1/54. Neuroanatomical correlates to central deafness. Our research experience with five centrally deaf patients showed that damage to various anatomical sites could result in central deafness. This finding was contrary to the commonly held notion that both Heschl's gyri must be severely damaged to yield central deafness. To discover whether lesions in various brain areas could cause central deafness, we reviewed 33 cases of central deafness reported in the literature which had sufficient radiological data to determine the anatomical regions involved. Both Heschl's gyri were involved in the majority of these cases, but there were definite exceptions. In these exceptional cases of central deafness, subcortical areas were involved (usually the internal capsule), as was the insula. overall findings are discussed and recommendations are offered for the future study of centrally deaf patients. ( info) |
2/54. Isolated metastases of adenocarcinoma in the bilateral internal auditory meatuses mimicking neurofibromatosis type 2--case report. A 56-year-old male with a history of lung cancer presented with isolated metastases of adenocarcinoma in the bilateral internal auditory meatuses (IAMs), mimicking the bilateral acoustic schwannomas of neurofibromatosis type 2, and manifesting as rapidly worsening tinnitus and bilateral hearing loss. magnetic resonance imaging showed small tumors in both IAMs with no sign of leptomeningeal metastasis. The preoperative diagnosis was neurofibromatosis type 2. Both tumors were removed and the histological diagnoses were adenocarcinoma. neuroimaging differentiation of a solitary metastatic IAM tumor from a benign tumor is difficult, although rapidly progressive eighth cranial nerve dysfunction suggests a malignant process. Metastases should be considered as a rare diagnostic possibility in a patient with small tumors in both IAMs. ( info) |
3/54. 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. ( info) |
4/54. 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. ( info) |
5/54. First Croatian auditory brainstem implantation. A deaf female patient was diagnosed with bilateral acoustic neurinomas. diagnosis incorporated the standard audiological battery for sensorineural hearing loss, computed tomography and magnetic resonance imaging. The left side had been operated on four years previously in another clinic using the suboccipital approach. The auditory brainstem implant surgery was performed on the 'second side' using the same approach. It was an uneventful operation with good anatomy and no serious post-operative complications. Post-operatively, the patient performed exceptionally well, with up to 50 per cent of words recognized in the opened set and 85 per cent in the closed set, both without lip-reading. ( info) |
6/54. First auditory brainstem implantation in poland: auditory perception results over 12 months. Auditory brainstem implants (ABIs) are a modern method of treatment of total bilateral deafness in cases of extracochlear origin. In most cases therapy is applied in patients with neurofibromatosis type 2 (NF2). This paper presents the results of surgical treatment and rehabilitation in a 28-year-old woman with bilateral, multiple tumours of the central nervous system causing total deafness. Simultaneous removal of the tumours and implantation of ABI allowed treatment of the potentially lethal pathology and hearing restoration. Improving auditory skills and excellent tests results were noted in the year following implantation. ( info) |
7/54. First auditory brainstem implant in the czech republic. In the czech republic, the first implantation of a stimulation electrode into the brainstem was performed on 11 January 1999 in the Department of ORL, head and neck Surgery, The First Medical faculty, Charles University in Prague, University Hospital Motol. The selected patient was a 40-year-old woman with neurofibromatosis type 2 (NF2) who had previously undergone bilateral vestibular schwannoma surgery. Both tumours had been radically removed, the left-sided tumour in 1987, the right-sided one in 1988. She had been completely deaf since the last operation, i.e., for 11 years. The surgery was realized by the international cooperation of three teams. Placement of the electrode pad of the Nucleus CI21 1M system on the ventral and dorsal cochlear nuclei was performed. Electrically evoked auditory brainstem responses (EABRs) proved the correct position of the electrode array. The post-operative course was uneventful. Six weeks after the surgery the patient received her speech processor. Since that time, the patient already absolved several sessions of a speech processor tune-up. She uses the device as an aid in lip-reading. No adverse or pathological side effects have been observed. The patient was the 45th person in europe to receive an ABI and the first in the czech republic. ( info) |
8/54. 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. ( info) |
9/54. Brainstem electronic implants for bilateral anacusis following surgical removal of cerebello pontine angle lesions. The multichannel auditory brainstem implant (ABI) has been used successfully to treat deafness in individuals with neurofibromatosis type II. The device has been implanted in nearly 150 recipients worldwide, and clinical trials with the device are approaching completion. The implantation and fitting of the multichannel ABI differ significantly from cochlear implantation, and the processes are illustrated in a series of case studies. Performance data also are included from recipients with up to 7 years experience. ( info) |
10/54. Hearing restoration with auditory brainstem implants after radiosurgery for neurofibromatosis type 2. The auditory brainstem implant (ABI) is designed to restore useful auditory sensations in patients with neurofibromatosis Type 2 (NF2). The implantation is usually performed at the time of tumor removal in patients who do not undergo radiation treatment. The authors evaluated the performance of ABIs in three patients with NF2 in whom vestibular schwannoma continued to grow after radiation treatment. These three patients with NF2 received a 21-channel ABI; a translabyrinthine approach was used for both the tumor removal and the ABI placement. The interval between radiosurgery and the tumor removal plus device implantation ranged from 2 to 11 years. In all cases, the tumor was growing and the patients presented with total deafness. The mean number of active electrodes in these three patients was equivalent to the average results reported in other patients who received ABIs. The patients in this study used the ABI regularly for everyday life and obtained useful levels of environmental sound recognition. It is concluded that hearing function can be rehabilitated using ABIs in patients with NF2, even if radiosurgery fails to control the tumor growth. ( info) |