Residency · Residency · Neurosurgery

Pterional and Frontotemporal Approaches

Overview

The pterional (frontotemporal) craniotomy is arguably the most versatile and commonly performed craniotomy in neurosurgery. Developed and popularized by Yasargil, it provides access to the sylvian fissure, anterior and posterior circulation aneurysms, suprasellar and parasellar lesions, and anterolateral skull base pathology. Mastering this approach is a foundational skill for every neurosurgical resident.

Indications

The pterional approach is used for anterior circulation aneurysms (AComA, MCA, ICA, ophthalmic segment), posterior communicating artery and basilar tip aneurysms, suprasellar tumors (craniopharyngiomas, tuberculum sellae meningiomas), sphenoid wing meningiomas, temporal and frontal lobe tumors, Sylvian fissure pathology (insular tumors, Sylvian fissure AVMs), and cases requiring orbitozygomatic extension for deeper skull base access.

Surgical Anatomy

Surface Landmarks

The pterion is the H-shaped suture junction of the frontal, parietal, temporal, and sphenoid bones. The superior temporal line marks the superior attachment of the temporalis muscle, while the zygomatic arch defines the inferior extent of the temporal fossa. The keyhole (MacCarty's point) sits at the junction of the frontal process of the zygomatic bone, temporal bone, and greater wing of the sphenoid, providing access to the anterior fossa floor and periorbita.

Subfrontal and Sylvian Anatomy

The Sylvian fissure separates the frontal and temporal lobes and contains the MCA branches and superficial Sylvian veins. The sphenoid ridge separates the anterior and middle cranial fossae and must be drilled to increase basal exposure. The anterior clinoid process is a key landmark overlying the optic nerve and ICA. The superficial Sylvian vein, with its connections to the vein of Labbe, drains toward the sphenoparietal sinus or the vein of Labbe and must be preserved.

Technique

Positioning

The patient is placed supine with the head in a Mayfield clamp, elevated 15-20 degrees above the heart to facilitate venous drainage. The head is rotated 15-45 degrees contralateral, with the degree varying by target: 30-45 degrees for AComA aneurysms, 15-30 degrees for MCA aneurysms, and 15-20 degrees for basilar tip lesions. Slight extension allows the frontal lobe to fall away from the anterior fossa floor with gravity. The malar eminence should be the highest point.

Skin Incision

The incision begins 1 cm anterior to the tragus, below the zygomatic arch to preserve the superficial temporal artery should it be needed for bypass. It curves superiorly within the hairline and extends to the midline or just past the midpupillary line, staying behind the hairline for cosmesis. The superficial temporal artery (STA) should be identified and preserved during the incision, as it may be needed later for an EC-IC bypass.

Soft Tissue Dissection

Interfascial dissection protects the frontotemporal branch of CN VII. The frontal branch runs within or just deep to the superficial layer of the deep temporal fascia. This layer is incised and reflected with the skin flap, using the fat pad between the fascial layers as the key landmark. The temporalis muscle is reflected inferiorly and posteriorly, either by cutting along its fibers or by reflecting it as a myocutaneous flap. Subperiosteal dissection completes the exposure of the temporal fossa floor.

Craniotomy

Typically 2-3 burr holes are placed, including one at the keyhole. The keyhole burr hole at MacCarty's point is critical, as it straddles the junction of the frontal and temporal fossae. The craniotomy flap includes frontal and temporal components. The greater wing of the sphenoid is then drilled flat to the level of the meningo-orbital band to maximize basal exposure and minimize brain retraction. The lateral orbital wall may be drilled for additional exposure.

Dural Opening

A C-shaped incision based on the sphenoid ridge and Sylvian fissure is made, and the dura is reflected anteriorly and inferiorly toward the skull base. Tack-up sutures are placed to prevent epidural hematoma.

Sylvian Fissure Dissection

The inside-out technique, described by Yasargil, begins at the Sylvian point where the MCA branches first appear in the fissure and works proximally toward the ICA bifurcation. The alternative outside-in technique begins at the superficial aspect and dissects deeper. Sharp arachnoid dissection is used throughout, avoiding bipolar coagulation on arachnoid near vessels. The superficial Sylvian vein is identified and preserved, ideally retracted with the temporal side. Progressive dissection exposes the MCA bifurcation, ICA terminus, A1, and the circle of Willis.

