Transcranial Doppler ultrasonography represents a noninvasive means to
study the cerebral vasculature. By varying the depth and angle of a p
ulsed sound wave, a map of the cerebral arteries can be generated. Thi
s information can be used to guide medical strategies in the neurocrit
ical care unit. This article provides an overview of the use of transc
ranial Doppler ultrasonography and its application to specific neurolo
gic problems, and also outlines its potential use in the future.