Intracerebral hemorrhage outcome: apolipoprotein E genotype, hematoma, and edema volumes

The influence of apolipoprotein E genotype on outcome after spontaneous subarachnoid hemorrhage: a preliminary study

OBJECTIVE

Possession of an apolipoprotein E (APOE)epsilon4 allele has been shown to be associated with a poor outcome after closed head injury and spontaneous intracerebral hemorrhage but not after ischemic stroke. This study assessed the influence of the APOE genotype on outcome in patients admitted to a neurosurgical unit with spontaneous subarachnoid hemorrhage.

METHODS

A total of 100 patients with spontaneous subarachnoid hemorrhage were studied. Four patients were excluded because the diagnosis of subarachnoid hemorrhage was not confirmed. The incidence of rehemorrhage and delayed ischemia and the outcome at 6 months were determined using the Glasgow Outcome Scale. APOE genotypes were determined by polymerase chain reaction and restriction enzyme digestion.

RESULTS

Allele frequencies in this patient group were 0.04 for epsilon2, 0.86 for epsilon3, and 0.1 for epsilon4. Of 96 patients, 72 had an aneurysmal hemorrhage and 1 had a hemorrhage from an arteriovenous malformation. In 14 patients, the results of angiography were negative, and in 9, no angiogram was performed. Of the 96 patients, 20 had one or more epsilon4 allele. Outcome at 6 months was no worse in patients with one or more epsilon4 allele than in those with no epsilon4 allele (odds ratio, 0.98; 95% confidence interval, 0.35-2.74). None of the 12 patients who experienced delayed ischemic deterioration had an epsilon4 allele. Of the 20 patients with an epsilon4 allele, 3 had a rehemorrhage, as compared with 6 of 76 patients without an epsilon4 allele.

CONCLUSION

There was underrepresentation of the epsilon4 allele in this group when compared with previously studied cases of subarachnoid hemorrhage with a fatal outcome and with the general population. This suggests that patients with the epsilon4 allele who have a subarachnoid hemorrhage are less likely to be admitted to a neurosurgical unit. This study does not support an association between possession of an epsilon4 allele and poor outcome in patients admitted to a neurosurgical unit with spontaneous subarachnoid hemorrhage, although the wide confidence interval does not preclude a clinically relevant association between APOE genotype and outcome. The findings indicate that an association between genotype and the development of delayed ischemic complications after subarachnoid hemorrhage may be possible.

The role of apolipoprotein E in Alzheimer's disease, acute brain injury and cerebrovascular disease: evidence of common mechanisms and utility of animal models

The epsilon 4 allele of apolipoprotein E (APOE denotes gene; apoE denotes protein) is a major risk factor for Alzheimer's disease (AD). More recent evidence indicates an association with a poor outcome after acute brain injury including that due to head trauma and intracerebral hemorrhage. APOE gene polymorphism also influences the risk of hemorrhage in cerebral amyloid angiopathy. These diverse brain disorders seem to have some mechanisms in common. The multiplicity of the roles of apoE within the central nervous system is currently being unraveled. For example, apoE can interact with amyloid beta-protein and tau, proteins central to the pathogenesis of AD. In addition to these effects, it is proposed that one of the major functions of apoE is to mediate neuronal protection, repair and remodeling. In all of the different roles proposed, there are marked apoE-isoform specific differences. Although it remains to be clarified which is the most important mechanism(s) in each disorder in which apoE is involved, these isoform specific differences seem to underly a genetically determined susceptibility to outcome from acute brain injury and to AD with APOE epsilon 4 conferring relative vulnerability. This review focuses on apoE research, from clinical studies to animal models, in AD, acute brain injury and cerebrovascular disease and explores the common mechanisms that may explain some of the complex underlying neurobiology.