Subfrontal and Extended Subfrontal Craniotomy/Transbasal Approach

Indications

• The subfrontal approach allows access and excellent visualization to the majority of the anterior cranial fossa floor. This includes vital structures adjacent to the anterior midline and parasellar regions such as the tuberculum sella, anterior communicating artery, optic chiasm and optic nerves, posterior orbit, orbital apex and the internal carotid arteries.

• With appropriate pre-surgical management, minimal cerebral retraction is required, reducing the potential retraction-related cortical injury. With a bilateral orbital osteotomy, the extended subfrontal approach allows decompression of the optic nerves bilaterally, and increases the clival exposure while brain retraction is minimized. The expanded subfrontal approach is indicated in smaller and more posterior lesions (those that would require extensive fontal lobe retraction without the elevation of the supraorbital osteotomy) or those lesions with substantial superior extension.

• Both approaches provide a large and direct surgical view allowing en bloc resection of craniofacial malignancies that require negative margins for optimal oncological control. In such cases the subfrontal/extended subfrontal can be combined with a transfacial or endoscopic approach depending on the extension of the tumor to the soft tissues (transfacial preferred when soft tissue is involved) (see Chapters 28 and 30 ).

Potential Contraindications

• Patients with less extensive lesions that can be accessed through an endoscopic minimally invasive approach.

• Active sinonasal infection (infection can be spread after opening the frontal sinus to the intracranial space).

• Lesions located in the middle cranial fossa can be difficult to access using the bifrontal approach and therefore it is not indicated in such circumstances. Lesions positioned retrochiasmatically and subchiasmatically are preferably approached via a lateral exposure instead (e.g. pterional, orbitozygomatic osteotomy).

• However, the bifrontal/extended bifrontal approach can be combined with an orbitozygomatic osteotomy for anterior skull base tumors that are also extending posteriorly or to the temporal fossa.

Preoperative Considerations

• Preparation prior to surgery to reduce the intracranial pressure will allow reduced retraction. Intravenous mannitol, furosemide, steroid boluses (and antibiotics) as per protocol will also aid this. In some extreme cases this can be achieved by placing a lumbar drain, or external ventricular drain (EVD) if necessary, to bypass CSF as well as elevating the head above the level of the heart.

• These approaches allow harvesting of a pericranial flap for closure of the clival dura mater and anterior skull base reconstruction.

Surgical Procedure