Endoscopic controlled clipping of anterior circulation aneurysms via keyhole approach: Our initial experience
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.170095
Source of Support: None, Conflict of Interest: None
Introduction: Surgical clipping is the most definite treatment for intracranial aneurysms. Its aim is to achieve complete aneurysmal occlusion without compromising the lumen of a parent vessel or perforators, and with minimal brain tissue trauma.
Keywords: Clipping; endoscopy; intracranial aneurysms; keyhole approach
Surgical clipping is the most definite treatment for intracranial aneurysms. The goal of aneurysm surgery is to achieve complete occlusion of an aneurysm without compromising the lumen of the parent vessel or perforators, and with minimal brain tissue trauma.
However, even in expert hands, the incidence of inadequately clipped aneurysms and parent vessel occlusion on postoperative digital subtraction angiography (DSA) is 4–19%,,,,, and 0.3–12%,,,,, respectively. Intraoperatively, direct visual inspection, micro-Doppler sonography, and intraoperative indocyanine green angiography are different methods used to assess for proper clip placement and patency of parent vessel. However, all these methods are limited by their requirement of a direct line of view in the assessment of clip blades and the relationship of the clips to aneurysmal sac and parent vessel, thereby rendering visualization of the area behind the aneurysm/vessel difficult. An endoscope with its ability to provide close multi-angled view can be a very helpful tool in such a situation and can thus potentially prevent the aforementioned complications in aneurysm surgery. Endoscopic visualization of the regional vascular anatomy and the relationship of the aneurysm to the surrounding structures before, during, and after aneurysmal clipping can be very helpful in preventing damage to normal structures and in assuring an adequate aneurysmal clipping.,,,,,
Using the concept of "keyhole surgery" can minimize brain tissue trauma. The keyhole surgery achieves this goal by planning an appropriately placed craniotomy, thereby providing direct access to the area of interest. The concept of "endoscopic keyhole surgery" represents a further advancement of the concept of "keyhole surgery." It combines the advantages of the concept of keyhole surgery, that is, minimizing tissue trauma by decreasing the size of incision and craniotomy, with the concept of endoscopic surgery, that is, better illumination and wider, multi-angled, close-up view at depth and at corners.
We present our experience in the last 1 year, in managing 14 patients with intracranial aneurysms, who underwent clipping via the endoscopic keyhole approach. Endoscope-assisted micro-neurosurgery has been well described in the literature. In this procedure, an endoscope is used to complement the microscope in visualizing the regional anatomy before or after clipping.,,,,, We used the endoscope in place of the microscope for pre-clipping dissection, clipping, and post-clipping inspection.
This was a retrospective study carried out at a tertiary-care neurosurgical center to evaluate our experience with the endoscopic keyhole approach (supraorbital and mini-pterional) for clipping of anterior circulation aneurysms. We analyzed 14 patients with intracranial aneurysms who underwent clipping via this approach during the last 1 year. The preoperative digital subtraction angiograms (DSA), in-patient records, operative notes, and postoperative records were analyzed to collect data. Complete intraoperative video recordings were available for all the patients included in the study.
Patients with acute subarachnoid hemorrhage (SAH), thick SAH/intraventricular hemorrhage (IVH), poor SAH grade, complex aneurysms, posterior circulation aneurysms and aneurysms with multiple blebs were not selected for endoscopic controlled clipping. The average time interval between the ictus and surgery in patients included in the present study was 60 days.
All patients underwent a preoperative DSA. The patient's DSA was evaluated in detail before undertaking the decision to operate. All patients underwent surgery via either a supraorbital or a mini-pterional keyhole approach.
In the supraorbital keyhole approach, the patient's head was fixed in a Mayfield's head holder. The head was extended by 30°. An eyebrow incision was given on the lateral 2/3rd of the eyebrow and a small supraorbital craniotomy was made (2.5 cm × 2.0 cm). The inner table of bone was bevelled. The dura was dissected off the orbital roof, and orbital roof ridges (juga cerebralia) were drilled to improve the exposure and decrease the need for brain retraction. The dura was then opened, and the dural flap reflected inferiorly.
In the mini-pterional keyhole approach, a small curvilinear incision was made just behind the hairline. The skin flap was then reflected anteriorly along with the temporalis fascia. The temporalis muscle was split and the key burr hole was made with a drill. A small bone flap was elevated centered over the pterion. The dura was opened in a curvilinear fashion and reflected antero-inferiorly.
