Abstracts

RATIONALE: EEG is traditionally used to assess the duration of hemispheric anesthetization and to monitor return of function in the anesthetized hemisphere during the intracarotid amobarbital procedure (IAP), but EEG changes are not consistently seen. We evaluated the role of continuous transcranial Doppler (TCD) monitoring as an alternative to EEG. METHODS: We performed continuous TCD in addition to EEG during the IAP in 10 patients with medically intractable partial epilepsy. Mean velocities were monitored continuously in both middle cerebral arteries(MCA) and changes in MCA velocities time-locked with the EEG changes. RESULTS: The average mean MCA velocities were within normal limits bilaterally (68-85cm/sec)in all patients at baseline. Mean MCA velocities increased in all patients to 95-105cm/sec soon after the injection and dropped gradually on the ipsilateral side after injection of sodium amobarbital to values of 5-33cm/sec. They returned to the baseline average in all with the recovery of hemiparesis. In 8 patients, the duration of EEG slowing coincided with the TCD changes. In the remaining 2 patients, EEG remained normal throughout the IAP despite the presence of contralateral hemiparesis and drop in mean MCA velocities on TCD on the ipsilateral side. CONCLUSIONS: Continuous TCD monitoring may be a more accurate method than EEG in determining the duration of hemispheric anesthetization during the IAP. Since the items for assessment of memory are presented during the period of hemispheric anesthetization, TCD may also be helpful in more precisely defining the time window for memory testing.