title: Role of Multimodal Evaluation of Cerebral Hemodynamics in Selecting Patients with Symptomatic Carotid or Middle Cerebral Artery Steno-occlusive Disease for Revascularization.
abstract: BACKGROUND
  The circle of Willis provides collateral pathways to perfuse the affected vascular territories in patients with severe stenoocclusive disease of major arteries. The collateral perfusion may become insufficient in certain physiological circumstances due to failed vasodilatory reserve and intracranial steal phenomenon, so-called 'Reversed-Robinhood syndrome'. We evaluated cerebral hemodynamics and vasodilatory reserve in patients with symptomatic distal internal carotid (ICA) or middle cerebral artery (MCA) severe steno-occlusive disease.
  
  
  METHODS
  Diagnostic transcranial Doppler (TCD) and TCD-monitoring with voluntary breath-holding according to a standard scanning protocol were performed in patients with severe ICA or MCA steno-occlusive disease. The steal phenomenon was detected as transient, spontaneous, or vasodilatory stimuli-induced velocity reductions in affected arteries at the time of velocity increase in normal vessels. Patients with exhausted vasomotor reactivity and intracranial steal phenomenon during breath-holding were further evaluated by (99)technetium(m)-hexamethyl propylene amine oxime single photon emission computed tomography (HMPAO-SPECT) with acetazolamide challenge.
  
  
  RESULTS
  Sixteen patients (age 27-74 years, 11 men) fulfilled our TCD criteria for exhausted vasomotor reactivity and intracranial steal phenomenon during the standard vasomotor testing by breath holding. Acetazolamide-challenged HMPAO-SPECT demonstrated significant hypoperfusion in 12 patients in affected arterial territories, suggestive of failed vasodilatory reserve. A breath-holding index of ≤0.3 on TCD was associated with an abnormal HMPAO-SPECT with acetazolamide challenge. TCD findings of a breath holding index of ≤0.3 and intracranial steal during the procedure were determinants of a significant abnormality on HMPAO-SPECT with acetazolamide challenge.
  
  
  CONCLUSIONS
  Multimodal evaluation of cerebral hemodynamics in symptomatic patients with severe steno-occlusive disease of the ICA or MCA is helpful in the identification and quantification of failed vasodilatory reserve. This approach may be useful in selecting patients for possible revascularization procedures.
authors.affiliation: From: Department of Neurology, National University Hospital, Singapore (VKS, HLT, BKCO, BPLC), Department of Neurology, Democrition University of Thrace, Alexandroupolis, Greece (GT), Department of Diagnostic Imaging, National University Hospital, Singapore (VFHC, AKS), Division of Neurosurgery, National University Hospital, Singapore (CN), General Army Hospital, Athens, Greece (CB).
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Sharma
authors.forename: Georgios
authors.initials: G
authors.lastname: Tsivgoulis
authors.forename: Chou
authors.initials: C
authors.lastname: Ning
authors.forename: Hock L
authors.initials: HL
authors.lastname: Teoh
authors.forename: Chrisostomos
authors.initials: C
authors.lastname: Bairaktaris
authors.forename: Vincent Fh
authors.initials: VF
authors.lastname: Chong
authors.forename: Benjamin Kc
authors.initials: BK
authors.lastname: Ong
authors.forename: Bernard Pl
authors.initials: BP
authors.lastname: Chan
authors.forename: Arvind K
authors.initials: AK
authors.lastname: Sinha