Carotid pseudo-occlusion on CTA in patients with acute ischemic stroke: A concerning observation

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Abstract

Objective

Differentiation between an occluded and a patent extracranial internal carotid artery (ICA) is crucial in the diagnostic workup of patients with acute ischemic stroke; particularly in patients eligible for endovascular treatment. We report neurological and radiological findings of cases in which CTA in the acute phase incorrectly revealed an occlusion of the ICA.

Methods

In our image data base of 54 patients with acute ischemic stroke eligible for endovascular treatment, we searched for patients with an occluded extracranial ICA on CTA whereas DSA proved that this artery was patent. Of these patients, all available images were re-examined to investigate possible causes of these so-called pseudo-occlusions.

Results

We detected 6 patients (11%) with a pseudo-occlusion. The pseudo-occlusions on CTA were associated with reduced flow due to carotid T-occlusions (4 cases) or a combination of a high degree stenosis of the extracranial ICA and MCA occlusion (2 cases).

Conclusion

CTA in the acute phase of ischemic stroke needs to be interpreted with severe caution, and in endovascular treatment decisions we should be aware that an extracranial ICA occlusion may be a false positive finding.

Introduction

Extracranial ICA occlusion is not uncommon in patients with acute ischemic stroke with estimations up to 24% [1]. These patients have poor prognosis with profound disability and death [2]. For example, Intravenous thrombolysis (IVT) resulted in recanalization of the occluded extracranial ICA in only 26–31% of the patients, compared to 59–88% in patients with an occlusion of the middle cerebral artery (MCA) [3], [4]. Furthermore, endovascular treatment is often unsuccessful in patients with a tandem occlusion of an extracranial ICA and a major intracranial artery, unless an aggressive approach with angioplasty and stenting of the proximal occlusion and thrombectomy of the intracranial occlusion is performed [5].

CTA is the imaging modality of choice to evaluate patency of arteries in the acute phase of ischemic stroke. In a population of patients suspected of carotid artery stenosis, it has been shown that CT is accurate in detecting occlusions [6]. However, previous studies have shown that the use of CTA may result to incorrect diagnosis [7]; Kim et al. [8] reported 6 out of 100 consecutive patients suspected of acute cerebrovascular event in which 64-slice CTA incorrectly suggested an occluded ICA.

In this study, we retrospectively searched our image data base of 54 patients with acute ischemic stroke eligible for endovascular treatment in which CTA incorrectly suggested an extracranial ICA occlusion. For these cases, we explored potential causes of these so-called pseudo-occlusions.

Section snippets

Methods

Cases were derived from prospectively collected stroke databases (Nov 2009 to Dec 2010) of two medical centers containing 54 patients with acute ischemic stroke of the anterior circulation who underwent 64-slice CTA because endovascular treatment was considered. Table 1 shows details of the scan protocols. Permission of the medical ethics committee was given for this retrospective analysis of anonymous patient data. Informed consent was waived because no diagnostic tests other than routine

Results

In our database of 54 patients with acute ischemic stroke eligible for endovascular treatment, we identified 6 patients (11%) with a pseudo-occlusion on CTA made in the acute phase of stroke. The agreement of the observers was perfect: both observers selected the same 6 patients. The NIHSS score of these patients varied between 7 and 19. Clinical data are summarized in Table 2. In the CTA images, contrast was absent in the extracranial (case 6), intracranial segments (case 1), or both (case 2,

Discussion

In our database of 54 patients with acute ischemic stroke eligible for endovascular treatment, we identified 6 patients in whom CTA in the acute phase showed an extracranial ICA occlusion, whereas DSA revealed that this vessel was patent. In 4 cases the patient had a carotid T-occlusion (Fig. 1). Two pseudo-occlusions were associated with a severe stenosis in the extracranial ICA with a MCA occlusion (Fig. 2). This alarming finding implies that CTA in the acute phase of stroke, used for

Conclusion

In our patient of patients with acute ischemic stroke, we found a high rate of 11% of patients where reduced flow due to occlusion of intracranial arteries or due to high-degree stenosis in patient with acute ischemic stroke, CTA may incorrectly suggest an extracranial ICA occlusion. This concerning finding implies that the use of CTA in the acute phase of stroke for decisions on endovascular treatment needs to be interpreted with extra caution. Performing a delayed CT when an ICA occlusion is

Competing Interests

None

Funding

None

Acknowledgement

None

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