Transpetrosal

The petroclival junction lies deep to the temporal bone, hidden behind the cranial nerves of the CPA and the tentorium. Transpetrosal approaches shorten the distance to this region and widen the angle of view by removing part of the petrous bone. Al-Mefty, Fox and Smith described the petrosal approach for petroclival meningiomas in 1988, combining a presigmoid retrolabyrinthine exposure with a subtemporal craniotomy and tentorial division^[1]; Kawase described the anterior petrosectomy from the middle fossa^[2,3].

• Anterior petrosectomy (Kawase): upper petroclival lesions above the IAC; preserves hearing^[2].
• Retrolabyrinthine (presigmoid): removes the mastoid in front of the sigmoid sinus while preserving the labyrinth; preserves hearing, with a modest gain in exposure.
• Partial labyrinthectomy or translabyrinthine: more exposure, with risk to or loss of hearing^[4].
• Transcochlear: maximum ventral exposure, sacrificing hearing and rerouting the facial nerve^[5].
• Combined petrosal: supratentorial and infratentorial exposure with tentorial division for large lesions extending into both fossae^[1].

• Petroclival meningiomas, the principal indication.
• Chordomas and chondrosarcomas lateral to the paraclival carotid.
• Large epidermoids and trigeminal schwannomas spanning the middle and posterior fossae.
• Mid-basilar trunk aneurysms and ventrolateral pontine cavernous malformations.

• Lateral or supine position with the head turned; lumbar drain.
• Temporo-occipital craniotomy across the transverse–sigmoid junction combined with a mastoidectomy.
• Skeletonise the sigmoid sinus to the jugular bulb and the superior petrosal sinus, leaving the labyrinth intact (retrolabyrinthine) unless more exposure is needed.
• Open the presigmoid and temporal dura, ligate the superior petrosal sinus, and divide the tentorium toward the incisura behind the trochlear nerve.
• Preserve the vein of Labbé and the sigmoid sinus throughout; review the venous anatomy on preoperative imaging.
• Close with fat, fascia and careful sealing of the mastoid.

• Temporal-lobe venous infarction from injury to the vein of Labbé: the most feared complication; check its insertion into the transverse sinus.
• Facial-nerve palsy and hearing loss, related to the extent of petrosectomy.
• CSF leak through mastoid air cells or the Eustachian tube.
• Trochlear, abducens and trigeminal nerve palsies during tentorial and clival work.