AUTHOR(S): Chehrazi, B. Barry, M.D. Department of Neurological Surgery, University of California, Davis, Sacramento, California Neurosurgery 30; 957-961, 1992 ABSTRACT: Operative management of cerebral aneurysms remains a technically challenging problem in modern neurosurgery despite major advances in microsurgical techniques. This is largely caused by the difficulty of exposing and handling these aneurysms, which are located around the circle of Willis at the base of the brain. Large cranial windows, generous brain retraction, and local brain resection have, at times, been employed to overcome these difficulties. In the present report, an exclusively temporal approach to the anterior aspect of the circle of Willis for surgical treatment of aneurysms arising from the anterior circulation is described. This approach limits the surgical preparation and the craniotomy to the temporal area, protects the temporal branch of the facial nerve from injury, and provides a superior cosmetic appearance soon after surgery. It provides a lateral transsylvian exposure to the base of the brain and thus permits the safe dissection and exposure of the aneurysms using microsurgical techniques with minimal, if any, retraction of the frontal lobe. The need for routine resection of the gyrus rectus for exposure of anterior communicating artery aneurysms is alleviated. This approach can be considered in patients harboring large or small incidental or acutely ruptured anterior circulation aneurysms. The outcome of 96 consecutive patients who underwent this procedure is described to illustrate its safety and effectiveness. KEY WORDS: Aneurysm; Subarachnoid hemorrhage; Transsylvian approach INTRODUCTION Since the historical report of an operation for intracranial aneurysms via the subfrontal approach by Dott (4) in 1933, a number of craniotomy flaps have been devised for the surgical approach to anterior circulation aneurysms (5,9,18). In 1944, Dandy (3) reported on a frontotemporal flap for access to intracranial aneurysms (Fig. 1). Kempe (14) popularized a modification of Dandy's flap. By removing the lateral sphenoid bone, Yasargil (21) and Yasargil et al. (22) introduced the frontotemporosphenoidal craniotomy, which they termed the pterional approach. Brock and Dietz (2) demonstrated the feasibility of a subfrontal approach through a small craniotomy in elective treatment of selected aneurysms. In the approach to anterior circulation aneurysms, most surgeons utilize the pterional approach and proceed with primary frontal

lobe retraction (5,6,11). Yasargil (22) has emphasized the value of opening the medical aspect of the sylvian fissure in reducing the injury of brain retraction. The present report describes a lateral transsylvian approach through a small craniotomy placed beneath the temporalis muscle. This approach provides adequate access to the anterior aspect of the circle of Willis for management of aneurysms arising from the anterior circulation. The small craniotomy limits the surgical preparation and incision to the preauricular temporal region, and the intrafascial dissection protects the temporal branch of the facial nerve from injury (Fig. 2). The low-lying angle of approach along the skull base made possible by the extensive opening of the sylvian fissure minimizes the need for retraction in the management of even difficult aneurysms. The temporal transsylvian exposure obviates the need for routine resection of the gyrus rectus in surgery of aneurysms arising from the anterior communicating artery (ACA). The potential for this procedure has been evaluated in 96 consecutive patients treated at the Neurosurgical Service at the University of California, Davis Medical Center, with acute or incidental anterior circulation aneurysms. This approach can be considered for the management of all anterior circulation aneurysms. SURGICAL PROCEDURE Preparation After general anesthesia has been achieved, a lumbar spinal catheter is inserted for the intraoperative drainage of the cerebrospinal fluid (CSF). The patient is placed in the supine position on the operative table, and the head is secured in a Mayfield skull clamp as described by Yasargil et al. (22) for the pterional approach. The hair is shaved anterior to the ear, over the temple and extending up toward the superior temporal line (Fig. 3A). Incision and muscle dissection The skin incision extends superiorly from the zygomatic arch, 1 cm anterior to the auricle, and curves anteriorly over the temple toward the anterior extent of the superior "keyhole" (Fig. 2). In individuals with a receding hairline, the anterior limb of the incision is extended into the non-hair-bearing temporal scalp parallel with the skin creases, and a subcuticular reapproximation of this portion of the incision is performed at closure. The skin incision is extended deep to the superficial fascia of the temporalis muscle, which is reflected anteriorly with the skin flap and placed under traction with fishhooks. The temporalis muscle is incised along its anterior border just behind the orbital rim and the frontal process of the zygomatic bone down to the horizontal section of the zygomatic arch. One or two Cushing subtemporal retractors are secured to the base of the Greenberg retractor set (Codman & Shurtleff, Inc., Randolph, MA) with rubber bands, and these are used to retract the skin flap, temporalis fascia, and the anterior portion of the temporalis muscle anteriorly to provide full exposure of the base of the greater wing of the sphenoid bone. The

