Bill Johnson, Dunmore, PA writes;
I must assume there is collateral flow from somewhere. I would have to doubt
the ophthalmic was supplying much, if flow was also abnormal in the terminal
ICA on the left also, and the left ECA is compromised by the CCA occlusion.
Not having information about the left ACA is unfortunate. Any hint about that
from the right side? Any chance to see across midline from the right window?
That the PCA's and right ACA were WNL makes speculation difficult. I would
think, for the left MCA to be "normal," there must be an active collateral
somewhere, and a clue to its presence.
This is just speculative, but I wonder if the ECA branches are stealing from
what little flow they can get from the ICA. Could you see the superior
thyroid? In my limited experience with CCA occlusions, it is most often the
branch supplying the bifurcation and maintaining ICA patency. What direction
was flow in the most proximal ECA, and was it to-fro? If the ECA system did
not have a good collateral source of flow, you would probably have the same
condition found in to-fro flow in a vertebral with a subclavian stenosis.
Would love to see the results of the old-time Periorbital Study. You
remember those still? Might be helpful in this unusual case. I think the
left ICA is trying to meet the needs of the external and cerebral circulation
simultaneously. Just depends what part of the cardiac cycle where the need
is greatest and which way it wants to go.
What were the velocities in the right ICA? And the means in the right ACA,
PCA and left PCA. That might be helpful. Were they "high" normal? Seems
obvious the left ICA is not helping much.
Sounds like an interesting case study.