Aim. Comparison of the trascranial Doppler （TCD） characteristics of cerebral circulation in persistent vegetative status （PVS）

locked in syndrome and brain death patients. Methods. Using TCD ultrasound to detect the flow velocity and waveform patterns of middle cerebral artery （MCA） and basilar artery （BA） in patients with PVS

locked in syndrome and brain death. Results. The mean velocities of middle cerebral artery （Vmca） and basilar artery （Vba） were 30.0cm/s and 24.3cm/s in PVS patients respectively

which decreased 45.0% and 14.4% in comparing with normal value. For patients with locked in syndrome

Vmca and Vba were 49.7cm/s and 9.8cm/s

which decreased 5.0% and 61.7% than the normal value respectively. These results showed that the decrease of anterior circulation was predominant in PVS

and the decrease of posterior circulation was predominant in locked in syndrome. A unique diastolic reverse flow

short peak systolic wave or undetectable flow signal in middle cerebral artery were predominant in brain death patients

which was completely different from that of either PVS or locked in syndrome. Conclusion. TCD was a valuable tool in distinguishing PVS

locked in syndrome and brain death patients according to the differences in velocities and patterns of anterior and posterior cerebral arteries.