What is the purpose and technique of the pterional (pertaining to the pterion) approach in neurosurgery?

Pterional Approach in Neurosurgery

Overview and Primary Purpose

The pterional approach is a fundamental neurosurgical craniotomy technique that provides access to the anterior circulation, skull base, and parasellar regions through a frontotemporal bone window, serving as the workhorse approach for treating anterior circulation aneurysms, skull base tumors, and lesions of the basal forebrain. 1

The approach is specifically indicated for:

• Aneurysms of the anterior circulation and basilar apex 1
• Tumors of the sellar, parasellar, chiasmatic, and subfrontal regions 2
• Lesions of the cavernous sinus, medial sphenoid ridge, and superior orbital fissure 2
• Arteriovenous malformations and cavernous hemangiomas of the basal forebrain 1
• Gliomas involving the insula, frontal/temporal opercula, and mediobasal temporal region 1

Surgical Technique

Patient Positioning and Incision

• The patient is positioned supine with the head rotated 15-30 degrees away from the surgical side and extended slightly to allow the frontal lobe to fall away from the skull base 1
• The skin incision begins just anterior to the tragus at the level of the zygomatic arch and curves posteriorly behind the hairline, then anteriorly toward the midline 2
• Critical preservation of the frontotemporal branch of the facial nerve is mandatory during dissection, as injury causes permanent forehead paralysis 2

Craniotomy Execution

• The bone flap centers on the pterion (the junction of frontal, parietal, temporal, and sphenoid bones) and extends approximately 4-5 cm in diameter 1
• The sphenoid ridge is drilled flat to maximize basal exposure and minimize brain retraction 2
• Removal of the lateral sphenoid wing provides access to the anterior and middle cranial fossae 1

Intradural Approach

• The Sylvian fissure is opened widely using microsurgical technique, splitting the arachnoid between the frontal and temporal lobes 2
• Preservation of the Sylvian veins is critical, as sacrifice can lead to venous infarction 2
• The lenticulostriate arteries must be identified and protected during fissure dissection 2
• Gentle frontal lobe retraction (not temporal lobe retraction) provides the primary working corridor 2

Modern Variations

Minipterional Approach

The minipterional technique has emerged as a safe and effective alternative with equivalent outcomes but improved cosmetic results and potentially reduced complications. 3

• The craniotomy size averages approximately 1050 mm² compared to larger traditional pterional openings 4
• In a series of 102 anterior circulation aneurysms, the minipterional approach achieved excellent outcomes in 77.9% with a mortality rate of 13.9% 3
• The superficial temporal artery can be preserved with careful planning, as the STA bifurcation typically occurs 20.5 mm above the zygomatic arch 4

Lateral Supraorbital Approach

The lateral supraorbital approach represents a more anterior and subfrontal trajectory that is simpler, faster, and less invasive than the classical pterional approach for most anterior circulation pathology. 5

• This modification has been used successfully in over 2000 operations with almost no craniotomy-related complications 5
• The approach is not suitable for lesions requiring exposure from a more temporal perspective 5

Critical Anatomical Pitfalls

Vascular Structures

• The recurrent artery of Heubner must be identified and preserved, as it supplies the anterior limb of the internal capsule and caudate head 2
• Sylvian veins demonstrate significant anatomical variation and must be carefully preserved or sacrificed only when absolutely necessary 2

Neural Structures

• The olfactory nerve is vulnerable during frontal lobe elevation and should be preserved whenever possible to maintain smell function 2
• Excessive temporal lobe retraction with cottonoids (rather than fixed retractors) minimizes risk of temporal lobe contusion 2

Comparison with Alternative Approaches

For large pituitary adenomas with significant suprasellar extension, combined transsphenoidal and transcranial approaches are recommended rather than attempting complete resection through either corridor alone. 6

For cavernous sinus lesions such as angioleiomyomas, the pterional approach with or without orbitozygomatic osteotomy has been most frequently reported, achieving gross total resection in 84.6% of cases. 6

For pineal region tumors, the pterional approach is not the primary corridor; instead, infratentorial supracerebellar, occipital transtentorial, or interhemispheric transcallosal approaches are preferred based on tumor location and venous anatomy. 6

Key Technical Considerations

• Adequate bony exposure is essential and directly correlates with extent of resection and reduced complications 6
• The approach provides access to lesions from the orbital apex anteriorly to the prepontine cistern posteriorly 2
• Anterior clinoidectomy can be performed intradurally when necessary to expand exposure of the optic nerve and carotid artery 4
• Contralateral approaches through a unilateral pterional craniotomy are feasible for select midline lesions 4

Common Complications to Avoid

• Frontotemporal branch facial nerve injury from improper soft tissue dissection 2
• Sylvian vein sacrifice leading to venous infarction 2
• Lenticulostriate artery injury causing basal ganglia stroke 2
• Olfactory nerve transection from aggressive frontal lobe elevation 2
• Excessive brain retraction causing frontal or temporal lobe contusion 2