Acoustic Schwannomas

Abstract

After arteriovenous malformations, acoustic schwannomas have been the most rewarding condition to treat in the Gamma Knife, which is reflected by the large number of patients treated world wide. Nonetheless, the correct way to treat this difficult condition is a matter of debate. Surgery may be performed, by the translabyrinthine approach by an ENT surgeon. It may also be performed through the posterior fossa by a neurosurgeon. Ideally both forms of surgery may be available with collaboration between the specialities involved. A third operation, through the middle fossa has been reserved for hearing preservation in small, primarily intracanalicular tumours. Another quite different form of treatment is of course that provided by the Gamma Knife. In 1991 two major assessments of acoustic treatment were presented. One was an article summing up the results of a century of treatment. The other was the first international acoustic “neuroma” conference held in Copenhagen, where top expertise from all relevant specialities and most parts of the world were present. On the basis of data provided from these two sources, it is fair to say that there is a considerable range of opinion on the subject of what constitutes optimal treatment. As far as the Gamma Knife is concerned, it has been and indeed to some extent remains the convention to say, that the Gamma Knife is appropriate for the treatment of patients who are a high surgical risk, of advanced age or who refuse open surgery for whatever reason. The correctness of this view will be debated further a little later on. As a neurosurgeon the author would like to deplore the use of the term acoustic neuroma for this tumour. This is an etymological misuse which has become widespread. If scientific prose is to be precise then the terminology must be used precisely. The word neuroma indicates that the tumour’s cell of origin is a nerve cell which is not the case. The tumours are thought to be derived either from Schwann cells or neurilemmal cells and are thus variously referred to as schwannomas, neurinomas or a neurilemmomas. The use of any of these three terms can be defended: but neuroma is nosologically incorrect. In this text schwannoma is preferred.