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Neurosurgery 1992-98 June 1992, Volume 30, Number 6 957 A Temporal Transsylvian Approach to Anterior Circulation Aneurysms Technical Note

Craniotomy A single burr hole is centered over the exposed wing of the sphenoid. The dura over the temporal and frontal aspects of the sphenoid wing is exposed through this burr hole and a small (3 × 4 cm) free bone craniotomy is performed (Fig. 1). The craniotomy is centered over the sylvian fissure (Fig. 4). The remainder of the sphenoid wing is removed with a curved narrow-tip Beyer rongeurs (Codman, Johnson & Johnson Co., Randolph, MA) until the bone starts to turn toward the anterior clinoid. There is a wide variation in the size and thickness of the greater wing of the sphenoid, and, at times, a portion of the periorbita may be exposed to obtain adequate bony resection. The orbital rim, however, is preserved. The dura is opened in a Yshaped fashion with its posterior limb located over the sylvian fissure and the anterior limbs extending in frontal and temporal directions. This creates a triangular portion of the dura, which is snugly draped over the resected greater wing of the sphenoid (Fig. 4). Sylvian fissure dissection By starting over the convexity, about an inch posterior to the separation of the frontal and temporal lobes, and working anteriorly, the surgeon can take down the arachnoid over the sylvian fissure under operative magnification by sharp dissection with a number 59S Beaver blade (Rudolph Beaver Inc., Waltham, MA). The arachnoidal dissection is carried out on the frontal side of the middle cerebral veins. The dissection is extended into the fissure toward the incisura. Exposure of the vessels within the sylvian fissure is obtained by gentle retraction on a cottonoid by the tip of the neurosurgical sucker, which is maintained at about 10 mm Hg negative pressure during the surgery. Care is taken to follow the course of the middle cerebral artery candelabra within the fissure and not to injure the frontal or temporal cortex. Deep within the sylvian fissure, the frontal lobe often protrudes laterally, indenting the temporal lobe. Failure to recognize this anatomical variation may result in an inadvertent injury to the frontal lobe. Mannitol and hyperventilation are used to obtain brain relaxation during this portion of the procedure. The drainage of the CSF from the indwelling lumbar subarachnoid catheter is delayed until the dissection of the sylvian fissure is well advanced to avoid collapse of the subarachnoid spaces within the sylvian fissure, which would slow down the dissection. Once the fissure has been opened to a depth of about 2 cm, 50 to 100 ml of the CSF is drained, and the self-retaining Greenberg retractors are placed within the opened sylvian fissure over the frontal and temporal opercula to maintain exposure. In this fashion, a line of vision is established to the base of the brain through a pyramidal space based on the dura overlying the resected sphenoidal wing.

