Visual activity predicts auditory recovery from deafness after adult cochlear implantation.

Modern cochlear implantation technologies allow deaf patients to understand auditory speech; however, the implants deliver only a coarse auditory input and patients must use long-term adaptive processes to achieve coherent percepts. In adults with post-lingual deafness, the high progress of speech recovery is observed during the first year after cochlear implantation, but there is a large range of variability in the level of cochlear implant outcomes and the temporal evolution of recovery. It has been proposed that when profoundly deaf subjects receive a cochlear implant, the visual cross-modal reorganization of the brain is deleterious for auditory speech recovery. We tested this hypothesis in post-lingually deaf adults by analysing whether brain activity shortly after implantation correlated with the level of auditory recovery 6 months later. Based on brain activity induced by a speech-processing task, we found strong positive correlations in areas outside the auditory cortex. The highest positive correlations were found in the occipital cortex involved in visual processing, as well as in the posterior-temporal cortex known for audio-visual integration. The other area, which positively correlated with auditory speech recovery, was localized in the left inferior frontal area known for speech processing. Our results demonstrate that the visual modality's functional level is related to the proficiency level of auditory recovery. Based on the positive correlation of visual activity with auditory speech recovery, we suggest that visual modality may facilitate the perception of the word's auditory counterpart in communicative situations. The link demonstrated between visual activity and auditory speech perception indicates that visuoauditory synergy is crucial for cross-modal plasticity and fostering speech-comprehension recovery in adult cochlear-implanted deaf patients.

Evolution of crossmodal reorganization of the voice area in cochlear-implanted deaf patients.

Psychophysical and neuroimaging studies in both animal and human subjects have clearly demonstrated that cortical plasticity following sensory deprivation leads to a brain functional reorganization that favors the spared modalities. In postlingually deaf patients, the use of a cochlear implant (CI) allows a recovery of the auditory function, which will probably counteract the cortical crossmodal reorganization induced by hearing loss. To study the dynamics of such reversed crossmodal plasticity, we designed a longitudinal neuroimaging study involving the follow-up of 10 postlingually deaf adult CI users engaged in a visual speechreading task. While speechreading activates Broca's area in normally hearing subjects (NHS), the activity level elicited in this region in CI patients is abnormally low and increases progressively with post-implantation time. Furthermore, speechreading in CI patients induces abnormal crossmodal activations in right anterior regions of the superior temporal cortex normally devoted to processing human voice stimuli (temporal voice-sensitive areas-TVA). These abnormal activity levels diminish with post-implantation time and tend towards the levels observed in NHS. First, our study revealed that the neuroplasticity after cochlear implantation involves not only auditory but also visual and audiovisual speech processing networks. Second, our results suggest that during deafness, the functional links between cortical regions specialized in face and voice processing are reallocated to support speech-related visual processing through cross-modal reorganization. Such reorganization allows a more efficient audiovisual integration of speech after cochlear implantation. These compensatory sensory strategies are later completed by the progressive restoration of the visuo-audio-motor speech processing loop, including Broca's area.

Binaural stimulation through cochlear implants in postlingual deafness: a positron emission tomographic study of word recognition.

HYPOTHESIS: Bilateral stimulation through cochlear implants induces a brain activity pattern closer to the normal one than unilateral stimulation. BACKGROUND: Although it has been shown that speech comprehension through bilateral cochlear implants leads to better performances than after unilateral implantation, the existence of neural underpinnings of this improvement remains to be studied. METHODS: We performed an H2O positron emission tomographic study of word recognition in 5 patients with bilateral cochlear implants and 5 normal-hearing controls. Subjects had to distinguish words from nonwords in binaural and monaural conditions. RESULTS: There was no overactivation in patients for binaural stimulation, with a hypoactivation in the right temporal cortex. For monaural stimulation, patients demonstrated more activation contralaterally to the stimulation side in the posterior temporal cortex and in the cerebellum. CONCLUSION: Binaural stimulation through cochlear implants is advantageous compared with the monaural at the neurofunctional level because the pattern of brain activity is closer to the normal one.

Correlations between CT scan findings and hearing thresholds in otosclerosis.

CONCLUSION: High-resolution computed tomography (CT) scan may reveal an isolated fenestral form of otosclerosis, and an extensive form, which involves multiple foci around the otic capsule. Pre- and postoperative hearing thresholds are poorer in patients with extensive otosclerosis and their chance of overclosure is reduced by 90%. OBJECTIVES: To evaluate the relationship between CT scan extension of otosclerotic foci and hearing thresholds in the operated ear, before and after stapedotomy. METHODS: A preoperative CT scan was performed in 200 patients suspected of having otosclerosis. CT scan findings were categorized as negative, isolated fenestral otosclerosis, and extensive otosclerosis. Preoperative and 2 months postoperative air-conduction (AC) and bone-conduction (BC) thresholds were collected. RESULTS: In the operated ear, 150 CT scans (75%) revealed an isolated fenestral otosclerosis; 35 (17.5%) were classified as extensive otosclerosis. Mean preoperative BC was significantly poorer in extensive otosclerosis (30.3 dB) than in isolated fenestral otosclerosis (24.6 dB). Mean postoperative BC remained lower in extensive otosclerosis (30.3 dB) than in isolated fenestral otosclerosis (21.2 dB). An overclosure greater than 10 dB was found in 20% of isolated fenestral otoscleroses and in 2.85% of extensive otoscleroses (chi-square: 5.5; p = 0.02).

