In our study, we found high grade, ipsilateral arterial pathologies in around 23% of all patients with TIA diagnosed by acute CTA and a need for invasive treatment in around 7% of cases. These numbers indicate that CTA in the acute setting of TIA is justified in selected patient subgroups. As predictors, we identified male sex, cardiovascular disease, a short period of symptoms, hemiparesis and pyramidal signs, which might be useful for patient selection. In contrast, established TIA-scores turned out to be not predictive for high risk vascular pathologies.
TIA and ischemic stroke, both indistinguishable in the acute setting in most cases, require vascular imaging. Besides CTA, there are other imaging methods to be considered for neurovascular status evaluation like magnetic resonance imaging and neurovascular ultrasound. Neurovascular ultrasound of the brain supplying arteries has a high spatial resolution and is able to detect atherosclerotic changes, as well as thrombi in the proximal carotid artery very well. However, it is limited by investigator dependency and availability. Neurovascular Ultrasound in the acute setting can also result in treatment delays due to longer investigation times and patient factors like incompliance, anatomical problems like insufficient transtemporal doppler window and the fact that distal intracranial arteries as well as distal parts of the internal carotid arteries cannot be visualized.  Therefore, neurovascular ultrasound is not recommended in the acute phase of ischemic stroke if fast and targeted therapy like IVT and EVT is available. Magnetic resonance imaging (MRI) is one of the most important methods to assess the brain tissue. However, it has been shown that CT combined with CTA provides a comparable quality to diffusion-weighted MRI in stroke patients. Considering the fact that MRI resources are more limited compared to CT, which is available 24/7 in all stroke centres, also is significantly faster and has a high sensitivity for the diagnosis of vessel occlusions and haemorrhages, CT imaging is the technology of choice in the acute setting of stroke.
The evaluated ABCD2-score, ABCD3-score and SPI-II, that stratify the risk for stroke after TIA, were not predictive for ipsilateral vascular pathologies or the need for invasive treatment in our study. This observation corresponds to findings from Lou et al. concerning the ABCD2-Score as a possible predictor for intervention. In their study, including 121 patients with TIA, they found that the ABCD2-Score was equally distributed in patients no matter if they received an intervention or not. Reasons for the missing predictive value of these scores might be, that TIA scores have been developed to predict recurrence rates of TIA or stroke in those patients. Many factors incorporated in these scores (admission blood pressure, age, diabetes mellitus and heart failure) were equally distributed in our cohort, raising the suspicion, that these factors are likely to be usable to quantify instability (risk of recurrence) of the underlying pathology, but are not predictive for the underlying pathology itself. Also, most items are related to the neurologic symptoms presented at admission. As the most important predictors for vascular disease like chronic arterial hypertension, high heart rate, smoking habit and other vascular diseases are not considered in these scores, this might explain the lack of prediction. [17, 18]
Our results advise to consider a certain risk profile if to decide to perform a CTA or not.
Concerning the association between male sex and the incidence of cerebro- and cardiovascular diseases in general[19–23], the high prevalence of carotid stenosis in patients with coronary artery disease,[21, 24, 25] it is not surprising, these patient characteristics predict ipsilateral high-risk pathologies diagnosed by CTA in our study. Our findings suggest that patients at risk for macroangiopathic vessel disease and TIA should receive CTA in the acute setting to diagnose high risk vascular pathologies and to initiate targeted therapy. CTA in this case could contribute to a time gain to diagnosis and could contribute to reduce the risk for TIA recurrence or a manifest ischemic stroke.
A short duration of Symptoms in TIA patients is likely to be associated with macroangiopathic arterial disease of brain supplying arteries and can be found in most patients with carotid artery stenosis. A prototype of a short lasting neurologic deficit associated with carotid artery stenosis is the Amaurosis fugax, a special form of TIA.[26, 27] Already in the seventies Pessin et al. and Harrison et al. found that TIA-patients with a symptom duration under one hour were more likely to have a carotid artery stenosis and should get an angiography.[28, 29] These findings go in line with our finding, that a short duration of symptoms increases the risk for a high grade, ipsilateral vascular pathology and the need for an invasive treatment in patients with TIA. In contrast, cardiac emboli are more likely to cause permanent and more severe focal neurological deficits.[24, 30, 31] The difference in duration of symptoms caused by arterial or cardiac emboli could be explained by a difference in spontaneous revascularization due to a variation of constitution and size of the thrombi.[29, 32, 33] Another point to consider is the collateralisation status in patients with arterial emboli caused by vessel stenosis compared to cardiac embolization with no associated vessel stenosis. Arterial stenosis formation take month to years inducing intracranial collateralization, which is not present in cardiac embolization. This fact could explain short symptom duration in patients with arterial stenosis, where hemodynamics can adapt in a few seconds. Therefore, short duration of symptom should not be discarded as trivial by the clinician, but raise the suspicion of macroangiopathic disease with associated findings in CTA.
Strength of our study is the high number of patients included in our study cohort as well as the use of “real word” data from a large volume, tertiary stroke centre. Limitations include the monocentric, retrospective design of the study. Moreover, a selection bias must be assumed, as only 66% of patients with TIA received a CTA in the emergency department. The reason for the decision to perform or not to perform a CTA in the acute setting could be influenced by multiple factors like preference of the consultant neurologist in charge, patient factors like kidney disease and medical history of the patient.