ReviewSt. Marianna Med. J.

Vol. 32, pp. 219�226, 2004

Recent Advances in Surgical Approaches to Parasellar Lesions

Yoshio Taguchi, M.D.

�Received for Publication: September 15, 2004�

Key words

Surgical approaches, Parasellar lesions

Introduction

Recent advances in microsurgical instruments

and refinement of surgical techniques have made it

possible to operate the lesions situated at the medial

end of the sphenoid wing, in the third ventricle,

around the anterior tentorial hiatus, and in the

interpeduncular fossa. Although these parasellar le-

sions are commonly encountered, they may be

di$cult to expose without considerable and poten-

tially harmful brain retraction when approached by

using the conventional surgical approaches, such as

bifrontal, frontotemporal, or temporal craniotomy

developed in the era of the dawn of brain surgery.

Therefore, an alternative approach that avoids

these di$culties would be welcome in appropriate

circumstances. Jane et al.1� have refined the supraor-

bital approach originally developed by McArthur2�

in 1912 and Frazier3� in 1913. More recently, various

surgical techniques have been reported to o#er an

excellent exposure of the cranial base with minimal

brain retraction and to avoid bothersome postop-

erative complications. In the present paper, these

surgical approaches will be reviewed after learning

anatomy and pathology of the parasellar region.

Intrasellar lesions including pituitary adenomas will

be excluded because surgical approaches are quite

di#erent from the lesions described here.

Anatomy and pathology of the parasellar region

Anatomical relations of the parasellar struc-

tures are complex �Fig. 1�. The optic nerve proximal

to its entrance into the optic canal is covered by a

reflected leaf of dura, the falciform ligament, of

which length may vary from less than 1 mm to as

much as 1 cm. The relation of the optic chiasm to

the sella is an important determinant of the ease

with which the pituitary fossa may be exposed by

the trans-frontal surgical route. The normal chiasm

overlies the diaphragma sellae and the pituitary

gland. In approximately 70 percent of cases, the

chiasm is in the normal position. Of the remaining

30 percent, about half are prefixed and half

postfixed4�. The diaphragma sellae, a special form of

arachnoid membrane, forms the roof of the sella

turcica. The diaphragma tends to be concave or

convex rather than flat, and is rectangular and

somewhat thicker at the periphery5�. All the arterial

Fig. 1 Photograph showing the anatomical relationship

around the sella turcica.

Division of Neurosurgery, St. Marianna University Yokohama City Seibu Hospital

1197�1 Yasashi-cho, Asahi-ku, Yokohama Kanagawa Japan 241�0811

219

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components of the circle of Willis and the adjacent

carotid artery give origin to multiple perforating

branches, which include the superior hypophyseal

artery and other branches passing to the optic

nerve, chiasm, anterior hypothalamus, and anterior

perforated substance. The posterior communicating

artery courses posteromedially above and medial to

the oculomotor nerve and gives rise to multiple

perforators. The anterior choroidal artery is di-

rected posterolaterally below the optic tract. These

arteries may become stretched over parasellar tu-

mors and may feed them. The dura covering the

anterior clinoid process lateral to the optic nerve

and the carotid artery continues to the interclinoid

ligament and the free edge of the tentorium cerebelli

forming the roof of the dural osteum of cranial

nerve III. This dural osteum is in the roof of the

cavernous sinus. The oculomotor nerve perforates

the dura at this osteum of the oculomotor trigone.

Meckel[s cave containing Gasserian ganglion of thetrigeminal nerve is located underneath the tento-

rium, posteroleteral to the oculomotor trigone. The

medial wall of Meckel[s cave consists of the wall ofthe cavernous sinus. The abducens nerve penetrates

the dura inferomedial to Meckel[s cave. Thetrochlear nerve skirts the free edge of the tentorium

cerebelli and joins the upper part of the cavernous

sinus at the level of its posterolateral angle6�.

Parasellar lesions candidates for a surgical

treatment include cerebral aneurysms, neoplasms,

and rarely congenital lesions. Cerebral aneurysms

are the most common among them. Since the intro-

duction of endovascular coil embolization, the basi-

lar quadrification aneurysms are rarely treated with

a direct surgery. Hence, the anterior circulation

aneurysms are the subjects of this article. Meningio-

mas tend to arise at the tuberculum sellae, the

paraclinoidal region, the lateral wall of cavernous

sinus, the upper clivus, or the cavernous sinus itself.

Radiosurgery appears to take the place of the skull

base surgery in the management of bona fide cav-

ernous sinus meningiomas, because the periopera-

tive morbidity and mortality associated with cav-

ernous sinus surgery is appreciable due to the adja-

cent neurovascular structures7�. Craniopharyngio-

mas commonly grow underneath the optico-

hypothalamic complex to displace it superiorly, and

occasionally in the third ventricle. Neurinomas may

arise fromMeckel[s cave. Dermoids or epidermoidsmay be encountered around the sellar region.

The conventional surgical approaches

to the parasellar region

The conventional surgical approaches to the

parasellar region are as follows: 1� anterior ap-proaches, 2� anterolateral approaches, and 3�lateral approaches �Fig. 2�.

