Indications

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  The unilateral and bilateral subfrontal approaches are the workhorse approaches for access to nearly the entire anterior cranial fossa floor; anterior midline parasellar structures such as the tuberculum sella, anterior communicating artery, and optic chiasm; posterior orbit; and orbital apex.

  
  
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  A unilateral subfrontal approach is sufficient for most orbital lesions and midline lesions that are largely eccentric to one side.

  
  
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  For large or purely midline lesions, the increased flexibility of view provided by a bifrontal approach is preferable.

  
  
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  In smaller and more posterior lesions or lesions with significant superior extension, removal of the supraorbital bar may reduce retraction-related cortical injury and improves visualization.

Contraindications

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  Lesions in the middle fossa are difficult to access with this approach.

  
  
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  Retrochiasmatic and subchiasmatic lesions are best accessed via a lateral approach.

Planning and positioning

Positioning for bilateral subfrontal approach. The positioning for either approach is supine.

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  For the unilateral approach, the inferior pins are placed above the mastoid process, and the single pin is placed in the forehead just behind the hairline. The head is rotated approximately 15 degrees toward the contralateral shoulder, the neck is slightly extended, and the head is elevated such that the ipsilateral orbital rim is the highest point of the head. The neck is slightly extended and elevated.

Procedure

Skin incision. The skin incision for either side of this approach begins at the posterior aspect slightly anterior to the tragus and reaches the zygomatic root at its inferiormost extent. Care should be taken to preserve the superficial temporal artery if possible. The incision extends superior and anterior in a curvilinear fashion to reach the hairline in the sagittal midline. If a bifrontal approach is planned, these incisions should meet in a gradual anteriorly directed peak.

Soft tissue elevation. Forehead pericranium should be harvested with any subfrontal or bifrontal approach for repair of anterior fossa floor bony defects and for exclusion of the frontal sinus from the intracranial space. After the scalp has been reflected forward over the superior orbital rim, a large rectangular piece of pericranium is cut with a monopolar cautery and reflected anteriorly over the forehead with its blood supply. The frontalis nerve is contained in a fat pad that lies superficial to the temporalis fascia. This fat pad should be reflected over the frontozygomatic process using either a suprafascial or a subfascial technique.

Identification of landmarks. If orbital osteotomy is planned, it is important to dissect the periorbita away from the orbital bone using gentle dissection because tears in the periorbita, besides increasing the risk of orbital complications, cause the orbital fat to extrude outward, making the osteotomy much more difficult. For unilateral orbital osteotomies, the dissection should begin underneath the superior orbital rim slightly medial to the supraorbital foramen and notch and extend laterally underneath the lateral orbital rim down to the level of the frontozygomatic suture. The dissection should continue as far posteriorly into the orbit as is possible. If the supraorbital nerve is restrained by a bony foramen, this can be freed using an oblique cut with an osteotome to convert the foramen to a notch. The scalp dissection should continue down until the nasofrontal suture is visualized because the detaching cut of a bifrontal orbital osteotomy would run slightly superior to this suture.

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