RELATIONSHIP BETWEEN THE FLOW PATTERN AND VASOMOTOR REACTIVITY IN THEOPHTHALMIC ARTERY, SIPHON AND VESSELS WITHIN THE CIRCLE OF WILLIS IN THE UNILATERAL INTERNAL CAROTID-ARTERY OCCLUSION

The aim was to study a relationship between the flow pattern in the op hthalmic artery (OA), the siphon and vessels within the circle of Will is. 27 patients, 22 males and 5 females, mean age 63 +/- 15 years (SD) with unilateral occlusion of the internal carotid artery (ICA) were e xamined by 3-dimensional Transcranial Doppler scanner. Flow signals fr om the OA, the siphon and intracranial vessels were registered before and after i.v. injection of 1 g acetazolamide. Pathological flow patte rn was found in 18 patients in the OA on the occluded side consisting of 12 retrograde and 6 isoelectric flow directions. After acetazolamid e injection retrograde systolic velocities (SV) increased significantl y (p < 0.01), but anterograde velocities remained unchanged as did 3 i soelectric flow patterns, 2 turned to retrograde and one to anterograd e flow direction. In the siphon lower resting anterograde mean velocit ies (MV) were found on both sides (p < 0.05) compared to normal subjec ts. Six patients had the same retrograde flow as in the OA. After acet azolamide MV in the siphon increased (p < 0.01) only on the nonocclude d side. Baseline retrograde ophthalmic SV and MV in the siphon correla ted (p < 0.01) and p < 0.05 respectively) with MV in the middle cerebr al artery (MCA) according to linear regression analysis (r = 0.78 and 0.59 respectively). All patients, having impaired vasomotor reactivity (VMR) less than or equal to 11% in the anterior cerebral artery (ACA) on the occluded side, had pathological flow pattern in the OA. Patien ts with greatest difference (Delta) between MV in the ACA on the nonoc cluded and occluded side had a tendency to anterograde flow (r = 0.56, p < 0.05). Pulsative index (PI) in the ACA on the occluded side was l owest in the category with retrograde flow in the OA (0.67 +/- 0.14) a nd differed (p < 0.05) from normals and from the category with isoelec tric and anterograde flow Correlation of retrograde flow direction in the OA and baseline MV in the MCA and low PI in the ACA on the occlude d side indicates a supplying ophthalmic collateral to the anterior bra in circulation. Impaired VMR in the ACA on the occluded side in connec tion with pathological flow pattern in the OA may reflect an exhaustio n of the ACA as a supplying vessel.