The pterional craniotomy (also known as a frontotemporal, or frontotemporal sphenoidal craniotomy) is one of the most widely used neurosurgical approaches. It facilitates a broad frontobasal exposure, while simultaneously minimizing brain retraction. This grants access to several important intracranial spaces, including the anterior and middle fossa, sylvian fissure, basal cisterns, suprasellar space, and cavernous sinus. With this versatility, it can be employed to treat a variety of pathologies.
Frontotemporal approaches were developed and used for most of the 20th century, although the first modern pterional was described by Yasargil in 1975.1,2 Over the subsequent decades, the procedure has undergone an assortment of modifications. These include variable removal of the zygoma, sphenoid wing, and orbital roof, or performing an intra vs extradural clinoidectomy. The specific technical details are indeed adaptable, depending on the indications and surgeon preference. Some procedures, including the supraorbital craniotomy and the orbitozygomatic craniotomy, derive from the “classic” pterional but are now often classified in their own right.
- Patient preparation
- Skin incision
- Scalp dissection
- Temporalis muscle incision
- Retraction of scalp/temporalis flaps
- Drilling of keyhole burrhole
- Craniotomy and bone flap removal
- Drilling of sphenoid wing
This craniotomy is centered over and gets its name from the pterion, the anatomic region of the skull where the frontal, parietal, temporal (squamous part), and sphenoid (greater wing) join together. The underling bony structures are complex and intimately related with several intracranial compartments, conferring the versatility of the operation.
The incision for this exposure should begin approximately 1cm anterior to the tragus, starting at the zygoma. This avoids damaging the superficial temporal artery, which runs posteriorly, along with the frontalis branch of the facial nerve, which lies anteriorly in a superficial fat pad. While the temporalis muscle is often mobilized and retracted with the skin in a single flap, incising and dissecting the temporalis separately (shown here) can enable a more caudal exposure and minimize post-op cosmetic changes. When dissecting the temporalis separately, great care must be taken to avoid damaging the frontalis branch.
The keyhole refers to the depression encountered at the junction of the superior orbital ridge, zygomatic bone, and superior temporal line. A burr hole at this location grants simultaneous access to the floor of the anterior fossa and the orbit.
Once the bone flap is removed, the lesser sphenoid wing is thinned out in a medial direction, until encountering the lateral edge of the superior orbital fissure. This is a key step which flattens the space between the anterior and middle fossa, therefore broadening access to the basal cisterns and Circle of Willis.
Pterional craniotomies are most frequently utilized for the surgical treatment of intracranial aneurysms. The majority of sporadic aneurysms are located at or near the Circle of Willis, and these locations are accessible with this approach. This includes aneurysms of the intracranial internal carotid, anterior communicating artery, posterior communicating artery, middle cerebral bifurcation, or basilar apex. Some lesions located on more distal divisions are also accessible, particularly with middle cerebral branches in the sylvian fissure. It is important to obtain high quality imaging prior to surgery, ideally with digital subtraction angiography (DSA), to characterize the aneurysm’s location and architecture. This helps optimize the technical details and method of approach. In recent years, aneurysms are increasingly being treated with endovascular methods, usually embolization with coils.3 Although coiling has become more common, surgical clipping remains a time tested and durable technique, which remains an especially important option for aneurysms not amenable to embolization. Patients presenting with subarachnoid hemorrhage require treatment to secure the ruptured aneurysm if possible. For un-ruptured aneurysms, the decision to treat and by which modality depends on the natural history of the aneurysm, patient risk factors, and center experience.4
Tumors in the suprasellar region are often approached with this craniotomy. Common tumors in a suprasellar location or with extension into this space include pituitary adenomas, craniopharyngiomas, meningiomas, and germ cell tumors, among others. Usually, magnetic resonance imaging (MRI) or other radiography is useful to delineate the tumor’s location. Some tumors in this location are amenable to medical and/or radiation therapy, and this should be considered when possible.
The exposure can also be used to resect tumors of the sphenoid wing, subfrontal or perisylvian regions, and for lesions in the cavernous sinus.
Contraindications are similar to other craniotomies in general. Patients who are poor surgical candidates may wish to consider conservative management or other therapeutic options if applicable (endovascular for aneurysms, chemo/radiation for tumors, etc).
General endotracheal anesthesia is used with locally injected anesthetic.
Patients should be admitted to a neurological intensive care or step down unit for close neurological monitoring, at least overnight. For patients treated electively, hospital recovery generally ranges from 1-3 days.
Patients admitted with subarachnoid hemorrhage from ruptured aneurysms require a much longer stay, with a full protocol to manage vasospasm, hydrocephalus, and other complications.5
- Bleeding, intra-op (aneurysm rupture) or post-op
- Neurological injury
- Anesthetic complications
- Yasargil MG, Fox JL, Ray MW. The operative approach to aneurysms of the anterior communicating artery. In: Krayenbuhl H ed. Advances and Technical Standard in Neurosurgery. Vienna, Austria: Springer-Verlag; 1975: 113-170.
- Altay T, Couldwell WT. The frontotermporal (pterional) approach: A historical perspective. Neurosurgery. 71(2); 481-4891. 2012.
- Molyneux A, Kerr R, Stratton I, et al. Internatonal Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneruryms: a randomized trial. Lancet. 360;(9342) ;1267-74. 2002.
- Wiebers DO, Whisnart JP, Huston J, et al. Unruptured intracranial aneurysms: natural history, clinical outcome, and risks of surgical and endovascular treatment. Lancet 362(9378): 103-10. 2003.
- Bekelis K, Root B, Khan I, Singer RJ, Ball PA. “Principles of Neurocritical Care.” In: Yeomans Neurological Surgery Expert Consult, 7e. Eds Winn, HR. Saunders; In press.