Transorbital

Moe, Bergeron and Ellenbogen described transorbital neuroendoscopic surgery (TONES), using small incisions around the orbit to pass an endoscope along the orbital walls into the skull base^[1]. Each portal (superior eyelid crease, precaruncular, lateral retrocanthal, transconjunctival) leads to a different region. The superior eyelid (lateral) portal, which removes the lateral orbital wall and greater sphenoid wing, has become the most widely used neurosurgical corridor, reaching the anterior temporal fossa, the lateral wall of the cavernous sinus and Meckel's cave. Kong and colleagues have set out the indications and limitations of the superior eyelid route for spheno-orbital meningiomas, the tumour for which it is most often used^[2].

• Spheno-orbital meningiomas and other lesions of the greater sphenoid wing and orbit.
• Trigeminal schwannomas and other lesions of Meckel's cave.
• Lesions of the lateral cavernous sinus and the anterior temporal fossa.
• Repair of anterior and lateral skull-base CSF leaks and encephaloceles, and orbital decompression.

• Make the incision in the upper eyelid crease (lateral portal) and dissect to the lateral orbital rim.
• Elevate the periorbita and retract the globe gently and intermittently, monitoring pupil and intraocular pressure where possible.
• Remove the lateral orbital wall and the greater sphenoid wing to the superior orbital fissure and the middle fossa.
• Proceed extradurally to the lateral wall of the cavernous sinus and Meckel's cave between the dural layers, or open the dura for intradural lesions.
• Reconstruct the orbital wall if a large defect is created to prevent enophthalmos.

• Diplopia, ptosis and enophthalmos from orbital manipulation or wall removal.
• Optic nerve and globe injury from excessive or prolonged retraction.
• Narrow corridor with limited manoeuvrability for large intradural tumours.
• Frontotemporal branch and lacrimal gland injury with lateral incisions.