Primary study on imaging in transient ischemic attacks

Background Although transient ischemic attacks (TIA) is a clinical diagnosis, imaging findings are important for its diagnosis and treatment. This study evaluated the value and limitations of conventional CT, CT cerebral perfusion imaging and transcranial Doppler sonography (TCD) in patients with TIA. Methods Conventional CT, CT cerebral perfusion imaging and TCD were performed in 20 patients with TIA. After regular CT examination, 40-second dynamic scans were performed on selected slice, while 40 ml of non-ionic contrast materials was bolus-injected through antecubital vein with power injector. These dynamic images were processed with the perfusion software package on workstation. Cerebral blood flow (CBF) and time to peak (TTP) were measured in specific regions of the brain. TCD was also performed in 20 patients with TIA. Comparative analysis was made on the basis of the results of conventional CT, CT cerebral perfusion imaging and TCD. Results In the 20 patients with TIA, conventional CT turned out to be normal. However, persisting abnormal perfusion changes corresponding to clinical symptoms were found in 13 cases with the prolonged TTP. The other 7 cases were normal. TTP of the affected side (11.6±3.0)s was significantly prolonged (t=4.782,P<0.01) in comparison with the contralateral side (8.8±1.5)s. The difference in CBF was not statistically significant (t=1.912, P=0.073) between the affected side [(223.9±19.6) ml·min-1·L-1] and the contralateral side [(227.7±19.8) ml·min-1·L-1] . TCD revealed severe stenosis or occlusion of the carotid artery in 10 patients, arteriosclerosis in 6 patients, blood speed decrease in 2 patients, vasospasm in 1 patient. Conclusions Conventional CT can exclude intracerebral diseases. Perfusion CT provides valuable hemodynamic information and shows the extent of perfusion disturbances. TCD can demonstrate abnormalities of the involved arteries in patients with TIA. The combination of these three imaging methods can provide more diagnostic information.