Prominent auditory deficits in primary progressive aphasia: A case study

A Japanese Patient With Progressive Word Deafness and Logoclonia

Primary progressive aphasia (PPA) is classified into several types. However, syndromes that do not belong to these typical types of PPA have been reported, such as cases where only progressive apraxia of speech (AOS) is present in the early stages of the disease. Moreover, there have been a few case reports of patients with progressive word deafness complicated with logoclonia as a speech disorder. Herein, we report a case of degenerative disease with phonological paraphasia, AOS, impaired speech sound cognition, and logoclonia with disease progression. The written language comprehension of the patient was superior to that of spoken language, and she could communicate in writing. She was neurologically normal; had no apraxia, agnosia, or memory impairment; and was independent in activities of daily living. Although she had moderate hearing loss, her speech-related hearing loss was disproportionately high. In analyses of brain imaging, dilation of the left Sylvian fissure, atrophy, and hypoperfusion of the superior temporal gyrus were prominent, and hypoperfusion of the left lateral frontal lobe was observed. Cerebrospinal fluid examination suggested that Alzheimer's disease (AD) pathology was unlikely, and decreased uptake was observed on a dopamine-active transporter scan. Word deafness was thought to be the most likely cause of the dissociation between spoken and written language in our patient. Our case and previous studies suggested that there is a syndrome presenting word deafness and speech movement disorders among patients with progressive communication disorders as a different entity from PPA. Although patients with this syndrome may experience agrammatism, inner language disorders are generally not as severe, and disorders in areas closer to the primary area, such as the motor and auditory areas, as well as cortical and subcortical disorders, are involved in this syndrome.

Primary progressive aphasia: six questions in search of an answer

Here, we review recent progress in the diagnosis and management of primary progressive aphasia-the language-led dementias. We pose six key unanswered questions that challenge current assumptions and highlight the unresolved difficulties that surround these diseases. How many syndromes of primary progressive aphasia are there-and is syndromic diagnosis even useful? Are these truly 'language-led' dementias? How can we diagnose (and track) primary progressive aphasia better? Can brain pathology be predicted in these diseases? What is their core pathophysiology? In addition, how can primary progressive aphasia best be treated? We propose that pathophysiological mechanisms linking proteinopathies to phenotypes may help resolve the clinical complexity of primary progressive aphasia, and may suggest novel diagnostic tools and markers and guide the deployment of effective therapies.

The effect of aging, hearing loss, and tinnitus on white matter in the human auditory system revealed with fixel-based analysis

Introduction

Aging negatively influences the structure of the human brain including the white matter. The objective of our study was to identify, using fixel-based morphometry, the age induced changes in the pathways connecting several regions of the central auditory system (inferior colliculus, Heschl's gyrus, planum temporale) and the pathways connecting these structures with parts of the limbic system (anterior insula, hippocampus and amygdala). In addition, we were interested in the extent to which the integrity of these pathways is influenced by hearing loss and tinnitus.

Methods

Tractographic data were acquired using a 3 T MRI in 79 volunteers. The participants were categorized into multiple groups in accordance with their age, auditory thresholds and tinnitus status. Fixel-based analysis was utilized to identify alterations in the subsequent three parameters: logarithm of fiber cross-section, fiber density, fiber density and cross-section. Two modes of analysis were used: whole brain analysis and targeted analysis using fixel mask, corresponding to the pathways connecting the aforementioned structures.

Results

A significantly negative effect of aging was present for all fixel-based metrics, namely the logarithm of the fiber cross-section, (7 % fixels in whole-brain, 14% fixels in fixel mask), fiber density (5 % fixels in whole-brain, 15% fixels in fixel mask), fiber density and cross section (7 % fixels in whole-brain, 19% fixels in fixel mask). Expressed age-related losses, exceeding 30% fixels, were particularly present in pathways connecting the auditory structures with limbic structures. The effect of hearing loss and/or tinnitus did not reach significance.