Anterior approaches and their refinement

Major anterior approaches to the parasellar

region are an interhemispheric approach and a sub-

frontal approach.

In an approach through the frontal interhemi-

spheric fissure, dividing the bridging veins associ-

ated with prolonged retraction often causes contu-

sional hemorrhage in the frontal lobe. To avoid this

complication, a craniotomy is made lower than that

of the conventional bifrontal craniotomy because

bridging veins are not found near the frontal base

�Fig. 3�. The lower the approach is, however, themore the chance of damaging the olfactory nerves.

And the opening of the frontal sinus is inevitable.

Fujitsu et al.8� developed the basal interfalcine ap-

proach to overcome the complications described

above. They made two trapezoid craniotomies just

above the supraorbital bar. The basal portion of the

falx cerebri is split into two leaves with a dissector.

There may be multiple tears and holes in the split

falx that can protect the olfactory nerves. When

wider exposure is needed, one or both of two leaves

are cut. The author feels this technique is somewhat

complex, and believes that meticulous dissection

techniques of the arachnoid of the interhemispheric

fissure and around the olfactory nerves following a

simple division of the falx do not give away any

harmful e#ect. In an approach through the frontal

interhemispheric fissure, the lower craniotomy in-

volving the central supraorbital bar is essential to

access aneurysms of the anterior communicating

artery complex or craniopharyngiomas in the third

ventricle without damaging the structures around

the corridor.

The subfrontal approach has been refined to

develop new surgical techniques. The bifrontal

transbasal approach originally developed by Der-

ome and Guiot9� has now become one of the stan-

dard skull base surgical approaches and has been

applied to various kinds of midline skull base le-

sions with some modification10�12�. Kawakami et al.10�

described an extensive transbasal approach consist-

ing of a bilateral frontal craniotomy followed by an

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en bloc removal of the whole supraorbital bar in

association with the orbital roofs �Fig. 4�. With thisrefinement, retraction forces to the basal frontal

lobe are apparently lessened and reconstruction of

the skull base become to be much easier. The bi-

frontal transbasal approach not only permit a wider

lateral field of vision which is not available with a

transrhinoseptal or transpalatal approach, but also

allows the surgeon to go deeply as far as the infra-

sellar region, the anterior margin of the foramen

magnum, the anterior arch of the atlas and even the

body of C213� �Fig. 5�. Spetzler et al.14� reported atechnique to spare the olfactory function because,

in the bifrontal transbasal approach, the cribriform

plate is usually removed.

No matter what way the surgeon takes, en-

croachment to the frontal sinus is inevitable. There-

fore, great care should be paid to prevent postop-

erative infections. The following method is com-

monly used: the mucosa of the frontal sinus is re-

moved, and the frontonasal ducts are sutured and

covered by fibrin glue. The author uses this method

when the supraorbital bar is totally removed to

access parasellar lesions, and applies the pericranial

flap to obliterate the space of opened frontal sinus.

It seems important not to leave any dead space in

the cranial cavity �cranialization�.Reconstruction of the midline frontal base is

also an important issue requiring a watertight sepa-

ration between the cranial cavity and the upper

respiratory tract, with a support for the brain. Vari-

ous forms of reconstructive procedures have been

reported including skin grafts, full-thickness scalp

grafts, pericranial flaps15�, galeal frontalis myofascial

flaps16�, and free flaps. The author routinely uses the

Fig. 2 The conventional surgical approaches to parasel-

lar region are indicated in a 3D-CT angiogra-

phy: 1� anterior approach, 2� anterolateral ap-proach, and 3� lateral approach. Note that asmall aneurysmal dilatation is seen at the ante-

rior communicating artery complex.

Fig. 3 Operative corridors of the conventional �solidlines� and transbasal �broken lines� approachesare shown. Note that MRI shows a craniopha-

ryngioma in the third ventricle.

Fig. 4 Illustration showing the author[s original cranio-

tomies of an extensive transbasal approach. Two

bone flaps are made: a bifrontal bone flap �F1�and a flap involving the entire supraorbital bar

�F2�.

Surgical approaches to parasellar lesions 221

3

pericaranial flap because this technique is easy to

perform and reliable to prevent infections as well as

CSF rhinorrhea. To reinforce the structural sup-

port, cranial base bone defects anterior to the sella

turcica is reconstructed by using a vascularized

outer table calvarial bone graft17�. The author does

not feel the necessity of bony reconstruction when

the size of a bone defect is less than two thirds of the

anteroposterior length of the anterior cranial fossa.

The bone defect larger than that described above

will be supported by titanium mesh18�.

Anterolateral approaches and their refinement

Until recently, the most common approach to

parasellar lesions has been widely used frontotem-

poral or pterional approach19�. As a matter of fact,

most cerebral aneurysms have been successfully

treated19�. However, this approach has often en-

countered excessive brain retraction and residual

deficits of a disabling nature, when used to access

medially located, large lesions20�. Various types of

craniotomy including the supraorbital bar have

been developed to lessen brain retraction1�.

