Central Auditory Processing in Alzheimerʼs Disease

TLDR

The study aimed to assess whether early‑to‑middle stage Alzheimer’s disease patients exhibit impaired central auditory processing relative to nondemented elderly. The authors administered a comprehensive peripheral and central auditory test battery—including audiometry, otoacoustic emissions, and synthetic sentence, dichotic, pitch, and duration tasks—to 10 mild‑to‑moderate AD patients and 10 age‑matched controls. AD patients showed lower low‑frequency thresholds in the left ear and performed significantly worse on four of five central auditory tests, while peripheral hearing and speech recognition were comparable, indicating central auditory dysfunction that warrants screening in this population.

Abstract

This investigation was designed to determine whether people in the early to middle phases of Alzheimer's disease (AD) show impaired central auditory processing as compared with nondemented elderly.A peripheral and central auditory test battery was administered to 10 subjects diagnosed with mild-to-moderate AD based on a neuropsychological test battery and radiographic techniques, and a control group of 10 subjects with no evidence of dementia, matched for age, gender, and average degree of hearing loss. Immittance audiometry, pure-tone and speech audiometry, and otoacoustic emissions were recorded in all subjects. Central auditory assessment included the synthetic sentence identification with ipsilateral competing message, dichotic digits, dichotic sentence identification, pitch patterns, and duration patterns.Peripheral auditory status was statistically similar between subject groups. Neither average high frequency hearing sensitivity nor mean speech recognition ability was significantly different. However, a significant difference was noted between groups for average low frequency hearing sensitivity in the left ear (p < 0.05). Subjects with AD showed slightly poorer low frequency thresholds versus matched controls. Based on analysis of performance on each measure of the central auditory test battery, the AD group scored significantly lower than the matched control group on four of the five measures utilized. Differences for right versus left ear performance were found among AD subjects.Overall patterns in findings cannot be easily explained as artifacts of cognitive decline. Results support screening for central auditory dysfunction in the AD population, since impaired processing could influence psychiatric assessment of cognitive deficit as well as audiologic management of peripheral hearing loss in this population.