Assessment of brain perfusion in coma and comparison between SPECT and CT scan data: preliminary report

In this study we submitted 24 comatose patients (Glasgow Coma Score <8) to Single Photon Emission Tomography (SPECT) during the clinical course of coma to verify its utility and the relationship between SPECT and CT scan data. SPECT was recorded following i.v. injection of Xe-133 in 17 patients and of Tc-99m-HMPAO or Tc-99m-ECD in the remaining 7. SPECT data recorded during the acute phase of coma did not show a clear correlation between cerebral blood flow (CBF) and outcome. SPECT and CT scan detected abnormalities in the same areas in 6 cases (25%); 6 patients (25%) with focal CT-scan lesions showed no focal CBF alterations in the same regions; conversely, in the remaining 12 cases (50%) SPECT disclosed severe perfusion abnormalities where no lesions were detectable on CT-scan. SPECT allowed us to recognize different regional flow patterns, such as absolute or relative hyperemia or oligoemia, which could not be checked with other means, thus improving patient's management. Apart from cerebral ischemia, there was no relationship between lesions on CT-scan and flow pattern. Our preliminary results suggest that SPECT can improve both the knowledge of patient's neurological conditions and management in comparison to the use of only CT scan.