Infratemporal Fossa

In 1978 Fisch described a group of infratemporal fossa approaches to tumours of the temporal bone and skull base^[1]. The type A approach exposes the jugular foramen and the vertical petrous carotid artery by permanent anterior transposition of the facial nerve, a radical mastoidectomy with closure of the external auditory canal, and control of the internal jugular vein and carotid in the neck. Type B reaches the petrous apex and clivus by removing the zygomatic arch and displacing the mandibular condyle; type C extends anteriorly to the nasopharynx, pterygopalatine fossa and parasellar region.

• Type A: jugular paragangliomas (Fisch class C and D), jugular-foramen schwannomas and meningiomas, and other lesions of the infralabyrinthine region^[1,2].
• Type B: petrous apex and clival lesions, such as chordomas, chondrosarcomas and cholesteatomas.
• Type C: nasopharyngeal and pterygopalatine lesions with lateral extension, such as juvenile angiofibromas.

The jugular foramen lies below and medial to the labyrinth and the facial nerve; the vertical segment of the facial nerve in the mastoid stands directly in the way of a lateral approach to the jugular bulb, which is why the nerve is transposed. The internal carotid artery enters the carotid canal immediately anterior to the jugular foramen. The lower cranial nerves (IX–XI) exit through the medial (pars nervosa) part of the foramen; the inferior petrosal sinus opens into the medial wall of the jugular bulb between them^[3].

• Postauricular incision with a neck extension; identify the internal jugular vein, carotid arteries and lower cranial nerves in the neck.
• Transect and close the external auditory canal as a blind sac; perform a canal-wall-down mastoidectomy.
• Skeletonise the facial nerve from the geniculate ganglion to the stylomastoid foramen and transpose it anteriorly.
• Remove the tympanic bone and the styloid process to expose the vertical petrous carotid.
• Ligate the sigmoid sinus and the internal jugular vein; open the jugular bulb and remove the tumour, packing the inferior petrosal sinus openings.
• Obliterate the cavity with abdominal fat and close in layers.

• Facial weakness after transposition: usually recovers to House–Brackmann grade I–III^[4].
• New lower cranial-nerve deficits, the main cause of long-term morbidity; leave tumour on the medial bulb wall when the nerves are working^[2].
• Conductive hearing loss after closure of the ear canal.
• Carotid artery injury: assess with angiography and balloon test occlusion beforehand when the artery is involved.
• CSF leak with intradural extension: watertight dural repair and fat obliteration.