. "Case Study 51: Acoustic Trauma Caused by the Telephone: A Report of Two Cases." Environmental Medicine: Integrating a Missing Element into Medical Education. Washington, DC: The National Academies Press, 1995.
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Environmental Medicine: Integrating a Missing Element into Medical Education
picked up on the midfrequency hearing loss, or paid any particular attention to them and therefore have not reported the cases. These accidents may easily be misdiagnosed as beginning Menière’s disease or sudden deafness due to viral infection.
The typical acoustic trauma notch in the 3- to 6-kHz range is not a common finding in this group of patients. This unfortunate experience with human subjects illustrates the findings of many experimental studies documenting the relation between maximum stimulation and maximum damage positions along the organ of Corti [6–8] by using pure tones or narrow band noises as stimuli. The morphological substrate underlying temporary threshold shifts (TTS) has been extensively studied with some controversial results. TTS may be detected without any significant ultrastructural change suggesting a metabolic disturbance; more intense stimulations result in temporary swelling of dendrites to inner hair cells. The resulting TTS lasts for several hours . Vascular disturbances in the pathogenic sequences after an acute noise exposure have also been reported [10–13]. Changes in microcirculation may still be present 3 weeks after short-term and mild noise exposure . In the light of the most recent studies, at the electron microscopy level, more subtle and consistent changes have been described. The most common finding observed in several different animal models [14–16] is depolymerization of the actin filaments at the base of the hair cells stereocilia reducing their stiffness which returned to normal within 6 weeks after exposure .
It is imperative that physicians and audiologists become aware of the potential hazard that telephones may produce under certain circumstances. The greatest danger results from telephones (cordless or not) in which the ringing device is located in the ear receiver. For this reason, these telephones should be prohibited. Unlike the patients of Singleton et al.  or Orchick et al. , our 2 patients have fortunately recovered normal hearing; however, such a favorable outcome is not always predictable and, at the present time, no treatment is known for reestablishing normal hearing after acoustic trauma.
1 Singleton, G.T.; Whitaker, D.L.; Keim, R.J.; Kemker, F.J.: Cordless telephones: a threat to hearing. Ann. Oto-Lar. 93:565–568 (1984).