Recovery of cognitive function after surgery for aneurysmal subarachnoid hemorrhage

BACKGROUND AND PURPOSE - Abnormalities in neurocognitive function are common after surgery for aneurysmal subarachnoid hemorrhage, even among patients with good functional outcomes. The time course of neurocognitive recovery, along with the long-term effects of mild intraoperative hypothermia (33°C) and aneurysm location, is unknown. We determined these in a subset of subarachnoid hemorrhage patients enrolled in the Intraoperative Hypothermia for Aneurysm Surgery Trial (IHAST). METHODS - We performed a longitudinal, multicenter, prospective, blinded study of adult IHAST patients with a Glasgow Outcome Score=1 or 2 (independent function), 3 months postsurgery and a matched control group (n=45). Subjects were tested with a 5-test cognitive function battery and standard neurological evaluations at 3, 9 and 15 months postsurgery. The primary outcome measure was a composite score on cognitive test performance. RESULTS - There were 303 IHAST patients available for inclusion: 218 eligible, 185 enrolled (89 hypothermic, 96 normothermic). Significant cognitive improvement was noted from 3 to 9 (P<0.001) and 3 to 15 (P<0.001) months in both hypothermic and normothermic groups, even after adjusting for practice effects observed in the control group. No significant change was identified between 9 and 15 months. Neither mild hypothermia nor aneurysm location (anterior communicating artery versus others) had a significant effect on recovery over time or frequency of cognitive impairment. Compared with control group, the frequency of cognitive impairment (Z score <-1.96) in all patients at 3, 9 and 15 months was 36%, 26% and 23%, respectively. CONCLUSIONS - In this population, cognitive improvement continued beyond 3 months, with a plateau between 9 and 15 months. This was not affected by the use of intraoperative hypothermia or anatomical location of aneurysm.