Transpetrosal Approaches

The anterior brainstem, clivus, and CVJ can be accessed through the temporal bone. The entire exposure can be obtained by removing bone without retracting the brain or brainstem. More than one approach can be used, depending on the type of lesion and the amount of space needed to work safely. At times, the sacrifice of hearing is necessary to provide adequate exposure. Very large lesions can require transposition of the facial nerve, with a corresponding temporary facial paralysis. The potential for these complications demands a detailed discussion of the risks and benefits with the patient and family members.

There are three basic types of temporal (petrous) bone dissections. The most limited dissection is the extended retrolabyrinthine technique, which removes a large portion of the temporal bone but preserves the otic capsule ( Fig. 28.1 ). This approach does not sacrifice hearing and offers limited exposure due to the overhanging semicircular canals. In comparison, the translabyrinthine technique removes more temporal bone and sacrifices hearing ( Fig. 28.2 ). The most extensive modification is the transcochlear technique, which involves maximal removal of the temporal bone, sacrifices hearing ( Fig. 28.3 ), and transposes the facial nerve. Moving through these three variations of surgical exposure gradually increases the amount of temporal (petrous) bone resection and, concomitantly, the exposure of the brainstem, clivus, and CVJ. These approaches can be combined with a supra-infratentorial craniotomy (i.e., combined approach) ( Fig. 28.4 ) as well as a far-lateral approach ( Fig. 28.5 ) if necessary to provide additional exposure of the skull base. The translabyrinthine and transcochlear approaches have the advantage of wide exposure of the cerebellopontine angle without extensive cerebellar retraction as well as access to the facial nerve in an area uninvolved with tumor.

Patient Positioning

Typically, the patient is positioned supine. The head is parallel to the floor, inclined slightly downward and flexed onto the opposite shoulder, and fixed to the operating table with a May-field three-pin head holder. A soft roll may be placed under the ipsilateral shoulder to provide support if necessary. In this position, the temporal bone can be dissected quickly and easily. Of note, the extreme rotation of the neck, which is advantageous for retrosigmoid approaches, is not necessary. Occasionally, however, the patient must be placed in the park bench position for the far-lateral position.8 The neurotologist must become facile with far-lateral positioning because the usual relationships among bony landmarks and soft tissue are altered.

Transpetrous and Modified Transpetrous Exposures

Transpetrosal Approaches	Combined Supra- and Infratentorial Approaches	Far-Lateral Combined Supra- and Infratentorial Approaches
Retrolabyrinthine	Retrolabyrinthine	Retrolabyrinthine
Translabyrinthine	Translabyrinthine	Translabyrinthine
Transcochlear	Transcochlear	Transcochlear

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