Aneurysm exposure The posteromedial extent of the sylvian fissure dissection exposes the petroclinoid ligament. The operative microscope is now angled in an anterosuperior direction to expose the arachnoid overlying the carotid artery and the optic nerve. Arachnoidal adhesions are taken down, the carotid cistern is opened, and the carotid artery is isolated for proximal control. With further dissection of the arachnoid, as needed, the posterior communicating artery, choroidal artery, carotid artery bifurcation, and both anterior cerebral arteries may be visualized. The ACA region is exposed by gently lifting the frontal lobe. There is no need for the resection of the gyrus rectus, since the line of vision to this region is through the temporal fossas, well below the floor of the anterior fossa. For aneurysms arising from the middle cerebral artery bifurcation, the opening of the sylvian fissure is limited to its anterior extent until the carotid or the proximal middle cerebral has been isolated. Dissection is then extended posteriorly within the sylvian fissure to expose the aneurysm and the middle cerebral artery branches. This approach provides an adequate space for the resection of the anterior clinoid process, when necessary, in the exposure of carotid-ophthalmic artery segment aneurysms. The isolation of the aneurysm neck is carried out under temporary clipping of the feeding vessel. The duration of temporary clipping is limited to 8 minutes and is usually less than 5. The small size of this bony opening can make application of the aneurysm clip difficult. The direction of the operating microscope may need to be readjusted during clip application so the view of the aneurysm neck and the clip blades is not obstructed. With the use of temporary clips, electrocoagulation of the aneurysm neck, and variangle clip appliers such as Sano (Mizuho Ikakogyo Co., Bunkyoku Tokyo, Japan), we have been successful in clipping all aneurysms arising from the anterior circulation by this approach. Closure After the closure of the dura, the free bone flap is secured in place with wire sutures. Bone chips, sandwiched between two layers of Surgicel, are used to fill the defect resulting from the resection of the sphenoid bone. The temporalis muscle and fascia are then reapproximated separately, and a local wound dressing is applied after a two-layer closure of the scalp. SUMMARY OF PATIENTS Illustrative patient This 48-year-old, right-handed woman was referred for treatment of a ruptured anterior communicating artery aneurysm 1 week after the sudden onset of severe headaches, dizziness, and loss of consciousness. On arrival, she was Grade I. Cerebral angiography revealed an anteroinferiorly pointing aneurysm arising from the ACA (Fig. 5A). Additionally, there was an incidental aneurysm at the junction of the left internal carotid and ophthalmic

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temporalis muscle is reflected off the skull with a periosteal elevator in a posteroinferior direction. The pterion and the entire greater wing of the sphenoid bone over the skull are exposed.

Other patients Ninety-six patients with cerebral aneurysms were treated by the temporal transsylvian approach to the anterior aspect of the circle of Willis (Table 1). There were 54 women and 42 men, with an average age of 55 and 48 years, respectively. The aneurysms were located around the internal carotid artery in 34% of patients, middle cerebral artery in 26%, and ACA in 25%. Seventy-eight patients had suffered a subarachnoid hemorrhage; 80% of these sought treatment within 3 days of the hemorrhage and 91% within 1 week. Based on the scale of Botterell et al. (1) , their clinical grades on admission were 50% Grade I, 6% Grade II, 22% Grade III, 19% Grade IV, and 3% Grade V. The time from the subarachnoid hemorrhage to surgery varied; however, 72% were operated on within 2 weeks of the hemorrhage. The outcome at a 6-month follow-up was assessed by an independent observer based on the Glasgow Coma Outcome score (13) (Table 1). Eighteen of the 96 patients had elective surgery for incidental aneurysms during this time, and 95% had a good recovery. In comparison, 45 of the patients with subarachnoid hemorrhages did not develop clinical vasospasm during their hospital stay, and 96% had a good recovery or moderate deficit at follow-up (Table 1). One patient died secondary to the rupture of an undiagnosed aneurysm of the posterior inferior cerebellar artery. There were two cases of postoperative palsy of the temporal branch of the facial nerve, one of which was transient. There were no wound complications. Patients had a satisfactory cosmetic appearance by discharge. DISCUSSION A number of authors have reported their experiences with the approach to intracranial aneurysms arising from the anterior circulation (7,8,10, 12,15,16,17,19,22) . The frontotemporal approach initially reported by Dandy (3) employed a large, mainly frontal craniotomy and a lateral subfrontal exposure along the sylvian fissure (Fig. 1). Kempe (14) modified this craniotomy in a more temporal direction and utilized a more temporal exposure along the sylvian fissure, coagulating the temporal basal veins and retracting the temporal pole. The "microtechnical pterional approach" popularized by Yasargil et al. (22) utilized a miniature of Kempe's frontotemporal craniotomy by limiting its posterior extent and adding the extensive resection of the lateral aspect of

