Temporary surgical clipping of flow-diverted arteries in an experimental aneurysm model

Optimal Use of Temporary Clip Application during Aneurysm Surgery - In Search of the Holy Grail

Temporary clips are invaluable safety tools during the clipping of an aneurysm. Controversies regarding maximum permissible duration and safety, however, remain unanswered. This descriptive narrative attempts to review the literature to provide valuable insights on controversies clouding the use of temporary clips among neurosurgeons. Popular databases, including Pub Med, Medline/Medscape, Scopus, Cochrane, Embase, Google Scholar, were searched to find available literature on temporary clips. The searched MeSH terms were "Temporary Clip," "Temporary Clipping," "Cerebral Aneurysm," and "Aneurysm." Temporary clips have been in use since 1928 and have undergone considerable structural and technical modifications. A temporary clip's optimal safety limit is not yet defined with literature evidence ranging from immediate to 93 min. It is not yet definite whether temporary clips application aggravates vasospasm, but emergency temporary clips application, especially in poor-grade aneurysmal subarachnoid hemorrhage patients, is associated with poor outcomes. A temporary clip needs to be applied with caution in patients treated earlier by endovascular technique and having indwelling stents. Nitinol Stent is feasible, while a Cobalt-Chromium alloy stent does not get occluded and gets deformed under the closing pressure of a temporary clip. Although a temporary clip application is a fundamental strategy during the clipping of an aneurysm; the exact safe duration remains to be decided in randomized control trials. Their utility for the shorter duration is beneficial under un-conclusive evidence of neuroprotective agents and intraoperative monitoring. Neurosurgeons need to consider all aspects of their pros and cons for optimal use.

Re-treatment of residual aneurysms after flow diversion: An experimental study

Aim Flow diverters are increasingly used to treat aneurysms, but treatment is not always effective. The management of aneurysms that fail to occlude following flow diversion is problematic. We aimed to reproduce failures in an animal model and study re-treatment with additional flow diverters alone or with flow diverters and liquid embolic agent. Material and methods Twenty wide-necked aneurysms were created at the carotid-lingual bifurcation in 10 dogs, and were treated with flow diverters 4-6 weeks later. Follow-up angiography was performed at three months. Suitable residual aneurysms were randomly allocated: re-treatment with flow diverters alone ( n = 6), or with the injection of liquid embolic between two layers of flow diverters ( n = 4) or no re-treatment ( n = 2). Angiography was repeated three months later, followed by euthanasia, photography and pathology. Results Patent wide-necked aneurysms were produced in 17/20 attempts (85%); three months after flow diversion there were 15/17 (88%) residual aneurysms. In three cases, re-treatment was not possible because the flow diverter had prolapsed into the aneurysm, leaving 12 aneurysms to study. Re-treated aneurysms showed improved angiographic results at six months (median score of 2; P = 0.03), but residual aneurysms were present in all cases. Parent artery occlusion occurred in two aneurysms treated with flow diverter plus liquid embolic. At pathology, aneurysms were only partially filled with thrombus; leaks through the flow diverters were found in the neointima connecting the arterial lumen to residual aneurysms. Conclusion Re-treatment of residual flow-diverted experimental aneurysms with additional flow diverters did not lead to aneurysm occlusion.