The role of intraoperative micro-Doppler ultrasound in verifying proper clip placement in intracranial aneurysm surgery

We present the results of a retrospective study employing intraoperative micro-Doppler ultrasonography (MDU) in verifying proper clip placement during cerebral aneurysmal surgery. One hundred and thirty-four patients surgically treated for 147 intracranial aneurysms were studied. Thirteen patients harboring 17 aneurysms were surgically treated on an elective basis, while 121 patients with 130 aneurysms, presented with subarachnoid hemorrhage (SAH). Blood flow velocities of the parent and adjacent vessels as well as the aneurysmal sac were measured using a Conforma Micro-Doppler (Cook Vascular Inc., Leechburg, PA, USA). Pre- and post-operative cerebral angiography was obtained in all our patients. In 23 aneurysms (15.6%) there was decreased or absent flow in the parent vessel or in one of the adjacent vessels after clipping. In another 19 aneurysms (12.9%), MDU demonstrated flow through the aneurysmal dome even though the aneurysmal neck appeared to be totally obliterated. Presence of SAH, anatomic location and size of the aneurysm were associated with improper clip placement in a statistically significant fashion. The false positive rate for MDU was 2% while there were no false negative findings in our study. MDU appears to be a non-invasive, reliable alternative methodology to intra-operative angiography. This inexpensive method may lend itself to routine usage in aneurysm surgery.