Cases reported "Hearing Loss, Central"

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1/8. The neural correlates of 'deaf-hearing' in man: conscious sensory awareness enabled by attentional modulation.

    Attentional modulation of normal sensory processing has a two-fold impact on human brain activity: activation of a network of localized brain regions is associated with paying attention, and activation of specific sensory regions is enhanced relative to passive stimulation. The mechanisms underlying attentional modulation of perception in patients with lesions of sensory cortices are less well understood. Here we report a unique patient suffering from extensive bilateral destruction of the auditory cortices (including the primary auditory fields) who demonstrated conscious perception of the onset and offset of sounds only when selectively attending to the auditory modality. This is the first description of such an attentively modulated 'deaf-hearing' phenomenon and its neural correlates, using H(2)(15)O-PET. Increases in cerebral blood flow associated with conscious awareness of sound that was achieved by listening attentively (compared with identical auditory stimulation presented when the patient was inattentive) were found bilaterally in the lateral (pre)frontal cortices, the spared middle temporal cortices and the cerebellar hemispheres. We conclude that conscious awareness of sounds may be achieved in the absence of the primary auditory cortex, and that selective, 'top-down' attention, associated with prefrontal systems, exerts a crucial modulatory effect on auditory perception within the remaining auditory system.
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ranking = 1
keywords = cortex
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2/8. Cortical deafness to dissonance.

    Ordinary listeners, including infants, easily distinguish consonant from dissonant pitch combinations and consider the former more pleasant than the latter. The preference for consonance over dissonance was tested in a patient, I.R., who suffers from music perception and memory disorders as a result of bilateral lesions to the auditory cortex. In Experiment 1, I.R. was found to be unable to distinguish consonant from dissonant versions of musical excerpts taken from the classical repertoire by rating their pleasantness. I.R.'s indifference to dissonance was not due to a loss of all affective responses to music, however, since she rated the same excerpts as happy or sad, as normal controls do. In Experiment 2, I.R.'s lack of responsiveness to varying degrees of dissonance was replicated with chord sequences which had been used in a previous study using PET, in examining emotional responses to dissonance. A CT scan of I.R.'s brain was co-registered with the PET activation data from normal volunteers. Comparison of I.R.'s scan with the PET data revealed that the damaged areas overlapped with the regions identified to be involved in the perceptual analysis of the musical input, but not with the paralimbic regions involved in affective responses. Taken together, the findings suggest that dissonance may be computed bilaterally in the superior temporal gyri by specialized mechanisms prior to its emotional interpretation.
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ranking = 1
keywords = cortex
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3/8. Cortical motion deafness.

    The extent to which the auditory system, like the visual system, processes spatial stimulus characteristics such as location and motion in separate specialized neuronal modules or in one homogeneously distributed network is unresolved. Here we present a patient with a selective deficit for the perception and discrimination of auditory motion following resection of the right anterior temporal lobe and the right posterior superior temporal gyrus (STG). Analysis of stimulus identity and location within the auditory scene remained intact. In addition, intracranial auditory evoked potentials, recorded preoperatively, revealed motion-specific responses selectively over the resected right posterior STG, and electrical cortical stimulation of this region was experienced by the patient as incoming moving sounds. Collectively, these data present a patient with cortical motion deafness, providing evidence that cortical processing of auditory motion is performed in a specialized module within the posterior STG.
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ranking = 0.0031119512234233
keywords = visual
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4/8. 'So-called' cortical deafness. Clinical, neurophysiological and radiological observations.

