Stroke MRI: Detection, Preparation, and Treatment Explained

What is a stroke?

A stroke occurs when the blood supply to the brain is suddenly interrupted, depriving brain cells of oxygen and nutrients due to a blocked or burst blood vessel. It can lead to the development of physical disabilities and brain damage and sometimes even be life-threatening.

Some risk factors of strokes include high blood pressure, smoking, genetics and ageing. Other signs that you, or someone you know, may be having a stroke include mild paralysis on one side of the body, suddenly having trouble speaking, blurred vision, and sudden weakness.

A stroke is considered a medical emergency and requires immediate treatment. However, not all strokes are treated in the same way, so it’s important to diagnose what type of stroke an individual is experiencing. 

To diagnose a stroke, doctors will order multiple tests, including blood tests, an electrocardiogram and imaging tests, such as a computed tomography (CT) scan or a Magnetic Resonance Imaging (MRI). The latter two are considered the most effective ways to identify the type of stroke while ruling out all other potential causes of stroke symptoms.

Types of strokes

If you’re experiencing any concerns about the different types of strokes, don’t hesitate to request an appointment with Thomson Medical. Our specialist will help guide you through the MRI process, answer any questions you may have, and provide you with tailored recommendations.

How are MRI scans used in diagnosing strokes?

A Magnetic Resonance Imaging (MRI) is a non-invasive diagnostic tool that uses strong magnetic fields and radio waves to create detailed images of the body’s internal structures. Unlike a CT scans, MRIs do not use radiation, making them a safer option for imaging soft tissues, such as the brain.

Difference between MRI and CT scan

An MRI uses magnetic fields, radiofrequency pulses and computers to reveal any changes in the brain. Similar to a stroke CT scan, a stroke MRI takes multiple images of the inside of the head. 

However, unlike a typical CT scan, which takes several hours to reveal any blockages of blood flow, an MRI can uncover any brain damage within one hour of the onset of the stroke symptoms.

A brain MRI, or a head MRI, is an excellent way to diagnose whether a stroke is ischaemic or haemorrhagic, and it's also great at finding abnormalities in the skull and spinal cord. While CT scans can only provide images from one orientation, MRIs can produce multiple pictures in several orientations.

MRIs are also more accurate and sensitive than CT scans. MRIs are able to show all issues related to a stroke and any other diseases or concerns involving the brain. MRIs are also better at detecting the smallest abnormalities, which are often too small to be clearly seen in a CT scan.

However, in some circumstances, an MRI scan may not be the ideal choice for an individual in need of rapid treatment to reduce the potentially debilitating side effects of a stroke. This is because MRI scans take longer and are not available as quickly as CT scans.

Furthermore, because it uses magnetic fields to create images, it is not a good choice for people with metal or electronic implants, such as pacemakers.

What types of MRI can be used to detect a stroke?

Different MRI scans are used to detect and assess strokes, each serving a specific purpose. Here’s a simplified explanation of the main types:

• Diffusion-Weighted Imaging (DWI):

  • DWI is a special MRI technique that looks at how water moves in the brain.

  • In the early stages of an ischaemic stroke (when a blood vessel is blocked), brain cells can’t get enough energy, so water gets trapped inside them, causing swelling.

  • DWI can spot these changes within minutes, making it the most sensitive and accurate scan for detecting a fresh stroke—much better than a regular CT scan or other MRI methods.

• Fluid-attenuated inversion recovery (FLAIR):

  • FLAIR is designed to make fluid (like the fluid around the brain and spine) less visible on the scan, which helps doctors see brain injuries more clearly.

  • It’s especially useful for figuring out how old a stroke is: early on (within the first 2–3 hours), FLAIR might not show anything, but after that, changes become visible.

  • FLAIR can also help detect small bleeds near the brain’s surface.

• Gradient echo (GRE):

  • GRE is very sensitive to small amounts of blood or substances like iron in the brain.

  • It’s good at finding bleeding in the brain, almost as well as a CT scan, though CT is still preferred in emergencies because it’s faster.

