Bedside Emergency Transcranial Doppler Diagnosis of Severe Carotid Disease Using Orbital Window Examination

Abstract

The reversed OA sign at 50 to 60 mm depth is very specific for identifying cICA occlusion or critical stenosis. When OA flow is anterograde, a low mean flow velocity or pulsatility index is also useful to identify cICA critical stenosis or occlusion.

Transcranial Doppler and Transcranial Color Duplex in Defining Collateral Cerebral Blood Flow

“…Our group demonstrated the utility of the TCD orbital window at depth of 50–60 mm for identifying a reversed OA in acute stroke setting with higher specificity (100%) and sensitivity (75%) for ICA occlusion or critical stenosis than the previous studies . In addition, we did demonstrate a unique TCD finding that when the OA flow direction is antegrade, the MFV and PI could discriminate patients who have critical carotid stenosis or occlusion.…”

“…Anterior communicating artery signature (AcomA) on transcranial Doppler and power M mode Doppler (reproduced from Saqqur et al). (A) Anterior communication artery signature through the temporal window at 70–80 mm depth (stenotic signal away from the probe on the donor side).…”

“…Interestingly, in the presence of critical ICA stenosis or occlusion, there is an increase in the flow of blood through the AcomA as it becomes the collateral route of blood supply to the ipsilateral MCA and ACA making it easier to insonate . In addition, AcomA can be defined on power M mode TCD through the temporal window as a stenosis signal at midline at depth of 70–75 mm or at a depth of 60–65 mm through the orbital window (Figs A and B).…”

“…Reversed OA through the orbital window (top right): Low pulsatility flow directed away from the probe (blue signal) via transorbital window at 40–60 mm depth. The signal is obtained through the orbital window by aiming the probe medially (bottom) (reproduced from Saqqur et al).…”

“…Patient with left internal carotid artery (ICA) near occlusion and antegrade ophthalmic artery (OA) flow (reproduced from Saqqur et al). (a) Left OA signature: mean flow velocity <15.…”