Aneurysm Surgery Techniques

A comprehensive set of aneurysm clips and clip appliers is critical, including several of each clip type for techniques such as tandem clipping with identical aneurysm clips. Clip appliers also come in a variety of configurations, which is important in allowing maximum degrees of flexibility to the aneurysm surgeon during clip application.

Because direct inspection does not always accurately confirm that the surgery has been successful, many surgeons use adjuncts to demonstrate complete aneurysm occlusion and patency of parent and branch arteries. These include intraoperative endoscopy, Doppler ultrasonography, intraoperative angiography, and near-infrared indocyanine green videoangiography. Aneurysm surgeons should familiarize themselves with all of these adjuncts and find which ones they prefer. Frame and frameless stereotactic techniques are not required for most intracranial aneurysms; however, they may be useful for distal anterior cerebral artery aneurysms.

3.2 Neuroanesthesia, Monitoring, and Brain Relaxation

The keys are to avoid marked blood pressure fluctuations throughout the operation, avoid maneuvers that lower cerebral perfusion pressure or increase cerebral metabolism and thus increase the risk of cerebral ischemia, and maximize brain relaxation. Osmotic diuresis and mild hyperventilation are often used to achieve the latter. The anesthesiologist should always be prepared for massive blood loss. For proximal carotid aneurysms where intracranial proximal control may not be achieved early on, they should know where the carotid artery is in the neck for compression if necessary.

During temporary clipping, additional maneuvers are sometimes employed for cerebral protection. Propofol, pentobarbital, or etomidate may be administered to achieve burst suppression on electroencephalography (EEG). The arterial pressure is also often increased. Intraoperative moderate hypothermia was not neuroprotective in one trial of good-grade patients with subarachnoid hemorrhage. The rest of these techniques have not been studied in randomized clinical trials.

3.3 Operative Procedure for Intracranial Aneurysms

Once the bony exposure is complete and the dura is opened, the surgeon should assess the adequacy of brain relaxation. If insufficient, additional relaxation can often be achieved through a ventriculostomy or lumbar drain. Once adequate brain relaxation has been achieved, the operative microscope is brought into the field.

Microsurgical dissection of the aneurysm starts with obtaining proximal and distal arterial control followed by preparation of the aneurysm neck for clipping. Dissection usually involves retraction with suction and cottonoids, spreading the arachnoid with bipolar forceps, and sharp arachnoid dissection. Arachnoid that is not easily separated has to be cut with a knife or microscissors. Typically, the suction tip can be used to create gentle traction upon the arachnoid bands, which can then be divided sharply with microscissors or an arachnoid knife. The suction should be regulated to be able to suction fluid without injuring the pia.

It is important to attain proximal arterial control prior to dissection and manipulation of the aneurysm. For many paraclinoid aneurysms and the occasional posterior communicating artery aneurysm that arises from a foreshortened carotid, it may be difficult to achieve proximal control, and it may need to be obtained by isolation of the cervical carotid artery. Distal control is the next step and involves the same techniques as for establishing proximal control. Following dissection of the proximal and distal vessels, including preparation for temporary clipping, the surgeon dissects the arachnoid planes around the fundus and neck of the aneurysm. Retraction of the aneurysm with the blunt suction tip will place arachnoidal bands on stretch, permitting sharp division with microscissors or an arachnoid knife. Blunt tearing of arachnoid bands should be avoided to minimize risk of intraoperative aneurysm rupture. It is generally advisable to begin separation of surrounding branches and the wall of the parent vessel from the midportion of the fundus, carefully developing a plane and extending the dissection proximally from the fundus to the aneurysm neck. Dissection more distally toward the aneurysm dome, on the other hand, should be avoided. Once a plane is developed, a smooth dissector is passed on either side of the aneurysm neck to simulate passage of an aneurysm clip blade. No force should be needed, and the aneurysm should not move.

3.3.1 Temporary Arterial Occlusion

Some surgeons use temporary occlusion in all cases. Most use it selectively for large or complex aneurysms and for intraoperative aneurysm rupture. This is almost always done with temporary clips. Adjuncts to protect the brain during temporary clipping may be employed as already discussed. The principles are to minimize the time of temporary clipping, apply the clips in a manner that avoids obscuration of the aneurysm, and avoid occluding perforating arteries. Proximal occlusion only is usually adequate, but trapping may be needed to control aneurysm rupture or for large and giant aneurysms that need to be opened or collapsed for clipping.

For proximal carotid aneurysms, a suction decompression technique can be used ( ▶ Fig. 3.1). The aneurysm can also be decompressed by inserting a needle into it when it is trapped and then sucking it out ( ▶ Fig. 3.1). Keep in mind that, like opening the aneurysm, this creates a point of no return where the aneurysm has to be occluded, which may be fine for ruptured lesions but bears consideration when operating on asymptomatic, unruptured lesions.

Fig. 3.1 Suction-decompression technique. (a) “Dallas” technique for proximal internal carotid aneurysms. The extracranial cervical carotid and intracranial carotid arteries distal to the aneurysm are temporarily clipped and the aneurysm is aspirated through a catheter inserted into the extracranial carotid. (b) Needle decompression technique. Similar suction decompression can be achieved by first trapping the intracranial arterial segment and then puncturing the aneurysm dome with a “butterfly” needle connected to suction ( ▶ Fig. 3.1a reproduced with permission from Roberts GA, Dacey RG Jr. General techniques of aneurysm surgery. In: Le Roux PD, Winn RH, Newell DW, eds. Management of Cerebral Aneurysms. Philadelphia, PA: Saunders; 2004:563–582.)

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