A Case of 'Spontaneous Otoacoustic Emission'

Abstract

\s=b\A 25-year-old man produced a continuous high-pitched pure tone (6.1 kHz, 37.2-dB sound pressure level) in his right ear. The tone was not audible to the patient. He had sensorineural deafness over 1 kHz with a dip of 45 dB at 6 kHz.The tone was considered to be emitted through the eardrum from the inner ear, ie, a "spontaneous otoacoustic emission." Tinnitus is either a subjective or objective disorder. Objective tin¬ nitus can be heard by other persons as well as by the patient himself. Howev¬ er, there is a sound that cannot be heard by the patient though it is audible to others around him. This sound does not fall under the category of tinnitus, yet it is closely related to tinnitus in that it originates from the ear. Recently, we experienced a case of high-pitched pure-tone emission, of which the patient was unaware but that could easily be heard by others. This patient was diagnosed as having "spontaneous otoacoustic emission." REPORT OF A CASEA 25-year-old man presented with a 15-year history of nonprogressive impaired hearing and the complaint that people around had noticed a high-pitched tone coming from his right ear since ten years before. The sound could not be heard by the patient himself but was audible to a nor¬ mal-hearing person about 10 cm away from the right concha in a soundproof room. The loudness of this sound was not affected by changes in the middle ear pressure such as that caused by swallow¬ ing, yawning, and tympanic inflation, nor was it attenuated by manipulation of the vascular system, as by compression of the jugular vein, neck torsion, and changes of (Dr Yamamoto). head position. When a liquid was applied to the external auditory canal, however, the high-pitched tone disappeared. An otorhinolaryngological examination revealed no abnormalities. Both eardrums were nor¬ mal. Tube inflation was normal. The ear roentgenograms, simple and computed tomographic, gave no abnormal images. Moreover, no abnormalities were detected during a general examination. AudiometryThe pure-tone audiogram result was normal in the left ear but showed a moder¬ ate sensorineural hearing loss over 1 kHz with a slight dip at 6 kHz in the right ear (Fig 1). Further detailed tests showed high short-increment sensitivity index values, a reduced amplitude on Békésy tracing at 1.4 kHz for the right ear, and a negative tone decay test for both ears, thus establishing the diagnosis of right-sided cochlear deaf¬ ness. In the impedance test, the tympano¬ gram was type A for both sides, and the stapedial reflex was recognizable. In the auditory brain-stem response test, no sig¬ nificant differences were noted between the ears with respect to the type and latency of each wave. The Sound and Its Origin First, the frequency and wave type of the high-pitched tone generated by the right ear were studied. The sound from the right ear was recorded by a microphone placed 10 cm from the ear while the subject rested in the supine position in a soundproof room. Figure 2 shows the results of the frequency analysis with a one-th...

Spontaneous otoacoustic emissions, threshold microstructure, and psychophysical tuning over a wide frequency range in humans

“…A similar connection between a 6.1 kHz SOAE and elevated (i.e., poorer) thresholds was also reported in a 25 yr-old man (Yamamoto et al, 1987). An earlier report connected a 7.5 kHz SOAE to poorer thresholds slightly below the emission frequency in an adult (Ruggero et al, 1983).…”

“…In contrast, some high-frequency SOAEs have been associated with hearing loss and cochlear pathology in the literature (Ruggero et al, 1983;Yamamoto et al, 1987;Mathis et al, 1991). Hence, an apparent dichotomy between lowand high-frequency SOAEs has emerged.…”

“…Given the reports linking high-frequency (and high level) SOAEs to hearing loss in humans (Huizing and Spoor, 1973;Ruggero et al, 1983;Yamamoto et al, 1987;Mathis et al, 1991) and animals (Clark et al, 1984;Ruggero et al, 1984;Nuttall et al, 2004), we expected threshold microstructure to be either absent or altered near SOAEs at high frequencies. Contrary to this expectation, SOAEþ ears produced normal-like threshold microstructures across the wide frequency range examined.…”

“…SOAEs linkable to cochlear pathology or hearing loss have almost exclusively been observed at high frequencies in both humans (Ruggero et al, 1983;Yamamoto et al, 1987;Mathis et al, 1991) and other species such as chinchilla (Clark et al, 1984) and dog (Ruggero et al, 1984). Furthermore, damage-related SOAEs are often, but not exclusively, observed in cases of notched or abruptly sloping hearing losses (e.g., Ruggero et al, 1983;Mathis et al, 1991), although there have been reports in ears with losses of flat configuration (Yamamoto et al, 1987) as well.…”

“…Furthermore, damage-related SOAEs are often, but not exclusively, observed in cases of notched or abruptly sloping hearing losses (e.g., Ruggero et al, 1983;Mathis et al, 1991), although there have been reports in ears with losses of flat configuration (Yamamoto et al, 1987) as well. Although there are a number of reports linking highfrequency SOAEs with hearing impairment or cochlear damage, the vast majority of SOAEs seem to be by-products of normal cochlear function.…”