Intracranial Arterial Disease

The Warfarin Aspirin Intracranial Disease trial was terminated due to excessive hemorrhagic complications and lack of efficacy for warfarin over aspirin to prevent recurrent stroke in patients with symptomatic (350%) intracranial stenoses (29). Nevertheless, ultrasound screening for the presence of the intracranial vessel disease is still necessary, as intracranial stenosis is an independent and serious risk factor for stroke (30-32) and therapies other than anticoagulation are being developed (33-35).

Detection of intracranial stenoses with TCD is most reliable for the middle cerebral artery (MCA), terminal ICA, and basilar artery (36-38). Various velocity thresholds have been introduced to predict significant intracranial stenoses. As symptomatic MCA stenosis of >50% bears an approximate 7% to 10% annual risk of recurrent stroke (29-32), we have adjusted our criteria to optimize screening with TCD to predict the presence of these lesions (39). We use a cut-off of >100 cm/sec for the mean flow velocity (MFV) and the prestenotic:stenotic ratio of 1:>2 for defining >50%-diameter reduction of the MCA (Fig. 2) (39). Other groups have developed their own velocity criteria for transcranial duplex imaging (41) and TCD (42,43). When applying these published criteria, it is important to establish how the investigators measured percent stenosis at angiography and if angle correction was employed with duplex scanning.

Performance of TCD requires evaluation of vessels other than the MCA, because an increase in the number of vessels with significant intracranial stenoses linearly increases the risk of subsequent stroke. More than 50% of symptomatic Chinese patients with 6 or more stenotic vessels suffered a stroke during follow-up (43). If TCD shows recurrent embolization and/or an increasing degree of intracranial stenosis (44-47) with fluctuating neurologic deficit or recurrent events, despite the best medical therapy, patients with these findings may be considered for experimental intracranial angioplasty stenting procedures (34 ).

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