Clipping of Basilar Trunk Aneurysm - Case Report -

Clipping of Basilar Trunk Aneurysm

- Case Report -

Tai-Ki Yang, M.D., Chul-Jin Kim, M.D., Byung-Jo, Ahn M.D.

Department of Neurosurgery, Chonbuk National UniversitySchool of Medicine, Chonju, Korea

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= ^Abstract ====

뇌기저동맥 체간부에 발생한 뇌동맥류 결찰술

전북대학교 의과대학 신경외과학교실 양태기·김철진·안병조

neurysm of the basilar artery trunk are rare and the surgical approach is very difficult because of the complexity of surgical anatomy around the basilar trunk and the vulnerable adjacent neurovascular structures. The develop- ment of brain CT and MRI makes the accurate diagnosis and produces the improvement of surgical approaches at the lesion of the skull base. One of the surgical approaches of basilar trunk aneurysms, the retrolabyrinthine presi- gmoid transtentorial transpetrosal approach to the aneurysm of the basilar trunk has some advantages of minimal retraction of cerebellum and temporal lobe, intact auditory and facial nerve function by the preservation of the vesti- bulocochlear and facial nerves, a preservation of sigmoid sinus and vein of Labbe and a relatively good operation field. We had a good result with this approach for the patient of basilar trunk aneurysm and reported the case with the review of literatures.

KEY WORDS：Basilar trunk aneurysm・Retrolabyrinthine presigmoid transtentorial transpetrosal approach.

Introduction

Aneurysms of the basilar artery trunk are very rare and these represent a surgical challenge because of the direct proximity of highly vulnerable neural structures such as the brain stem and cranial nerves. A direct approach to this aneurysm is often blocked by the petrous bone. A number of approaches have been attempted over the years to gain this lesion. Only recently have lateral approaches, such as the anterior transpetrosal⁸⁾, the retrolabyrinthine-transsig- moidal¹⁾ and the combined supra/infratentorial-posterior transpetrosal approaches⁷⁾ been reported for surgery of basilar trunk and vertebrobasilar aneurysms. The combined approach stems from the Fraenkel and Hunt description in 1904 of a suboccipital-translabyrinthine approach²⁾. In 1939, Bailey described a combined supratentorial-infratentorial

approach¹⁾, incorporating incision of the tentorium and ligation of the sigmoid sinus. Morrison and King⁸⁾ used a combined subtemporal and translabyrinthine approach for a acoustic tumor. This approach provides the following ad- vantages：1) the cerebellum and temporal lobes are mini- mally retracted；2) the operative distance is shortened；

3) the surgeon has a direct line of sight to the lesion and the anterior and lateral aspects of the brain stem；4) the neural and otologic structures, including the cochlea, laby- rinth, and facial nerves are preserved；5) the transverse and sigmoid sinuses, as well as Labbe’s vein and the basal and occipital veins are preserved；6) multiple axes for dissection are provided⁹⁾. We present our experience of one patient of basilar artery trunk aneurym in which we operated via retrolabyrinthine presigmoid transtentorial tranpetrosal approach.

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Case Report

This 30 year-old-male patient suffered a severe mental deterioration. On admission to our hospital, he was graded as Hunt and Hess grade 5 and showed a severe subarach- noid hemorrhage on brain CT.

In past history, he had been admitted to local clinic due to psychological problems for 2-3 months. On neurological examination, he showed a comatous mentality, isocoric pupil, and Babinski’s sign was positive. The initial angiogram taken on the admission showed a saccular form aneurysm in the midportion of the basilar trunk and a marked vasospasm (Fig. 1). The combined supura/infratentorial transpetrosal approach was made three months later at Hunt and Hess grade 3 and obtained satisfactory results after clipping of aneurysm.

1. Operation

The patient was taken to the operation room. Under left lateral position, an L-shaped incision was used, starting in the temporal region slightly above the ear, curving poster- iorly and finishing parallel and slightly below the mastoid process. The temporal and suboccipital musculature was incised and retracted together with the scalp using fishhooks and self-retaining retractors, so as to expose the temporo- basal and lateral suboccipital skull as well as the complete

mastoid process. A combined supura/infratentorial cranio- tomy is performed. After the bone flap has been elevated, complete unroofing of the sigmoid sinus was accomplished with the aid of a high speed drill. This was followed by a radical posterior petrosectomy to gain sufficient exposure of the presigmoid dura from the superior petrosal sinus to the level of the jugular bulb by ENT teams(Fig. 2). Upon completing the extradural bone work, the temporal dura was incised parallel to the transverse sinus and floor of the temporal fossa. After that, the presigmoid dura was incised up to the superior petrosal sunus, which was ligated and cut.

