Can the ASSR be misleading in the diagnosis of auditory neuropathy spectrum disorder (ANSD)?

Introduction Several studies demonstrated good correlations between ASSR-thresholds and pure-tone-thresholds as well as Click-ABR-thresholds. However, this is ambiguous in patients with ANSD, because there are often big mismatched between mostly better ASSR-thresholds and worse, if at all detectable click-ABR-thresholds. The aim of the present study is to evaluate, if an ANSD may be overseen due to the presence of normal ASSR-thresholds and if ASSR-thresholds correlate with pure-tone-thresholds or with the thresholds of cochlear microphonics (CM) in ANSD.

Materials and methods: 28 patients (4 adults, 24 children) with ANSD were examined. A pure-tone- or behavioral audiometry, Click-ABR and ASSR were performed in all patients. 21 patients showed CM in Click-ABR (n=16) or in electrocochleography (EcochG) (n= 11).

Results None of the patients with ANSD showed completely normal ASSR-thresholds. The ASSR-thresholds were usually better as expected from Click-ABR results. No correlation of the single frequencies of the pure-tone-thresholds and the frequency specific ASSR-thresholds could be demonstrated. A correlation between ASSR-thresholds especially at 2 and 4 kHz and click evoked CM-thresholds in the EcochG was detected (r=0.49-0.69).

Summary/discussion At present there are only few studies concerning the value of ASSR in the diagnosis of ANSD. None of the patients in the present study showed normal ASSR-thresholds, which implies that an ANSD is not likely to be overseen due to the ASSR results. The ASSR by itself is not sufficient in the diagnosis of ANSD, because it´s thresholds are usually better than Click-ABR-thresholds. However, the ASSR can be a useful additional diagnostic tool in ANSD, which correlates with CM of the EcochG.

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Artikel online veröffentlicht:
10. Juni 2020