CPA approach

Approach	Indications	Surgical Corridor	Bone removal with drill	Preserved Bony Structures	Exposure	Dural Opening	Hearing Preservation	Facial Nerve Visualization	Pros	Cons
Retrosigmoid	CPA tumors, VS, Lateral brainstem tumors	Posterior to sigmoid sinus, via craniotomy	Minimal (mainly craniotomy)	Entire bony labyrinth (semicircular canals, cochlea), petrous apex preserved	CPA, lateral brainstem, cerebellum	Posterior to sigmoid sinus	Yes—commonly preserved	Good near IAC/CPA but not from brainstem to IAC	Efficient, minimal bone work, familiar anatomy	More cerebellar retraction, limited anterior/ventral exposure
Translabyrinthine	CPA tumors with poor hearing, large VS, extensive CPA tumors	Through mastoid and bony labyrinth, anterior to sigmoid	Extensive (labyrinth drilled out)	Petrous apex preserved, bony labyrinth (cochlea, semicircular canals) removed	CPA, full IAC circumference	Via drilled corridor to IAC	No—hearing sacrificed	Excellent—entire nerve from brainstem to IAC	Direct access, wide field, excellent facial nerve visualization	Hearing loss, technically complex, risk to facial nerve
Transcochlear	CPA tumors with anterior extension, extensive petrous apex/chordoma	Through labyrinthectomy and cochlea removal	Most extensive (labyrinth + cochlea, posterior/superior canal, middle ear)	Little preserved—most inner ear and petrous apex removed	Petroclival, anterior CPA, wider access	Anterior to labyrinth	No—hearing sacrificed	Good, variable depending on exposure	Maximal anterior/ventral exposure	Most destructive, complex, may affect facial nerve
Retrolabyrinthine	Petroclival meningioma, posterior petrous lesions, ventral CPM	Mastoidectomy, skeletonization of sigmoid, route behind labyrinth	Moderate (mastoid + skeletonization)	Entire bony labyrinth, cochlea, petrous apex (mostly) preserved	Posterior petrous face, lateral CPA, VII/VIII	Presigmoid dura behind labyrinth	Yes—preserves labyrinth	Partial	Preserves hearing, less cerebellar retraction	Cannot access IAC/petrous apex directly, anatomy variable
Transotic	CPA/temporal bone tumors with poor hearing	Transmastoid, skeletonization and removal of labyrinth/cochlea	Extensive, involves cochlear drilling	Some mastoid/facial canal may be preserved; labyrinth/cochlea lost	CPA, temporal bone, posterior fossa	Transmastoid, via cochlea	No—hearing lost	Good but partial	Widest access without middle fossa approach	Hearing/balance lost, complex vascular anatomy
Middle Cranial Fossa	Tumors caudal to IAC, anterior petrous apex	Floor of middle fossa, extradural	Extradural, floor drilling	All labyrinth, cochlea, petrous apex preserved (unless anterior petrosectomy)	Convex floor, lateral petrous apex	Extradural	Preserved	Limited	No cerebellar retraction, direct lateral access	Limited posterior fossa access, may miss petrous apex/pathology

Comparison between approaches

Retrosigmoid approach

Translabyrinthine appraoch

(A) Translabyrinthine approach to a pre-pontine tumor seen schematically in axial view.

- (B) Translabyrinthine approach to a pre-pontine tumor seen in surgical perspective. Ventral exposure superior to the retrosigmoid approach, but is still limited by the lateral aspect of pons and the VII-VIII complex. (5, trigeminal nerve - 7, facial nerve - 8, audiovestibular nerve.)

Transcochlear approach

Feature	Anterior Petrosectomy (Kawase’s Approach)	Posterior Petrosectomy (Retrolabyrinthine/Presigmoid Approach)
Anatomical Route	From the middle cranial fossa, drilling the petrous apex “anterior” to the IAC	From the mastoid region, “posterior” to the labyrinth/IAC, via presigmoid dura
Main Bony Landmarks	Kawase triangle—bounded by the GSPN, V3, IAC, petrous ridge, petrous ICA	Trautmann’s triangle—bounded by sigmoid sinus, labyrinth, and superior petrosal sinus
Structures Exposed	Petrous apex, clivus, ventral brainstem, upper basilar artery, petroclival region	Posterior fossa, CPA, lower clivus, petrosal surface of cerebellum, ventrolateral brainstem
Dura Opened	Posterior fossa dura exposed via anterior drilling; tentorium may be cut	Presigmoid/posterior fossa dura exposed through mastoidectomy
Hearing Preservation	Yes, if cochlea/IAC not drilled	Yes, if labyrinth not opened (retrolabyrinthine); translabyrinthine variant sacrifices hearing
Clinical Indication	Petroclival meningiomas, ventral brainstem tumors, basilar aneurysms	CPA tumors, petroclival and posterior fossa lesions, large meningiomas
Pros	Direct anterior/ventral access, less cerebellar retraction	Wide ventrolateral exposure, can be combined with tentorial/temporal extension
Cons	Technically demanding, temporal lobe retraction, risk to cochlea/ICA/V nerves	Risk of CSF leak, risk to labyrinth, facial nerve, sigmoid/transverse sinus manipulation

For presigmoid approach classification

Hoz2023.pdf

5.2 MiB

Proposed classification system for the presigmoid approach with an artistic depiction of the 9 subclasses from a left presigmoid view. The anterior translabyrinthine group includes 5 variations based on the extent of bone resection: 1) partial translabyrinthine, 2) transcrusal, 3) translabyrinthine proper, 4) transotic, and 5) transcochlear. The posterior retrolabyrinthine group includes 4 variations based on the target area and the trajectory required in relation to the IAC: 6) retrolabyrinthine inframeatal, 7) retrolabyrinthine transmeatal, 8) retrolabyrinthine suprameatal, and 9) retrolabyrinthine trans-Trautman’s triangle. Illustrations starting from the upper left corner and tracing a path down, to the right, and up depict approaches from 1 to 9