Exposure Achieved

Through this approach, the surgeon can visualize the ipsilateral ICA, MCA, and ACA, the AComA complex, the optic nerve and chiasm, the pituitary stalk and sellar region, the basilar apex (through the opticocarotid or carotid-oculomotor triangle), and the interpeduncular cistern with CN III.

Orbitozygomatic Extension

This modification adds removal of the orbital rim and/or zygomatic arch, providing a more inferior-to-superior trajectory that reduces brain retraction. It is indicated for basilar tip aneurysms, large craniopharyngiomas, and complex skull base tumors. The one-piece technique removes the orbital rim with the craniotomy, while the two-piece technique removes them separately.

Modifications

The mini-pterional is a smaller craniotomy centered on the Sylvian fissure, used primarily for MCA aneurysms. The lateral supraorbital approach is a keyhole technique for simple anterior circulation aneurysms. The extended pterional uses a larger bone flap with more temporal exposure, appropriate for insular tumors.

Complications

Injury to the frontotemporal branch of CN VII causes ipsilateral forehead paralysis with inability to raise the eyebrow and is prevented by interfascial dissection. Temporalis muscle atrophy produces a cosmetic deformity from devascularization and is minimized by careful dissection and reattachment. Epidural hematoma may result from middle meningeal artery injury or dural stripping. Brain contusion from excessive retraction is reduced by CSF drainage via the Sylvian fissure or lamina terminalis. Vascular injury to MCA branches or perforators may occur during Sylvian fissure dissection.

<image> Stepwise illustration of the pterional craniotomy. Panel A: lateral view of the head showing the curvilinear skin incision from anterior to the tragus, curving behind the hairline. The superficial temporal artery is marked. Panel B: the interfascial dissection technique showing the superficial and deep layers of the deep temporal fascia with the fat pad between them, and the course of the frontotemporal branch of CN VII. Panel C: the craniotomy bone flap with burr holes at the keyhole and along the superior temporal line. The sphenoid ridge is shown before and after drilling. Clean surgical illustration with labeled anatomical structures. </image>

<image> Intraoperative view through a completed pterional craniotomy showing a wide-open sylvian fissure. The frontal lobe is retracted superiorly, and the temporal lobe is retracted inferiorly. Visible structures include the MCA bifurcation, M1 segment with lateral lenticulostriate arteries, ICA terminus, A1 segment, optic nerve, and the anterior clinoid process. The superficial sylvian vein is preserved on the temporal side. Detailed microsurgical illustration with labeled neurovascular structures. </image>

Clinical Pearls

The keyhole burr hole at MacCarty's point is the most important single burr hole in neurosurgery, as it defines the basal extent of the pterional craniotomy. Sphenoid ridge drilling is essential and often underappreciated by trainees; inadequate bone removal leads to excessive brain retraction. The frontotemporal branch of CN VII is reliably protected by interfascial dissection, and learning the fascial layers and fat pad landmark is critical. Sylvian fissure dissection is a fundamental microsurgical skill that demands sharp dissection and careful protection of MCA branches and perforating arteries. The superficial temporal artery should be preserved during the skin incision, as it may be needed later for an EC-IC bypass. CSF drainage via the basal cisterns (chiasmatic, carotid cisterns) early in the approach dramatically improves brain relaxation and reduces retraction injury. The pterional approach can reach the basilar apex through the opticocarotid triangle (between the optic nerve and ICA) or the carotid-oculomotor triangle (between the ICA and CN III).

References

• Yasargil MG. "Microneurosurgery, Vol. I." Georg Thieme Verlag, 1984.
• Yasargil MG, et al. "Pterional Approach to Aneurysms of the Basilar Bifurcation." Surgical Neurology. 1976;6(2):83-91.
• Rhoton AL Jr. "The Supratentorial Cranial Space: Microsurgical Anatomy and Surgical Approaches." Neurosurgery. 2002;51(Suppl 1).
• Chaddad-Neto F, et al. "The Pterional Craniotomy: Tips and Tricks." Arq Neuropsiquiatr. 2012;70(9):727-732.

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