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The most reliable indicator for acoustic neuromas from the ABR is the interaural latency differences in wave V: the latency in the impaired ear is prolonged. Different studies have indicated the sensitivity of ABR for detection of acoustic neuromas 1cm or larger to be between 90 and 95%. Sensitivity for neuromas smaller than 1cm are 63-77%.
A vestibular schwannoma (VS), also called acoustic neuroma, is a benign tumor that develops on the vestibulocochlear nerve that passes from the inner ear to the brain. The tumor originates when Schwann cells that form the insulating myelin sheath on the nerve malfunction. Normally, Schwann cells function beneficially to protect the nerves which ...
Tumours can arise in the cerebellopontine angle. Four out of five of these tumours are vestibular schwannomas (commonly known as acoustic neuromas). [3] Others found include: Arachnoid cyst; Facial nerve tumour; Lipoma; Meningioma; Schwannoma of other cranial nerves (e.g. CN V >VII>IX, X, XI) Metastasis; Intracranial epidermoid cyst
The misnomer of acoustic neuroma is still often used. The vestibular schwannomas grow slowly at the inner entrance of the internal auditory meatus (meatus acousticus internus). They derive from the nerve sheaths of the upper part of the nervus vestibularis in the region between the central and peripheral myelin (Obersteiner-Redlich-Zone) within ...
Neurofibromatosis type II, in which bilateral acoustic neuromas (tumors of the vestibulocochlear nerve or cranial nerve 8 (CN VIII) also known as schwannoma) develop, often leading to hearing loss. [16] Schwannomatosis, in which painful schwannomas develop on spinal and peripheral nerves. [17]
Graph showing a typical Auditory Brainstem Response. The auditory brainstem response (ABR), also called brainstem evoked response audiometry (BERA) or brainstem auditory evoked potentials (BAEPs) or brainstem auditory evoked responses (BAERs) [1] [2] is an auditory evoked potential extracted from ongoing electrical activity in the brain and recorded via electrodes placed on the scalp.
Firstly, non-auditory side-effects, such as vertigo, limit the overall number of electrodes that can deliver useful frequency information. Electrodes found to cause one of these side-effects are deactivated, resulting in fewer signals reaching the brain. In addition, the brainstem is unable to offer the same tonotopic range as the cochlea.
Transneuronal degeneration is the death of neurons resulting from the disruption of input from or output to other nearby neurons. [1] It is an active excitotoxic process when a neuron is overstimulated by a neurotransmitter (most commonly glutamate) [2] causing the dysfunction of that neuron (either damaging it or killing it) which drives neighboring neurons into metabolic deficit, resulting ...