Pterional

Yaşargil and Fox described the microsurgical pterional approach to intracranial aneurysms in 1975^[1], and it became the standard craniotomy for the anterior circulation and for many lesions of the anterior and middle skull base. Yaşargil also described interfascial dissection of the temporalis fascia to preserve the frontal branch of the facial nerve^[2]. Wide opening of the Sylvian fissure and the basal cisterns, rather than brain retraction, is the essence of the approach.

• Aneurysms of the internal carotid, middle cerebral, anterior communicating and posterior communicating arteries, and of the basilar apex.
• Medial and lateral sphenoid wing, clinoidal, tuberculum and olfactory-groove meningiomas.
• Craniopharyngiomas, pituitary tumours with lateral or suprasellar extension and optic pathway lesions.
• Insular and frontotemporal gliomas, and cavernous sinus lesions combined with an extradural clinoidectomy.

The pterion is the H-shaped junction of the frontal, parietal, temporal and sphenoid bones. Beneath the lesser sphenoid wing lies the superior orbital fissure; the meningo-orbital band links the periorbita to the temporal dura and is divided to begin an extradural anterior clinoidectomy. The Sylvian fissure contains the superficial Sylvian veins, which usually drain to the sphenoparietal sinus, and the middle cerebral artery; opening it from distal to proximal (or proximal to distal) leads to the carotid cistern, the optic nerve and the carotid bifurcation.

• Supine, head turned 30–45° toward the opposite side, extended so that the malar eminence is the highest point, and fixed in a pin holder.
• Curvilinear incision behind the hairline from the zygoma to the midline; interfascial or subfascial dissection to protect the frontal branch^[2].
• Elevate the temporalis muscle and make the craniotomy centred on the pterion, with a keyhole burr hole.
• Drill the lateral sphenoid wing flat down to the meningo-orbital band; remove the orbital roof ridges.
• Open the dura in a curve based on the sphenoid wing.
• Release CSF from the basal cisterns and split the Sylvian fissure along the frontal side of the Sylvian veins.

• Frontalis palsy from injury to the frontal branch of the facial nerve: stay deep to the superficial fat pad.
• Temporalis atrophy and a hollowed temple: preserve the deep temporal nerves and blood supply; reattach the muscle carefully.
• Vascular injury and ischaemia from perforator damage or temporary occlusion.
• Venous congestion from sacrificing large Sylvian veins.
• Frontal sinus opening with CSF leak: exenterate and seal the sinus if it is entered.