Conclusions

Our results show that although an age-related reduction of fibers is present in pathways connecting several auditory regions, the connections of these structures with limbic structures are even more reduced. To what extent this fact influences the symptoms of presbycusis, such as decreased speech comprehension, especially in noise conditions, remains to be elucidated.

Auditory phonological identification impairment in primary progressive aphasia

OBJECTIVE

To examine the audiological characteristics and neuroanatomical regions associated with auditory phonological identification impairment in primary progressive aphasia (PPA).

METHODS

Twenty-seven patients with PPA [13 non-fluent/agrammatic variant PPA (nfvPPA), three logopenic variant PPA (lvPPA), seven semantic variant PPA (svPPA), and four mixed type PPA] were included in the study. Neuropsychological, language, audiological, and neuroradiological examinations were also performed. Auditory function examinations consisted of a pure-tone threshold test, a phonological identification task, and temporal auditory acuity tests, such as click counting or fusion. As an evaluation value of phonological identification ability, we calculated the discrepancy scores, which were the smaller discrepancy (left or right ear) in phonological identification ability scores between measured and expected values from the pure-tone threshold. In the neuroradiological examination, we evaluated the regional cerebral blood flow using 123I-iodoamphetamine single-photon emission computed tomography.

RESULTS

Eight of the 27 patients were allocated to the impaired phonological identification group, and four were considered to have significant impairment on further analysis. Two of these patients, one with lvPPA and one with mixed type of lvPPA and nfvPPA, showed apparent phonological identification deficits that could be observed in daily life. The discrepancy scores were not significantly related to the results of neuropsychological, language, or any other auditory examinations, except for the click counting score in the left ear. Voxel-based correlation analyses revealed that regional cerebral blood flow in the bilateral superior temporal gyrus and bilateral primary auditory cortex was significantly and positively correlated with phonological identification ability.

CONCLUSIONS

Our results suggest that progressive dysfunction of the bilateral superior temporal gyrus and bilateral primary auditory cortex due to neurodegenerative diseases leads to phonological identification impairment in PPA syndrome.

The Auditory Agnosias: a Short Review of Neurofunctional Evidence

PURPOSE OF REVIEW

To investigate the neurofunctional correlates of pure auditory agnosia and its varieties (global, verbal, and nonverbal), based on 116 anatomoclinical reports published between 1893 and 2022, with emphasis on hemispheric lateralization, intrahemispheric lesion site, underlying cognitive impairments.

RECENT FINDINGS

Pure auditory agnosia is rare, and observations accumulate slowly. Recent patient reports and neuroimaging studies on neurotypical subjects offer insights into the putative mechanisms underlying auditory agnosia, while challenging traditional accounts. Global auditory agnosia frequently results from bilateral temporal damage. Verbal auditory agnosia strictly correlates with language-dominant hemisphere lesions. Damage involves the auditory pathways, but the critical lesion site is unclear. Both the auditory cortex and associative areas are reasonable candidates, but cases resulting from brainstem damage are on record. The hemispheric correlates of nonverbal auditory input disorders are less clear. They correlate with unilateral damage to either hemisphere, but evidence is scarce. Based on published cases, pure auditory agnosias are neurologically and functionally heterogeneous. Phenotypes are influenced by co-occurring cognitive impairments. Future studies should start from these facts and integrate patient data and studies in neurotypical individuals.

Case Report: Semantic Variant Primary Progressive Aphasia With Impaired Verbal Word Discrimination

Some patients with primary progressive aphasia (PPA) present with various types of hearing deficits. Research on the auditory function and speech sounds in PPA, including temporal, phonemic, and prosodic processing, revealed impairment in some of these auditory processes. Many patients with PPA who present with impaired word recognition subsequently developed non-fluent variant PPA. Herein, we present a patient with semantic variant PPA (svPPA) who demonstrated impaired verbal word discrimination. Audiological examinations revealed normal auditory brainstem responses and slightly impaired pure-tone perception. By contrast, verbal word discrimination and monosyllable identification were impaired, and temporal auditory acuity deteriorated. Analyses of brain magnetic resonance images revealed a significant decrease in the gray matter volume in bilateral superior temporal areas, predominantly on the left, compared with those of patients with typical svPPA, which appeared to be associated with impaired word recognition in our patient.

