Lab Values: Normal Readings After A Stroke?

A stroke is a medical emergency that occurs when the flow of blood to the brain is blocked. While a stroke can be indicated by symptoms such as weakness on one side of the body or slurred speech, specific tests are required to confirm a stroke diagnosis. Blood tests can be used to determine the risk factors, cause, complications, and differential diagnosis of a stroke. However, there is no blood test that can diagnose a stroke. Instead, blood tests are used to pinpoint triggers for a stroke, such as blood clotting problems, or to check for other complications like blood clots in the heart.

Blood tests to check for stroke symptoms

Blood tests alone cannot be used to diagnose a stroke, but they can be very helpful in identifying the cause of stroke symptoms. Doctors may order a specific set of blood tests to evaluate the distribution of blood cells, the number of platelets, and the levels of various substances in the blood.

• Complete Blood Count (CBC): This test measures the overall health of your blood cells and helps detect infection, clotting, anemia, and other potential health issues.
• Serum Electrolytes: This test looks at substances in your blood that carry an electric charge, called electrolytes. An electrolyte problem can cause stroke-like symptoms such as confusion or muscle weakness. Electrolytes also show whether you are dehydrated, which can cause confusion or tiredness. This test can also show whether you have kidney problems, which can change the stroke tests and treatments your doctor performs.
• Blood Clotting Tests: These tests measure how quickly your blood clots. If your blood clots too quickly, your stroke may have been caused by a clot (ischemic stroke). If your blood clots too slowly, your stroke may have been caused by bleeding (hemorrhagic stroke).
• Thyroid Tests: Your doctor may measure your thyroid hormone levels with a blood test. Having hyperthyroidism raises your risk of atrial fibrillation, which can lead to stroke.
• Blood Glucose: This test measures the glucose (sugar) in your blood. Low blood sugar is a common complication of diabetes treatments. Low blood sugar can cause symptoms of a stroke, even when it's not a stroke.
• Cholesterol Tests: This test examines whether high blood cholesterol might have led to your stroke.
• C-Reactive Protein Test and Blood Protein Test: These tests look for substances in your blood that your body releases in response to swelling or inflammation. Damage to arteries is one cause of inflammation. Your doctor might order these tests to understand your stroke risk better and to determine how to treat your stroke.

Imaging tests to see inside the brain

Imaging tests are crucial for diagnosing a stroke and determining its type, location, and cause. Here are some of the imaging tests used to visualise the inside of the brain:

• Computed Tomography (CT) Scan: This is often the first test performed to diagnose a stroke. It uses X-rays to create multiple images of the brain from different angles, helping doctors identify any abnormalities, such as tumours, blood clots, or bleeding within the brain. CT scans can distinguish between haemorrhagic and ischemic strokes and rule out other potential causes of stroke-like symptoms.
• Magnetic Resonance Imaging (MRI): MRI machines use magnetic fields, radio waves, and computers to create detailed images of the brain and other soft tissues. MRIs can detect brain changes caused by a stroke sooner than CT scans and are more sensitive, making them better at detecting tiny abnormalities. They can also be used to assess blood flow and rule out tumours.
• CT or MR Angiogram: An angiogram is an X-ray movie of the blood vessels that visualises blood flow. A dye is injected into the veins to highlight the blood vessels and provide a detailed picture of blood flow after a stroke.
• Carotid Ultrasound: This test uses sound waves to visualise the carotid arteries, which supply blood to the brain. It is often used in conjunction with a CT or MR angiogram to check for plaque build-up that may be blocking blood flow to the brain.
• Trans-cranial Doppler (TCD) Ultrasound: The TCD ultrasound also uses sound waves but specifically helps doctors find the blocked artery in the brain by measuring blood flow.

These imaging tests play a critical role in the early diagnosis and treatment of strokes, helping doctors identify the type of stroke and determine the best course of treatment to reduce potential disabilities and save lives.

Electrocardiogram (ECG or EKG) to detect heart problems

An electrocardiogram (ECG or EKG) is a simple, painless, and fast test that can help detect heart problems. It measures the electrical impulses of your heart to check for signs of heart disease. Here's how it works and what it can reveal about your heart health:

ECG/EKG uses small electrode patches attached to the skin of your chest, arms, and legs. These electrodes measure the electrical activity of your heart, which controls your heartbeat. The procedure is simple and painless, and it only takes about 10 minutes to attach the electrodes and complete the resting ECG/EKG test. The actual recording takes just a few seconds.

