Diffusion- and Perfusion-weighted Magnetic Resonance (MR) Imaging and MR Angiography in Apolipoprotein E Polymorphism and Stroke

Apolipoprotein E (ApoE) allele ε4 may have both adverse and beneficial effects in patients with acute stroke. ApoE allele ε4 is associated with increased vulnerability of the brain, which is reflected in relatively greater lesion growth and low threshold for the brain tissue to survive stroke and in the lack of correlation between the imaging findings and clinical outcome in ε4 carriers. Conversely, ε4 has at least a seemingly beneficial effect on the cerebral blood flow, i.e. collateral blood flow is better in ε4 carriers compared with non-carriers. In the clinical studies that focus on the relationship between harbouring ε4 and clinical outcomes in ischaemic stroke patients, the adverse and beneficial effects may be compromised. In any case, when possible, ApoE allele ε4 should be classified as a confounding factor when studying stroke either by imaging methods or clinically.