Neurol India Home 

Year : 2015  |  Volume : 63  |  Issue : 6  |  Page : 829--831

Endoscopic keyhole technique for anterior circulation aneurysms: Present status

Suresh N Mathuriya 
 Senior Consultant, Medipulse Hospital, Jodhpur (Rajasthan), and Ex-Head, Department of Neurosurgery, PGIMER, Chandigarh, India

Correspondence Address:
Suresh N Mathuriya
Senior Consultant, Medipulse Hospital, Jodhpur (Rajasthan), and Ex-Head, Department of Neurosurgery, PGIMER, Chandigarh

How to cite this article:
Mathuriya SN. Endoscopic keyhole technique for anterior circulation aneurysms: Present status.Neurol India 2015;63:829-831

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Mathuriya SN. Endoscopic keyhole technique for anterior circulation aneurysms: Present status. Neurol India [serial online] 2015 [cited 2020 Sep 25 ];63:829-831
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The operative management of intracranial aneurysms requires neurosurgical skills of the highest caliber. The International Subarachnoid Aneurysm Trial has completely transformed the basic philosophy of dealing with aneurysmal subarachnoid hemorrhage (SAH) and has led to significant advances in the endovascular techniques (EVTs), including progress in the technology of coils (both balloon and stent assisted), as well as in the introduction of onyx, flow diverters, and web devices. The surgical techniques for securing aneurysms, however, did not undergo parallel advancements. The truth of the matter is that both the stand-alone techniques, clipping and coiling, cannot comprehensively secure aneurysms; both must coexist and be continuously updated with newer innovations. They are, in fact, complimentary to each other.

The pterional approach is the most popular, convenient, and comprehensive approach for clipping most of the anterior circulation aneurysms, with the exception of the distal anterior cerebral artery aneurysms. There is always a scope for improvement both in the approach and in the technology to achieve the best possible intraoperative milieu, patient satisfaction and operative results. Novel surgical approaches offer definite and substantial advantages over the traditional standard approaches while ensuring that the operative morbidity remains equal or becomes lower. This requires a rapid evolution of the minimally invasive approaches, the development of newer intraoperative monitoring devices, and also the inclusion of endoscopic surgery in the armamentarium of cerebrovascular surgery.

The concept of keyhole surgery may be defined as a limited optimum craniotomy that is perfectly planned and executed to ensure a safe corridor to the lesion with geometric precision. It ensures visualization of all relevant anatomical details, ensures a safe and optimum dissection with unrestricted maneuverability of the working instruments, and protects the surrounding tissues from an operative injury. An adequate exposure of the surgical field is mandatory for its success. The goals that cannot be compromised include a safe dissection of the aneurysm, preservation of the perforating vessels, complete exclusion of the aneurysm from the circulation, ascertaining that the parent vessel is not endangered, and ensuring that no aneurysmal remnant has been left out after the final clip placement.[1]

The approaches that confirm to the concept of open minimally invasive procedures include the supraorbital approach for anterior communicating artery aneurysms and small ophthalmic segment aneurysms, and a mini-pterional craniotomy for internal carotid trunk and bifurcation as well as middle cerebral artery aneurysms. Both these approaches ensure a wide sylvian dissection to access the aneurysm. The other approaches include the lateral supraorbital approach and the interhemispheric approach (the latter for the A2 segment and the distal anterior cerebral artery aneurysms). Selection of an appropriate approach is made after a logical understanding of the operative steps involved and by formulating a mental image of the orientation of the aneurysm with respect to the surrounding neurovascular structures. This is an essential prerequisite for the successful execution of the minimally invasive craniotomies, as the scope for subsequent modifications in the approaches is limited.[2]

The endoscopic approach ideally forms the pinnacle of the minimally invasive approaches. Its ideal indications include both ruptured and unruptured anterior circulation aneurysms in patients presenting with good Hunt and Hess grade. The proposed contraindications for the use of the approach include the presence of a large clot with mass effect, the presence of paraclinoid or giant aneurysms, the presence of brain edema with compressed ventricles (so that intraventricular cerebrospinal fluid drainage will have no significant bearing in achieving a relaxed brain), and an extremely poor patient's preoperative clinical grade.