the sphenoid wing. It employed a microscope for a lateral subfrontal approach along the sylvian fissure, with the opening of the arachnoid over the medical aspect of the sylvian fissure to reduce the retraction on the frontal lobe (22). The temporal lobe had to be retracted occasionally for internal carotid aneurysms, and a portion of the gyrus rectus was resected for ACAs. Sano (20) reported on a small osteoplastic frontotemporal craniotomy with an intradural approach similar to that of Yasargil. Through a small, laterally placed frontal craniotomy, Brock and Dietz (2) described a purely subfrontal approach in the treatment of small and medium-sized aneurysms with a well-defined neck. They favored this route for its limited bony resection and protection of the sylvian veins. The present approach utilizes a skin incision that is limited to the temporal area and a small craniotomy that is placed inferior and lateral to the superior temporal line and is effectively covered by the temporalis muscle. The dissection of the sylvian fissure separates the frontal and temporal lobes, and the basal exposure is obtained through the sylvian fissure with a line of vision that is more inferior than the floor of the frontal fossa. This exposure further reduces the need for frontal lobe retraction. It obviates the need for the resection of the gyrus rectus on the approach to ACAs and offers the advantage of exposing and treating all aneurysms of the anterior circulation by the same microsurgical technique. The small temporal skin incision keeps cosmetic disruption to a minimum, which is especially satisfying to patients undergoing surgery for incidental aneurysms, and the reduced need for brain retraction provides for a very satisfactory neurological outcome. Received for publication, May 3, 1991; accepted, final form, November 25, 1991. Reprint requests: B. Barry Chehrazi, M.D., Department of Neurological Surgery, University of California, Davis, 2516 Stockton Blvd., 2nd Floor, Sacramento, CA 95817. REFERENCES: (1-22) 1.

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Botterell EH, Lougheed WM, Morley TP, Vandewater SL: Hypothermia in the surgical treatment of ruptured intracranial aneurysms. J Neurosurg 15:4-18, 1958. Brock M, Dietz H: The small frontolateral approach for the microsurgical treatment of intracranial aneurysms. Neurochirurgia (Stuttg) 21:185-191, 1978. Dandy WE: Intracranial Arterial Aneurysms . New York, Comstock, 1944. Dott NM: Intracranial aneurysms: Cerebral arterio-radiography: Surgical treatment. Edinb Med J 40:219-234, 1933. Fein JM: Internal carotid posterior communicating artery aneurysms, in Fein JM, Flamm ES (eds): Cerebrovascular Surgery. New York, Springer-Verlag, 1985, vol 3, pp 874-884.

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arteries. A left-sided transsylvian approach was undertaken for the simultaneous treatment of both aneurysms (Fig. 3A). Sylvian fissure exposure was obtained through a temporal minicraniotomy (Fig. 4). After the successful clipping of the ruptured ACA aneurysm, the left anterior clinoid was resected, and the external ring of the carotid artery was dissected for the clipping of the left ophthalmic artery aneurysm. Postoperative angiography revealed the obliteration of both aneurysms (Fig. 5B). Skin sutures were removed at her follow-up visit in 1 week (Fig. 3B).

