||Acoustic neuromas typically develop at the junction of the central (neuroglial) and the peripheral (neurolemmal) portions of the vestibular nerve, the so-called neuroglialneurolemmal junction (glial head). This junction may lie in the posterior cranial fossa or within the internal auditory canal. Accordingly an acoustic neuroma may present with predominantly central or peripheral auditory and vestibular symptoms. Audiograms show progressive sensorineural hearing loss and decreased speech discrimination. The availability of high-resolution CT scanning, magnetic resonance imaging, and brain stem auditory evoked response (BAER) audiometry have all enhanced the capability for early diagnosis of these tumors.
Acoustic neuromas grow slowly, and over time will compress the host and adjacent nerves within the internal auditory canal, causing sensorineural hearing loss, tinnitus, and decreased vestibular function. Often patients experience minor symptoms of difficulty understanding the meaning of words. As the tumor follows the path of least resistance the adjacent cranial nerves (trigeminal, facial, glossopharyngeus, vagus, and spinal accessory) and the brain stem structures in the cerebellopontine angle will also be compressed. Pressure necrosis from an enlarging acoustic neuroma may cause the bony internal auditory canal to become enlarged and funnel-shaped. Increased intracranial pressure may result in ataxia, vomiting, and headaches. Occasionally the patient will report paraesthesia.