After opening the dura, the endoscope was brought into the surgical field. At the beginning of the dissection, a 0°, 18 cm endoscope (Karl Storz) was used. A 30°/30 cm endoscope was used in the later stages of the dissection. The endoscope was mounted in a holder but not fully tightened and was held by an assistant with his arm supported. The holder along with the endoscope was intermittently adjusted as per the requirement. We used regular micro-instruments (routinely used in micro-neurosurgery) during the procedure. While passing the instruments along the shaft of the endoscope, the tip of the instrument was visualized with naked eye until it was seen on the screen. Under endoscopic visualization, first of all, the Sylvian fissure and carotid cisterns were opened [Figure 1] and cerebrospinal fluid (CSF) was released for 5–10 min. This not only relaxed the brain by draining the CSF, but also facilitated a proximal/distal control in the case of intraoperative rupture of the aneurysm. The internal carotid artery (ICA), M1, and A1 segments were prepared for proximal control. Temporary clip placement was practiced several times at this stage. This was very important as the space available during the keyhole approach is narrow and there is no scope for change of plan. Aneurysmal rupture can thus be a catastrophic event in the absence of proximal and distal control. After applying the temporary clips on the parent vessels, dissection was started around the neck of the aneurysm and its relationship to adjacent vessels was defined [Figure 2] and [Figure 3]. The dissection was bimanual and dynamic (with the assistant moving the scope according to the surgeon's requirements). Special attention was given to the presence of a normal vessel or a perforator adherent to the neck/sac on the backside of the aneurysm. After defining the neck on all sides, a permanent clip was applied. The endoscope was then maneuvered to bring the posterior aspect of the aneurysmal sac into view. If required, an angled endoscope (30° or 70°) was used. Post-clipping endoscopic evaluation was done to detect for any residual neck, occlusion of the parent vessel, or inclusion of a normal vessel/perforator within the clip blades [Figure 3]. If any of these issues were present, the clip was re-adjusted accordingly. The dura was then closed in a watertight fashion and bone flap replaced and fixed with mini plates and screws. Skin incision was then closed meticulously.
The age of the patients ranged from 28 to 56 years. There were eight female and six male patients. Six patients had comorbidities (four were hypertensive and two were diabetic). All patients underwent a preoperative DSA. Ten patients presented with subarachnoid hemorrhage, while 4 patients had an incidentally detected unruptured aneurysm. Seven patients had an anterior communicating segment (ACom) aneurysm, 4 patients had a middle cerebral artery (MCA) bifurcation aneurysm, 2 patients had an ICA bifurcation aneurysm, and 1 patient had a posterior communicating artery aneurysm. Among the patients with ruptured aneurysms, four had Hunt and Hess (H and H) grade II and six had H and H grade I SAH. The patient details and aneurysmal characteristics are presented in [Table 1].
Seven patients were approached via the supraorbital keyhole approach and the other seven via the mini-pterional keyhole approach. In none of the patients was a tense, bulging brain encountered. We were able to dissect the aneurysmal neck in all patients under endoscope visualization. The endoscope provided a clear view of the regional vascular anatomy in all patients. One patient had a premature intraoperative rupture of aneurysm (ACom). Since the temporary clip was already in place before the aneurysmal sac dissection started, the rent within the aneurysmal sac could easily be coagulated. The post-clipping inspection revealed an inadvertent inclusion of a perforator in two of the patients (MCA bifurcation and ACom). The clip was immediately re-adjusted to exclude the perforator from the clip blades. There was no residual neck/incompletely clipped aneurysm or parent vessel occlusion detected on post-clipping inspection. There was no morbidity directly attributable to the endoscope.
The postoperative course was uneventful except in 1 patient with a ruptured ACom artery aneurysm who developed right lower limb weakness (power - 3/5) secondary to vasospasm. The patient underwent an intra-arterial nimodepine injection. The power in his lower limb recovered completely. None of the patients worsened or developed fresh neurological deficits.
