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Jon,
At this time all published criteria are based upon the first 3 cm of the
ICA.  I am not aware of any published criteria for bulb and cca.  However,
if the bulb stenosis extends up to the ICA with the highest velocities in/or
just at the proximal the ICA then the standard criteria's can be used.  If
the bulb stenosis is more proximal and the highest velocities are not at the
origin of the ICA, then the criteria's cannot be used with reliability.  At
Cedars Sinai and at Ochsner Clinic, we used the following rational with
fairly good correlation results.  Due to the increased diameter of the CCA
and Bulb as well as the combination ICA/ECA flow dynamics we would overcall
stenosis by ~ 10 - 20% and reconcile this call based upon visual findings.
Likewise for stenosis of the vertebral artery similar rational was used.
Due to the decreased diameter of the vert's, althought generally their flow
characteristics are the same as those in the ICA, we would undercall by ~
10 - 20% and reconcile this call based upon visual findings.
Keep in mind that in 70% of cases the left vertebral is dominant and that
the right may be hypoplastic with a more high resistant flow signal.  Does
anyone else have any non-published or know of any published criteria for the
CCA or bulb.  I have seen some published criteria for vertebrals, one from
extracranial work and two from intracranial work.

Cathy Mankin, LPN, RVT