[Excision and drainage of cholesterol granulomas of the petrous apex with preservation of hearing under computer-assisted navigation surgery (CANS)].

Diagnosis of cholesterol granuloma of the petrous apex has become easier today with new imaging techniques such as MRI and CT. The therapy of choice is surgery, which is still considered a delicate procedure. The objective is to demonstrate hearing-preserving excision and drainage of cholesterol granulomas of the petrous apex using the Bernese system of computer-assisted navigation surgery. Between 1995 and 1999, 3 patients with severe temporal headache, tinnitus and nonspecific vertigo had surgery for cholesterol granuloma of the petrous apex with drainage and excision in the University ENT Clinic, Berne. In the first patient, a combined transmastoidal and transtemporal approach was adopted with infralabyrinthine and subcochlear partial petrosectomy and extirpation of the granuloma in the petrous apex (surgery time 7 h). In the following 2 patients computer-assisted navigation surgery was used and transmastoidal infralabyrinthine-subcochlear drainage and excision of the granuloma in the petrous apex was performed after antefacial hypotympanal drilling with partial exposure of the internal carotid artery (surgery time 2.5 h). After surgery patients were rapidly releaved of symptoms. Postoperative CT showed the newly aerated cells in the petrous apex with permanent drainage. Hearing was preserved with slight residual conductive loss. The surgical method of choice for hearing-preserving excision and drainage is made through an infralabyrinthine-subcochlear approach. The application of computer-assisted navigation surgery in the lateral skull base allows permanent intraoperative monitoring of the precise position of the microsurgical instruments (accuracy < 1 mm) giving a high security level for minimally invasive function preserving surgery.