Even in experienced hands, unexpected branch occlusion, partial vessel occlusion with significant blood flow reduction, and incomplete aneurysmal occlusion have been reported.,,,,, Occlusion of a normal vessel usually leads to permanent deficits and re-exploration for re-adjustment of the clip in such a scenario is usually a futile exercise. Aneurysmal remnants may require further treatment in the form of coiling. Such adverse outcomes place surgical clipping on a backfoot when comparisons are drawn with endovascular coiling. Therefore, it is imperative to prevent such events from happening in the first place.
One of the reasons for the occurrence of such unexpected and unacceptable events is the difficulty to visualizing the aneurysmal sac obscured from the line of sight of a microscopic view. Although microsurgical dissection and gentle retraction of the fundus may provide a view of the structures located behind the aneurysmal sac, such maneuvers carry a significant risk of intraoperative aneurysm rupture. An intraoperative DSA was introduced as a method to overcome such problems in aneurysm surgery;,, however, it has failed to gain widespread acceptance for various reasons.,,
Endoscopic techniques have certain features that can help to overcome the shortcomings inherently existing during microsurgical clipping of aneurysms: (a) It takes the light source close to the field of interest, thereby providing better illumination; (b) it provides a clear close-up view of the anatomy (flash light effect); and, (c) it provides a multi-angled view of the region which helps in looking around the corners.
These features of the endoscopic technique can help in better visualization and understanding of the neuro-vascular anatomy and the relationship of the aneurysm to the surrounding vessels, and might help in reducing unwanted outcomes. Several studies have actually shown that a combination of straight and angled endoscopes provide a view that facilitates looking around the corners and have proved to be useful in aneurysm surgery.,,,,,
Perneczky and Boecher-Schwarz  in their experience with 66 patients undergoing clipping utilizing the endoscope-assisted micro-neurosurgery, reported better control over the aneurysm and surrounding vessels and nerves during dissection and clipping with an endoscope. They attributed the decreased rate of intraoperative rupture of aneurysms to a better visualization with an endoscope. They used the endoscope in place of a microscope for dissection and clipping of the aneurysm in some of their patients.
Frazze et al., in 1997 reported the use of a penscope which is a 3 mm ball tip endoscope cum dissector with a 5 mm focal length that was used for clipping a ruptured pericallosal artery aneurysm. They concluded that it is possible to visualize, dissect, and clip cerebral aneurysms using only endoscopes.
Wang et al., in their experience with endoscopic-assisted micro-neurosurgery for aneurysms reported that in 29% of cases, the endoscope provided information that would not have been obtained with a microscope alone. Postoperatively, none of their patients had a residual aneurysmal neck. They reported no complications directly attributable to the use of the endoscope. They used a rigid, curved 1 mm endoscope (that was utilized as a viewing dissector).
Similarly, Fischer et al., in their retrospective series, analyzed 180 aneurysms in 124 patients in whom an endoscope was used during surgery. They used an endoscope (4.0 mm, 0°, 30° or 45°) for pre-clipping visualization of the anatomy in 150 (83%) patients. Clipping under endoscopic view was performed in only 4 cases. Post-clipping endoscopic inspection was done in 130 cases. In 50 cases, only a pre-clipping endoscopic visualization was done. Post-clipping visualization was not performed due to two reasons:First, the surgeon was satisfied with the pre-clipping visualization and did not find the need for a post-clipping visualization; and second, in cases with posterior circulation aneurysms, endoscopic visualization was not feasible after clip application. In the cases where only pre-clipping endoscopic visualization was done, 5 incompletely clipped aneurysms and 4 branch/perforator occlusions were identified postoperatively. On the other hand, in the patients in whom post-clipping endoscopic visualization was done, only two aneurysmal remnants and one branch occlusion were identified postoperatively. The authors reported the need for re-arrangement of the applied clip or application of an additional clip in 26 of the 130 cases (20%). Thus, the authors were able to avoid unexpected and unwanted results in 20% of their cases in whom post-clipping endoscopic visualization was done. The incidence of incomplete aneurysmal clipping/aneurysmal remnant would have been 18.9% instead of 2.7% if post-clipping endoscopic visualization had not been carried out.
Kalavakonda et al., performed endoscope-assisted microsurgery in 79 patients with an intracranial aneurysm. The endoscope (4.0/2.7 mm, 0°, 30°, or 70°) was used both before and after the clipping. They noted a better visualization of the regional anatomy and better delineation of the aneurysmal neck, sac and its relationship to the parent and adjacent vessels/perforators in 26 patients. In 15 (19%) of their cases, this information could only be obtained with an endoscope. The clip required re-adjustment after an initial placement in 6 patients because of the presence of vessel occlusion or residual neck. They also reported a shortened temporary clipping time of parent vessels with the use of an endoscope.
