Combined Sub-temporal and Pterional Exposure for Clipping of Posterior Cerebral Artery Aneurysm

Girish Menon; Arla Sai Varsha; Vinod Kumar; Ajay Hegde

doi:10.4103/jcvs.jcvs_1_22

CASE REPORT

Year : 2021 | Volume : 9 | Issue : 2 | Page : 115-117

Combined Sub-temporal and Pterional Exposure for Clipping of Posterior Cerebral Artery Aneurysm

Girish Menon¹, Arla Sai Varsha¹, Vinod Kumar², Ajay Hegde¹
¹ Department of Neurosurgery, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, Karnataka, India
² Consultant Neurosurgeon, First Neuro Hospital, Mangalore, Karnataka, India

Date of Submission	04-Jan-2022
Date of Decision	10-Jan-2022
Date of Acceptance	14-Jan-2022
Date of Web Publication	5-Apr-2022

Correspondence Address:
Dr. Ajay Hegde
Department of Neurosurgery, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, Karnataka
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jcvs.jcvs_1_22

Abstract

Posterior cerebral aneurysms are rare posterior circulation aneurysms. Clinical presentation can be varied from life-threatening subarachnoid hemorrhage to mass effect on adjacent structures. Due to their complex anatomical location, microsurgical clipping is not without challenges. Several approaches have been described based on the location of the aneurysm in relation to the segment of the posterior cerebral artery (PCA). We describe a combined approach for surgical clipping of a postcommunicating anterior segment PCA aneurysm.

Keywords: Aneurysm, microsurgical clipping, posterior cerebral artery

How to cite this article:
Menon G, Varsha AS, Kumar V, Hegde A. Combined Sub-temporal and Pterional Exposure for Clipping of Posterior Cerebral Artery Aneurysm. J Cerebrovasc Sci 2021;9:115-7

How to cite this URL:
Menon G, Varsha AS, Kumar V, Hegde A. Combined Sub-temporal and Pterional Exposure for Clipping of Posterior Cerebral Artery Aneurysm. J Cerebrovasc Sci [serial online] 2021 [cited 2022 May 22];9:115-7. Available from: http://www.jcvs.com/text.asp?2021/9/2/115/342553

Introduction

Aneurysms of the posterior cerebral artery (PCA) are uncommon, representing 1%–2% of all intracranial aneurysms.^[1] Its deep anatomic location, proximity to critical neurovascular structures, and narrow operative corridor make it surgically challenging lesions to treat. Although the advent of newer endovascular techniques has enabled its endovascular treatment, it is not without adjuncts such as balloon assistance, stent deployment, parent vessel occlusion, or flow diversion.^[2] The use of these adjuncts usually calls for long-term antiplatelet therapy. In large and giant aneurysms, failure to address the mass lesion may not always be favorable in treating the presenting complaint. A combination of these factors has made surgical clipping a valuable and time-tested option, with 77% of PCA aneurysms being still subjected to microsurgical clipping at some centers.^[1] We describe the surgical technique for a case of an unruptured large left PCA aneurysm clipped at our institute.

Case Report

A 59-year-old man with no known comorbidities presented with the complaints of sudden-onset diplopia and dropping of his left eyelid for 2 months. He complained of occasional headache, mild to moderate in intensity not suggestive of a subarachnoid hemorrhage (SAH). On examination, he had left oculomotor nerve palsy with pupillary involvement. Rest of the neurological examination was normal. A magnetic resonance imaging scan performed revealed a lesion suspicious of an aneurysm in the medial temporal region along the posterior communicating artery (PComA). There was no evidence of bleeding. He underwent a digital subtraction angiogram which confirmed a saccular aneurysm at the P1–P2 junction of the left PCA with the flowing part measuring 1.61 cm × 1.07 cm × 0.90 cm, neck 2.8 mm filling on vertebral injection [Figure 1]a, [Figure 1]b, [Figure 1]c, [Figure 1]d. He was counseled regarding treatment options, and he consented to microsurgical clipping of the aneurysm.

Figure 1: (a) Magnetic resonance imaging T2 FLAIR demonstrating an aneurysm along the left medial temporal lobe. (b and c) Computed tomography angiogram three-dimensional reconstruction and DSA showing aneurysm. (d) Postoperative computed tomography angiogram demonstrating clip in situ

