• Helene Zachrisson, Marita Fouladiun, Christian Blomstrand, Jan Holm, and Reinhard Volkmann.
• Clinical Physiology, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden. helene.zachrisson@lio.se
• Clin Physiol Funct Imaging. 2012 May 1; 32 (3): 241-6.

BackgroundDuplex ultrasound (DUS) has shown a >90% accuracy compared to angiography, concerning the degree of internal carotid artery (ICA) stenosis. However, uncertainty may occur in a severe stenosis, in which peak systolic velocity (PSV) may decrease owing to high flow resistance or high backward pressure. We investigated intracranial collateral flows using transcranial Doppler (TCD) to further evaluate the hemodynamic significance of high-grade ICA stenosis.MethodsIn this retrospective study, 320 consecutive symptomatic patients were examined. The degree of ICA stenosis and collateral capacity in the circle of Willis was investigated by DUS and TCD. In addition, magnetic resonance angiography (MRA) was added in a subgroup of 204 patients. The criterion for hemodynamic significant ICA stenosis was established collateral flow.ResultsIn 91% of all symptomatic vessels (291 vessels), an ICA stenosis of ≥70% was found. Established collateral flow always indicated precerebral carotid artery disease of ≥70%. Furthermore, in 11% of the whole study material, collateral reserve capacity was found despite high-grade (≥70%) ICA stenosis. PSV in ICA <2·5 m s(-1) was combined with established collateral flow and MRA stenosis of ≥70% in 9% (19 arterial systems). In 4%, doubt existed concerning the degree of stenosis after DUS.ConclusionTranscranial Doppler helps to determine whether an ICA stenosis is of hemodynamic significance and to assess collateral patterns. Established collateral blood flow will help to identify patients with ≥70% (ECST) carotid artery disease. TCD might be of value when flow velocity criteria combined with plaque assessment by DUS are inclusive. Other diagnostic methods may also be considered.© 2012 The Authors. Clinical Physiology and Functional Imaging © 2012 Scandinavian Society of Clinical Physiology and Nuclear Medicine.

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