In this case there is a complete reversal of flow in right vertebral artery with sharp single systolic peak. There are biphasic waveforms within the distal subclavian arteries. The origin is not visualized. The left vertebral artery shows antegrade flow with a normal waveform and velocity. A high grade stenosis was confirmed by CT angiography. There is also a complete occlusion of left vertebral artery artery from its origin to the V1 segment. The V2 segment is supplied by collaterals arising from left subclavian artery.
There are characteristic flow change in the right vertebral artery flow due
to stenosis in the ipsilateral subclavian artery proximal to origin of vertebral
artery. This stenosis produces a pressure gradient between cerebral circulation
and subclavian artery. The severity of stenosis is also reflected in the
vertebral artery Doppler.
- 45% stenosis- Pre- bunny waveform pattern, two systolic peak
with sharp first and rounded second peak with preservation of antegrade flow.
- 55% stenosis-Bunny waveforms producing a deeper cleft
between two systolic peaks.
- 80% stenosis there will be to and fro bidirectional flow.
Initial antegrade followed by retrograde flow.
Complete reversal of flow in VA is caused by severe stenosis
in proximal subclavian artery.