The Clinical Study Of Transient Ischemic Attack By CT Perfusion Imaging Combined With CT Angiography

Objective: Transient ischemic attack (TIA) is a common cerebrovascular disease, it is known as an important risk factor and the indicator of cerebral infarction. If it isn't treated actively and effectively, 1/3 cases of TIA may develope to complete ischemic stroke, 1/3 may have onset repeatedly and 1/3 may alleviate naturally. Therefore, it is vital significant to study TIA for preventing TIA from cerebral infarction. In recent years, with the development of neuroimaging technology, CT, MRI, CTPI, CTA, and DSA are applied more and more widely in clinic, we get more understandings about TIA than before. This study conducted by CT perfusion imaging (CTPI) and CT angiography (CTA) was to investigate the cerebral perfusion and the cerebral vascular stenosis in TIA patients. To explore the value of CTPI and CTA in the diagnosis of TIA, and the relationship between clinical manifestation and radiological findings of TIA was discussed, and then further explore the etiology, pathogenesis of TIA so as to guide the treatment of TIA, by means of making the treatments individually to improve the therapeutic results.Methods: 1 Patients with TIA admitted in Tangshan Worker Hospital neurology and emergency department during 2005.10~ 2006.12 were enrolled into the study. All patients were diagnosed TIA according to the revised diagnostic criteria for acute ischemic cerebrovascular disease in the Fourth National Conference. And they would be divided into two groups as carotid system and vertebrobasilar system TIA by clinical manifestation.2 A detailed history was investigated by asking the TIA patients and their family members and the NIHSS score was noted according to the situation of TIA onset.3 Each patients must undergo CT scan to preclude cerebral hemorrhage, be informed, consent and not be allergic to iodine. Eligible patients underwent CT angiography and CTPI. The basal ganglia and pons were chose as the interest slice in carotid system and vertebrobasilar system TIA respectively when practised CTPI.4 Data would be transmitted to the workstation, and processed by CT perfusion image software, then CBF, CBV, MTT, TTP image maps were obtained. Regions of interest (ROI) were marked on ischemia side and corresponding regions on opposite side in CTPI map and paired t-test were carried for statistics. Based on CT perfusion imaging, the stages of TIA were demonstrated as follows: (Ⅰ1)TTP was delayed, MTT, CBF and CBV were normal; (Ⅰ2) TTP and MTT were delayed, CBF was normal, and CBV was normal or slightly increased; (Ⅱ1) TTP and MTT were delayed, CBF was decreased, and CBV was normal or slightly decreased; (Ⅱ2) TTP and MTT were delayed, CBF and CBV were decreased. As CTA completed, CTA software help us get CTA graph, which was about the location and severity of the vascular stenosis would be noted in details.5 All the CTA and CTPI information would be read and analysis by two experienced neurologist respectively, and then reach consensus finally, and the typical images would be reserved.6 Statistical Methods: Quantitative data analyzed by t-test analysis, qualitative data analyzed by chi-square test, results were regarded as significance when p < 0.05. SAS 6.12 statistical analysis software is used to deal with the data.Results:1 A total of 124 cases were enrolled in the research, male 81, female 43, 86 cases of carotid system TIA and 38 cases of vertebrobasilar system TIA; all 124 patients were underwent CTA inspection and 69 cases had CTPI inspected, which consist of 38 cases with carotid system TIA and 31cases with vertebrobasilar system TIA.2 There were 29 cases (76.3%) with carotid system TIA revealed abnormalities in CTPI and 23 cases (74.2%) with vertebrobasilar system TIA. There were 6 cases (15.8%) in stageⅠ1, 12 cases (31.6%) in stageⅠ2, 8 cases (21.0%) in stageⅡ1,3 cases (7.9%) in stageⅡ2 in carotid system TIA. And there were 4 cases (12.9%) in stageⅠ1, 3 cases (9.7%) in stageⅠ2, 14 cases (45.2%) in stageⅡ1, 2 cases (6.5%) in stageⅡ2 in vertebrobasilar system TIA.3 The relation of abnormality in CTPI and the clinical manifestation of TIA3.1 Cerebral hypoperfusion correlated with increased NIHSS score in TIA patients. The positive rate (91.7%) in NIHSS≥4 group during TIA onset was significantly higher than the NIHSS<4 group (66.7%). The higher the NIHSS score during TIA attacked, the more obvious the severity of ischemia in CTPI.3.2 Cerebral hypoperfusion correlated with the duration of TIA onset. There was significant difference among duration less than 10min group, 10-60min group, and