Transcranial Doppler assessment of cerebral embolic disorders.

Transcranial Doppler ultrasound allows noninvasive monitoring of the large intracranial vessels. Microembolic signals (MES) have been observed under a variety of circumstances, especially in symptomatic carotid stenosis, high-risk cardiac conditions, and surgical procedures (such as carotid endarterectomy and cardiopulmonary bypass surgery). Technical considerations have presented numerous challenges to the interpretation of these signals, many of which appear to represent small emboli traveling in the blood flow. The technical aspects of these MES are discussed and their significance in relation to cerebral ischemia and its prevention are examined in some detail.