Apolipoprotein E polymorphism and outcome after mild to moderate traumatic brain injury: A study of patient population in India

Background: The nature and extent of recovery after traumatic brain injury (TBI) is heterogeneous. Apolipoprotein E (APOE) plays a major role in repair of cell membrane and growth of neurites following injury to cells. Studies done on the western population have shown that the APOE e4 genotype is associated with poor survival following neurotrauma. Aim: To explore the association of APOE polymorphism and outcome following TBI in a patient population from a tertiary care hospital exclusive for neurological diseases in south India. Patients and Methods: Ninety eight patients who sustained mild to moderate TBI (computed tomography (CT) scan brain showing traumatic parenchymal contusions) were the subjects of the study and the study period was from November 2003 to December 2008. APOE polymorphism status was determined by PCR technique using venous blood. Patients were assessed on follow-up with a battery of four neuropsychological tests as well as Glasgow outcome scale. Results: Of the 98 patients, 20 (20%) patients had at least one APOE e4 allele. A follow-up of minimum six months was available for 73 patients. None of the12 patients who had at least one APOE e4 allele had a poor outcome at six-month follow-up whereas 11(18%) patients without an APOE e4 allele had a poor outcome (Fisher′s Exact test, P=0.192). On the neuropsychological tests, performance of patients with APOE e4 allele did not differ significantly from those without these alleles. Conclusion: This study does not support the current contention that the presence of APOE e4 allele should have a significant negative effect on the outcome after TBI