Acoustic neurinoma distinctly elevates level-difference thresholds while most hearing impairments do not.

Evidence

The results show that most of the hearing-impaired patients indicate level discriminations that are the same or almost the same as those of normally hearing subjects. In this case, the median values of the just-perceptible level differencies, 11L, may be a little different from those of hearing-impaired subjects, but the interquartile ranges overlap so that no clear decision can be made about whether the level discrimination ability is changed or not. Such small differences occur for the impairment of conductive hearing loss, sudden hearing loss, noise-induced hearing loss, infantile or toxic non-progressive sensory neural hearing loss, Meniere’s disease and presbyacusis. For these hearing impairments no differentiation is possible, because the interquartile ranges of the data and those produced by normally hearing subjects clearly overlap. The hearing impairment resulting from acoustic neurinoma, however, shows a strong difference as indicated in Fig. 16.25. While the normally hearing subjects show a level-difference threshold near 1.5 dB, results for the patients with acoustic neurinoma are about a factor of 3 larger, i.e. 4.5 dB. The medians range from 4 to 4.7 dB and the interquartile ranges do not overlap at all. Because there were 52 patients for the data set, it is clear that there is a distinct increase in the level-difference threshold for patients with acoustic neurinoma. The finding that 49 out of 52 patients with proven acoustic neurinoma showed distinctly increased level-difference threshold emphasizes the attractiveness of this method. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1898

Categorization

• XREF: Connects to clinical audiology and differential diagnosis of hearing disorders, distinct from the psychoacoustic theory chapters.
• SEED: Angle: an old-school, low-tech psychoacoustic test that outperforms elaborate clinical equipment for detecting acoustic neurinoma — a case study in diagnostic elegance.