Written by Professor Michael Gleeson
Otologic lateral skull base surgery is largely described by the infra-temporal fossa approaches. Safe access to the infra-temporal fossa requires a well-balanced command, expertise and familiarity with otology, head and neck surgery and neurosurgery. It was never the province of the general otologist any more than of the head and neck surgeon or neurosurgeon. Otologic skull base surgery requires a surgeon who is familiar with the special pathologies that are almost unique to the temporal bone, a surgeon who is capable of crossing the boundaries of adjacent subspecialties and recognises the potential problems of doing so. This requirement has forced the otologist, who was previously mainly concerned with middle ear problems, to become a temporal bone micro-surgeon equally competent in the head and neck and able to cross the dura. This evolution has expanded the boundaries of “otologic” surgery and greatly transformed the understanding of temporal bone anatomy and pathology for the benefit of many patients.
Four infra-temporal fossa approaches have been described and found utility in dealing with pathological involvement above, below, anterior, posterior and medial to the otic capsule and labyrinth. Each will be illustrated in this lecture. They build upon the fundamental cornerstone of temporal bone surgery, a complete exenteration of the pneumatic cell tracts of the temporal bone – the subtotal petrosectomy. Most of today’s general otologists are not familiar with this and it is certainly outside the compass of ENT trained head and neck surgeons. Applications include the management of CSF otorrhoea, otitic meningitis, intra-temporal facial nerve injuries and extensive or congenital cholesteatoma. Extensions of a subtotal petrosectomy with resection of the cochlea and labyrinth, skeletonization of the facial nerve, sigmoid sinus, jugular bulb and internal carotid artery, provides excellent access to the internal auditory canal. Known as the transotic approach, it is a major work-horse in lateral skull base surgery.
The type A infra-temporal fossa approach is a cranio-temporal-cervical approach that combines anterior transposition of the facial nerve with a subtotal petrosectomy. In that way tumours in the infra-labyrinthine compartments of the temporal bone, mainly jugular and vagal paragangliomas can be removed completely. The type B approach affords access to the apical compartment of the temporal bone and clivus, including the horizontal segment of the internal carotid artery. It achieves this by resecting the mandibular fossa and posterior aspect of the zygomatic arch. In that way the internal carotid artery can be mobilised from the neck to the foramen lacerum and lesions medial to it dealt with safely. The type C approach requires an additional anterior extension with mobilisation of the zygomatic arch and lateral aspect of the orbit. It allows access to the nasopharynx.
The scope of the otologic lateral skull base surgeon has been extended by a multi-disciplinary approach that includes interventional neuroradiology. Using endovascular techniques to reduce the vascularity of tumours, encasement and invasion of the ICA, many tumours previously thought to be inoperable and not treatable or manageable by radiotherapy are being controlled.