Imaging in posterior circulation stroke

This thesis focuses on correct infarct localisation in the posterior circulation (PC) (Chapter 2), diagnostic and predictive value of various imaging derived parameters in the PC (Chapter 3-6) and ends with the protocol of the currently BASICS trial (Chapter 7).
Chapter 2 investigates if biographical and clinical characteristics can aid in the identification of patients with clinical signs of an acute infarction in the anterior circulation (AC) but with a PC infarction as the final diagnosis. Most of the PC infarcts (75%) were lacunar infarcts in the pons and thalamus. None of the baseline characteristics had a statistically significant relation with the presence of a PC infarct.
Chapter 3 reports the additional value of CT perfusion (CTP) to non-contrast CT (NCCT) and CT angiography (CTA) source images for infarct detection and localisation in patients suspected of acute ischemic PC stroke. Discrimination of 3 hierarchical logistic regression models (NCCT [A], added CTA source images [B], and CTP [C]) was compared with C-statistics and showed that CTP has significant additional diagnostic value to NCCT and CTA source images for detecting ischaemic changes in these patients.
In Chapter 4 we propose a 10-point CTA based grading system: the posterior circulation collateral score (PC-CS). We assessed the prognostic value of the PC-CS for the prediction of outcome in 140 patients with acute BAO from the Basilar Artery International Cooperation Study (BASICS) registry. Additionally, we analysed the relation between the presence and size of posterior communicating arteries and outcome. The PC-CS predicted poor outcome at one month. Both the absence and smaller calibre of posterior communicating arteries predicted poor outcome.
We assessed clot length on CTA in 149 patients with an acute BAO from the BASICS registry. Clot length was related to recanalisation and outcome at 1 month. We found that clot length predicted recanalisation but not outcome at 1 month in patients with a BAO. Additionally, we found 2% more poor outcome and 10% less recanalisation with every centimetre increase in clot length in the analysis of clot length as a continuous variable. (Chapter 5)
In Chapter 6 we describe the prevalence and outcome of vertebral artery (VA) stenosis ≥50% or occlusion in 141 patients with acute BAO enrolled in the BASICS registry, assessed on CTA. Sixty-six of 141 patients (47%) had unilateral or bilateral intracranial VA stenosis ≥50%. Forty-six of 72 patients (64%) with available intra-and extracranial CTA had uni-or bilateral VA occlusion or stenosis ≥50%. Overall, VA occlusion or stenosis ≥50% was not associated with the risk of poor outcome. Patients with intra- and extracranial CTA and bilateral VA occlusion had a higher risk of poor outcome than patients without bilateral VA occlusion.
BASICS is a randomised controlled trial investigating the efficacy and safety of intra-arterial therapy (IAT) in addition to best medical management in patients with BAO. Patients are randomised between best medical management with additional IAT and best medical management alone. The primary outcome parameter is favourable outcome at day 90 defined as an mRS of 0-3. (Chapter 7)