At a glance
- Also called
- Anterior petrosectomy; Kawase approach
- Bone removed
- Kawase rhomboid (petrous apex)
- Targets
- Upper petroclival region, Meckel's cave, mid-basilar artery
- Hearing
- Preserved (cochlea and IAC are the limits)
- Main risks
- Temporal-lobe injury, GSPN/facial nerve, CSF leak
Overview and history
Kawase described the transpetrosal approach in 1985 for aneurysms of the lower basilar artery, removing the petrous apex medial to the internal auditory canal to reach the basilar trunk without sacrificing hearing[1]. He later extended it, with division of the tentorium, to sphenopetroclival meningiomas[2]. It combines a middle-fossa craniotomy with an extradural anterior petrosectomy and opening of the posterior-fossa dura and tentorium.
Indications
- Petroclival and sphenopetroclival meningiomas, mostly above the internal auditory canal.
- Trigeminal schwannomas spanning the middle and posterior fossae.
- Petrous apex lesions (cholesterol granuloma, chondrosarcoma, epidermoid).
- Selected mid-basilar trunk aneurysms and cavernous malformations of the lateral pons.
Surgical anatomy
The area of bone removed, the Kawase rhomboid, is bounded by the greater superficial petrosal nerve (GSPN) laterally, the mandibular division of the trigeminal nerve (V3) and the trigeminal ganglion anteriorly, the arcuate eminence posteriorly, and the petrous ridge medially; its deep limits are the cochlea, the internal auditory canal and the horizontal petrous carotid artery[1,3]. The cochlea lies in the angle between the GSPN and the internal auditory canal, near the geniculate ganglion.
Operative steps
- Supine with the head turned, or lateral; lumbar drain to relax the temporal lobe.
- Temporal craniotomy flush with the middle fossa floor.
- Elevate the dura from posterior to anterior to avoid traction on the GSPN; identify the middle meningeal artery at the foramen spinosum, the arcuate eminence and the GSPN.
- Drill the petrous apex within the rhomboid, skeletonising the internal auditory canal and the petrous carotid without opening them.
- Open the temporal dura and the posterior fossa dura, ligate the superior petrosal sinus, and divide the tentorium behind the trochlear nerve.
- Close with fat graft and careful sealing of any opened air cells.
Complications and how to avoid them
- Temporal-lobe contusion and venous infarction, particularly of the vein of Labbé: minimise retraction and preserve the temporal bridging veins.
- Facial-nerve palsy from traction on the GSPN and geniculate ganglion.
- Hearing loss from injury to the cochlea or internal auditory canal.
- CSF leak through opened petrous air cells.
- Trochlear and abducens nerve palsies during tentorial division and clival work.
Take-home
Surgical pearls
- Elevate the middle-fossa dura from back to front to protect the GSPN and geniculate ganglion.
- The cochlea is in the angle between the GSPN and the IAC; stop drilling there.
- The approach reaches above the IAC well but not the lower clivus; combine it with a posterior route when needed.
Related
References
- 1.Kawase T, Toya S, Shiobara R, Mine T. Transpetrosal approach for aneurysms of the lower basilar artery. J Neurosurg. 1985;63(6):857-861.
- 2.Kawase T, Shiobara R, Toya S. Anterior transpetrosal-transtentorial approach for sphenopetroclival meningiomas: surgical method and results in 10 patients. Neurosurgery. 1991;28(6):869-876.
- 3.Rhoton AL Jr. The temporal bone and transtemporal approaches. Neurosurgery. 2000;47(3 Suppl):S211-S265.
General education for medical professionals. It summarises published literature and is not advice for any individual patient or a substitute for supervised surgical training.