The advantages of the keyhole approaches are numerous. They include a shorter surgical procedure, a cosmetically pleasing small skin incision, preservation of the superficial temporal artery (in case it is required for a subsequent bypass procedure and also to ensure the maintenance of vascularity of the scalp flap), and preservation of the frontal branches of the facial nerve as well as the supraorbital nerve and artery. The blood supply to the region is usually excellent, thereby minimizing the risk of problems associated with wound healing. A mini-pterional craniotomy and a supraorbital approach may be completed in an operative time that is 70% of that taken by a conventional pterional approach. Atrophy of the temporalis muscle and transient paralysis of the frontalis muscle are significantly rarer with the former approach as compared with the latter. There is a limited resection of the gyrus rectus while approaching the anterior communicating artery aneurysms during the supraorbital approach that may be avoided by an anterior interhemispheric dissection during the pterional approach. This factor is insignificant when other advantages of the minimally invasive approaches are also considered.

The disadvantages of the minimally invasive approaches include a narrow surgical corridor, which may compromise a proper visualization of the anatomical structures and may restrict the manipulation of microinstruments. In case the aneurysm ruptures before proximal control has been obtained, the limited maneuverability of instruments and restricted field of vision may prove to be catastrophic. Hence, the keyhole approaches are often not considered in patients who have been admitted with recent-onset SAH. The skin flap may violate the frontal sinus. There is a small risk of eyebrow alopecia and anesthesia. A proper preoperative planning using computed tomography angiographic reconstructions; visualizing the operative field by the microscope positioned at different angles, improving the illumination at the operative site, and using low-profile instruments that minimize restriction of the surgeon's field of view, help in ensuring a good result.

The use of an endoscope during minimally invasive access for clipping intracranial aneurysms significantly reduces many of the difficulties encountered while using the microscope. It provides a higher magnification, an increased light intensity, and a clearer depiction of details close to the surgical field. The extended viewing angles provided by the use of 0- and 30-degree endoscopes help in achieving a circumferential inspection of the parent blood vessel to ensure that all perforators are free, and in observing the hidden parts of the aneurysm. The working area obtained with an endoscopic mini-pterional craniotomy and supraorbital approach is greater than that obtained with the pterional approach.[3] Surgeons can "look around corners" and observe areas that were previously considered inaccessible using the microscope. The endoscope may be used during all the essential steps of aneurysm surgery, including exploration of the surgical field after opening of the cisterns, dissection and clipping of the aneurysm, checking the patency of the parent vessel and the adjacent perforating arteries, and complete obliteration of the aneurysm after the final clipping.

The endoscope has some unique uses under special circumstances during aneurysm surgery. It helps in visualizing the origin of the superior hypophyseal arteries and branches of the internal carotid artery directed toward the pituitary stalk as well as the medial aspect of the distal dural ring. A 2.7-mm endoscope especially provides space for dissection and ensures significantly lesser tissue damage. Perforating branches arising from both the medial and the lateral aspects of the carotid and posterior communicating arteries may be followed distally from their origin with the use of the 30- and 45-degree endoscopes. The premamillary artery, the anterior choroidal artery, and the small arteries entering the anterior perforated substance, the lamina terminalis, the chiasm, and the hypothalamus may be visualized. The anterior infracallosal area harboring the A1 and A2 segments as well as the recurrent artery of Huebner, and the perforating arteries directed posteriorly from the anterior communicating artery and the M1 segment of the middle cerebral artery, may be visualized. However, the endoscope offers no additional advantage while clipping a middle cerebral artery bifurcation aneurysm. The ability of the endoscope to visualize the vessels from all the sides and from several directions ensures that the fundus of the aneurysm is not unnecessarily manipulated and retracted to visualize the blood vessels on its other side to ensure that they are not coming in the clip. The duration of temporary clipping is also reduced. Following clipping of an aneurysm using a microscope, visualization of the clip position using an endoscope has led to the modification of the final clip position in 7%–20% of cases on discovering either the entrapment of perforators within the blades of the clip or the presence of incomplete clipping of the aneurysm. The microscopic and endoscopic images may be observed simultaneously in the "picture-in-picture format" to provide a better visualization of the operative field. An endoscopic indocyanine green (ICG) angiography is visualized for a tenfold longer duration and gives a more intense illumination than an ICG angiography performed using a microscope.[4]

A few additional points need a fleeting mention. Before clipping of the aneurysm and after obtaining proximal control of the parent vessel, a trial temporary clipping should be performed on this vessel. This will ensure that temporary clipping of the proximal vessel may be performed with ease in case there is an intraoperative rupture of the aneurysm. Using a da Vinci surgical system during a supraorbital craniotomy may be another potential application of the endoscopic keyhole surgery. However, it mandates the development of appropriate clip applicators and related instrumentation.[5]

Sharma et al.,[6] have, in this issue, described their versatile technique of aneurysmal clipping, exclusively using an endoscope. Their study is the culmination of groundwork in the cadaveric dissection laboratory, demonstrates the development of dexterity through years of surgical experience, and gives an extensive in-depth understanding of the subject.


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