Background and purpose: The insonation of the posterior communicating artery (PcomA) is often hampered by the unfavorable insonation angle when the temporal acoustic bone window (TBW) is used. This problem may be ameliorated by a lateral frontal bone window (LFBW). This study evaluated the TBW and LFBW for the assessment of collateral intracranial flow conditions and aimed at defining diagnostic transcranial color-coded duplex sonography (TCCS) criteria that do not need compression maneuvers.
Methods: The A1 segment of the anterior cerebral artery (ACA), the PcomA, and the P1 segment of the posterior cerebral artery (PCA) were insonated by TCCS in 40 controls and 20 patients (16 internal carotid artery [ICA] occlusions or high grade stenoses, 3 middle cerebral artery stenoses or occlusions, 1 PCA stenosis).
Results: Detection rates for the A1 ACA and P1 PCA were higher for the TBW (94%, 98%) compared to the LFBW (86%, 81%) in controls. The PcomA was identified more frequently through the LFBW (86%) compared to the TBW (80%). Through the LFBW angle, corrected flow velocity (FV) measurements were possible for the PcomA with an average correction of 6.5 degrees. In controls, in > 80% of identified PcomAs, flow was directed towards the ICA. Side to side differences were below 7% for peak systolic FVs. In the patients with ICA disease, a flow reversal in the ipsilateral A1 ACA and a FV difference of > 30% seemed feasible for diagnosis of anterior communicating artery crossflow. Criteria for PcomA crossflow were side differences of FVs in the PcomA of > or = 30% and in the P1 PCA of > or = 20%.
Conclusions: The LFBW proved useful as a complementary insonation plane to assess intracranial crossflow conditions, especially via the PcomA. We were able to define TCCS criteria for functional relevant collateralization without the need of compression maneuvers.