Application of technetium-99m hexamethylpropylene amine oxime single-photon emission tomography to neurologic prognosis in patients undergoing urgent carotid surgery.

In this study we aimed to work out a quantitative prognostic index for preoperative assessment of brain technetium-99m hexamethylpropylene amine oxime (HMPAO) single-photon emission tomography (SPET) in patients referred for urgent carotid endarterectomy due to acute obstructive disease of the internal carotid artery (ICA) and neurological deficit. To this end we compared data from preoperative SPET studies with the postinterventional changes in neurological status in 20 patients (17 males, three females; mean age 53 years, SD 4 years) with acute ischaemic cerebral disorders induced by obstruction of the ICA. Carotid obstruction was diagnosed by ultrasound B-mode study. All patients underwent urgent carotid endarterectomy from the ICA. Patients were divided into two groups in accordance with the results of postoperative follow-up: group A comprised patients with significant (more than 3 points) postoperative improvement in neurological condition as quantified by the Canadian Neurological Scale (11 patients); group B consisted of patients with minimal improvement or deterioration (nine, three of whom died). All patients were studied preoperatively by 99mTc-HMPAO SPET. The volume of nonperfused tissue (VS, cm3) was quantified using the Mountz technique. Hypoperfused volume (Vhypoperf, cm3) in the affected hemisphere was calculated as the total volume of voxels with 99mTc-HMPAO uptake < 90% of the contralateral symmetric voxels. Discriminant prognostic function was calculated by discriminant analysis as: PF = 0.072 x VS + 29.46x(VS/Vhypoperf). Patients with preoperative PF values < 8.20 demonstrated postoperative improvement in neurological status, while the group with PF > 8.90 comprised patients who demonstrated minimal improvement or deterioration. PF values in the range 8.20-8.90 carried an indefinite prognosis. We conclude that the preoperative 99mTc-HMPAO SPET can be used for the selection of patients in whom improvement in neurological status may be expected after urgent surgical correction of acute extracranial obstruction of the ICA.