title: Decreased transcranial Doppler carbon dioxide reactivity is associated with disordered cerebral metabolism in patients with internal carotid artery stenosis.
abstract: OBJECTIVE
  The hemodynamic effect of stenosis of the internal carotid artery (ICA) can be assessed by measuring, with transcranial Doppler (TCD), the carbon dioxide (CO(2)) reactivity of the cerebral vessels. The aim of this study was to determine whether a decreased CO(2) reactivity is associated with a compromised cerebral metabolism, as evaluated with (1)H magnetic resonance spectroscopy (MRS).
  
  
  METHODS
  Sixty-six patients with unilateral or bilateral stenosis of the ICA, who were scheduled for carotid endarterectomy (CEA) and who had undergone both a TCD CO(2) reactivity test and a MRS examination, were included in this study. The ICA stenosis on one side (CEA side) was always more than 70%, and the extent of the stenosis on the contralateral side varied.
  
  
  RESULTS
  The CO(2) reactivity and the N-acetyl aspartate (NAA)/choline ratio were correlated in both hemispheres (r =.43; P <.001). Patients with an ICA occlusion contralateral to the CEA side are especially at risk for disordered cerebral hemodynamics and metabolism; in the contralateral hemisphere, the mean CO(2) reactivity and NAA/choline ratio were abnormal (18% and 1.52, respectively), and lactate was present in 85% of the patients. Changes indicative of disordered hemodynamics were found more often in symptomatic than in asymptomatic patients.
  
  
  CONCLUSIONS
  A decreased CO(2) reactivity appears to be associated with a disordered cerebral metabolism. Patients with severe bilateral ICA stenosis are at risk for disordered cerebral metabolism and hemodynamics. Therefore, the indication for CEA based on the degree of ICA stenosis and clinical grounds might be refined with an additional test, such as the TCD CO(2) reactivity test.
authors.affiliation: Department of Clinical Neurophysiology, University Hospital Utrecht, The Netherlands.
authors.forename: G H
authors.initials: GH
authors.lastname: Visser
authors.forename: J
authors.initials: J
authors.lastname: van der Grond
authors.forename: A C
authors.initials: AC
authors.lastname: van Huffelen
authors.forename: G H
authors.initials: GH
authors.lastname: Wieneke
authors.forename: B C
authors.initials: BC
authors.lastname: Eikelboom
mesh_terms: D000368:Aged; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000097:blood; D001783:Blood Flow Velocity; D001921:Brain / Q000098:blood supply / Q000473:pathology; D002245:Carbon Dioxide / Q000097:blood*; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D016893:Carotid Stenosis / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D002560:Cerebrovascular Circulation; D002794:Choline / Q000032:analysis; D016894:Endarterectomy, Carotid; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D012044:Regression Analysis; D017585:Ultrasonography, Doppler, Transcranial
chemical_list: D002245:Carbon Dioxide; D001224:Aspartic Acid; C000179:N-acetylaspartate; D002794:Choline