BACKGROUND: The cause of ischemic stroke remains undetermined in 30-40% of the cases, but circulating blood clots (thromboemboli) are a postulated common denominator in approx. 75% of patients. Transcranial Doppler monitoring (TCDM) is a non-invasive method of detecting circulating microemboli (CME) in the human cerebral circulation. The method is not used systematically in unselected groups of patients with repeated long-term registrations. New ultrasound equipment is ambulatory, less unpleasant for the patient and allows extended monitoring sessions. This may vastly simplify the implementation of TCDM as a clinically useful diagnostic tool.

AIMS: Determine the usefulness of TCDM in acute stroke diagnostics by assessing prevalence and frequency of CME in unselected patients with ischemic stroke, the influence of antithrombotic drugs on CME and the relationship between MES and recurrent stroke or transient ischemic attack (TIA).

HYPOTHESES: Prevalence and frequency of CME are higher during the first 24 hours than at later follow-up. Stroke etiology can be assessed by the presence or absence of CME. Presence of CME is associated with increased risk of recurrent TIA of stroke within 3 months and 1 year. Cessation of CME after the start of antithrombotic treatment is associated with reduced risk of recurrent TIA or stroke.

• Standardized questionnaire
• Clinical work-up in accordance with hospital standard operating procedures, i.e. radiological and cardiological procedures, neurovascular ultrasound, clinical scoring, etc.
• 1st Transcranial Doppler monitoring (TCDM) at admission if within 24 hours after stroke onset (day 1). TCDM is repeated at 18-36 hours and at day 3. Microembolic signals are automatically registered by the software and subsequently verified manually.

Inclusion Criteria:

• Admitted to hospital < 24 hours after onset of ischemic stroke

Exclusion Criteria:

• Temporal bone window inadequate for transcranial Doppler examination
• Participation in ongoing sonothrombolysis study (NOR-SASS 2)
• Reduced ability to cooperate
• No informed consent can be obtained

Patients with acute ischemic stroke or TIA admitted to Haukeland University Hospital. All stroke sub-types, severities and vascular distributions are eligible.