TCD and Cerebral Circulation Practice Test

In Doppler signals, a narrowed vessel forces the blood to speed up to maintain flow, so a focal narrowing shows up as a high velocity at that artery. If only one side—the MCA on one hemisphere—has this elevated velocity while the opposite side is normal, it points to a localized problem rather than a global process. The clean spectral trace matters: it means the signal is reliable and not due to a poor window or noise. Put together, this pattern most strongly suggests unilateral intracranial stenosis or occlusion, and it should be followed up with confirmatory imaging such as CTA, MRA, or catheter angiography to determine the degree of stenosis and guide management. This is distinct from a global vasospasm, which would typically affect multiple vessels, or from a measurement artifact or normal variant, which would not show a unilateral, real high velocity with a clear trace.