Microembolic Signals - Transcranial Doppler (MES)

What is Microembolic Signals (MES)?

MES is a specialised Transcranial Doppler (TCD) ultrasound test that detects high-intensity signals in the blood flow of the brain’s arteries. These signals could represent small particles, such as clots or air bubbles, travelling in the bloodstream to the brain.

Your doctor may recommend this test to:

• Investigate the source of stroke or transient ischemic attack (TIA)
• Monitor patients with known vascular conditions
• Evaluate blood flow abnormalities 

How should I prepare for the MES?

• Non-invasive (no needles)
• Radiation-free
• A sonographer will be present throughout the process. If you feel unwell, please inform the sonographer.

If you have any questions or concerns, please contact your designated neurodiagnostic laboratory or healthcare team

How is MES performed?

The test is done by a sonographer and takes approximately 1 hour.

• The test is performed while you are lying on a bed
• A clear, water-soluble gel is applied to two small ultrasound probes to help transmit sound waves.
• The probes are placed at your temples and secured with a soft, padded headframe.
• You may hear a continuous “whooshing” sound, which represents blood flow in your brain arteries.
• These probes continuously monitor blood flow in the brain’s arteries.
• Once the test is complete, the headframe is removed, and the gel cleaned off.
• A report will be sent to your doctor and he/she will discuss the results with you at your next appointment.

Frequently Asked Questions about MES

Is the test safe?

• Non-invasive (no needles)
• Radiation-free
• A sonographer will be present throughout the process. If you feel unwell, please inform the sonographer.

If you have any questions or concerns, please contact your designated neurodiagnostic laboratory or healthcare team.

Can I use Medisave to pay for this test?

This test may be claimable under:

• Flexi-MediSave for Seniors; or
• Outpatient scans for diagnosis or treatment of a medical condition. 

Please refer to the Ministry of Health's Outpatient Care page for the latest claim limits and eligibility criteria.

The information is correct as of July 2026 and subject to revisions without notice.