Subarachnoid Hemorrhage and Long-Term Stroke Risk After Traumatic Brain Injury.

BACKGROUND: Recent studies suggest that traumatic brain injury (TBI) is a risk factor for subsequent ischemic stroke, even years after the initial insult. The mechanisms of the association remain unclear. The presence of traumatic subarachnoid hemorrhage (tSAH) may mediate the effect of TBI on long-term stroke risk, as it has previously been linked to short-term vasospasm and delayed cerebral ischemia.

METHODS: Using administrative claims data, we conducted a retrospective cohort study of acute care hospitalizations. Patients discharged with a first-recorded diagnosis of tSAH were followed for a primary diagnosis of stroke. They were matched to patients with TBI but not tSAH. Cox proportional hazards modeling was used to assess the association between tSAH and stroke while adjusting for covariates.

RESULTS: We identified 40 908 patients with TBI (20 454 patients with tSAH) who were followed for a mean of 4.3 + 1.8 years. A total of 531 had an ischemic stroke after discharge. There was no significant difference in stroke risk between those with tSAH (1.79%; 95% confidence interval [CI] 1.54%-2.08%) versus without tSAH (2.12%; 95% CI 1.83%-2.44%). The same pattern was found in adjusted analyses even when the group was stratified by age-group or by proxies of TBI severity.

CONCLUSIONS: Our findings do not support a role of tSAH in mediating the association between TBI and protracted stroke risk. Further study is required to elucidate the mechanisms of long-term increased stroke risk after TBI.