title: Reversed flow in the external carotid artery despite a patent but stenosed common carotid artery.
abstract: OBJECTIVE
  Occlusion of the common carotid artery (CCA) is generally associated with an occlusion of the ipsilateral internal carotid artery (ICA) or of the external carotid artery (ECA) or of both. Sometimes, collateral circulation to the ECA may preserve patency of the ICA via retrograde perfusion through the bulb. We herewith report a case of reversed flow in the ECA in the presence of a patent but stenosed CCA as diagnosed with color-coded duplex flow imaging (CDFI).
  
  
  METHODS
  This 85-year-old right-handed man was admitted for rapidly regressive acute dysarthria associated with left hemiparesis. Diffusion-weighted magnetic resonance (MR) imaging showed an acute ischemic lesion in the territory of the right middle cerebral artery. MR angiography showed patency of the right ICA and ECA but an occlusion of the CCA was suspected. CDFI demonstrated patency of the right CCA with a high-resistance pattern due to a large, partially calcified, stenosing atheromatous plaque. Surprisingly, reversed flow was observed in the right ECA of which signal was dampened.
  
  
  CONCLUSIONS
  Collateralization with reversed flow in the ECA may occur in a patent but stenosed CCA associated with a high-grade stenosis of the carotid bifurcation. CDFI is a very useful tool to detect such hemodynamic conditions.
authors.affiliation: HUG, University Hospital and Medical Faculty of Geneva, Department of Neurology, Neurosonology Unit, CH-1211 Geneva, Switzerland.
authors.forename: Elena
authors.initials: E
authors.lastname: Savva
authors.forename: Roman
authors.initials: R
authors.lastname: Sztajzel
authors.forename: Theodor
authors.initials: T
authors.lastname: Landis
authors.forename: Fabienne
authors.initials: F
authors.lastname: Perren
mesh_terms: D000369:Aged, 80 and over; D016893:Carotid Stenosis / Q000150:complications* / Q000000981:diagnostic imaging* / Q000209:etiology*; D018618:Echocardiography, Doppler, Color / Q000379:methods*; D006801:Humans; D008297:Male