Pure word deafness after bilateral primary auditory cortex infarcts

In pure word deafness, comprehension and repetition of speech are impaired, but reading, writing, and spontaneous speech are preserved. Pure word deafness is distinguished from generalized auditory agnosia by the preserved ability to recognize environmental sounds. We examined a patient with pure word deafness associated with bilateral infarctions of the primary auditory cortex, who could use auditory affective intonation to enhance comprehension. The primary auditory cortex seems to be essential for comprehending speech, but comprehension of nonverbal sounds and affective prosody may be mediated by other cerebral structures such as the auditory association cortex.     

Nonverbal auditory agnosia with lesion to Wernicke's area

We report the case of patient M, who suffered unilateral left posterior temporal and parietal damage, brain regions typically associated with language processing. Language function largely recovered since the infarct, with no measurable speech comprehension impairments. However, the patient exhibited a severe impairment in nonverbal auditory comprehension. We carried out extensive audiological and behavioral testing in order to characterize M's unusual neuropsychological profile. We also examined the patient's and controls’ neural responses to verbal and nonverbal auditory stimuli using functional magnetic resonance imaging (fMRI). We verified that the patient exhibited persistent and severe auditory agnosia for nonverbal sounds in the absence of verbal comprehension deficits or peripheral hearing problems. Acoustical analyses suggested that his residual processing of a minority of environmental sounds might rely on his speech processing abilities. In the patient's brain, contralateral (right) temporal cortex as well as perilesional (left) anterior temporal cortex were strongly responsive to verbal, but not to nonverbal sounds, a pattern that stands in marked contrast to the controls’ data. This substantial reorganization of auditory processing likely supported the recovery of M's speech processing.     

Language disorders in Landau-Kleffner syndrome

In the present long-term study, we analyzed language disorders in four patients with Landau-Kleffner syndrome. Their common first symptoms were disability in understanding spoken words, followed by inarticulation and a decreased amount of speech. All patients showed auditory verbal agnosia to some degree at some stage of their illness. However, one patient showed typical sensory aphasia as the first symptom, and another patient showed nonverbal auditory agnosia followed by pure word deafness. Thus, patients with Landau-Kleffner syndrome show sequential and sometimes hierarchical language disorders beginning with sensory aphasia, followed by auditory agnosia, and finally word deafness during their disease process. During long-term follow-up (20 to 30 years), all patients showed marked recovery in language without any intellectual handicap, but with some disability in spoken language, auditory verbal perception, and a discrepancy between Wechsler Verbal and Performance IQ scores.     

Auditory agnosia restricted to environmental sounds following cortical deafness and generalized auditory agnosia

We encountered a case of auditory agnosia restricted to environmental sounds, which was associated with the development of bilateral subcortical lesions after suffering a bilateral putaminal hemorrhage. The patient had a history of a putaminal hemorrhage on her left side without any major disability. Three years later, she suffered a putaminal hemorrhage on the other side. The clinical picture started with cortical deafness, then changed to generalized auditory agnosia for verbal and environmental sounds, and finally developed into auditory agnosia confined to the perception of environmental sounds. Her errors in a test of sound recognition were discriminative rather than associative in nature. Neuro-radiological examinations revealed bilateral subcortical lesions involving the fibers from the medial geniculate body to the temporal lobes after bilateral putaminal hemorrhage. This case suggested that the subcortical lesion involving bilateral acoustic radiation could cause either cortical deafness, auditory agnosia of all sounds, or auditory agnosia restricted to environmental sounds.     

A case of auditory agnosia with the lesion of bilateral auditory radiation

A 53-year-old man showed central auditory disturbance with recurrent cerebral hemorrhage. At his acute stage he had deafness and auditory anosognosia. Two or three months later, there was no deafness and auditory anosognosia, but he could not comprehend words, environmental sounds and music. Auditory brainstem responses showed no peripheral or brainstem damage, and the lesion of bilateral auditory radiation was detected by MRI. His auditory agnosia did not improve over one and a half year. There is no report like such permanent auditory agnosia with the lesion of bilateral subcortical temporal lobe.     

A case of tentorial meningioma presented with pure word deafness]

It has been known that an isolation of Wernicke's area from auditory input results in pure word deafness. In this report, a 73-year-old female case with tentorial meningioma suffering from pure word deafness is reported. The patient initially presented with hydrocephalus, and was treated with a ventriculo-peritoneal(V-P) shunt. A year after the V-P shunt, she suffered from a symptom of deafness. On admission, her repetition and auditory comprehension were severely impaired, while reading and visual comprehension were almost normal. Auditory brain stem response(ABR) revealed normal latency between wave I and V, while wave VI and VII was disappeared. Middle latency response(MLR) showed no wave peak. On MRI, tentorial meningioma compressed bilateral medial geniculate bodies, but not auditory radiation or temporal lobe. 99mTc-HMPAO single photon emission computed tomography(SPECT) showed hypoperfusion in the left temporal lobe, considered as a diaschisis resulting from the isolation of left temporal lobe from auditory input via bilateral medial geniculate bodies.     