Revision stapes surgery: the "lateralized piston syndrome".

OBJECTIVE: The need for revision stapes surgery has many causes, and among these, we describe a particular displacement of the piston: the "lateralized piston syndrome". The goal of this study is to define criteria and surgical management of this syndrome. STUDY DESIGN: Retrospective study over 13 years. SETTING: Tertiary reference center. PATIENTS: A review of 1,289 consecutive stapes operations revealed 119 revisions (9%) from which 22 cases (18.5%) could be classified under the lateralized piston syndrome. INTERVENTION: Revision stapedotomy. MAIN OUTCOME MEASURES: Medical files, preoperative and postoperative audiograms, computed tomographic scans, and operative reports. RESULTS: The 22 cases presented as a delayed conductive hearing loss in 95.5% of cases. Preoperative computed tomographic scans showed a lateralized piston out of the stapedotomy in 81% of cases and touching the tympanic membrane in 54.5% of cases. Revisions revealed a lateral displacement of the piston out of the entire oval window in 86% of cases, with closure of the stapedotomy in all cases and incus necrosis in 77% of cases. Conventional pistons were fitted in 12 cases. In case of a significantly eroded incus, total prostheses (TORPs) in 6 cases and offset pistons in 4 cases were placed. Air-bone gap (ABG) was closed to within 20 dB in 82% of cases. Air-conduction puretone audiometry improvement was 17.2 dB (standard deviation [SD], 19.2), with a mean postoperative ABG of 16.2 dB (SD, 12.7). Only 1 ear, operated with TORP, had a sensorineural deterioration of 20 dB. With offset pistons, ABG was closed to within 20 dB in 100% of cases with a mean postoperative ABG of 8.8 dB (SD, 7.2). CONCLUSION: The lateralized piston syndrome was found in 18.5% of stapes surgery revisions. Surgical management was effective in correcting the conductive hearing loss. In the event of significant eroded incus, we observed better results with offset pistons than with TORPs.

Reliability of high-resolution CT scan in diagnosis of otosclerosis.

OBJECTIVE: To assess the reliability of high-resolution computed tomographic scan (HRCT scan) for the diagnosis of otosclerosis and to determine its usefulness to predict hearing deterioration and surgical difficulties. STUDY DESIGN: Prospective study. SETTING: Tertiary reference center. PATIENTS: Two hundred nine ears (200 patients) presenting progressive conductive hearing loss with normal tympanic membrane, abnormal stapedial reflex, and scheduled for stapes surgery. The mean age was 47.3 years. INTERVENTION: All patients underwent HRCT scan before surgery (slice thickness of 0.6 to 1 mm). Stapedotomy was performed in 99% of cases. MAIN OUTCOME MEASURES: High-resolution computed tomographic scan results were categorized as positive, doubtful, or negative. We classified a CT scan as positive for otosclerosis when a hypodense focus was seen around the otic capsule. Preoperative and postoperative air- and bone-conduction thresholds were collected. RESULTS: Of 209 HRCT scans, 84.2% were classified positive, 8.6% doubtful, and 7.2% negative. In all patients with positive CT scan, otosclerosis was confirmed in surgery. Among 15 negative cases, we found 4 minor malformations and 1 fracture of the stapes. Footplate incidents (mobilized, floating, or fractured footplate; 5.3%) occurred significantly more frequently when an HRCT scan was negative or doubtful (p = 0.05). Mean preoperative air-bone gap was 27.7 dB (standard deviation, 10). Mean postoperative air-bone gap was within 10 dB in 65% and within 20 dB in 92% of cases. Greater than 10 dB deterioration of bone-conduction thresholds occurred in 2% of cases. Mean preoperative and postoperative bone-conduction thresholds were significantly lower in cases of round window obliteration, pericochlear, or internal auditory canal hypodensities (p < 0.005 and p < 0.0001, respectively). CONCLUSION: In our series, the sensitivity of HRCT scan to otosclerosis was 95.1%. Hypodense otosclerotic foci were mostly localized at the anterior part of footplate. Negative or doubtful cases were associated with the highest incidence of stapes footplate complications. Foci involving otic capsule, internal auditory canal, or round window led to a significantly higher risk of sensorineural hearing loss.