  • GRE and FLAIR together can help spot blood clots in brain arteries, but how well they work depends on the clot’s size and location.

• Magnetic resonance angiography (MRA)

  • MRA is used to get images of blood vessels in the brain and neck, which is crucial for stroke treatment planning.

  • The “time of flight” (TOF) MRA is commonly used but can sometimes make vessel narrowing look worse than it is and takes longer to perform.

  • Contrast-enhanced MRA (CE MRA) uses a dye to show blood vessels more clearly, especially in the neck, but has lower detail and requires an injection.

  • Phase-contrast MRA (PCA) can show moving blood without using dye, which is helpful for children or pregnant women. Newer machines can scan the whole head and neck in under a minute.

• MR perfusion

  • Perfusion imaging shows how blood flows through the brain and is vital for identifying areas that might still be saved after a stroke.

  • Dynamic susceptibility contrast (DSC) perfusion uses a dye to quickly capture detailed images of blood flow and is widely used.

  • Arterial spin labelling (ASL) is a newer, dye-free way to measure blood flow, usually taking about a minute.

In summary, these MRI techniques give doctors detailed information about where and when a stroke happened, whether there’s bleeding, how blood is flowing, and which brain areas might still be saved with treatment.

What does a stroke look like on an MRI?

The way a stroke looks on an MRI depends on the type of MRI machine and how long it has been since the onset of the stroke. An old stroke will look different on the MRI scans than a recent stroke, as compared to an early-onset stroke. 

Overall, an MRI can also show areas where brain tissue has shrunk. This phenomenon happens when brain cells die from a lack of blood flow.

How long will a stroke show up on an MRI?

A stroke can show up on an MRI within minutes after it occurs. Diffusion-weighted imaging (DWI) is particularly sensitive to acute strokes and can detect changes in brain tissue almost immediately.

MRI scans can also detect silent strokes. Sometimes, a person may not know they experienced a stroke or a TIA. The symptoms they experienced may have been mild, or the person may have mistaken the symptoms for something else.

A person may also have an MRI scan later in life for a different reason and find out that they had a stroke in the past. Thus, evidence of a stroke can be visible on an MRI even decades later, as the brain experienced visible changes and does not look the way it did before a stroke.

How do I prepare for my MRI?

Preparing for an MRI is straightforward; there are just a few things you need to do before you go for the  stroke MRI scan, such as:

1. Remove all metal objects, such as jewellery

2. Inform your doctor about any implants or devices (e.g., pacemakers)

3. Wear comfortable clothing; you may need to change into a hospital gown

4. Discuss any claustrophobia concerns with your healthcare provider

What happens during the MRI procedure?

During the scan:

1. You will lie on a movable exam table that slides into the MRI machine.
2. If you have claustrophobia, or if a child getting an MRI scan has trouble staying still, a sedative may be administered to them prior to the scan.
3. Earplugs may be provided to reduce noise from the MRI machine, as the MRI scanner will make loud banging noises during the procedure.
4. A helmet-like device (brain coil) may be placed around your head.
5. If contrast is required, an IV line will be inserted into your arm.
6. After the table slides into the machine, an MRI technician will take several pictures of your brain; that will take a few minutes.
7. It is normal for the area being imaged to feel slightly warm. There will be a microphone present in the machine, allowing you to communicate with the staff if it bothers you.
8. The scan lasts 30–60 minutes while you remain still to ensure clear images.

What happens after the MRI scan?

After the scan, the technologist may ask you to wait while the radiologist checks the images in case more are needed. The MRI technologist will then remove your IV line (if you needed sedation or contrast dye for the procedure) and place a small dressing over the insertion site. 

If you were sedated for the exam, staff may move you to a recovery area until you wake up, usually one to two hours after you received the sedative. If contrast dye was used for the scan, remember to drink extra water to help flush it out.

If you did not require sedation, no recovery period is necessary. You may resume your usual activities and normal diet immediately after the exam. On very rare occasions, a few patients experience side effects from the contrast material. 