Clinical and audiological findings in a case of auditory agnosia

Summary A case is reported of severe agnosia for verbal and non-verbal sounds without associated aphasic disorder. A CT scan revealed bilateral, temporal lobe lesions from two ischaemic accidents that had occurred 9 months apart. The search for subtle deficits in this patient showed normal sensitivity to changes in the intensity and frequency of simple sounds; in contrast, his ability to discriminate sound duration and musical note sequences was severely impaired. The simultaneous recording of the whole auditory-evoked response pattern revealed no abnormality in the early components, which reflect the activation of the auditory nuclei and pathways of the brain stem. However, the middle and late components were delayed and slowed. These results and others in the literature suggest that the neocortex in man, as in other mammals, plays an essential role in the temporal aspects of hearing. Also, the two main ingredients commonly recognized in auditory agnosia, i.e. word deafness and the inability to interpret non-verbal sounds, are caused by the disruption of elementary, bilaterally represented cortical functions which start the processing of every kind of auditory information.     

The assessment of auditory function in CSWS: Lessons from long-term outcome

In Landau-Kleffner syndrome (LKS), the prominent and often first symptom is auditory verbal agnosia, which may affect nonverbal sounds. It was early suggested that the subsequent decline of speech expression might result from defective auditory analysis of the patient's own speech. Indeed, despite normal hearing levels, the children behave as if they were deaf, and very rapidly speech expression deteriorates and leads to the receptive aphasia typical of LKS. The association of auditory agnosia more or less restricted to speech with severe language decay prompted numerous studies aimed at specifying the defect in auditory processing and its pathophysiology. Long-term follow-up studies have addressed the issue of the outcome of verbal auditory processing and the development of verbal working memory capacities following the deprivation of phonologic input during the critical period of language development. Based on a review of neurophysiologic and neuropsychological studies of auditory and phonologic disorders published these last 20 years, we discuss the association of verbal agnosia and speech production decay, and try to explain the phonologic working memory deficit in the late outcome of LKS within the Hickok and Poeppel dual-stream model of speech processing.     

Acute auditory agnosia as the presenting hearing disorder in MELAS

MELAS is commonly associated with peripheral hearing loss. Auditory agnosia is a rare cortical auditory impairment, usually due to bilateral temporal damage. We document, for the first time, auditory agnosia as the presenting hearing disorder in MELAS. A young woman with MELAS (A3243G mtDNA mutation) suffered from acute cortical hearing damage following a single stroke-like episode, in the absence of previous hearing deficits. Audiometric testing showed marked central hearing impairment and very mild sensorineural hearing loss. MRI documented bilateral, acute lesions to superior temporal regions. Neuropsychological tests demonstrated auditory agnosia without aphasia. Our data and a review of published reports show that cortical auditory disorders are relatively frequent in MELAS, probably due to the strikingly high incidence of bilateral and symmetric damage following stroke-like episodes. Acute auditory agnosia can be the presenting hearing deficit in MELAS and, conversely, MELAS should be suspected in young adults with sudden hearing loss.     

Modulation of neural responses to speech by directing attention to voices or verbal content

We studied with functional neuroimaging the cortical response to auditory sentences, comparing two recognition tasks that either targeted the speaker's voice or the verbal content. The right anterior superior temporal sulcus responded during the voice but not during the verbal content task. This response was therefore specifically related to the analysis of nonverbal features of speech. However, the dissociation between verbal and nonverbal analysis was only partial. Left middle temporal regions previously implicated in semantic processing responded in both tasks. This indicates that implicit semantic processing occurred even when the task directed attention to nonverbal input analysis. The verbal task yielded greater bilateral activation in the fusiform/lingual region, presumably reflecting an implicit translation of auditory sentences into visual representations. This result confirms the participation of visual cortical regions in verbal analysis of speech.     

Cortical auditory disorders: clinical and psychoacoustic features.

The symptoms of two patients with bilateral cortical auditory lesions evolved from cortical deafness to other auditory syndromes: generalised auditory agnosia, amusia and/or pure word deafness, and a residual impairment of temporal sequencing. On investigation, both had dysacusis, absent middle latency evoked responses, acoustic errors in sound recognition and matching, inconsistent auditory behaviours, and similarly disturbed psychoacoustic discrimination tasks. These findings indicate that the different clinical syndromes caused by cortical auditory lesions form a spectrum of related auditory processing disorders. Differences between syndromes may depend on the degree of involvement of a primary cortical processing system, the more diffuse accessory system, and possibly the efferent auditory system.     

On pure word deafness, temporal processing, and the left hemisphere.