ECG/EKG can provide valuable information about your heart's function and detect various heart problems:

• Heart rhythm and rate: ECG/EKG can check your heart rhythm and detect abnormal heart rhythms (arrhythmias).
• Blood flow to the heart: It can determine if there is poor blood flow to your heart muscle (ischemia).
• Heart attack: ECG/EKG can help diagnose a heart attack, both current and past.
• Heart muscle thickness: It can detect thickened heart muscle.
• Electrolyte abnormalities: ECG/EKG can identify electrolyte abnormalities, such as high potassium or high/low calcium levels.
• Enlarged heart chambers: It can reveal if there are any enlargements in the heart chambers.
• Blocked or narrowed arteries: ECG/EKG can help identify blocked or narrowed arteries in your heart.

Your doctor may order an ECG/EKG if you are experiencing symptoms that could indicate heart disease, such as dizziness, lightheadedness, or a fast or irregular heartbeat. It is often the first test performed if your doctor suspects a heart condition. Additionally, ECG/EKG can be used to monitor the effectiveness of heart medications or treatments, such as pacemakers, and to assess your heart's health before planned surgery.

Carotid ultrasound to check for blocked blood flow

A carotid ultrasound is a test that uses sound waves to create images of your carotid arteries, which are the two large arteries in your neck that supply blood to your brain. This test is painless and safe, and it can help detect whether there is any blockage or narrowing in these arteries that could lead to a stroke.

During the test, a healthcare provider called a sonographer or ultrasound technologist will apply a clear gel to the sides of your neck and use a transducer (a small handheld device) to send and receive sound waves, which create images of the inside of your carotid arteries. The procedure typically takes around 30 to 45 minutes, and you can resume your normal activities afterward.

The carotid ultrasound can detect the presence of plaque, which is made up of fat, cholesterol, calcium, and other substances in the blood. Over time, plaque can build up on the inner walls of your arteries, leading to a condition called carotid artery disease. This buildup can narrow or block your carotid arteries, reducing blood flow to your brain and increasing the risk of a stroke.

If plaque is detected during the carotid ultrasound, your doctor may recommend medical or surgical treatments to reduce or remove the plaque buildup. These treatments may include lifestyle changes, medications, or procedures such as carotid endarterectomy or angioplasty.

Lumbar puncture to test spinal fluid

A lumbar puncture, also known as a spinal tap, is a diagnostic procedure that can be used to test for conditions affecting the brain, nerves, and spinal cord. During a lumbar puncture, a healthcare provider will insert a needle into the lower back to remove a sample of cerebrospinal fluid (CSF) for testing. This fluid is a clear fluid that surrounds the brain and spinal cord, providing cushioning and essential support to the nervous system.

• The patient will be asked to remove any clothing, jewelry, or other objects that may interfere with the procedure and will be given a gown to wear.
• The patient will be reminded to empty their bladder before the procedure begins.
• The patient will lie on their side with their chin tucked to their chest and knees tucked to their abdomen, or they may sit on the edge of the exam table with their arms draped forward. This position arches the back, widening the spaces between the vertebrae.
• The provider will clean the patient's back with an antiseptic solution and drape it with sterile towels. They will wear sterile gloves during the procedure.
• A local anesthetic will be injected to numb the skin. This may sting momentarily but will reduce pain during the procedure.
• The provider will insert a hollow needle through the numbed skin and into the space where the CSF is located. The patient will feel pressure during this step and must remain still.
• The CSF will drip out of the needle, and a small amount (about one tablespoon) will be collected into test tubes.
• If needed, the provider will inject medicine through the same needle after collecting the CSF.
• Once finished, the needle will be removed, and a bandage will be placed over the injection site. The collected CSF will be sent to a lab for testing.

A lumbar puncture can be helpful in diagnosing various diseases and conditions, including:

• Meningitis: inflammation of the membrane covering the brain and spinal cord, usually due to infection.
• Encephalitis: inflammation of the brain, often caused by a virus.
• Certain cancers: involving the brain and spinal cord.
• Subarachnoid hemorrhage: bleeding in the area between the brain and the tissues covering it.
• Reye syndrome: a rare and sometimes fatal disease linked to giving aspirin to children, causing severe problems with the brain and other organs.
• Myelitis: inflammation of the spinal cord or bone marrow.
• Neurosyphilis: a stage of syphilis where bacteria invade the central nervous system.
• Guillain-Barré syndrome: a disorder where the body's immune system attacks the nervous system.
• Demyelinating diseases: conditions that attack the protective coating of nerve fibers, such as multiple sclerosis.
• Headaches of unknown cause: a lumbar puncture can help diagnose certain inflammatory conditions that result in headaches.
• Pseudotumor cerebri: a condition with elevated pressure in the subarachnoid space, where the cause is unclear.
• Normal pressure hydrocephalus: a rare condition mainly affecting older adults, characterized by urinary control loss, memory problems, and an unsteady gait.

Additionally, a lumbar puncture can be used to measure CSF pressure and inject medications directly into the spinal cord, such as spinal anesthetics, contrast dye for X-ray studies, or chemotherapy drugs.

Frequently asked questions