The Importance of Cross-Validation in the Diagnosis of Auditory Neuropathy Spectrum Disorder: A Case Report

This article reports on a 42-year-old woman diagnosed with Auditory Neuropathy Spectrum Disorder (ANSD) in childhood. Pure-tone Audiometry revealed a minimal decrease in bilateral low-frequency thresholds, and speech tests were within normal limits and compatible with the audiogram. Acoustic Immittance testing revealed all ipsilateral reflexes except for 500 Hz bilat- erally. Distortion Product Otoacoustic Emissions (DPOAE) were obtained bilaterally in all frequency bands. In the Turkish Matrix Test (TurMatrix), it was observed that the speech understanding rate decreased more than normal as the signal-to-noise ratio de- creased. In the diagnostic Auditory Brainstem Response (ABR) test with click stimuli, no response was observed at the maximum intensity level. Cochlear Microphonics (CM) were observed only in the left ear. In the electrocochleography (ECochG) test, an action potential was obtained with a tip-trode electrode bilater- ally. In the advanced audiological evaluation, prolonged waves were obtained in the auditory evoked cortical potential test, but Acoustic Change Complex (ACC) waveforms and latencies were within normal limits.

Although no response was observed on ABR, acoustic reflexes and action potentials were obtained, suggesting that the neurons in the cochlear nerve fired synchronously, but there was a dis- turbance of synchrony in the rostral structures of the auditory pathway. It was noted that the patient was diagnosed with ANSD because acoustic reflexes were not assessed in infancy. When making the diagnosis of ANSD, the patient should be assessed with ABR, DPOAE, and A.Immittansemetry tests and these tests should be cross-validated. It is not possible to determine the ex- act location of the pathology with the available tests.

Keywords: ANSD, ECochG, Cross-check principle