Dynamic Aphasia as a Variant of Frontotemporal Dementia

We describe two individuals with progressive verbal difficulty who exhibited impairment of propositional language, with relatively well-preserved auditory comprehension, naming, and repetition-a profile that is consistent with dynamic aphasia. By providing a brief review of pertinent literature and the results from our neurologic, speech and language, neuropsychological, and neuroimaging testing, this report sheds light on the infrequently reported dynamic aphasia in the context of frontotemporal dementia. Our patients' insights into their verbal difficulty tend to support the notion that dynamic aphasia results from interference at the stage where thoughts are converted into verbal messages-that is, the thought-verbal interface.

Primary Progressive Aphasia: Toward a Pathophysiological Synthesis

PURPOSE OF REVIEW

The term primary progressive aphasia (PPA) refers to a diverse group of dementias that present with prominent and early problems with speech and language. They present considerable challenges to clinicians and researchers.

RECENT FINDINGS

Here, we review critical issues around diagnosis of the three major PPA variants (semantic variant PPA, nonfluent/agrammatic variant PPA, logopenic variant PPA), as well as considering 'fragmentary' syndromes. We next consider issues around assessing disease stage, before discussing physiological phenotyping of proteinopathies across the PPA spectrum. We also review evidence for core central auditory impairments in PPA, outline critical challenges associated with treatment, discuss pathophysiological features of each major PPA variant, and conclude with thoughts on key challenges that remain to be addressed. New findings elucidating the pathophysiology of PPA represent a major step forward in our understanding of these diseases, with implications for diagnosis, care, management, and therapies.

Non-fluent/Agrammatic Variant of Primary Progressive Aphasia With Generalized Auditory Agnosia

Cortical neurodegeneration-induced non-fluent/agrammatic variant of primary progressive aphasia (nfvPPA) is a clinical syndrome characterized by non-fluent speech, such as apraxia of speech or agrammatism. We describe the case of an 80-year-old right-handed woman who exhibited nfvPPA. Atypically, our patient also presented with generalized auditory agnosia. Brain magnetic resonance imaging revealed left-sided predominant atrophy of the bilateral perisylvian area, including the inferior frontal and superior temporal lobes. In a series of auditory tasks assessing generalized auditory agnosia, our patient was unable to accurately identify verbal sounds, environmental sounds, or familiar Japanese songs that she could sing. In the context of recent studies, our study indicates the existence of a clinical syndrome characterized by progressive speech disorder with auditory agnosia. This case report thus provides novel insights into the spectrum of language impairment induced by neurodegenerative disease.

Clinical and neuroimaging characteristics of clinically unclassifiable primary progressive aphasia

Many patients who meet core/root criteria for Primary Progressive Aphasia (PPA) are not classifiable as a recognized variant and are often excluded from neuroimaging studies. Here, we detail neurological, neuropsychological, speech and language assessments, and anatomic and molecular neuroimaging (MRI, PiB-PET, and FDG-PET) for fifteen (8 female) clinically unclassifiable PPA patients. Median age of onset was 64 years old with median 3 years disease duration at exam. Three patients were amyloid positive on PiB-PET. 14/15 patients had abnormal FDG-PETs with left predominant hypometabolism, affecting frontal, temporal, parietal, and even occipital lobes. Patients had mild to severe clinical presentations. Visualization of the FDG-PETs principal component analysis revealed patterns of hypometabolism similar to those seen in the PPA variants and suggests the brain regions affected in unclassifiable PPA patients are no different from those who are more easily classifiable. These findings may inform future modifications to the diagnostic criteria to improve diagnostic classification.