title: Postoperative transient neurological symptoms and chronic subdural hematoma after extracranial-intracranial bypass for internal carotid/middle cerebral atherosclerotic steno-occlusive diseases: negative effect on cognitive performance.
abstract: BACKGROUND
  The mechanisms underlying post-extracranial to intracranial (EC-IC) bypass neurocognitive changes are poorly understood.
  
  
  METHODS
  Data from 55 patients who underwent a unilateral EC-IC bypass for atherosclerotic internal carotid artery (ICA)/middle cerebral artery (MCA) steno-occlusive disease were retrospectively evaluated. These patients underwent neuropsychological examinations (NPEs), including assessment by the Wechsler Adult Intelligence Scale-Third Edition and Wechsler Memory Scale-Revised (WMS-R) before and 6 months after EC-IC bypass. Results of NPEs were converted into Z-scores from which preoperative cognitive composite scores (CSpre) and postoperative cognitive composite scores (CSpost) were obtained. The association between the change of composite score between pre- and postoperative NPEs (CSpost-pre = CS post - CS pre) and various variables were assessed. These latter variables included occluded artery (ICA or MCA), preexisting ischemic lesion as verified in preoperative T2WI, robust bypass patency as verified by MRA performed approximately 6 months postoperatively, and postoperative transient neurological symptoms and/or postoperative chronic subdural hematoma (CSDH), both of which were dichotomized as postoperative events.
  
  
  RESULTS
  Postoperative MRI follow-up (median, 6 months; interquartile range, 5-8 months) confirmed successful bypasses in all patients, with no additional ischemic lesions on T2WI when compared with preoperative imaging. Further, MRA showed patent bypasses in all patients. A nearly statistically significant CS post-pre decrease was observed in patients with postoperative events when compared with those without postoperative events (-0.158 vs. 0.039; p = 0.069). A multiple regression model predicting CSpost-pre was performed. After controlling for occluded arteries, postoperative events were identified as an independent predictor of a decline in CSpost-pre (p = 0.044). In the group rate analysis, three of four postoperative NPE scores (Performance IQ, WMS-memory, WMS-attention) were significantly improved relative to preoperative NPE scores.
  
  
  CONCLUSIONS
  Postoperative transient neurological symptoms and/or CSDH might play a significant role in the subtle decline in cognition following an EC-IC bypass. However, this detrimental effect was small, and based on the group rate analysis, we concluded that a successful unilateral EC-IC bypass does not adversely affect postoperative cognitive function.
authors.affiliation: Department of Neurosurgery, Fuji Brain Institute and Hospital, 270-12 Sugita, Fujinomiya-shi, Shizuoka, 418-0021, Japan. t.inoue-fujinsu@beige.plala.or.jp.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Inoue
authors.affiliation: Health Management Center, JCHO Tokyo Shinjuku Medical Center, Tokyo, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Ohwaki
authors.affiliation: Department of Neurosurgery, Fuji Brain Institute and Hospital, 270-12 Sugita, Fujinomiya-shi, Shizuoka, 418-0021, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Tamura
authors.affiliation: Department of Neurosurgery, Showa General Hospital, Tokyo, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Tsutsumi
authors.affiliation: Department of Neurosurgery, Fuji Brain Institute and Hospital, 270-12 Sugita, Fujinomiya-shi, Shizuoka, 418-0021, Japan.
authors.forename: Isamu
authors.initials: I
authors.lastname: Saito
authors.affiliation: Department of Neurosurgery, University of Tokyo, Tokyo, Japan.
authors.forename: Nobuhito
authors.initials: N
authors.lastname: Saito
mesh_terms: D000368:Aged; D001157:Arterial Occlusive Diseases / Q000601:surgery*; D002343:Carotid Artery, Internal / Q000601:surgery*; D002548:Cerebral Revascularization / Q000009:adverse effects* / Q000379:methods; D003072:Cognition Disorders / Q000209:etiology*; D005260:Female; D020200:Hematoma, Subdural, Chronic / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000601:surgery*; D017063:Outcome Assessment, Health Care; D011183:Postoperative Complications / Q000209:etiology*; D012189:Retrospective Studies
keywords: Cognitive function; Extracranial-intracranial bypass; Hemodynamic impairment; Neuropsychological examination