Cystic lesions of the petrous apex: transsphenoid approach.

The transsphenoid approach to cystic lesions of the petrous tip has been made possible by the advances in techniques for diagnosis. These include polytomography, improved angiography, and computer tomographic (CT) brain scanning. The results of these studies can determine the size, shape, and thickness of the cystic lesion, as well as its exact relationship to the sphenoid sinus. A number of surgical approaches have been used to reach the cystic lesion of the petrous apex. Most notably, these include the middle fossa extradural craniotomy and posterior fossa craniotomy. These surgical techniques allow the cyst to be biopsied but do not establish permanent drainage. The translabyrinthine approach accomplishes wide access to the petrous apex, but cochlear and vestibular functions are sacrificed. The transsphenoid approach to cystic lesions of the petrous apex should be the ideal operation provided that the anterior aspect of the cyst abuts against the posterior wall of the sphenoid sinus. The cyst can be completely evacuated and permanent fistulization established into the sphenoid sinus using a septal mucosal flap and a silicone drainage device. The operation is accomplished without destruction to the inner ear.