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.