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The surgical procedure was slightly modified from the routine pterional craniotomy for aneurysm clipping. The patient was positioned in 3-pin fixation with head turned to the right by 50° and in slight extension. A mini-Faulkner's flap was marked, and a frontotemporal craniotomy was performed with importance given to reaching the temporal base. Once the dura was opened, the Sylvain fissure was dissected, and the internal carotid and its branches were traced. The PComA was identified, traced backward to identify the aneurysm. As further dissection and maneuvering were difficult, 2 cm of the inferior temporal gyrus was resected to gain access to the aneurysm. The aneurysm was unilobed, pointing anteriorly toward the tentorium. Aneurysm dome was dissected free from oculomotor nerve and perforator arteries. Being an unbleed aneurysm, dissection was carried out all around with ease. Neck was defined, and a standard YASARGIL^® side-angled aneurysm clip was applied along the axis of the PCA. The fundus was then opened, and thrombosed clot was removed. The third nerve which was adherent to the dome of the aneurysm was separated along the tent edge [Figure 2]a, [Figure 2]b, [Figure 2]c, [Figure 2]d. Indocyanine green angiography was used to confirm distal and proximal flow. A computed tomography angiogram performed in the postoperative period confirmed the same. The patient was discharged on the 6^th postoperative day with no fresh neurological deficits. On follow-up in outpatient at 1 month, his third nerve palsy had partially recovered.

Figure 2: (a) Aneurysm with clip (YASARGIL^® side-angled) across the base. (b) Opening of the aneurysm with the removal of thrombus. (c) Separation of the adherent third cranial nerve, (d) Final operative field with clip in place and brainstem and third cranial nerve decompressed

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A video clip of the surgical procedure and steps can be viewed at https://youtu.be/3n0fG6TtPJo.

Discussion

The PCA is divided into four segments: P1 (precommunicating segment), P2 (postcommunicating segment), P3 (quadrigeminal segment), and P4 (calcarine segment).^[3] The P2 segment is divided into P2A (anterior) or crural segment and P2P (posterior) or ambient segment. The P2 segment of the PCA has in its junction the origin of PComA. The P2A begins at the PComA and its way between the peduncle and uncus; the P2P begins at the posterior edge of the cerebral peduncle at the junction of the crural and ambient cistern. Of the PCA aneurysms, P2 segment aneurysms are rare, with an incidence of about 0.3%. Most PCA aneurysms are usually giant aneurysms (23%) versus 3%–5% at other locations.^[4] Giant aneurysms exert a mass effect on the surrounding tissues and may present with oculomotor nerve palsy, visual field defects, memory impairment, or epileptic seizures.^[4],[5]

Aneurysms of P1 and P1–P2 junction are treated preferably with the pterional approach. P2 and P3 aneurysms are usually handled through the subtemporal approach.^[4] Selection of the optimal surgical approach is based on the type of the aneurysm, the relationship between the aneurysm and its parent artery, the lie and the exact location of the aneurysm. The subtemporal approach is a classic approach advocated by Drake to treat aneurysms of the PCA.^[6] Other approaches suggested include the transpetrous approach^[7] and the orbitozygomatic approach, which minimize temporal lobe retraction and allow for better visualization. However, these approaches involve extensive skull base work, and all neurosurgeons may not be familiar with it. In the presence of good collateral circulation, trapping the P2 segment is a feasible option in giant aneurysms.^[8]

In most series, the common mode of presentation of PCA aneurysm remains SAH. Our patient presented with oculomotor nerve palsy secondary to the mass effect caused by the lesion. It was present just distal to the PComA in the P2A segment.^[9] Although these aneurysms are best approached by the subtemporal approach, we used a hybrid of the pterional and subtemporal to gain access to the cisternal spaces and release cerebrospinal fluid (CSF). We then proceeded to subtemporal where better visualization was achieved by resecting a part of the inferior temporal gyrus to prevent excessive retraction and injury to the vein of Labbe in the temporal lobe. However, the damage due to these complications can be minimal with the use of mannitol administration, lumbar puncture, or ventricular drainage during surgery, in addition to avoiding excessive traction. However, in young patients with voluminous brain and brain swelling secondary to SAH, these techniques may not be adequate, especially if the aneurysm is adherent to the medial temporal structures and in case of larger aneurysms with outward growth. Subtemporal retraction may also not be possible if there is previous hemorrhage and severe adhesion, which risks the aneurysm to intraoperatively rupture. Further, once the aneurysm ruptures during the operation, it is difficult to control because the proximal parent artery is blocked, especially when the aneurysm is large. Therefore, for this kind of aneurysm, a combined pterional and subtemporal with temporal lobe resection is preferred. Such an approach enables proper brain relaxation by drainage of CSF through the suprasellar cisterns and sometimes the lamina terminalis and enables proximal control of the PCA or the PComA.^[10] This resection should probably be considered akin to resection of the gyrus rectus performed routinely with anterior communicating artery aneurysm.

Conclusion

In the era of endovascular neurosurgery, aneurysms of the PCA can be safely clipped with microsurgical techniques. The added advantage of relieving mass effect in this critical area and complete occlusion is unparalleled with micro-neurosurgery. Adequate exposure with combined pterional and subtemporal exposure with resection of inferior temporal gyrus can minimize intraoperative and postoperative complications.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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