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|THE EDITORIAL DEBATE
|Year : 2015 | Volume
| Issue : 2 | Page : 136-137
Surgical management of giant intracranial aneurysms: A neurosurgeon's perspective
Sunil K Gupta
Department of Neurosurgery, Postgraduate Institute of Medical Education and Research, Chandigarh, India
|Date of Web Publication||5-May-2015|
Sunil K Gupta
Department of Neurosurgery, Postgraduate Institute of Medical Education and Research, Chandigarh
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Gupta SK. Surgical management of giant intracranial aneurysms: A neurosurgeon's perspective. Neurol India 2015;63:136-7
Giant intracranial aneurysms are one of the most difficult cerebrovascular lesions to treat. The natural history of these lesions is poor with a higher incidence of rupture and worse outcome as compared to smaller aneurysms.  Apart from rupture, giant aneurysms present with mass effect due to compression of the brain parenchyma, brain stem or the cranial nerves. Therefore, even unruptured or incidental aneurysms warrant treatment.
In recent years, more aneurysms are being treated by endovascular techniques and this trend is now increasing in India also with coiling being offered as the first option.  However, till date, the results of endovascular treatment for giant intracranial aneurysms, either by coiling alone or by stent-assisted coiling are not very promising with a significant incidence of partial occlusion, recanalization and regrowth, re-rupture, persistence of mass effect, and coil or stent-related complications. With the development of flow diverters, it is possible that better results will be reported. Still, there remains the issue of use of antiplatelet drugs and anticoagulants following such procedures to prevent stent or diverter thrombosis, which may limit their use in patients with ruptured intracranial aneurysms.
Neurosurgeons will have to continue to manage patients with both ruptured and unruptured giant intracranial aneurysms. The complex nature of these aneurysms demands a high degree of surgical skill and in most cases, availability and utilization of both endovascular and neurosurgical techniques will be required for an optimal and comprehensive management.
Even in patients with giant intracranial aneurysms, direct clipping of the aneurysm remains the treatment of choice, and due consideration should be given to this option in all patients. In the preoperative evaluation, cross compression studies should be performed by balloon test occlusion (BTO) to check for adequacy of blood flow from the contralateral side and through the posterior circulation. The sensitivity of BTO can be enhanced with an additional hypotensive challenge. Skull base approaches such as orbito-zygomatic craniotomy, anterior clinoidectomy, far lateral suboccipital craniotomy, and bifrontal basifrontal approach may be necessary to minimize brain retraction and provide enhanced exposure and working space.
For giant paraclinoid aneurysms, a skull base approach combined with anterior clinoidectomy with opening of the distal dural ring may be required. The basic principle of having a proximal control (in the neck) and a distal control of the parent vessel should always be followed. This can sometimes be combined with a suction-decompression technique to collapse the aneurysmal sac which allows placement of multiple clips across the aneurysmal neck parallel to the carotid artery. However, in giant aneurysms, the size of the aneurysm precludes exposure of the distal internal carotid artery in many cases. The neck may not be surgically accessible even after opening of the dural rings. Direct clipping is also not feasible with fusiform aneurysms, in the presence of an atherosclerotic plaque at the aneurysmal neck and occasionally in the cases having a postociling rerupture.  In such cases, a high flow bypass from the external carotid artery to the proximal middle cerebral artery is required. Both the saphenous vein and the radial artery have been used for this bypass graft. Most neurosurgeons prefer the radial artery because of its better long-term patency. The patency of the bypass can be tested by an intraoperative Doppler, an indocyanine green angiography or an intraoperative digital subtraction angiography. The aneurysm can then be tackled by either proximal internal carotid ligation  or by trapping. In the patients where distal carotid artery cannot be surgically accessed, distal endovascular occlusion can be done. A high flow bypass can also be combined with endovascular occlusion of the aneurysmal neck by coils to prevent refilling of the aneurysm through the ophthalmic artery or the meningohypophyseal trunk. Prolonged temporary clipping necessitates the availability of a good neuro-anesthetist for establishing procedures for cerebral protection and for neuromonitoring. 
The major complications related to a high flow bypass include bypass thrombosis and occlusion. A bypass graft and trapping promotes aneurysmal thrombosis which can result in occlusion of perforators or branch vessels which may arise from the aneurysm. Postoperative heparin and antiplatelet therapy can reduce the incidence of these complications significantly but are associated with a higher risk of intracranial hemorrhage.
Giant aneurysm of the middle cerebral artery should be viewed as a surgical disease. These aneurysms are often fusiform. With careful and wide splitting of the sylvian fissure, it is possible to obtain an adequate proximal and distal control in most cases and this gives the surgeon room for a variety of surgical maneuvers such as clip reconstruction, thrombectomy and endoaneurysmorrhaphy, excision of the aneurysm and placement of an interposition graft between the excised ends of the middle cerebral artery, proximal occlusion, and an extracranial-to-intracranial (EC-IC) high flow or low flow bypass.
The surgical treatment of giant posterior circulation aneurysms remains an issue. Distal parent vessel occlusion, proximal parent vessel occlusion and bypass graft with proximal ligation of the parent vessel have been attempted but with less than promising results. A few centers have used deep hypothermic circulatory arrest for clipping these aneurysms but the results again are unpredictable and its use has generally declined.
In future, endovascular management is likely to become the first line management of most intracranial aneurysms but the treatment of giant intracranial aneurysms, especially of the anterior circulation, will continue to demand a neurosurgical management and a high degree of surgical skill. Whenever surgery is undertaken in an attempt to directly clip the aneurysm, one must be mentally prepared to do an EC-IC bypass if maneuvers to clip the aneurysm are not successful. In the present era, all vascular neurosurgeons must be well-versed with the nuances and intricacies of different types of revascularization procedures. The neurosurgeons will be required to use endovascular adjuncts and procedures both preoperatively as well as intraoperatively to yield an optimal result. 
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