These may include nausea, headache, and pain at the site of injection. It is very rare that patients experience hives, itchy eyes, or other allergic reactions to the contrast material. If you have allergic symptoms, tell the technologist. A radiologist or other doctor will be available for immediate assistance.

If a stroke is detected, you will be admitted for immediate treatment. Your respective doctor and healthcare providers will assess the extent of damage and determine the cause of the stroke. Your doctor may also schedule follow-up imaging to monitor your recovery. 

What are the costs of stroke MRIs in Singapore?

The cost of a stroke MRI in Singapore typically ranges from $1,000 to $2,500 SGD per scan but can vary depending on the healthcare facility, the complexity of the scan, and whether contrast material is used. 

Here's a more detailed breakdown:

• General cost range:

  • Expect to pay between S$1,000 and S$2,500 for a stroke MRI. 

• Factors affecting cost:

  • Healthcare facility: costs can differ between public and private hospitals, as well as different imaging centres. 

  • Scan complexity: more complex scans or those requiring contrast agents will likely cost more. 

  • Specific MRI scans: the cost of MRI scans can vary depending on the specific type of scan.

The information provided is intended for general guidance only and should not be considered medical advice. For personalised recommendations and tailored advice, please consult a specialist at Thomson Medical. Request an appointment with Thomson Medical today.

What treatment options are available?

Your treatment and how well you recover from a stroke will depend on several factors, including:

1. Your general level of health and wellbeing
2. The type of stroke you had, either ischaemic or haemorrhagic
3. The time between having a stroke and diagnosis (whether it's in an early acute phase, a subacute phase or a later, chronic phase)

Emergency treatment for an acute ischaemic stroke includes thrombolytic therapy (medicines administered through the blood vessels to help break up blood clots) or surgery to drain fluid from the brain and remove blood clots (thrombectomy).

You will also be given long-term medications to help reduce your risk of blood clots and a further stroke, as well as medications to help lower your blood pressure and cholesterol if necessary. Long-term blood pressure medications are also used to treat haemorrhagic stroke patients.

It is important to note that having a stroke may leave you with speech, swallowing, and mobility problems. Your medical team will help you with rehabilitation to help you back to as normal a life as possible. With the right help, some stroke patients fully recover, particularly if surrounding blood vessels can support normal blood flow to the brain, a process called collateral circulation.

FAQ

Does a stroke show up on an MRI?

Yes, MRIs can detect strokes within minutes using specialised imaging techniques, like DWI.

Which is better for stroke, MRI or CT?

MRI provides more detailed images but takes longer; CT scans are faster and preferred in emergencies.

Do you ever go back to normal after a stroke?

Recovery varies depending on severity; many patients regain significant function with rehabilitation.

What are the three main causes of strokes?

The main causes are blood clots (ischaemic), bleeding (haemorrhagic), and temporary blockages (TIA).

What are the 5 warning signs of a stroke?

1. Sudden numbness or weakness

2. Confusion or trouble speaking

3. Vision problems

4. Difficulty walking

5. Severe headache

Who is more prone to strokes?

Individuals with high blood pressure, diabetes, obesity, smoking habits, or genetic predisposition are at higher risk.

How do I avoid a stroke?

Maintain a healthy lifestyle: exercise regularly, eat balanced meals, avoid smoking, and manage chronic conditions like hypertension.

What are good signs after a stroke?

Improved movement, speech recovery, and reduced dependence on assistance indicate positive progress.

What hurts before a stroke?

Some people report severe headaches or neck pain before haemorrhagic strokes.

What is the biggest indicator of a stroke?

Sudden weakness or numbness on one side of the body is often the most significant indicator.

Where is a stroke headache located?

Stroke-related headaches often occur suddenly and may be localised at the back of the head or near affected areas.

The information provided is intended for general guidance only and should not be considered medical advice. For personalised recommendations and tailored advice, please consult a specialist at Thomson Medical. Request an appointment with Thomson Medical today.