The temporal lobe was slightly elevated and the tentorium was transected parallel to the petrous bone preserving trochlear nerve and the vein of Labbe. After the tentorium had been cut completely, the sigmoid sinus and the rem- aining portion of the tentorium were retracted by a self- retaining retractor, exposing the clival and juxtaclival region along with the basilar artery from the upper basilar region down to the level of the vertebrobasilar junction and ipsilateral vertebral artery. After proximal and distal con- trol of the aneurysm-bearing vessel had been achieved, the origin of the aneurysm was dissected and clipped using a standard straight aneurysm clip. Watertight closure of the dura was achieved using a fascial and muscular graft aug- mented by fibrin glue. The bone flap was repositioned and secured with wire. The craniectomy defect was filled with

Fig. 1. A and B. Preoperative AP (A) and lateral(B) views of verte- bral angiograms showing a protr- uded saccular aneurym directed anterior, superior on the basilar trunk and marked vasospasms on the proximal, distal portion of ba- silar artery and vertebral artery.

Fig. 2. A and B. A：Drapping and skin incision marking. B：Mastoid- ectomy and the exposure of the dura；complete mastoidectomy was done for preserving the la- byrinth. The middle fossa dura(T) and the posterior fossa(P) were exposed.

A AA

A BBBB

AAA

A BBBB

a pedicled temporalis muscle flap. A subcutaneous drain was inserted and the surgical skin wound was closed.

2. Postoperative course

The patient awoke from anesthesia unchanged from the preoperative conditions. The postoperative angiography taken on operation day showed the aneurysmal sac and ba- silar artery had been clipped because of stenosis of basilar artery by clip(Fig. 3). However, the blood flow from an- terior circulation was visualized well to the level of clip through posterior communicatin artery. The postoperative course was uneventful. The patient developed a hydroce- phalus in follow up brain CT. So ventriculoperitoneal shunt was done. The patient was discharged with no other neu- rological aggravation.

Discussion

Surgery of aneurysms of the basilar trunk performed via routine supra- or infra-tentorial approaches is fraught with the difficulty of working through an extremely long and narrow tunnel bordered by bone and highly vulnerable neu- rovascular structures as well as the additional necessity of

retracting the temporal lobe, cerebellum, and brain stem to gain access to the aneurysm. The advantage of aggressive removal of the mastoid and petrous bone lies in the fact that a completely flat and tangential approach to clival and juxtaclival region parallel to the cranial nerves may be made while almost completely avoiding retraction of neural tissue⁵⁾¹⁰⁾.

The supra/infratentorial transpetrosal approach, which has gradually developed as a combination from standard otosurgical and neurosurgical approaches, stands as an ex- cellent example of the advance in skull base surgery⁴⁾⁷⁾⁸⁾. The first description of a combined supra/infratentorial approach to vertebrobasilar aneurysms was presented by Kasdon and Stein⁵⁾ in 1979. Their approach include transection of the transverse sinus. After reviewing the surgical techniques of transpetrosal exposure used by Morrison and King⁷⁾ and Hakuba⁵⁾ and coworkers, Hashi⁴⁾ et al. refrained from tra- nsection of the sigmoid sinus. Instead, after performing a posterior petrosectomy with sparing of the hearing and exposure of a limited area of the presigmoid dura, they di- vided the superior petrosal sinus, transected the tentorium, and exposed the vertebrobasilar area. Kawase and cowor-

Fig. 3. A and B：Postoperative angiography. A：AP(A1) and lateral(A2) view of vertebral angiogram demonstrating a clipping of aneurymal sac and basilar artery trunk. B：AP(B1) and lateral(B2) views of right side ICA showing a good blood flow to posterior cerebral artery and to clipping site of basilar artery aneurysm via posterior communicating artery.

A1 A1 A1

A1 A2A2A2A2 B2B2B2B2

B1 B1 B1 B1

kers⁶⁾ described their experience using an anterior trans- petrosal approach directed through the middle fossa and Kawase’s triangle for aneurysms of the lower basilar artery in two patients. Rosenberg and coworkers⁹⁾ reported on three patients with aneurysms of the vertebrobasilar circulation who were operated on via a retrolabyrinthine-transsigmoidal approach. Spetzler et al.¹⁰⁾ presented their surgical results of vertebrobasilar circulation aneurysms obtained using a combined supra/infratentorial approach.

Our experience with the use of the transpetrosal route for basilar trunk was in agreement with data from the literature.

However, the use of this petrosal approach must be con- sidered cautiously and weighed against the application of other more routine approaches to vertebrobasilar aneurysms.

