (sodium, potassium), and kidney and liver function markers. Abnormal glucose levels, for example, may cause symptoms similar to stroke and are indicative of diabetes, which increases the risk of stroke and heart attack.
Coagulation Tests
Coagulation tests, such as prothrombin time (PT), partial thromboplastin time (PTT), and international normalized ratio (INR), evaluate the ability of the blood to form clots. Abnormal levels of certain proteins can lead to excessive clotting, resulting in ischemic stroke, or impaired clotting, leading to hemorrhagic stroke.
Homocysteine Tests
Homocysteine tests check the levels of the amino acid homocysteine, which is associated with increased stroke risk and atherosclerosis. Elevated levels of homocysteine may indicate a genetic disorder that heightens stroke risk.
Cardiac Enzyme Tests
Enzyme tests like LDH isoenzymes, creatine kinase, and troponin can determine if the patient has had a heart attack, as clots can form within the heart after a heart attack and travel to the brain, causing a stroke.
Toxicology Tests
Toxicology tests are used to rule out the presence of recreational drugs, such as amphetamines and cocaine, and alcohol, which can cause stroke. Identifying drug use helps in counselling the patient to reduce the risk of future strokes.
D-Dimer Test
The D-Dimer test detects the presence of a protein fragment that indicates an increased tendency to form blood clots. A positive result suggests a higher risk of ischemic stroke and can also be indicative of a stroke associated with COVID-19 or cancer.
Antinuclear Antibody (ANA) Test
The ANA test screens for autoimmune and rheumatological disorders like systemic lupus erythematosus (SLE), which is associated with a doubled risk of stroke.
Antiphospholipid Antibody (APLA) Panel Tests
APLA tests, including anti-cardiolipin antibodies (ACL) and lupus anticoagulant (LA), are used to screen for SLE, which significantly increases the risk of stroke when accompanied by elevated APLA levels.
These blood tests, along with imaging techniques and a thorough patient history, help physicians diagnose stroke, identify stroke mimics, and detect critical comorbidities to guide treatment and prevent future stroke events.
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Clotting time: PT and PTT tests check how quickly blood clots, indicating potential bleeding problems
Clotting time is an important factor in diagnosing strokes. A pair of tests called the PT (prothrombin time) and PTT (partial thromboplastin time) can check how quickly a person's blood clots. If clotting takes too long, it could be a sign of bleeding problems. These tests are also known as blood clotting tests or coagulation panels.
PT and PTT tests are part of a series of diagnostic tests that help doctors determine whether a patient has had a stroke, what type of stroke it was, and what caused it. These tests are crucial for determining the appropriate treatment plan.
In addition to clotting time tests, doctors may also perform physical and neurological exams, imaging tests such as CT scans and MRIs, and blood tests to evaluate a patient's condition and confirm the presence of a stroke.
The timely diagnosis of a stroke is critical as it can help doctors determine if a patient is eligible for thrombolysis or acute stroke interventions.
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Carotid ultrasound: This test uses sound waves to detect fatty deposits blocking blood flow to the brain
Carotid ultrasound is a critical diagnostic tool for stroke patients, as it can detect fatty deposits blocking blood flow to the brain. This non-invasive and painless procedure uses sound waves to create detailed images of the carotid arteries, which supply blood to the brain. During the test, a healthcare provider called a sonographer or ultrasound technologist will apply a clear gel to the sides of the patient's neck, where the carotid arteries are located. They will then use a transducer, a small handheld device, to send sound waves into the arteries and capture their echoes, which are used to generate images. These images can reveal the presence and extent of any blockages or narrowings in the arteries, which are typically caused by plaque buildup, or atherosclerosis.
The procedure is safe and carries no risks. Patients may feel some pressure when the transducer is pressed against their neck, but it is not painful. The test typically takes around 30 to 45 minutes and does not require any special preparation. Patients are advised to wear comfortable clothing that does not cover their neck, and they can resume their normal activities immediately after the test.
The results of a carotid ultrasound will indicate the percentage of blockage in the carotid arteries. If the results show a significant blockage, healthcare providers can recommend lifestyle changes, such as improving diet and exercise habits and discontinuing tobacco use. Additionally, certain medications may be prescribed to dissolve blood clots, prevent future clots, lower cholesterol levels, or reduce blood pressure. In severe cases of blockage, a procedure called carotid endarterectomy may be recommended to remove the plaque.
Carotid ultrasound is a valuable tool for assessing stroke risk and guiding treatment decisions. It is often the first step in evaluating patients with stroke symptoms or risk factors, and it can help healthcare providers determine the most appropriate course of action to reduce the likelihood of a stroke occurring.
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Echocardiogram: An imaging test to detect clots in the heart that may have travelled to the brain
An echocardiogram is a test that uses ultrasound to show how the heart muscle and valves are working. It can help doctors diagnose a range of heart problems, including blood clots, which may have travelled to the brain and caused a stroke.
An echocardiogram is a non-invasive procedure that does not typically cause side effects. During the test, a doctor can see the size and thickness of the heart chambers, how the valves of the heart are functioning, the direction of blood flow through the heart, any blood clots in the heart, and areas of damaged or weak cardiac muscle tissue.
There are several types of echocardiogram, including:
- Transthoracic echocardiogram: This is the standard test, similar to an X-ray but without the radiation. It is performed outside the body, with a hand-held wand placed on the chest to take pictures of the heart's valves and chambers.
- Transesophageal echocardiogram: For this test, the transducer goes down the throat and into the oesophagus, as it is closer to the heart and can create a clearer picture.
- Stress echocardiogram: This test is performed while the patient is exercising on a treadmill or stationary bicycle, showing the motion of the heart walls and pumping action when it is working hard.
- Dobutamine stress echocardiogram: Instead of exercising, the patient is given a drug called dobutamine, which makes the heart feel like it is working hard.
- Intravascular ultrasound: The transducer is threaded into the heart's blood vessels through a catheter in the groin, providing more detailed information about atherosclerosis (a buildup of plaque) inside the blood vessels.
- Fetal echocardiography: This test takes detailed pictures of a baby's heart before they are born, to diagnose heart problems present at birth (congenital heart defects).
The test usually takes 40 to 60 minutes, but a transesophageal echo may take up to 90 minutes.
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Frequently asked questions
The initial diagnostic studies recommended for stroke patients include:
- Noncontrast brain CT or brain MRI
- Serum electrolytes and renal function tests
- Markers of cardiac ischemia
- Complete blood count, including platelet count
- Prothrombin time/international normalized ratio
- Activated partial thromboplastin time
- Hepatic function tests
- Arterial blood gas (if hypoxemia is suspected)
- Chest radiography (if lung disease is suspected)
- Lumbar puncture (if subarachnoid hemorrhage is suspected and CT scan is negative for blood)
- Electroencephalogram (if seizures are suspected)
The significant diagnostic imaging tests for stroke patients include:
- Computerized Tomography (CT)
- Magnetic Resonance Imaging (MRI)
The significant diagnostic blood tests for stroke patients include:
- Complete blood count
- Clotting time (PT and PTT)