This approach is utilized for intracanalicular tumors in which an attempt at hearing preser vation is desirable. The drawbacks of the approach are temporal lobe retraction, which can result in seizures and focal neurological signs, limited access if the tumor has extended beyond the porus into the CPA and the difficulty in identifying landmarks on the petrous ridge.
The patient is positioned supine with the head turned to the contralateral side, with the ear uppermost. Brain relaxation using osmotic diuretics and/or lumbar CSF drainage is mandatory. A pre-auricular incision is used and a middle fossa free flap craniotomy performed. This must be made as low as possible to minimize the amount of bone that needs to be removed with ronguers. The petrous bone is then exposed extradurally. The arcuate eminence and greater petrosal nerve are useful landmarks to localize the internal auditory canal. Once located, the internal auditory canal must be opened widely. The dural sleeve is opened along the long axis of the canal. The position of the facial nerve is confirmed. The tumor is then excised, with careful dissection from the nerves and vessels in the canal. The cochlear nerve is usually only revealed once the tumor has been resected. A small plug of fat is placed in the tumor bed. The dura is repaired and the craniotomy closed in standard fashion.
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