Subtle Structural Change Demonstrated on T2-weighted Images After Clipping of Unruptured Intracranial Aneurysm: Negative Effects on Cognitive Performance

Object: The mechanisms underlying neurocognitive changes after surgical clipping of unruptured intracranial aneurysms (UIAs) are poorly understood. The aim of this study was to investigate factors that determine postoperative cognitive decline after UIA surgery.

Methods: Data from 109 patients who underwent surgical clipping of a UIA were retrospectively evaluated. These patients underwent neuropsychological examinations (NPEs), including assessment by the Wechsler Adult Intelligence Scale-Third Edition and the Wechsler Memory Scale-Revised before and 6 months after surgical clipping of the UIA. Results of NPEs were converted into z scores, from which pre- and postoperative cognitive composite scores (CSpre and CSpost) were obtained. The association between the change in CS between pre- and postoperative NPEs (that is, CSpost - CSpre [CSpost - pre]) and various variables was assessed. These latter variables included surgical approach (anterior interhemispheric approach or other approach), structural change evidenced on T2-weighted imaging at 6 months, somatosensory evoked potential amplitude decrease greater than 50% during aneurysm manipulation, preexisting multiple ischemic lesions in the lacunar region detected on preoperative T2-weighted imaging, and total microsurgical time. Paired t-tests of the NPE scores were performed to determine the net effect of these factors on neurocognitive function at 6 months.

Results: A significant CSpost - pre decrease was observed in patients with a structural change on postoperative T2-weighted imaging when compared with those without such a change on postoperative T2-weighted imaging (-0.181 vs 0.043, p = 0.012). Multiple regression analysis demonstrated that postoperative T2-weighted imaging change independently and negatively correlated with CSpost - pre (p = 0.0005). In group-rate analysis, postoperative NPE scores were significantly improved relative to preoperative scores.

Conclusions: Minimal structural damage visualized on T2-weighted images at 6 months as a result of factors such as pial/microvascular injury and excessive retraction during surgical manipulation could cause subtle but significant negative effects on postoperative neurocognitive function after surgical clipping of a UIA. However, this detrimental effect was small, and based on the group-rate analysis, the authors conclude that successful and meticulous surgical clipping of a UIA does not adversely affect postoperative cognitive function.