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Binaural hearing after middle ear surgery. Masking-level difference for interaural time and amplitude cues
1Division of Otolaryngology, University of North Carolina School of Medicine, Chapel Hill.
Summary
Even after middle ear surgery corrects hearing thresholds, many patients exhibit abnormal binaural hearing. The masking-level difference (MLD) is often reduced, particularly for interaural time difference cues.
Area of Science:
- Audiology
- Neuroscience
- Otolaryngology
Background:
- Binaural hearing is frequently impaired in conductive hearing loss.
- Abnormalities persist even when hearing thresholds are normalized post-middle ear surgery.
Purpose of the Study:
- To further investigate the masking-level difference (MLD) in patients post-middle ear surgery.
- To assess sensitivity to interaural time difference (ITD) and interaural amplitude difference (IAD) cues independently.
Main Methods:
- Evaluated MLD in 15 patients after middle ear surgery.
- Utilized stimuli to independently assess ITD and IAD sensitivity.
- Correlated MLD abnormalities with lesion characteristics (duration, onset, asymmetry).
Main Results:
- Over one-third of patients showed abnormal MLDs despite normal hearing thresholds.
- Reduced MLD was more common for ITD cues than IAD cues.
- Long-standing, early-onset, and asymmetric hearing lesions were linked to reduced MLDs.
Conclusions:
- Middle ear surgery may not fully restore binaural hearing function.
- Impairments in MLD, especially for ITD cues, are prevalent post-surgery.
- Factors like lesion history significantly impact residual binaural processing.