Dynamic measurement of pressure and flow velocities in glass and silastic model berry aneurysms.

The pressure and flow patterns within intracranial aneurysms are little known. An investigation of intra-aneurysmal flow velocities was done on model glass and silastic aneurysms using a constant-temperature hot film anemometer (HFA) and a high frequency directional pulsed Doppler to measure flow velocities. Maximum turbulent flow occurred at the neck and minimum flow at the dome of aneurysms. The intra-aneurysmal flow behaved differently with different neck diameters and different volumes. Turbulent flow was more severe in broad neck aneurysms and those with a small volume, while maximum turbulent flow was demonstrated in small out-pouching aneurysms. Increased turbulent flow was also detected in loculated aneurysms and in those with thinner walls. The results suggested that the random turbulent forces may be a cause of out-pouching and enlargement at eroded or congenitally weak area of arterial walls. Enlargement occurs with further erosion of endothelial cells and the internal elastic membrane.