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a Institute of Laryngology and Otology,
University College London, 330 Gray's Inn Road, London, UK, b The National Hospital for Neurology and Neurosurgery,
Department of Neuro-otology, Queen Square, London, UK
Correspondence to: Dr Borka J Ceranic, Department of Neuro-otology, The National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK. Telephone 0044 171 837 3611 ext 3384; fax 0044 171 829 8775.
Received 10 November 1997 and in revised form 26 February 1998;
Accepted 12 March 1998
OBJECTIVE
Tinnitus may be caused by a lesion or
dysfunction at any level of the auditory system. This study explores
cochlear mechanics using otoacoustic emissions in patients with
tinnitus after head injury, in whom there seems to be evidence to
support dysfunction within the CNS.
METHODSThe study included 20 patients with
tinnitus and other auditory symptoms, such as hyperacusis and
difficulty in listening in background noise, after head injury, in the
presence of an "intact" auditory periphery (normal or near normal
audiometric thresholds). They were compared with 20 normal subjects and
12 subjects with head injury, but without tinnitus, who had similar audiometric thresholds. In all subjects otoacoustic emissions, including transient click-evoked (TEOAEs) and spontaneous otoacoustic emissions (SOAEs), were recorded, and a test of efferent medial olivocochlear suppression, consisting of recording of TEOAEs under contralateral stimulation, was performed.
RESULTSA significantly higher prevalence of SOAEs
(100%), higher TEOAE response amplitudes, and reduced
medial olivocochlear suppression in patients with tinnitus in
comparison with subjects without tinnitus have been found.
CONCLUSIONThese findings have been interpreted to
be an extracochlear phenomenon, in which the reduction in central
efferent suppression of cochlear mechanics, leading to an increase in
cochlear amplifier gain, was subsequent to head injury. Auditory
symptoms in these patients seemed to constitute the "disinhibition
syndrome".
This article has been cited by other articles:
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  U. Trulsson, M. Johansson, G. Jansson, A. Wiberg, and L. R.-M. Hallberg Struggling for a New Self: In-Depth Interviews with 21 Patients with Hyperacusis after an Acute Head Trauma J Health Psychol, July 1, 2003; 8(4): 403 - 412. [Abstract] [PDF]
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