title: Carotid pseudostring sign from vasa vasorum collaterals.
abstract: OBJECTIVE
  To describe the spectral and color Doppler imaging findings in 2 cases of internal carotid artery occlusion with vasa vasorum collateral flow, which we term the "pseudostring sign."
  
  
  METHODS
  Spectral and color Doppler imaging findings in both cases were reviewed. Magnetic resonance angiography in 2 cases and conventional angiography in 1 case were also reviewed.
  
  
  RESULTS
  Both patients had color Doppler images showing that the internal carotid artery was a narrow, stringlike vessel with arterial flow that had normal spectral Doppler features (velocity < 125 cm/s with a normal waveform). Magnetic resonance angiography in 1 patient showed total occlusion of the proximal internal carotid artery with patent vasa vasorum collaterals reconstituting the lumen distally. In the second patient, magnetic resonance angiography showed total occlusion of the proximal internal carotid artery, and conventional angiography showed proximal occlusion with collateral flow through the vasa vasorum.
  
  
  CONCLUSIONS
  Proximal internal carotid artery occlusion with vasa vasorum collateral flow should be considered when color Doppler imaging shows a seemingly narrow internal carotid artery with tortuosity and normal spectral Doppler features. Patients with these features should not undergo carotid endarterectomy directly on the basis of only the Doppler findings.
mesh_terms: D000368:Aged; D001157:Arterial Occlusive Diseases / Q000000981:diagnostic imaging*; D016893:Carotid Stenosis / Q000000981:diagnostic imaging*; D003097:Collateral Circulation; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D018615:Ultrasonography, Doppler, Color