How to Repair the Intracranial Aneurysm: Clipping or Coiling Decision Making

Middle Cerebral Artery Aneurysms

The MCA remains the vessel with the most discussion between aneurysm treatment modalities. Much literature is written that supports either treatment, with a recent review summarizing the overall results. ⁴ One situation where surgery is most often superior to endovascular treatment is in the presence of a large or giant MCA aneurysm. The incorporation of major branches into the aneurysm sack makes the endovascular treatment a high-risk procedure with a high rate of incomplete occlusion, where on the contrary different surgical options exist with acceptable results. ¹²

2.2.1 Ruptured MCA Aneurysms

According to a recent review, ruptured MCA aneurysms are best treated by coiling, which has the lowest rate of unfavorable outcome, although no firm conclusions could be drawn due to the variation in study design and lack of standardized reporting on MCA aneurysm treatments. ⁴ Nevertheless, certain situations make surgical treatment of this aneurysm the modality of choice, such as the presence of a broad-based aneurysm, or a significant subdural, intraparenchymal, or sylvian fissure hematoma.

When there is a large, space-occupying intracranial hematoma, the craniotomy needs to be large enough to expose the complete hematoma and allow for immediate decompression of the brain. In cases with a subdural hematoma, it can carefully be removed before proceeding with the aneurysm clipping procedure. Care must be taken to avoid excessive retraction of the arachnoid over the sylvian fissure and adjacent brain since the presence of subdural blood may mean the aneurysm has eroded through the arachnoid and is attached to the dura. When there is an intraparenchymal or sylvian fissure hematoma, we first make a large decompressive craniotomy with flattening of the sphenoid ridge so that the carotid artery can be identified with minimal brain retraction. After opening of the basal cisterns to release cerebrospinal fluid, the carotid artery is freed from arachnoid adhesions so that a temporary clip can be placed, if necessary. Next, we perform a small corticotomy at a noneloquent site and as close to the hematoma as possible, or we open the sylvian fissure superficially, to approach the hematoma. The hematoma is partially removed where some hematoma is left behind around the aneurysm to prevent a rebleed. After aneurysm clipping, we remove the remaining hematoma, keeping in mind that a hematoma in the sylvian fissure (identified as a serrated edge on the CT scan, indicating the insular gyri) might be difficult to remove ( ▶ Fig. 2.1a,b).

Fig. 2.1 (a) Preoperative CT scan with intraparenchymal and sylvian hematoma due to ruptured right middle cerebral artery aneurysm. (b) Postoperative CT scan after decompressive craniectomy, middle cerebral aneurysm clipping, and evacuation of intraparenchymal hematoma. The sylvian hematoma was not removed due to its tenacity and risk for damaging sylvian fissure arteries.

2.2.2 Unruptured MCA Aneurysms

In contrast to ruptured MCA aneurysms, unruptured aneurysms are better treated surgically, with less complications, better occlusion rates, and less retreatment rates. ⁴ Some morphological aspects on the preoperative angiography can facilitate the surgical strategy, where a shorter M1 segment, larger M1 angle opposed to the skull base, and posteroinferior aneurysm projection are related to a higher risk for surgical complications (Video 2.1).

2.3 Posterior Communicating Artery Aneurysms

When a posterior communicating artery (PcomA) aneurysm can be treated by both surgery and coiling, the latter modality tends to result in better functional outcome. Nevertheless, these aneurysms often have a wide neck and/or the PcomA originates at the neck of the aneurysm, making an isolated coiling procedure more risky. An alternative is the stent-assisted or balloon-assisted technique, with higher complication and lower obliteration rates, especially in PcomA aneurysms. ¹³^, ¹⁴ Thanks to the technical advances in neurosurgery, including improved microsurgical techniques and approaches by minicraniotomies, clipping a PcomA aneurysm has become a treatment with low risks and acceptable morbidity. It might therefore be a good alternative when a stent or balloon is necessary to coil the aneurysm, especially in case of ruptured aneurysms.

2.3.1 Posterior Communicating Artery Aneurysm with Oculomotor Deficits

When a PcomA aneurysm projects inferiorly, it can cause a (partial) oculomotor deficit (Video 2.2). Both treatment modalities can improve the deficits by either removing the compression on the nerve by surgical clipping or reducing the pulsations on the nerve by coiling. A review comparing both modalities in respect to oculomotor nerve palsies due to PcomA aneurysms shows that it resolves in a significant higher proportion of patients after surgical clipping. ¹⁵

In general, we prefer not to open unruptured aneurysms after they are clipped, but when clipping a PcomA aneurysm with oculomotor compression, we tend to puncture the aneurysm after occlusion, shrink it by bipolar coagulation, or cut out the dome of the aneurysm.

2.4 Anterior Communicating Artery Aneurysms

Clipping an AcomA aneurysm is challenging due to the difficult exposure of the vascular anatomy, complex angioarchitecture, and flow dynamics (Video 2.3). ¹⁶ An endovascular procedure might therefore be a good alternative with proven good functional outcome. ¹⁷

Only gold members can continue reading. Log In or Register to continue