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Definitive diagnosis of acoustic-nerve tumours was difficult until the development of modern scanning techniques. Prior to the introduction of the CT (computerised tomography) scanner, which became widely available in the UK during the early 1980s, acoustic nerve tumours were diagnosed by invasive and hazardous techniques involving the introduction of dye into the subarachnoid space, and manoeuvring it into the internal auditory meatus, the bony canal within the posterior cranial fossa through which the eighth nerve passes on its way from the brain stem to the inner ear. There was understandable reluctance to use these invasive techniques in the absence of good evidence of the presence of a neuroma, and combinations of specialised tests of hearing and balance with plain X-rays were used as a guide. As highdefinition CT scanning became possible this approach was modified, and with the introduction of magnetic resonance imaging, which became widely available in the UK from 1990 onwards, the imaging of acoustic neuromas of even very small size became straightforward. For legal purposes it is important to understand the evolution of diagnostic pathways for acoustic neuroma during the 15 years preceding the writing of this book in 1996.