[The infracochlear approach for diagnostic petrous apicotomy]

Diagnostic and therapeutic approaches to the petrous apex involve sub-/transtemporal, retrosigmoidal, infratemporal and-lesser invasive-e. g. infracochlear, infralabyrinthine or under favourable anatomic conditions, transsphenoidal surgical pathways. For diagnostic purposes, minimally invasive approaches should be preferred due to their lesser morbidity. This article illustrates the infracochlear approach to the petrous apex in the case of a diagnostic indication in a patient with an incidental, asymptomatic tumorous lesion of the right petrous apex with bony erosion. After the bone of the floor of the ear canal and the hypotympanum was removed, the carotid artery and the jugular bulb were identified using a diamond burr. The route to the petrous apex is triangled by the cochlea superiorly, the jugular bulb posteriorly, and the carotid artery anteriorly. After opening the petrous apex lesion, biopsies were taken. The defect in the floor of the ear canal and the hypotympanum was reconstructed with cartilage and temporalis fascia. The patient recovered quickly from surgery without vertigo or hearing loss. Histological evaluation showed a chondrosarcoma. The patient opted for primary radiation therapy (C12, 63 Gy). The infracochlear approach is minimally invasive and can offer access to the petrous apex with minimal morbidity. The pathway, however, is narrow and deep and bounded by the jugular bulb and the carotid artery. The available space can be estimated from preoperative CT scans and, if possible, with 3D reconstructions. Navigation can additionally enhance safety.