Is transcranial Doppler a worthwhile addition to screening tests for cerebrovascular disease?

Carotid duplex imaging has become the standard diagnostic evaluation for patients with suspected cerebrovascular disease. Transcranial Doppler ultrasonography expands the noninvasive diagnostic capabilities to the intracranial circulation. The purpose of this study was to evaluate the results of routine transcranial Doppler studies on patients referred for noninvasive cerebrovascular evaluation.

A total of 670 patients had routine transcranial Doppler examinations as part of their noninvasive cerebrovascular evaluation. Patients were categorized clinically and according to their severity of extracranial internal carotid artery stenosis (< 50%, 50% to 79%, 80% to 99%, occlusion). Transcranial Doppler examinations were classified as normal or abnormal (intracranial stenosis, collateral pathway, > 30% velocity difference normal or abnormal (intracranial stenosis, collateral pathway, > 30% velocity difference between sides, flow reversal, and velocities +/- SD from normal).

Forty-eight percent of the patients were women, and 52% were men. The average age was 65.5 years. Fifty-four percent of the patients were white, 42% were black, 3% were Hispanic, and 1% were other. Forty-eight percent presented with hemispheric symptoms, 34% had no symptoms, and 18% had nonhemispheric symptoms. Forty-five percent (304 of 670) had an interpretable transcranial Doppler examination. The ability to insonate the basal cerebral arteries through the temporal bone was significantly reduced in women (p < 0.0001), black patients (p < 0.0001), and older patients (p < 0.0001). The results of forty-four percent of interpretable examinations were normal, 19% demonstrated side-to-side velocity differences, 13% showed collateral pathways, 11% showed velocities +/- 2 SD, 10% showed an intracranial stenosis, and 4% showed reversed flow pattern. Although 56% of the patients had notable findings, no patient had their diagnostic or therapeutic plan altered by the transcranial Doppler results.

Less than 50% of the patients referred for first-time cerebrovascular examination had access for an interpretable transcranial Doppler examination. Though the number of positive findings is reasonably high, no material impact on diagnostic or treatment plans was seen in the patients in this series. These results indicate that selection criteria for examination of the intracranial arteries should be refined and that transcranial Doppler scanning should not be incorporated as part of the "routine" noninvasive cerebrovascular examination.