The concept of keyhole surgery was first introduced by Perneczky et al., and was based on the basic principle of making a minimum-sized craniotomy for accessing any intracranial pathology situated at a depth. They described the supraorbital keyhole approach. The keyhole concept has undergone various modifications since its initial description and has been applied to other skull base regions as well.
Although the keyhole concept has the advantages of minimal brain exposure and retraction, thereby minimizing brain tissue trauma and providing a better cosmesis, some of the major disadvantages of the keyhole approach are the narrow corridors and limited working angles. To overcome these disadvantages, Fischer et al., introduced the concept of endoscopic keyhole surgery for manipulating deep-seated lesions. The supraorbital keyhole approach provides a similar exposure and access to sellar/parasellar region and ACom complex in comparison to the standard pterional approach. However, the middle cranial fossa under the sphenoid ridge and the lateral sylvian fissure are obscured from view during the supraorbital keyhole approach. We, therefore, used the mini-pterional approach for accessing MCA aneurysms.,
During our initial experience with 14 patients who underwent an endoscopic clipping via the keyhole approach, we were successfully able to perform the pre-clipping dissection as well as clipping of the aneurysm under endoscopic visualization in all our patients using regular microscopic instruments and clip applicators. Post-clipping inspection was also done in all our patients that revealed an inadvertent perforator inclusion in the clip blades in 2 patients (2/14; 14%). The clip was re-adjusted to exclude the perforators. None of the patients had an incompletely clipped aneurysm or a residual neck. This fact was confirmed by perfoming a postoperative DSA that revealed a completely clipped aneurysm in all our patients. There was one intraoperative rupture that was not attributable to the use of the endoscope. There was no morbidity precipitated by the use of the endoscope in our patients.
Thus, in patients undergoing clipping for intracranial aneurysms, approximately 20% patients are directly benefited by the use of an endoscope. Better visualization due to the enlarged, multi-angled, well-illuminated view of the endoscope helps to reduce the amount of retraction required, thereby facilitating surgery through a small keyhole craniotomy. The endoscope facilitates anatomical recognition of vascular and neural structures, especially in hidden corners which otherwise would not have been visualized with the microscope due to its straight line of sight An endoscopic view, therefore, reduces the incidence of incompletely clipped aneurysms/residual neck as well as inadvertent parent vessel/perforator occlusion with an aneurysm clip. The confidence obtained from the precise and clear anatomical view provided by the endoscope may help to reduce the temporary clipping time. Also, there are no additional adverse effects attributable to the use of an endoscope.
The authors have used this technique in simple cases only. The average time interval between the ictus and surgery in patients included in the present study was 60 days and none of the patients had a thick SAH/IVH or features suggestive of raised intracranial pressure on preoperative scans. We did not use this technique for clipping complex aneurysms, aneurysms of posterior circulation, and for patients presenting with acute SAH. A wide opening up of the sylvian and carotid cisterns, exposure of the proximal vessels, and application of a temporary clip before starting the neck dissection are important and essential steps in order to prevent and manage the potentially catastrophic intraoperative aneurysmal rupture. In case difficulty is encountered, one should not hesitate to switch over to a microscopic view with which one is more familiar.
An endoscopic keyhole approach for clipping of intracranial aneurysms combines the advantages of the concept of keyhole approach and endoscopy. The disadvantage of having space constraints and narrow corridors in the keyhole craniotomy can be overcome by a well-illuminated close-up and multi-angled view provided by the endoscope. The use of an endoscope in aneurysm surgery can reduce the chances of incompletely clipped aneurysms/residual neck and the risk of parent vessel occlusion or inclusion of a perforator or a normal vessel in the clip blades. However, the use of an endoscope requires a learning curve. Practicing on cadavers and initially doing simple endoscopic procedures can overcome this drawback. Only after gaining adequate experience in aneurysm surgery and acquiring a high standard of endoscopic skills should one venture onto the endoscopic controlled keyhole approach for clipping of simple aneurysms, and that too, in selected cases only.
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Conflicts of interest
There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3]