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Single flap fronto-temporo-orbito-zygomatic craniotomy for skull base lesions. Correspondence Address:
Surgery was performed, through single flap fronto-temporo-orbito-zygomatic approach in 22 patients with skull base lesions. In two of these patients, this approach was combined with a transpetrosal approach. The pathological spectrum consisted of trigeminal neurofibromas (5), spheno-orbital meningiomas (4), carotico-ophthalmic aneurysms (4), basilar top aneurysms (2), cavernous sinus haemangiomas (2), invasive pituitary tumours (2) and one patient each of metastatic adenocarcinoma of the cavernous sinus, transcranial fungal granuloma and tubercular granuloma of the cavernous sinus. Of the 14 tumours, 10 were excised totally/near totally while a subtotal excision was achieved in four. Removal of the anterior clinoid process facilitated the clipping of all the carotico-ophthalmic aneurysms. One basilar top aneurysm was wrapped and the other clipped. One patient of fungal granuloma died of fungal meningitis and one patient of basilar top aneurysm expired as a result of thalamic infarct. The advantages of this approach included excellent exposure of the skull base lesions, making the dissection distance shorter and wider, minimal brain retraction and easy replacement of the single bone flap.
The orbito-zygomatic approach for skull base lesions of middle cranial fossa and upper part of clivus has become established.[1],[2],[3],[4] Since the original description of this approach,[5],[6] several modifications have been reported.[1],[7],[8],[9],[10],[11],[12],[13],[14],[15] In most of these, the orbito-zygomatic bony removal is done as a separate osteotomy from the frontal or fronto-temporal craniotomy flap.[1],[3],[5],[9],[10],[13],[14],[15]The reports of a single bone flap removal are only few.[2],[4],[11],[12] We describe our experiences with the single flap fronto-temporo-orbito-zygomatic craniotomy for a variety of skull base lesions consisting of tumours, aneurysms and granulomas.
The fronto-orbito-zygomatic approach was utilised for surgery of skull base lesions in 22 patients seen in 3 years (1997-1999). The pathological spectrum of these lesions is depicted in [Table I]. Operative Technique : The patient is placed supine. The head is rotated 45o to the opposite side of lesion so that the malar prominence is superior most. In addition, the neck is slightly extended and the head end elevated by about 20o. The head is fixed in the Sugita multipurpose head frame. At the time of skin incision, mannitol (1 gm/kg) is given to make the brain lax. The scalp incision begins just below the inferior border of the zygomatic arch in front of tragus. It curves superiorly and anteriorly just within the hairline upto the midline. On occasions when the hairline is posterior, the incision extends upto the opposite midpupillary line. The scalp flap is reflected anteriorly in 2 layers, preserving the pericranial flap for later use in dural closure, if necessary. In order to avoid damage to the branches of the facial nerve, the incision is not extended beyond 1 cm below the inferior border of the zygoma. The scalp flap is reflected exposing the fronto-temporal bone, the superior and lateral orbital rims and the zygomatic arch upto its roots. The extent of exposure of the malar prominence and the lateral part of the inferior orbital rim depends upon the lesion. Anterior dissection is done deep to the superficial temporalis fascia to avoid damage to the frontal branches of the facial nerve. The periorbita is gently separated from the superior and lateral orbital walls. The supraorbital neurovascular bundle is released either with a drill or a fine chisel and retracted along with the periorbita. Both the superior and inferior surfaces of the zygomatic arch are exposed by sharp dissection of the deep temporalis fascia. The temporalis muscle and fascia are incised along the superior temporal line, leaving behind a narrow myofascial cuff for reapproximation. The temporalis muscle and fascia are reflected over the zygoma at this stage. Burr holes are made and craniotomy is performed as shown in [Figure] [Figure. 1a] and [Figure 1b]. The midline anterior burr hole is extended into the orbital roof. Bony cuts are made in the roof of the orbit with fine chisels, as posterior as possible. This cut is extended to the lateral orbital wall and the malar prominence [Figure. 1a] and [Figure 1b]. The periorbita is protected with brain retractors during this procedure. The temporalis muscle and fascia are reflected back and zygomatic osteotomy is done just near its roots. The bone in the region of the sphenoidal ridge is nibbled. The entire bone flap is elevated as a single piece after fracture at the sphenoidal ridge [Figure. 2]. The region of the lesser wing of sphenoid is rongeured to expose the superior orbital fissure. In cases of carotico-ophthalmic aneurysms, the anterior clinoid process is drilled away. The temporal bone in the region of middle fossa floor is also rongeured to provide better and shorter access to the region of cavernous sinus and to the basilar top aneurysms. At the time of closure, if necessary, the pericranial flap and the temporal muscle and fascia are available for basal dural repair. The bone flap is replaced and fixed with vicryl sutures. The temporalis muscle and fascia are stitched back to the myofascial cuff. A subgaleal drain is kept for 48 hours.
