Background and purpose: Transcranial Doppler ultrasonography has been used to study changes in cerebral hemodynamics following head injury. However, most studies evaluated the anterior circulation and little information exists on transcranial Doppler of the vertebrobasilar arteries after head injury.
Methods: Thirty-two patients with a Glasgow Coma Scale (GCS) score between 4-8 and 11 patients with a GCS score between 9-14 were studied using transcranial Doppler ultrasonography for the first 10 days after injury. Daily variations in the mean blood flow velocities of all major cerebral arteries were recorded.
Results: In patients with GCS score between 4-8, the mean blood flow velocities in the middle cerebral and basilar arteries gradually increased beginning on day 2 postinjury and peaked on the 4th-5th day after injury. Those changes were more prominent, and appeared earlier, in the basilar artery. The ratio between the mean flow velocities of the middle cerebral artery and the basilar artery during the first 4 days was significantly lower than in normal controls, indicating a particular increase of flow velocity in the basilar artery. Nineteen out of 32 patients (60%) with severe head injury showed mean blood flow velocity increased over 75 cm/sec in the basilar artery. Mean blood flow velocity >90 cm/sec in the basilar artery, compatible with vasospasm, was observed in 12 of 32 patients (37%). Spasm in the middle cerebral artery was observed in 12 (37%) of patients; 10 of them also had evidence of basilar artery spasm. On the whole, 14 of 32 (43%) patients had evidence of spasm either in the middle cerebral or basilar arteries or in both. In 5 of 11 patients (50%) with moderate head injury (GCS score 9-14), blood flow velocity in the basilar artery greater than 75 cm/sec was observed, but in only two of them it reached the values over 90 cm/sec. Vasospasm in the middle cerebral artery was noted in one patient.
Conclusions: A significant number of patients develop increased flow velocities compatible with vasospasm in the basilar artery after severe head injury. This phenomenon may represent an additional factor that contributes to the poor outcome of severely head-injured patients.