One variant of primary progressive aphasia came with substantial hearing impairment suggestive of auditory pathway involvement in this neurodegenerative condition, researchers at one center found.
Those with nonfluent/agrammatic primary progressive aphasia (nfvPPA) required louder tones to hear the frequencies tested in pure-tone audiometry, with worse peripheral auditory function compared with healthy older controls and a group with Alzheimer‘s disease.
Increased functional interaural audiometric asymmetry suggested conjoint peripheral afferent and more central regulatory auditory dysfunction in these individuals, according to investigators Jason Warren, PhD, of University College London Institute of Neurology, and colleagues, in the study published online in JAMA Neurology.
Thus, the findings add to evidence that nfvPPA is “a disorder of communication signal processing that extends beyond neurolinguistic impairment; it may be timely to reevaluate the progressive aphasias from this fresh perspective,” they urged.
This condition may also be a model for interpreting the interplay of peripheral hearing and cognitive function in neurodegenerative disease more broadly and “evaluating physiologically informed hearing and communication therapies in people with dementia,” the authors wrote.
The link between cognitive impairment and hearing loss is still a “chicken and egg” question that researchers may have better luck answering in a more focal group like nfvPPA than in the larger population with Alzheimer‘s disease, agreed Zachary Miller, MD, of the University of California, San Francisco Memory and Aging Center.
“When someone has sensory impairments, does the brain become shut off and does it lose the ability to stay in touch with the world? There are these kinds of arguments that if you restore someone’s sight or hearing, could that be beneficial?” he said in an interview. “Nobody quite knows if there’s a directionality.”
It’s also possible that hearing loss is related to the underlying disease pathophysiology of nfvPPA, which would make hearing loss a possible biomarker for measuring therapy or disease progression, Miller added.
Warren’s group conducted their study on 19 consecutive patients with nfvPPA (mean age 70.3 years, nine women) who were compared to 20 Alzheimer‘s disease patients and 34 control participants at their center.
Differences between groups, which could not be attributed to age or general disease factors, were seen for:
- Better-ear scores: mean 36.3 dB vs 28.9 dB for controls (P=0.01) and 31.1 dB for Alzheimer’s (P=0.048)
- Worse-ear scores: mean 42.2 dB vs 31.7 dB (P=0.001) and 33.8 dB (P=0.005)
- Bigger deficits in the worse ear relative to the better ear: mean difference of 5.9 dB vs 2.8 dB (P=0.004) vs 2.8 dB (P=0.005)
Miller, calling the study findings “somewhat unexpected, even serendipitous,” suggested that the logical next step would be to look at the other two variants of primary progressive aphasia (semantic and logopenic) and to have the data validated in a larger population.
This work was supported by grants from the Alzheimer’s Society, the National Institute for Health Research University College London Hospitals Biomedical Research Centre, the University College London Leonard Wolfson Experimental Neurology Centre, Action on Hearing Loss–Dunhill Medical Trust, the Medical Research Council, the Association of British Neurologists, the Wolfson Foundation, and the Wellcome Trust.
Warren and Miller disclosed no conflicts of interest.