duration more than 60min group. The longer the duration of TIA attacked, the more obvious the severity of ischemia in CTPI.3.3 Cerebral hypoperfusion correlated with different frequency of TIA onset. There was significant difference between less than 1 time TIA onset/24h and more than 2 times TIA onset/24h. The more frequency of TIA attacked, the more obvious the severity of ischemia in CTPI.3.4 Cerebral hypoperfusion had no relation to the different interval time between TIA onset and CTPI. There was no significant difference between cerebral hypoperfusion in CTPI and different interval time between TIA onset and CTPI. There was a tendency of the shorter of interval time the higher of CTPI positive rate, but there was no significant difference among them.4 The vascular stenosis in patients with TIA4.1 In this study, 124 patients with TIA were enrolled. All patients were underwent CTA, and 11 cases (8.9%) were found no vascular stenosis, 113 cases revealed artery stenosis or occlusion. Among them 68 cases (54.8%) had intracranial arterial stenosis, 20 cases (16.1%) had extracranial arterial stenosis and 25 cases (20.2%) had both intracranial and extracranial stenosis. In this study the residents in north China were as the main target, the number of cases with simply intracranial arterial stenosis was more than both intracranial and extracranial stenosis, and more than extracranial arterial stenosis.4.2 There were 64/86 cases (74.4%) with carotid system TIA had vascular stenosis or occlusion (convict vascular), which were matched with clinical symptoms, 39 cases (60.9%) with stenosis of the middle cerebral artery. There were 18/38 cases (47.4%) with vertebrobasilar system TIA had convict vasculars, which were match with clinical symptoms, 11 cases (61.1%) with vertebral artery stenosis, 7 cases (38.9%) with basilar artery stenosis. Through statistical analysis, the coincidence rate of vascular stenosis and clinical manifestation in internal carotid system TIA is higher than that in vertebrobasilar system TIA.5 The relationship between CTPI positive rate and the convict stenosis: In 69 cases checked by both CTA and CTPI, there were 49 cases (80.3%) with convict vascular stenosis and perfusion abnormalities, which were matched with clinical symptoms. There were 3 cases (37.5%) with perfusion abnormalities but without convict vascular stenosis. Through statistical analysis, there was a significant difference between them. It suggested that the positive rate of CTPI were higher in the cases with convict vascular stenosis.6 The correspondence relationship between CTPI and CTA abnormality had the following 4 types. It suggested that the theory of hypoperfusion was the common cause of TIA.6.1 There were 49 cases (71.0%) with convict vascular stenosis accompanied by perfusion abnormalities. Among them 31 cases underwent DWI inspection in which 5cases (16.1%) were showed new infarction in DWI.6.2 There were 3 cases (4.3%) with perfusion abnormalities in CTPI but without convict vascular stenosis in CTA. All of them conduct DWI inspection and none of them revealed new infarction in DWI.6.3 There were 12 cases (17.4%) with convict vascular stenosis in CTA but without perfusion abnormalities in CTPI, 3 cases (25.0%) had new lacunars found in DWI.6.4 There were 5 cases (7.2%) neither had convict vascular stenosis nor had perfusion abnormalities, and none of them had new infarction in DWI.Conclusions:1 CTPI combined with CTA had a high sensitivity for the diagnosis of TIA. They can be used as the imaging basis of TIA diagnosis.2 There were still cerebral blood flow abnormalities in CTPI though the symptoms of TIA had alleviated. The application of CTPI and CTA can help to study the etiology, pathogenesis mechanism of TIA, to verify the hypoperfusion theory of TIA, to guide the treatment selection of patients with TIA. It can be used to provide reliable support and nuroimage basis for TIA anticoagulant, anti-platelet aggregation and bloon and stent.3 The study showed that simple intracranial arterial stenosis were more than both intracranial and extracranial stenosis, and more than simple extracranial arterial stenosis in patients with TIA in north China. The majority of vascular stenosis was the middle cerebral artery stenosis in carotid system TIA and the vertebral artery stenosis in vertebrobasilar system TIA.4 The study showed that the CTPI positive rate was higher in TIA patients with convict vascular stenosis, in addition, CTPI positive rate was still had relation to TIA clinical manifestation. It had a more important clinical value to advance of the imaging study from infarction to TIA.