Bifrontal Craniotomy

Indications

• The unilateral and bilateral 1subfrontal 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.
• A unilateral subfrontal approach is sufficient for most orbital lesions and midline lesions that are largely eccentric to one side.
• For large or purely midline lesions, the increased flexibility of view provided by a bifrontal approach is preferable.
• 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

• Lesions in the middle fossa are difficult to access with this approach.
• Retrochiasmatic and subchiasmatic lesions are best accessed via a lateral approach.

Planning and positioning

Bifrontal Craniotomy

Bifrontal Craniotomy 16-1

Bifrontal Craniotomy 16-1: Positioning for bilateral subfrontal approach. The positioning for either approach is supine.

• 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

Bifrontal Craniotomy

Bifrontal Craniotomy 16-2

Bifrontal Craniotomy 16-2: 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 i1ncision 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.

Bifrontal Craniotomy

Bifrontal Craniotomy 16-3

Bifrontal Craniotomy 16-3: 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.

Next    Bifrontal Craniotomy – Part 2

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