Having a stroke and it not showing up on a scan is possible, but quite rare. Most of the time, imaging tests like CT scans and MRI scans will detect signs of a stroke. However, there are some circumstances where a stroke may not be visible on initial scans.
Quick Answers
- Yes, it is possible to have a stroke that does not show up on imaging scans, but it is uncommon.
- Reasons a stroke may not appear on a scan include it being too small, too early, or in an area not well visualized by scans.
- Other tests like an EEG or angiogram may be done if a stroke is suspected despite normal scans.
- Around 1 in 20 strokes are not detected on initial scans.
- Missing stroke diagnosis early can delay important stroke treatment. Repeating scans helps detect initially hidden strokes.
When a Stroke May Not Appear on a Scan
There are a few reasons why a stroke may not show up on imaging scans like a CT scan or MRI when initially done:
- The stroke is too small – If a stroke affects a very small area in the brain, it may look normal or only show subtle changes on scans that are difficult to detect. Small strokes deep in the brain tissue can be missed.
- Scanning is done too early – Changes in the brain from a stroke can take hours to a few days to become visible on scans. Scanning done immediately after symptoms may not detect the stroke.
- The area involved is poorly visualized – Some areas of the brain like the brainstem, cerebellum, and small cortical areas can be difficult to fully evaluate on CT or MRI scans. Strokes in these areas may not show up.
- Uncommon stroke types – Some unusual types of stroke, like a superficial cortical stroke or isolated small vessel stroke, may not appear on initial scans.
Incidence of Silent Strokes
The rate of strokes not detected on imaging scans depends on the study, but is estimated to be around 1 in 20 strokes. Rates may be higher in certain groups:
| Group | Rate of Hidden Strokes on Initial Scan |
|---|---|
| General population | 5% of all strokes |
| Elderly patients | May be up to 3 times higher |
| People with small vessel disease | Up to 1 in 4 strokes undetected |
Overall, it is uncommon for strokes not to be visible on scans, but still occurs in a significant minority of cases. The risk seems higher in groups prone to smaller, subtle strokes.
Significance of Missing a Stroke Diagnosis
Failing to diagnose a stroke on initial imaging can have important implications for the patient:
- Delay in getting proper stroke treatment – Time is critical in stroke treatment. Missing the diagnosis delays using treatments like clot-busting tPA medication or clot removal procedures.
- Stroke cause misidentified – Without positive imaging, the cause of symptoms may be wrongly attributed to something other than stroke. This can hamper efforts to prevent a recurrence.
- Post-stroke rehabilitation delayed – Early rehab is most effective. Lack of stroke diagnosis on initial scans delays getting needed physical, occupational and speech therapy.
- Stroke complications worsen – Lack of diagnosis allows the stroke to progress untreated, potentially worsening disability or harming parts of the brain.
Therefore, a missed stroke diagnosis on the first scan has the potential to significantly impact patient recovery and long-term outcome.
Further Testing When Stroke is Suspected
If the clinical presentation strongly suggests a person is having a stroke but initial scans are normal, physicians have several options to help confirm the diagnosis:
- Repeat imaging – Getting a repeat CT or MRI scan within 24-48 hours often will reveal the stroke not seen originally. This is the most common approach.
- MRI with diffusion-weighted imaging – This special MRI technique is very sensitive for early ischemic stroke changes.
- Angiogram – This visualizes the cerebral blood vessels and can detect clots or abnormal flow.
- EEG – This measures the brain’s electrical activity and can reveal effects of strokes.
- Lab tests – Blood tests help rule out stroke mimics like seizures or metabolic disorders.
Even if scans are initially unrevealing, the medical team has ways to gather more information to determine if a stroke is occurring and enable rapid treatment.
Risk Factors for Hidden Strokes
Certain conditions and factors seem to increase someone’s risk of having a stroke not detected on initial neuroimaging. These include:
- Advanced age
- Long-standing high blood pressure
- Diabetes mellitus
- Previous silent strokes or small vessel ischemic changes on scans
- Known atrial fibrillation or structural heart disease
- Prior stroke or TIA (transient ischemic attack)
- Dementia diagnoses
- Younger age (rare causes more likely)
- Headaches at stroke onset
- Small vessel stroke or lacunar stroke syndrome clinically
Doctors have a higher index of suspicion for a stroke not appearing on scans when patients have several of these risk factors. This prompts more thorough diagnostic workup when imaging is normal but a stroke still seems likely based on the clinical situation.
Steps to Take if a Stroke is Suspected
What should you do if you or someone you are with has acute stroke-like symptoms but initial scans in the emergency room are normal?
- Report any past history of risk factors like high blood pressure, heart conditions, and previous strokes. Mention recent minor stroke-like symptoms too.
- Insist on a repeat scan within 24-48 hours if symptoms continue to suggest a stroke.
- Ask about other diagnostic tests like MRI, MRA, angiogram, EEG, echocardiogram to further evaluate.
- Have the physician consult a neurologist to help determine if this could still be an uncommon stroke presentation.
- Push for stroke prevention care, like starting aspirin and controlling risk factors, while cause remains uncertain.
- Return promptly if any further symptoms or signs develop that may indicate a stroke.
Advocating for more evaluation when stroke is suspected allows the best chance to detect it early and initiate needed care, even if initial scans are unrevealing.
Preventing Hidden Strokes
Steps important for preventing visible strokes are also key for avoiding hidden strokes that scans could initially miss:
- Control high blood pressure through medication, diet, exercise, and other lifestyle measures.
- Lower elevated cholesterol through statin medication.
- Get screened for atrial fibrillation and treat it with anticoagulants if present.
- Take a daily aspirin if over age 50 and at higher vascular disease risk.
- Prevent and control diabetes through medication, diet, exercise, and weight control.
- Eat a Mediterranean-style diet high in vegetables, fruits, fish and whole grains.
- Don’t smoke and avoid secondhand smoke.
- Restrict alcohol intake to moderate levels at most.
- Stay active with regular moderate-to-vigorous aerobic and strength-training exercise.
Addressing these and other stroke risk factors provides the best protection against hidden strokes just as it does for visible strokes. Consult your doctor about the specific prevention plan for your situation.
Key Takeaways
- Although uncommon, strokes can occur that don’t show up on initial CT scans or MRI scans.
- Suspect causes include the stroke being too small, scanning too early, or certain inadequately visualized brain locations.
- Around 5% of all strokes may be “silent” on the first imaging test.
- Repeat scanning within a day or two will usually reveal the findings.
- Other tests like EEG and angiogram also help diagnose otherwise hidden strokes.
- Prevention through controlling stroke risk factors remains essential to avoid strokes scans could miss.