Out of 14 tumours, 10 were excised totally/near totally while a subtotal excision was achieved in 4 patients with invasive pituitary adenomas and cavernous sinus haemangiomas.[2] In pheno-orbital meningiomas [Figure. 3], coagulation of the basal dura before dural opening reduced the tumour vascularity to a great extent. Two of the five trigeminal neurinomas were removed using a pure extradural approach. There were two giant dumb-bell trigeminal neurofibromas for which a combined fronto-orbito-zygomatic and transpetrosal approach was utilised [Figure. 4a], and [Figure. 4b]. In the patient with transcranial fungal granuloma [Figure. 5a] and [Figure. 5b], an excellent exposure of the cavernous sinus and infratemporal region was gained through the fronto-orbito-zygomatic approach and a total removal could be achieved. Removal of the anterior clinoid process extradurally facilitated the dissection of the neck of the caroticoophthalmic aneurysms, all of which were successfully clipped. One basilar top aneurysm was wrapped and one was clipped. One patient with a dumb-bell neurofibroma had a CSF leak from the wound which was managed with a lumbar drain. One patient of an invasive pituitary tumour invading the cavernous sinus had a partial 3rd nerve palsy which improved over 3 months. There were two deaths. The patient with fungal granuloma developed meningitis and died despite of antifungal (amphotericin-B + 5-fluocytosine) therapy. The second patient with basilar top aneurysm developed thalamic infarct and died.
In recent years, a large number of skull base techniques have been added to the options available to a neurosurgeon for lesions of the cavernous sinus, spheno-orbital, medial temporal and upper clival regions.[1],[2],[3],[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15] The advantages include enhanced exposure of deep lesions providing a shorter and wider view, while minimising brain retraction. Despite the advantages, these approaches are still not routinely used by neurosurgeons in neurosurgical practice. The reasons may be manifold: the impression that these approaches are required for only few select cranial lesions, the belief that these are too complicated procedures technically requiring extensive instrumentation and plating techniques and thirdly that probably these extensive procedures are really not required. Over the past three years, we have used the single flap fronto-orbito-zygomatic approach in management of various skull base lesions with satisfactory results. Hakuba et al[5] described the orbito-zygomatic infratemporal approach consisting of a fronto-orbito-temporal craniotomy, orbito-zygomatic osteotomy and sphenoid wing osteotomy, for lesions in the region of cavernous sinus. This complicated technique involved three separate muscle based bone flaps. Delashaw et al[11] raised a fronto-temporal flap incorporating superior and lateral orbital ridges as well as the frontal sinus, removing the zygomatic arch separately, for wide exposure of the anterior fossa, orbit, middle fossa and cavernous sinus. lkeda et al[4] described the orbito-zygomatic-temporopolar approach for high basilar top aneurysms, removing the fronto-orbito-zygomatic temporal flap en bloc. Although in most reports, the orbito-zygomatic flap is raised separately, we have found the single flap fronto-temporo-orbito-zygomatic osteotomy to be a technically easy and safe procedure. The bony cuts in the orbital roof can be easily and safely made with long and fine chisels without dural injury. The zygomatic arch at its roots can be divided either with a cutting drill or simply, a gigli saw. Similarly, the anterior medial burr hole can be easily extended into the orbit with a sharp fine chisel. At completion of the procedure, the bone flap is sutured in place by a few vicryl sutures, without the need for miniplates. The advantage of the single flap is that it fits back into place quite snugly and gives superior cosmetic results. Davies et al[13] reported diastasis at the bone cuts, where reabsorbable sutures had been used to fix the osteotomy sites. We had no such problem in any of our cases. Sekhar et al[9] preferred to remove the orbital bone separately because they felt that it reduced the risk of dural and periorbital injury. In addition it allowed removal of at least two thirds of the anteroposterior length of the orbital roof, a point also emphasized by Zabramski et al.