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Flamm ES: Anterior cerebral artery aneurysms, in Fein JM, Flamm ES (eds): Cerebrovascular Surgery. New York, Springer-Verlag, 1985, vol 3, pp 885-892. Flamm ES: Aneurysm of internal carotid and anterior communicating arteries, in Wilkins RH, Rengachary SS (eds): Neurosurgery. New York, McGraw-Hill, 1985, pp 1394-1404. Fox JL: Craniotomy for aneurysms, Intracranial Aneurysms. New York, SpringerVerlag, 1983, vol 2, pp 750-799. Fox JL: Management of aneurysms of anterior circulation by intracranial procedures, in Youmans JR (ed): Neurological Surgery. Philadelphia, Saunders, 1990, ed 3, vol 2, pp 1708 1722. French LA, Ortiz-Saurez HJ: Anterior communicating artery aneurysms: Technique of operation and results. Clin Neurosurg 21:115-119, 1974. Guidetti B, Nicole S: Carotid-ophthalmic aneurysms, in Fein JM, Flamm ES (eds): Cerebrovascular Surgery. New York, Springer-Verlag, 1985, pp 828-831. Heros RC, Ojemann RG, Crowell RM: Superior temporal gyrus approach to middle cerebral artery aneurysms: Technique and results. Neurosurgery 10:308-313, 1982. Jennett B, Teasdale G, Braakman R, Minderhound J, Heiden J, Kurze T: Prognosis of patients with severe head injury. Neurosurgery 4:283-289, 1979. Kempe LG: Cranial cerebral and intracranial vascular disease, Operative Neurosurgery, Berlin, Springer-Verlag, 1968, vol 1, pp 1-75. Krayenbuhl H, Yasargil MG, Flamm ES, Tew JM Jr: Micro- surgical treatment of intracranial saccular aneurysms. J Neurosurg 7:678-686, 1972. Peerless SJ: The surgical approach to middle cerebral and posterior communicating aneurysms. Clin Neurosurg 21:151-165, 1974. Pool JL: Bifrontal craniotomy for anterior communicating artery aneurysms. J Neurosurg 36:212-220, 1972. Pool JL, Potts DG: Methods of treatment, Aneurysms and Arteriovenous Anomalies of the Brain. New York, Harper & Row, 1965, pp 207-208. Rhoton AL Jr: Anatomy of saccular aneurysms. Surg Neurol 14:59-66, 1980. Sano K: Surgery of arterial aneurysms of the brain. Brain Nerve 23:1252-1264, 1971. Yasargil MG: Interfascial pterional (Frontotemporosphenoidal) craniotomy, Microneurosurgery. New York, ThiemeStratton, 1984, vol 1, pp 215-233. Yasargil MG, Fox JL, Ray MW: The operative approach to aneurysms of the anterior communicating artery, in Krayenbuhl H (ed): Advances and Technical Standards in Neurosurgery. New York, Springer-Verlag, 1975, vol 2, pp 113-170.

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6.

Figure 2. Comparison of skin incisions used in selected approaches to anterior circulation aneurysms.

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Figure 1. Comparison of selected craniotomies for the approach to aneurysms arising from the anterior portion of the circle of Willis. A, Dandy (3); B, Kempe (14); C, Yasargil (21); D, Brock (2); E, Chehrazi.

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Figure 3. A, skin incision demarcated for the transsylvian approach for a ruptured ACA aneurysm and an incidental left carotid-ophthalmic aneurysm. B, patient's appearance 1 week postoperatively.

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Figure 4. A, left temporal minicraniotomy centered around the sylvian fissure. B, artist's depiction. A Cushing subtemporal retractor (c) provides for adequate exposure over the resected greater wing of the sphenoid. A Y-shaped opening in the dura (d) exposes the frontal (fl) and temporal (tl) opercula. The superficial temporalis fascia (TF) is reflected anteriorly with the scalp; the temporalis muscle (TM) is reflected posteriorly off the skull (S).

Table 1. Outcome of Temporal Transsylvian Approach in Treatment of Anterior Circulation Aneurysms at 6 Months

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Figure 5. A, preoperative angiogram demonstrates an anteroinferiorly pointing ACA aneurysm and a small internal carotid-ophthalmic artery aneurysm. B, postoperative angiogram demonstrates adequate clipping of both aneurysms. Wire sutures demarcate the craniotomy.

A temporal transsylvian approach to anterior circulation aneurysms.

Operative management of cerebral aneurysms remains a technically challenging problem in modern neurosurgery despite major advances in microsurgical te...
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