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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. Methods-The study included 20 patients with tinnitus and other auditory symptoms, such as hyperacusis and diYculty 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 clickevoked (TEOAEs) and spontaneous otoacoustic emissions (SOAEs), were recorded, and a test of eVerent medial olivocochlear suppression, consisting of recording of TEOAEs under contralateral stimulation, was performed. Results-A 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. Conclusion-These findings have been interpreted to be an extracochlear phenomenon, in which the reduction in central eVerent 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". (J Neurol Neurosurg Psychiatry 1998;65:523-529)

Objective: To investigate auditory neural involvement in patients with Leber's hereditary optic neuropathy (LHON). Methods: Auditory assessment was undertaken in two patients with LHON. One was a 45 year old woman with Harding disease (multiple-sclerosis-like illness and positive 11778mtDNA mutation) and mild auditory symptoms, whose auditory function was monitored over five years. The other was a 59 year old man with positive 11778mtDNA mutation, who presented with a long standing progressive bilateral hearing loss, moderate on one side and severe to profound on the other. Standard pure tone audiometry, tympanometry, stapedial reflex threshold measurements, stapedial reflex decay, otoacoustic emissions with olivo-cochlear suppression, auditory brain stem responses, and vestibular function tests were undertaken. Results: Both patients had good cochlear function, as judged by otoacoustic emissions (intact outer hair cells) and normal stapedial reflexes (intact inner hair cells). A brain stem lesion was excluded by negative findings on imaging, recordable stapedial reflex thresholds, and, in one of the patients, olivocochlear suppression of otoacoustic emissions. The deterioration of auditory function implied a progressive course in both cases. Vestibular function was unaffected. Conclusions: The findings are consistent with auditory neuropathy-a lesion of the cochlear nerve presenting with abnormal auditory brain stem responses and with normal inner hair cells and the cochlear nucleus (lower brain stem). The association of auditory neuropathy, or any other auditory dysfunction, with LHON has not been recognised previously. Further studies are necessary to establish whether this is a consistent finding.

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Low level radio-frequency (RF) signals may produce disorientation, headache and nausea. This double blind study tested nine case-subjects, who complained of various symptoms after prolonged mobile telephone use and 21 control subjects. Each subject underwent a series of trials, in which a dummy mobile telephone exposure system was held to each ear for 30 min in (a) pulsed, (b) continuous RF emission or, (c) no emission test modes. In the active pulsed and continuous modes the same mean power as the output of a typical handset was delivered at a carrier frequency of 882 MHz and at a maximum specific absorption rate (SAR) value of 1.3 W kg(-1) (+/- 30%). In Experiment I (auditory), transient evoked otoacoustic emissions (TEOAE), which assess the outer hair cells in the inner ear, were conducted. In Experiment II (vestibular) the vestibulo-ocular reflex was recorded by video-oculography (VOG), at baseline and immediately post exposure. There were no significant TEOAE changes from baseline to post-exposure recording for any of the exposures and no significant differences in the TEOAEs' change from baseline to post exposure between cases and controls. The VOG did not identify any effect of the exposure on the vestibular end organ in either cases or controls. In conclusion, 30 min exposure to mobile phone RF did not show any immediate effects on vestibulocochlear function as measured by TEOAE and the VOR.