A microembolism is a small particle, often a blood clot, that becomes caught while traveling through the bloodstream and can cause blockage in a blood vessel. When many of these occur in in the blood vessels of the brain, they are known as cerebral microemboli.
A large number these microemboli may cause damage in the form of a transient ischemic attack (TIA), sometimes referred to as a microstroke or "warning stroke." Much more worrisome, frequent microemboli may indicate a high risk for a future large blockage (embolus) or stroke.
A stroke occurs when a blood vessel that supplies blood to the brain is blocked (ischemic stroke), leaks or bursts (hemorrhagic stroke). This blocked blood flow damages, and eventually kills, nerve cells in that area of the brain. As a result, the part of the body controlled by the damaged area of the brain cannot work properly.
Cerebral microemboli can occur without patients showing any symptoms or can occur during procedures used to treat intracranial stenosis.
When symptoms are present, they are often in the form of a TIA, or microstroke, which has symptoms similar to an ischemic stroke, but usually lasts between 2 and 30 minutes.
Patients who have experienced a TIA or ischemic stroke may have the following symptoms:
- Sudden numbness or weakness of the face, arm or leg, especially on one side of the body
- Sudden confusion
- Sudden trouble speaking
- Sudden trouble seeing in one or both eyes
- Sudden trouble walking
- Sudden dizziness, loss of balance or coordination
- Sudden, severe headache with no known cause
Some research findings suggest that cerebral microemboli may cause problems with brain function, but it is unclear whether this is due to undetected strokes or to the microemboli alone. Symptoms include:
- Abnormal forgetfulness
Causes and Risk Factors
The risk of developing cerebral microemboli increases with procedures that may cause obstructions to enter the bloodstream, including surgeries and treatments for heart disease.
The condition also is closely associated with arterial stenosis (narrowed blood vessels), which is caused by atherosclerosis, the buildup of plaque in the arteries. Atherosclerosis can begin in early adulthood, but symptoms may not be evident until many years later.
Microemboli can occur in patients with undertreated atrial fibrillation, and indicate the need for more aggressive blood thinning to prevent strokes.
The risk of developing atherosclerosis, arterial stenosis and cerebral microemboli is increased by:
Diagnosis of cerebral microemboli frequently happens after a patient has been diagnosed with atherosclerosis or has experienced a TIA or stroke.
To detect microemboli, patients are monitored by a transcranial doppler (TCD) ultrasound, which measures the blood flowing through the arteries at the base of the brain and can detect cerebral microemboli as they occur. TCD is noninvasive, simple and highly sensitive for the detection of microemboli. In comprehensive stroke centers, TCD is used to monitor patients over time to assess the effect of blood thinning and other stroke prevention treatments
Other imaging tests, including magnetic resonance imaging (MRI) and computed tomography (CT) angiography, may be used to diagnose the condition after the patient has experienced a stroke. These imaging tests can provide images of the blood vessels and identify which part of the brain is being affected by the condition.
Because they are at increased risk of stroke, patients with who have been diagnosed with cerebral microemboli require immediate medical care by an experienced, multidisciplinary team of experts, such as those in the comprehensive Stroke Program at Cedars-Sinai.
In patients with atherosclerosis and arterial narrowing, treatment will focus on prevention, using blood pressure, cholesterol, blood sugar and antiplatelet treatments, such as aspirin, clopidogrel or persantine. In patients with microemboli due to atrial fibrillation, strong blood thinners (anticoagulants) such as warfarin, Xarelto or Dabigatran will be used.
Other possible treatments include surgical procedures or filtering the patient’s blood to remove the blood clot as it returns to the heart.
If a patient has experienced a stroke, during their recovery and rehabilitation, physical and occupational therapy are often a key component to the treatment plan. These therapies aid patients in restoring muscle movement, coordination and balance, and can help patients relearn daily activities. Speech therapy may also be prescribed if a patient is experiencing difficulties talking or swallowing.