    Two patients with severe, persistent hearing loss caused by bilateral cerebral lesions are described. To determine the location of lesions responsible for the severe hearing loss, we examined magnetic resonance images and compared the lesions in these 2 patients with those in another with only mild hearing loss following extensive bilateral temporoparietal lesions. The extent of bilateral damage to the white matter adjacent to the posterior half of the putamen proved crucial in determining the severity of the hearing loss. hearing loss was more severe when the white matter immediately ventral and lateral to the posterior half of the putamen was involved bilaterally. Based on this observation and from a review of the literature, we infer that the auditory radiations in humans course in a dense tract from the medial geniculate body up to the sublenticular region, and disperse from there to the primary auditory cortex as well as to the other auditory-related areas, partly by coursing through the white matter immediately ventral to the posterior half of the putamen, and partly by penetrating the ventral and lateral portions of the posterior half of the putamen. Accordingly, bilateral lesions in the white matter ventral and lateral to the posterior half of the putamen appear to interrupt all the projection fibres from the medial geniculate bodies to the auditory-related areas, resulting in severe, persistent hearing loss.
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ranking = 1
keywords = cortex
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5/8. Psychoacoustic and electrophysiologic correlates of central hearing disorders in man.

    Evaluation of central hearing disorders in neuropsychologic patients is handicapped by their insufficient ability to describe auditory deficits and by the lack of easily applicable audiological tests. A novel psychoacoustic discrimination test (PDT) was developed to determine ear asymmetries in the discrimination of changes in intensity, frequency, or temporal structure of regularly presented dichotic stimuli. In 19 of 21 patients with lesions of the auditory cortex or the acoustic radiation according to CT scan evaluation a higher error score was observed for target stimuli presented at the ear contralateral to the side of brain infarction (6 right, 15 left). In the remaining 2 and in 3 other patients with lesions sparing auditory structures no significant ear asymmetries were seen. This may indicate that auditory perception is reduced in patients with only one intact auditory cortex or one intact acoustic radiation, possibly because of a limitation in information processing capacity. Auditory evoked potential results are presented for a normal subject and two patients to illustrate electrophysiologic correlates of central hearing disorders. Using a transformation of scalp into dipole source activity (Scherg and von Cramon 1986), a unilateral loss of middle latency activity was found in case A, who had a lesion of the left acoustic radiation. The extended lesion of the right auditory cortex in case B resulted in a loss of both middle and late latency dipole source potentials of the right temporal lobe. In both cases a corresponding increase in the PDT error score on the contralateral ear was found.
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ranking = 3
keywords = cortex
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6/8. Neuroradiologic evaluation of patients with central auditory lesions.

    CT and MR imaging have revolutionized diagnostic medical imaging. MR scanning in particular is the method of choice to evaluate the CP angle lesion or other posterior fossa lesion. With CT pneumocisternography, neurovascular structures of the internal auditory canal and lesions can be visualized. Experience indicates that MR scanning will replace CT.
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ranking = 0.0031119512234233
keywords = visual
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7/8. tinnitus and hearing loss in pineal region tumours.

    The authors report an underestimated symptom and sign arising in pineal region tumours: tinnitus and hearing loss. It has been observed in 13 out of 72 pineal region tumours (18%). Three illustrative cases are reported in this paper. The inferior colliculi, the structure more dense in fibres than any other auditory brain stem site and at which majority of the acoustic pathways relay, is closely adjacent to the pineal body. Displacement of this structure may be responsible for acoustic symptoms together with common visual symptoms.
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ranking = 0.0031119512234233
keywords = visual
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8/8. Central auditory information processing in patients with bilateral auditory cortex lesions.

    Severe auditory cognitive disorders in 10 patients who had bilateral lesions either to the auditory cortex and/or auditory radiations were studied audiologically with special attention to residual hearing. This auditory cognitive problem is called "auditory agnosia or cortical deafness". Our study revealed that auditory information processing for pure tones, monosyllable discrimination, environmental sound perception, and auditory comprehension is commonly but differently affected by bilateral lesions of auditory cortex or auditory radiation. In summary, these patients can discriminate loudness of pure tones and some environmental sounds but cannot clearly perceive any sounds of monosyllables and sentences. Generally their residual hearing is useful for auditory awareness and is often enhanced by lip reading.
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ranking = 6
keywords = cortex
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