There are several posterior fossa craniotomies/ craniectomies used to access the CPA. The retrosigmoid approach uses an opening in the suboccipital bone posterior to the sigmoid sinus, with dural exposure over the lateral cere-bellar hemisphere; for details of this approach, see the section on cerebello-pontine tumors.
The three transtemporal approaches (retro-labyrinthine, translabyrinthine and transcochl-ear) expose the posterior fossa dura anterior to the sigmoid sinus, but through the posterior aspect of the petrous pyramid. The transtemporal craniotomies require removal of bone, 1-2 cm behind the sigmoid sinus, to allow posterior displacement of the sinus. In the retro-labyrinthine approach, bone is removed up to the semicircular canals. This provides a limited view of the posterior aspect of the CPA. In the translabyrinthine approach, the canals are also removed - a maneuvre that provides access to the IAC and enhances CPA exposure. In the transcochlear approach, the entire inner ear (i.e. semicircular canals and cochlea) is removed and the facial nerve is re-routed posteriorly from its intratemporal course, thus providing access to the anterior aspect of the CPA and the space ventral to the brainstem.
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