Abstracts

The intracarotid amobarbital procedure (IAP) remains an important part of presurgical evaluation. The initial doses of amobarbital required to induce an adequate clinical response varies in adults. Variation in dosing in 2 patients with diffuse unilateral hemispheric abnormalities, who underwent IAP as part of a presurgical evaluation, is reported., 5 intracarotid amobarbital injections were performed in 2 adult presurgical patients with diffuse unilateral hemispheric abnormalities. The patients had previously undergone prolonged video EEG monitoring, MRI head imaging and neuropsychological testing. Angiography was performed first to determine the degree of crossfilling. EEG monitoring was performed throughout the procedure. Injected doses of amobarbital ranged from 62.5 to 150 mg. Effectiveness of dosing was determined by the presence of a contralateral hemiplegia, ipsilateral slowing on EEG and the absence of obtundation that precluded adequate clinical testing. Testing was performed to determine lateralization of language and memory function., The 2 patients studied had previously performed MRI imaging demonstrating diffuse left hemispheric abnormalites. In the first a multilobar neuronal migration abnormality was seen and in the second multilobar encephalomalacia was present. Neuropsychological testing in both patients was nonlateralizing. In both patients the IAP was performed with injection of the affected hemisphere first. An initial injection of 100 mg was increased to 125 mg in the first patient and to 150 mg in the second in order to achieve an effective dose. In injecting the contralateral, unaffected hemisphere, the first patient had an inital dose of 100 mg given that resulted in obtundation that precluded any clinical testing. This injection was later repeated at an initial dose of 50 mg that was then increased to 62.5 mg to achieve the desired effect with only brief obtundation. The second patient was given an initial dose of 75 mg that was effective with minimal obtundation., In the 2 patients with diffuse unilateral hemispheric abnormalities who underwent a bilateral IAP a significant difference in the required amobarbital dosing was observed. The effective dose of amobarbital was significantly less for the uninvolved hemisphere and was significantly higher for the affected hemisphere.,