Apolipoprotein E polymorphism in aneurysmal subarachnoid haemorrhage in West Sweden

Aneurysmal subarachnoid haemorrhage (aSAH) is associated with high morbidity and mortality despite novel treatments. Genetic variability may explain outcome differences. Apolipoprotein E (ApoE) is a glycoprotein with a major role in brain lipoprotein metabolism. It has three isoforms encoded by distinct alleles: APOEε2, APOEε3 and APOEε4. The APOEε4 allele is associated with Alzheimer's disease and worse outcome after traumatic brain injury and ischaemic stroke. This prospective blinded study explored the influence of the APOEε4 polymorphism on the risk of aSAH, risk of cerebral vasospasm (CVS) and 1-year neurological outcome.

The APOΕε4 polymorphism was analysed in 147 patients with aSAH. Allele and genotype frequencies were compared to those found in a gender- and area-matched control group of healthy individuals (n = 211). Early CVS was identified and treated according to neurointensive care unit (NICU) guidelines. Neurological deficit(s) at admittance and at 1-year follow-up visit was recorded. Neurological outcome was assessed by the National Institute of Health Stroke Scale, Barthel Index and the Extended Glasgow Outcome Scale.

APOEε4 and non-APOEε4 allele frequencies were similar in aSAH patients and healthy individuals. The presence of APOEε4 was not associated with the development of early CVS. We could not find an influence of the APOE polymorphism on 1-year neurological outcome between groups. Subgroup analyses of patients treated with surgical clipping vs endovascular coiling did not reveal any associations.

The APOEε4 polymorphism has no major influence on risk of aSAH, the occurrence of CVS or long-term neurological outcome after aSAH.