[1] We agree that the single piece osteotomy entails a little more bony removal of the orbital roof, but we have not had any dural or periorbital injury. In our opinion, the obvious advantages of an easier technical procedure and refixation outweigh the disadvantages. For tumour removal, the basal view provided by this approach has many advantages. The working distance to the lesions in the parasellar and interpeduncular fossa is about 3 cm shorter and the angle to the lesions about 1-2 cm lower than the pterional or subtemporal approaches.[5] This remarkably reduces the need and degree of brain retraction required for tumour removal. For lesions involving the cavernous sinus, this approach provides a good exposure of the infratemporal fossa and therefore permits access obliquely upwards to the lateral wall of the cavernous sinus via the shortest possible distance, with minimal temporal lobe retraction.[3] In an anatomical study performed on cadavers, it was concluded that with orbito-zygomatic removal, field view angle was increased by 75% in the subfrontal approach, 46% in the pterional approach and 86% in the subtemporal approach.[10] We also found that this approach made a deep lesion apparently superficial, thus providing a wider access for surgical removal. Another advantage was in the management of vascular tumours like sphenoid wing meningioma. Coagulation of the basal dura before opening it reduced the vascularity of the tumour to a great extent, making these tumours comparatively much less vascular, thus enhancing the ease with which they could be removed. Lesoin et al[12] observed that with this approach the internal maxillary and middle meningeal arteries can be easily isolated. In recent years, there has been an increasing use of the cranial base approaches for intracranial aneurysms.[4],[9],[14],[15] Aneurysms are lesions that occur in the subarachnoid space predominantly at the base of the brain and by traditional approaches, exposure is limited. By improving the angle of the surgeon's vision and the space available for working in the pathway to the aneurysm, cranial base approaches can convert a deep and narrow exposure to a shallow and wide one.[9] These approaches were used in about 20% cases of aneurysm.[9] Their use mainly depends on the surgeon's experience with aneurysm and skull base surgery. For aneurysm of the proximal ICA, such as carotico-ophthalmic, this approach combined with removal of the anterior clinoid and the optic strut makes dissection of the dural rings and gaining proximal ICA control much easier. In a recent review of the technical aspects and recent trends in management of basilar artery aneurysms, it was concluded that the orbito-zygomatic approach has largely supplanted the pterional subtemporal approach for upper basilar aneurysms.[15] The orbito-zygomatic approach provides the surgeon a view along the length of the basilar artery, enabling a clip to be applied to the neck of the aneurysm parallel to the parent vessel. In contrast, the transpetrosal approaches confront the aneurysm from the side and typically encounter the dome of aneurysm first.[15] In both our patients with basilar artery aneurysm, the orbito-zygomatic approach helped in getting to the neck of the aneurysm directly with a wider working area.
The single flap fronto-temporo-orbito-zygomatic craniotomy is a technically simple and safe procedure not requiring any special instrumentation and plating techniques. For skull base tumours and certain aneurysms, it provides excellent exposure reducing the need for brain retraction, shortening the dissection distance and providing a wider and shallower operating field. In addition, coagulation of basal dura reduces the vascularity of sphenoid wing meningiomas remarkably.
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