Audiometric evaluation in patients with Alzheimer's disease

The objective of this study is to assess the validity of ASSR as a complementary diagnostic test for peripheral hearing loss by proving a significant correlation between behavioral thresholds and ASSR. The design used in this study is monocentric prospective study from November 2014 to April 2015. The setting used in this study is the ENT-Head and Neck Surgery Department and Geriatrics Department in a French Regional and University Hospital. The participants are patients over 75 years with cognitive impairment (Alzheimer's disease or mild-cognitive impairment) with a Mini-Mental State Examination score under 27/30 and without hearing aids. Exclusion criteria were: otoscopic and middle ear abnormalities, retro-cochlear lesion, other types of dementia, and central nervous system disease altering cerebral lateralization. The intervention used in this study is pure-tone audiometry, speech audiometry, dichotic listening test, and auditory steady-state responses recording. The correlations between these exams were studied with Pearson's correlation coefficient and Student's t test. Results were significant if p < 0.05. Twenty-three ears were analyzed from 12 patients. There were six women and six men with cognitive impairment, mean age 82.1 (±4.6) years, and mean MMSE score that was 21.3/30 (±5.7). The correlation between pure-tone audiometry and ASSR was significant for all frequencies: r = 0.55 (p = 0.006) for 500 Hz, r = 0.58 (p = 0.005) for 1000 Hz, r = 0.61 (p = 0.003) for 2000 Hz, and r = 0.66 (p = 0.002) for 4000 Hz. There was no significant correlation between the MMSE and the difference between ASSR and PTA on each frequency. The dichotic listening test showed a right ear advantage (50.9 %, p = 0.039). The ASSR in patients with cognitive impairment and understanding troubles is a promising complementary technique to estimate the hearing thresholds.