Skull Base Tumors

adenocarcinoma of the ethmoid and the woodworking trade (especially hardwood exposure) began in 1965 in the UK [17,18]. The increased relative risk is similar to that for carcinoma of the bronchus in smokers, with a cumulative life-time risk of 1 in 120 and a 500-1,000 times greater risk than the general population of developing the condition. It became a recognized industrial disease in the UK in 1969.

Patients present with nasal symptoms, such as nasal obstruction and epistaxis. Orbital symptoms include swelling, diplopia and prop-tosis (see Fig. 15.3).

It is well recognized that, in the past, the poor prognosis associated with these tumors was a consequence of local recurrence engendered by inadequate resection. The realization that these tumors affect the inferior surface of the cribriform plate and roof of ethmoid (and hence are likely to have an intracranial component) led to the development of the combined skull base approach. This offered access and more rational, yet radical, resection choices, dependent on

Fig. 15.3. Coronal MRI of patient with carcinoma of paranasal sinuses with involvement of the anterior cranial fossa.

anatomic considerations. Many patients with these tumors would be treated with a combination of craniofacial resection and radiotherapy.

In 1998, Lund et al. [19] published the results of a series of 209 patients undergoing craniofacial resection for sino-nasal neoplasia. The 5-year actuarial survival was 44%, falling to 32% at 10 years for malignant tumors. In the analysis of their results, it became clear that when disease affects the frontal lobe itself (as opposed to dural involvement alone), then there was a uniformly bad prognosis.

Malignant Tumors of the Temporal Bone

Malignant tumors affecting the temporal bone account for only 0.05% of head and neck cancers [20]. Most are squamous cell carcinomas, arising in the external auditory canal and invading inward. Those arising within the middle ear/ mastoid are often associated with the longstanding inflammation of chronic middle ear disease.

Patients present with discharge from the ear and associated bleeding and pain. In addition, alteration of facial nerve function should alert the clinician to the possibility of malignancy. In these circumstances, biopsy of any polyp or ulcer is mandatory.

Diagnosis is often made late. CT scan and MRI are used to assess the extent of the primary, and its relationship to the dura, brain, facial nerve and carotid artery. CT is more useful for detailing the intratemporal anatomy and showing the presence of bone erosion (and hence, by inference, presence of tumor). MRI is more useful to define tumor from brain and from the reactive/inflammatory changes that may occur, and gives information regarding ICA or sigmoid sinus patency by the presence or absence of flow void signals. Carotid angiog-raphy may, however, be necessary to establish unequivocally involvement of the carotid artery.

No coherent staging system exists and the lack of such a staging system means that comparing various treatment options described in the literature is impossible. Hence, there is great debate regarding an optimum treatment strategy.

In general, surgery and radiotherapy in combination are considered the treatment of choice. A number of surgical approaches are feasible that largely depend on the extent of the tumor.

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