Pure word deafness (PWD) is a rare neurological syndrome characterized by severe difficulties in understanding and reproducing spoken language, with sparing of written language comprehension and speech production. The pathognomonic disturbance of auditory comprehension appears to be associated with a breakdown in processes involved in mapping auditory input to lexical representations of words, but the functional locus of this disturbance and the localization of the responsible lesion have long been disputed. We report here on a woman with PWD resulting from a circumscribed unilateral infarct involving the left superior temporal lobe who demonstrated significant problems processing transitional spectrotemporal cues in both speech and nonspeech sounds. On speech discrimination tasks, she exhibited poor differentiation of stop consonant-vowel syllables distinguished by voicing onset and brief formant frequency transitions. Isolated formant transitions could be reliably discriminated only at very long durations (> 200 ms). By contrast, click fusion threshold, which depends on millisecond-level resolution of brief auditory events, was normal. These results suggest that the problems with speech analysis in this case were not secondary to general constraints on auditory temporal resolution. Rather, they point to a disturbance of left hemisphere auditory mechanisms that preferentially analyze rapid spectrotemporal variations in frequency. The findings have important implications for our conceptualization of PWD and its subtypes.     

Word deafness as a cortical auditory processing deficit: a case report with MEG

Pure word deafness is a rare disorder dramatically impairing comprehension of spoken language, while auditory functions remain relatively intact. We present a 71-year-old woman with a slowly progressive disturbance of speech perception due to pure word deafness. MRI revealed degeneration of the temporal lobes. A magnetoencephalographic investigation using alternating single tone stimulation showed that N100 was followed by a second transient response and was abnormally prolonged up to 600-700 ms. We conclude that auditory processing is disturbed at long latency ranges following the N100, which may result in the clinical presentation of pure word deafness.     

Focal brain lesions and language dysfunction

To be a neurologist, training in cognitive/behavioral neuroscience is essential. In this review article, the author tries to emphasize the localization relationship between focal brain lesions and language dysfunction, by discussing from split-brain syndromes, hemispheric asymmetry, to pure word dumbness, pure word deafness (verbal auditory agnosia), pure agraphia, and pure word blindness (pure alexia; visual word agnosia), and finally to aphasia and aprosodia in general. Hopefully, after getting familiar with all the terms, the readers will feel free exploring language disturbances and behavioral neurology for their own interests.     

Impaired recognition of meaningful sounds in Alzheimer's disease

We studied recognition of meaningful nonverbal sounds using a sound-picture matching test in 18 patients with senile dementia of the Alzheimer type (SDAT) and 19 age-matched controls. A significant impairment of sound recognition was found in the SDAT group, consistent with auditory sound agnosia. Although sound recognition performance correlated significantly with auditory verbal comprehension scores, a sound recognition defect was also identifiable in the subgroup of patients with SDAT who had normal verbal comprehension. Qualitative analysis of sound recognition errors revealed that nonaphasic patients with SDAT made predominantly acoustic errors, whereas semantic errors were found almost exclusively in aphasic patients. These findings suggest that the auditory sound agnosia of patients with SDAT may be subdivided into perceptual-discriminative and semantic-associative types.     

Alexia and agraphia in Wernicke''s aphasia.

Three patients with otherwise typical Wernicke's aphasia showed consistently greater impairment of reading than auditory comprehension. While this syndrome resembles alexia with agraphia, the paraphasia of speech, repetition, and naming underline the aphasic nature of the disorder. Together with previous reports of isolated word deafness in Wernicke's aphasia, these cases suggest a relative independence of auditory and visual language processing.     

Reading aloud in jargonaphasia: an unusual dissociation in speech output.

A patient is described who showed several dissociations between oral and written language processing after bilateral retrorolandic vascular lesion. Dissociation was firstly between abolished auditory comprehension and preserved written comprehension and then involved confrontation naming, clearly superior in the written modality. The third striking dissociation involved oral output; spontaneous speech, although fluent and well articulated, consisted of neologistic jargon, while reading aloud was clearly superior though not perfect. Data are discussed with reference to a cognitive model of word processing. The pattern of dissociation in word production may be due to a failure in retrieving the phonological word form from the semantic system.     

A case of deaf–mutism as an expression of pure word deafness: neuroimaging and electrophysiological data

We report a case of pure word deafness, clinically expressed as deaf–mutism in a 17-year-old girl, who was affected from encephalitis when she was 18 months old and hadn't acquired language skills. Actually, physical examination revealed buccolingual apraxia and absence of spontaneous speech, auditory comprehension, repetition and denomination, whereas perception of non-verbal sounds was preserved. The seven waves of brainstem auditory evoked responses (BAER) were present with normal latencies; middle latency responses (MLR) were also normal. Magnetic resonance imaging (MRI) showed bilateral temporoparietal lesions. This case proves that lesions which may give rise to word deafness, when they occur in prelingual age, can determine a peculiar deafmutism clinical picture.