title: Impact of Severe Extracranial ICA Stenosis on MRI Perfusion and Diffusion Parameters in Acute Ischemic Stroke.
abstract: OBJECTIVE
  The aim of this study was to investigate the impact of a coexisting internal carotid artery (ICA) stenosis on lesion volumes as well as diffusion and perfusion parameters in acute ischemic stroke resulting from middle cerebral artery (MCA) occlusion.
  
  
  METHODS
  Magnetic resonance imaging data of 32 patients with MCA occlusion with or without additional ICA stenosis imaged within 4.5 h of symptom onset were analyzed. Both groups consisted of 16 patients. Acute diffusion lesions were semi-automatically segmented in apparent diffusion coefficient (ADC) MRI datasets. Perfusion maps of cerebral blood volume (CBV), cerebral blood flow, mean transit time and T max were calculated using perfusion-weighted MRI datasets. Tissue-at-risk (TAR) volumes were generated by subtracting the ADC lesion from the hypoperfusion lesion defined by T max >6 s. Median ADC and perfusion parameter values were extracted separately for the diffusion lesion and TAR and used for statistical analysis.
  
  
  RESULTS
  No significant differences were found between the groups regarding the diffusion lesion and TAR volumes. Statistical analysis of diffusion and perfusion parameters revealed CBV as the only parameter with a significant difference (p = 0.009) contributing a small effect (η(2) = 0.11) to the group comparison with higher CBV values for the patient group with a coexisting ICA stenosis, while no significant effects were found for the other diffusion and perfusion parameters analyzed.
  
  
  CONCLUSIONS
  The results of this study suggest that a coexisting ICA stenosis does not have a strong effect on tissue status or perfusion parameters in acute stroke patients except for a moderate elevation of CBV. This may reflect improved collateral circulation or ischemic preconditioning in patients with a pre-existing proximal stenosis balancing impaired perfusion from the stenosis.
authors.affiliation: Department of Computational Neuroscience, University Medical Center Hamburg-Eppendorf , Hamburg , Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Kaesemann
authors.affiliation: Department of Neurology, University Medical Center Hamburg-Eppendorf , Hamburg , Germany.
authors.forename: Götz
authors.initials: G
authors.lastname: Thomalla
authors.affiliation: Department of Neurology, University Medical Center Hamburg-Eppendorf , Hamburg , Germany.
authors.forename: Bastian
authors.initials: B
authors.lastname: Cheng
authors.affiliation: Department of Medical Biometrics and Epidemiology, University Medical Center Hamburg-Eppendorf , Hamburg , Germany.
authors.forename: Andras
authors.initials: A
authors.lastname: Treszl
authors.affiliation: Department of Diagnostic and Interventional Neuroradiology, University Medical Center Hamburg-Eppendorf , Hamburg , Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Fiehler
authors.affiliation: Department of Computational Neuroscience, University Medical Center Hamburg-Eppendorf , Hamburg , Germany ; Department of Diagnostic and Interventional Neuroradiology, University Medical Center Hamburg-Eppendorf , Hamburg , Germany.
authors.forename: Nils Daniel
authors.initials: ND
authors.lastname: Forkert
keywords: brain ischemia; diffusion; internal carotid artery stenosis; magnetic resonance imaging; perfusion