All aneurysms of the upper third of the basilar trunk are relatively easily accessible by either the pterional or the subtemporal approach, and most aneurysms of the vertebral artery can be satisfactorily reached by the far lateral trans- condylar approach；however aneurysms of the lower basilar trunk and vertebrobasilar junction are located in a sort of no man’s land. In this region, supra-or infratentorial appro- aches can only be applied with considerable difficulty and risk of damage to the neighboring neurovascular structures of the brain stem and cranial nerves. With the complex anatomy of the petrous bone and better experiences in skull base approaches, the application of this approach for opera- tion of selected vertebrobasilar aneurysms is straightforward, without relevant approach-related complications and follow- ing anatomical closure of the petrosectomy defect, produces an excellent cosmetic result.

The authors can emphasize the usefulness of this retrola- byrinthine presigmoid transtentorial transpetrosal approach in order to obtain enough exposure and space and in order to preserve hearing and labyrinthine function for clipping of the basilar trunk artery aneurysm.

• 논문접수일：2001년 5월 10일

• 심사완료일：2001년 9월 14일

• 책임저자：김 철 진

561-712 전북 전주시 덕진구 금암동 634-18 전북대학교 의과대학 전북대학교병원 신경외과학교실 전화：063) 250-1879, 전송：063) 250-1879 E-mail：[email protected]

References

1) Bailey P：Concerning the technique of operation for acoustic neurinoma. Zentralbl Neurochir 4：1-5, 1939

2) Fraenkel J, Hunt JR：Contribution to the surgery of neurofib- roma of the acoustic nerve. Ann Surg 40：293-319, 1904 3) Hashi K, Nin K, Shimotake K：Transpetrosal combined su-

pratentorial and infratentorial approach for midline vertebro- basilar aneurysms. Mod Neurosurg 1：442-448, 1982 4) Hakuba A, Nishimura S, Inoue Y：Transpetrosal-transtentorial

approach and its application in the therapy of retrochiasmatic craniopharyngiomas. Surg Neurol 24：405-415, 1985 5) Kasdon DL, Stien BM：Combined supratentorial and infraten-

torial exposure for low-lying basilar aneurysms. Neurosurgery 4：422-426, 1979

6) Kawase T, Toya S, Shiobara R, Bertalanffy H, Otani M：

Transpetrosal approach for aneurysms of the lower basilar artery. J Neurosurg 63：857-861, 1985

7) Malis LI：Surgical resection of tumors of the skull base, in Wilkins RH, Rengachary SS(eds)：Neurosurgery. New York： McGraw Hill, 1985, Vol 1, pp1011-1021

8) Morrison AW, King TT：Experiences with a translabyrinthine- transtentorial approach to the cerebellopontine angle. Techni- cal note. J Neurosurg 38：382-390, 1973

9) Rosenberg SI, Flamm ES, Hoffer ME, Schwartz DM：The retrolabyrinthine transsigmoid approach to midbasilar artery aneurysms. Laryngoscope 102：100-104, 1992

10) Spetzler RF, Daspit CP, Pappas CT：The combined supra- infratentorial approach for lesions of the petrous and clival regions：experience with 46 cases. J Neurosurg 76：588-599, 1992

뇌기저동맥 체간부에 발생한 뇌동맥류 결찰술

전북대학교 의과대학 신경외과학교실 양태기·김철진·안병조

= 국 문 초 록 =

뇌기저동맥 체간부에 존재하는 동맥류는 매우 희귀하며 그 수술적 치료는 복잡한 해부학적 구조와 근접해있는 중요한 신경혈관 구조때문에 수술적 접근이 매우 어려운 부위이다.

산화 단층촬영과 자기공명영상의 발달은 두개저 병변을 정확히 진단할 수 있게 하였고 두개저 부위의 수술적 접 근에 많은 발전을 가져오게 하였다. 뇌기저동맥 체간부에 존재하는 동맥류의 수술 방법중의 하나로 저자들은 소뇌 와 측두엽의 견인이 적어 소뇌 부종을 극소화 할 수 있고 와우, 미로, 안면신경등의 구조물을 보존하여 청력손실, 안 면신경마비등의 합병증이 없고 횡정맥동, S상정맥동의 보존뿐만 아니라 Labbe’s 정맥을 보존할 수 있으며 수술시 야가 비교적 좋은 장점들이 있는 후미로 전S상정맥동 경천막을 통한 추체로접근법을 이용하여 뇌기저동맥 체간부 에 발생한 동맥류의 직접 결찰수술을 시행하여 좋은 결과를 얻었기에 문헌고찰과 함께 보고하는 바이다.

중심 단어：뇌기저동맥 체간부 동맥류・후미로 전S상정맥동 경천막을 통한 추체로접근법.