Healthy-side dominance of middle- and long-latency neuromagnetic fields in idiopathic sudden sensorineural hearing loss

Authors

  • L. P. H. Li,

    1. Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan
    2. Laboratory for Integrated Brain Research, Department of Medical Research and Education, Taipei Veterans General Hospital, No. 201, Sect. 2, Shih-Pai Road, Taipei 112, Taiwan
    3. Department of Otolaryngology and
    4. Department of Otolaryngology, Taipei Veterans General Hospital, Taipei, Taiwan
    5. Department of Otolaryngology,
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  • A. S. Shiao,

    1. Department of Otolaryngology, Taipei Veterans General Hospital, Taipei, Taiwan
    2. Department of Otolaryngology,
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  • L. F. Chen,

    1. Laboratory for Integrated Brain Research, Department of Medical Research and Education, Taipei Veterans General Hospital, No. 201, Sect. 2, Shih-Pai Road, Taipei 112, Taiwan
    2. Center for Neuroscience, National Yang-Ming University, Taipei, Taiwan
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  • D. M. Niddam,

    1. Laboratory for Integrated Brain Research, Department of Medical Research and Education, Taipei Veterans General Hospital, No. 201, Sect. 2, Shih-Pai Road, Taipei 112, Taiwan
    2. Center for Neuroscience, National Yang-Ming University, Taipei, Taiwan
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  • S. Y. Chang,

    1. Department of Otolaryngology, Taipei Veterans General Hospital, Taipei, Taiwan
    2. Department of Otolaryngology,
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  • C. F. Lien,

    1. Department of Otolaryngology, Taipei Veterans General Hospital, Taipei, Taiwan
    2. Department of Otolaryngology,
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  • S. K. Lee,

    1. Department of Radiology, Su-Ao Veterans Hospital, I-Lan, Taiwan
    2. Department of Diagnostic Radiology, National Defense Medical Center, Taipei, Taiwan
    3. Department of Radiology, Chung Shan Medical University, Taichung, Taiwan
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  • J. C. Hsieh

    1. Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan
    2. Laboratory for Integrated Brain Research, Department of Medical Research and Education, Taipei Veterans General Hospital, No. 201, Sect. 2, Shih-Pai Road, Taipei 112, Taiwan
    3. Department of Anaesthesiology, Faculty of Medicine, School of Medicine and
    4. Institutes of Neuroscience and Brain Science, Schools of Life Science and Medicine, National Yang-Ming University, Taipei, Taiwan
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Dr Jen-Chuen Hsieh, 2Laboratory for Integrated Brain Research, as above.
E-mail: jchsieh@vghtpe.gov.tw

Abstract

Any lesion along the neural axis may induce a subsequent functional reorganization at the level above. The present study used magnetoencephalography to investigate auditory-evoked magnetic fields [a component of the middle-latency auditory evoked fields peaking at ~50 ms (P50m) and a component of the long-latency auditory evoked fields peaking at ~100 ms (N100m)] on stimulation of both healthy and affected ears in patients with acute unilateral idiopathic sudden sensorineural hearing loss (ISSNHL) of moderate degree in order to elucidate the functional plasticity of the auditory system. Sixteen right-handed, previously untreated adult patients with acute unilateral left (n = 8) or right (n = 8) ISSNHL of moderate degree were studied. Sixteen right-handed healthy volunteers with normal hearing served as control. Auditory neuromagnetic responses, measured by a whole-head 306-channel neuromagnetometer, were detected by monaural tone stimulation applied to affected and healthy ears, respectively, in different sessions. Intragroup and intergroup interhemispheric differences of peak dipole strengths and latencies of P50m and N100m, respectively, to monaural tones were evaluated. Healthy-side amplitude dominance of both P50m and N100m was found in ISSNHL, i.e. contralateral dominance was preserved on affected-ear stimulation but ipsilateral dominance was seen on healthy-ear stimulation. The phenomena could be attributed to the combined contralateral attenuation and ipsilateral enhancement of P50m and N100m activity in response to healthy-ear stimulation. Our findings confirmed that functional modulation can occur within the first few tens of milliseconds of evoked response at the auditory cortex in ISSNHL. The mechanisms of healthy-side dominance might be ascribed to a functional retune of auditory pathways, i.e. conjoined contralateral inhibition and ipsilateral excitation of the auditory pathway in response to healthy-ear stimulation. The effect could be registered in cortical responses.

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