Al-Mefty21� modified the supraorbital approach re-

fined by Jane et al1�. to enable to access cavernous

sinus lesions by temporal extension of the craniot-

omy. A mobilization of the zygoma in addition to

usual craniotomy has been reported to o#er an

excellent exposure of the cranial base with minimal

retraction22�. Fujitsu and Kuwabara23� reported the

zygomatic approach which involves detachment of

the zygomatic arch of the temporal bone as well as

a portion of the lateral orbital rim as a free bone

flap, and described that their approach permitted

obliquely upward access to the interpeduncular

fossa using the lowest possible supratentorial route.

Similar detachment of the zygomatic arch has been

reported from several institutions24�30�. Hakuba et

al.24, 25� stressed that, in their orbitozygomatic in-

fratemporal approach, manipulation of the vital

structures in the skull base became to be much

easier and safer than that with the conventional

approach because the working distance to the le-

sions in the parasellar region and the interpeduncu-

lar fossa is about 3 cm shorter and the angle to the

lesions about 1 or 2 cm lower than via either the

perional or subtemporal approach. Taguchi et al.31�

have developed a new surgical technique, the fron-

totemporal orbitozygomatico-alar approach, which

combined a supraorbital approach with a detach-

ment of the zygomatic arch. A similar surgical tech-

nique was reported by Zabramski et al.32� three years

later. The author confirmed the advantages de-

scribed above and added two more advantages:

viewing the lesion multidirectionally and accessing

the lesion medial to the optic canal much easier.

However, the author realized that the techniques

described previously needed skillful hands and in-

evitably resected a part of the basal bony structures

of the orbital roof, the sphenoid ridge and the

temporal bone resulting in enophthalmos33� or pul-

sating exophthalmos9�. Recently, Taguchi et al.34�

Fig. 5 a, b Photographs showing preoperative �a� andpostoperative �b� T1-weighted MRI of sagittalview. Note that a large cystic mass �craniopha-ryngioma� in the spheno-nasopharynx is totallyremoved and no cerebral herniation is present.

Taguchi Y222

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have modified the frontotemporal orbitozygomati-

co-alar approach and developed the frontotemporal

orbito-alar approach to reduce complex and exten-

sive osteotomies on the zygoma. This approach

consists of two bone flaps illustrated in Figure 6

providing a quite similar operative field to the fron-

totemporal orbitozygomatico-alar approach with-

out basal bony defects �Fig. 7�. This approach o#ersa definitive advantage in cranio-orbital approach by

avoiding postoperative complications and by o#e-

ring a simpler, less invasive surgical technique, in

addition to the advantages already provided by the

other cranio-orbital approaches that improve the

angle of the surgeon[s vision and the space availablefor working. Similar modifications to the orbitozy-

gomatic approach were reported more recently35�.

a

b

Fig. 6 a, b Illustrations showing the frontotemporal

orbito-alar approach. Burr holes and osteotomy

incisions are shown on its outer aspect �a� andinner aspect �b�.

a

b

Fig. 7 a, b Intraoperative photographs showing a wide

working space o#ered by the frontotemporal

orbito-alar approach: extradural view of the left

approach �a� and intradural view of the rightapproach �b�.

Surgical approaches to parasellar lesions 223

5

Lateral approaches and their refinement

Modern endovascular surgical techniques ap-

pear to take place the conventional surgical treat-

ment of posterior circulation aneurysms. The sub-

temporal approach had widely been applied to

obliterate basilar bifurcation aneurysms has now

been on the wane. A large parasellar lesions extend-

ing to the middle fossa can be successfully managed

with recently refined anterolateral approaches de-

scribed before �Fig. 8�. Hence, lateral approacheshave become to be used to access around Meckel[scave or the lesions behind the dorsum sellae ��Fig.9�. The subtemporal-transtentorial approach o#ersa surgical field encompassing the upper clivus, but

in which the petrous ridge obscures the surgical

view behind the petrous bone. A common disad-

vantage of this approach has been damage to the

temporal lobe caused by retraction, particularly if

the venous drainage is interrupted20, 36�. In order to

conquer this disadvantage, Kawase et al.37, 38� devel-

oped an anterior transpetrosal-transtentorial ap-

proach. They drilled away the anterior petrous

bone via the epidural route after making a temporal

craniotomy, that is surrounded by the trigeminal

impression anteriorly, the eminentia arcuata poste-

riorly, the major petrosal groove laterally, and the

carotid canal and the internal carotid artery inferi-

orly. Although the superior petrosal sinus is sacri-

ficed inevitably, the sphenopetroclival region down

to the internal auditory meatus can be accessed with

ease. The author, however, recommended a combi-

nation of a subtemporal- transtentorial approach

and an anterior transpetrosal-transtentorial ap-

proach, because the latter provided a fairly limited

working space and access to the petrous apex ex-

tradurally is limited by the subtemporal dura.

Conclusions

Regardless of various techniques described

here, there would be a number of advantages, in-

cluding 1� reducing the brain retraction; 2�shortening the distance to the target; 3� viewingthe lesion directly with a wide working space; and

4� accessing easily to regions used to be no man[sland.

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Fig. 8 Post-contrast T1-weighted MRI showing a well

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