Preservation of hearing in large acoustic neurinomas following removal via suboccipito-lateral approach

A consecutive series of 61 patients with pre-operative hearing underwent surgical removal of a large acoustic neurinoma via the lateral suboccipital approach between 1984 and 1996. Brain-stem auditory evoked potentials (BAEP) were present in all cases before surgery and all patients underwent intra-operative monitoring of BAEP. The average tumour size including the portion within the meatus acusticus internus was 30, 5 mm (range 20 mm-49 mm). Complete tumour removal was achieved in all but three cases. In 43.1% of patients with complete tumour removal hearing was preserved initially after surgery. Delayed postoperative hearing loss was observed in 11 patients and hearing recovery in 2 patients leading to 27.5% definite hearing preservation. Hearing preservation was achieved in 37% of cases with tumour size between 20 mm-29 mm and in 23.5% of case with tumour size larger than 30 mm. These results indicate that even in large neurinoms hearing preservation should be attempted in all patients with documented pre-operative hearing and BAEP.     

Afferent projection patterns in the auditory brainstem in normal and congenitally deaf white cats

Cochlear implantation in congenitally deaf children is developing to a successful medical tool. Little is known, however, on morphology and pathophysiology of the central auditory system in these auditory deprived children. One form of congenital hearing loss, that seen in the deaf white cat, was investigated to see if there are differences in the afferent pathways from the cochlear nuclei to the inferior colliculus. The retrogradely transported fluorescent tracer diamidino yellow (DY) was injected into different parts of the central nucleus of the inferior colliculus (ICC) of normal cats and deaf white cats. It was found that the main afferent projection patterns in deaf white cats were unchanged in spite of congenital auditory deprivation; minor differences were seen.     

Gram-scale synthesis of recombinant chitooligosaccharides in Escherichia coli

Basilar membrane (BM) noise, measured as a velocity signal under the quiet acoustic condition, was investigated in the guinea pig. The cochleas of anesthetized young healthy guinea pigs were surgically exposed and a hole was made on the lateral wall of the scala tympani of the first cochlear turn for visualization of the BM and measurement of the BM velocity with a laser interferometer. The amplitude and frequency of the BM velocity noise were analyzed by a spectrum analyzer under different conditions. The spectrum of the BM velocity noise was a band limited function with a peak velocity at the topographic best frequency of the measured location on the BM. The peak velocity ranged to about 8 microm/s and depended on the physiological condition of the cochlea. Saline blockage of the external auditory canal or the middle ear did not change the BM noise. BM noise was much smaller, or was not evident, when the cochlear sensitivity decreased. The suppression tuning curve of the BM velocity noise indicates that the maximum suppression caused by an acoustic pure tone occurred at the best frequency location. A low sound level wide band acoustic noise given to the external ear canal produced a spectrum function having the same frequency and amplitude response as the BM noise. Electrical stimulation of the crossed olivocochlear bundle significantly depresses the BM velocity noise. These data demonstrate that the BM noise is a representation of internal rather than external noise. The amplitude and frequency of the BM noise reflect the usual cochlear sensitivity and frequency selectivity. Since the organ of Corti in the sensitive cochlea is a highly sensitive and tuned mechanical system, the internal (to the animal) noise responsible for the BM noise may originate from mechanical vibrations remote from the cochlea and propagated to the ear, or may be caused by Brownian motion of cellular structures in the cochlea.     

Results of cochlear implantation in patients with severe to profound hearing loss--implications for patient selection

In patients with some residual hearing and minor benefit from conventional hearing aids, the benefits of cochlear implantation have to be weighed carefully against eventual adverse effects. In this study, pre- and post-operative thresholds as well as functional results after cochlear implantation are reported; 17 of 44 implanted adults had residual hearing pre-operatively (mean threshold(250 to 4000 Hz): 106 dB HL) in the implanted ear. Residual hearing in the implanted ear could not, in general, be preserved post-operatively. Seventeen of 44 implanted children had some amount of residual hearing in the implanted ear pre-operatively (implanted ear: 114 dB HL; contralateral ear: 109.9 dB HL; mean thresholds(250 to 4000 Hz))). Contrary to the results in adults, residual hearing in the implanted ear remained statistically unchanged. Hearing in the contralateral ear increased significantly from 109.9 to 101.9 dB HL post-operatively. This increase was mainly attributed to maturation of the central auditory pathway. In adults with residual hearing, the monosyllable word recognition scores increased significantly from 9 per cent pre-operatively to 42 per cent post-operatively. Children with residual hearing tended to perform better on speech-related test material compared to children without prior auditory experience. Cochlear implantation is indicated in adults and children with residual hearing and minor benefit from conventional amplification. The contralateral ear in children should be considered for additional acoustical stimulation.     

Brainstem auditory evoked potentials in young children before and after tympanostomy tube placement

To evaluate the effect of tympanostomy tube placement upon the hearing function of infants and young children, brainstem auditory evoked potentials (BAEP) were recorded in a group of young children (mean age 22 mos) receiving this treatment for otitis media with effusion (OME). For comparison, a group of healthy infants with normal behavioral audiometry were also tested with BAEP. Hearing loss was estimated for each ear using peak V latency-intensity curves. To evaluate the immediate effect of tube placement, 98 ears in 52 children were tested immediately before and after tube insertion. The 63 ears with effusion had prolonged peak latencies that decreased significantly (P < 0.001) immediately after tube placement and a mean hearing loss estimate of 22 dB that improved significantly (P < 0.0001) to 11 dB immediately after tube insertion. The 35 ears without effusion at myringotomy had a mean hearing loss estimate of 8 dB that did not change significantly after tube insertion. To evaluate the short-term effect of tube presence, 39 ears in 25 children were tested 3 weeks to 18 months after tube insertion. The 28 ears with dry tubes had a mean hearing loss estimate of 3 dB, and the 11 ears with otorrhea had a mean hearing loss estimate of 31 dB. The magnitude of mean hearing loss estimates in these young children with OME and the improvement in hearing function with tube placement is similar to that reported in older children studied with BAEP and audiometry. The study groups with a history of otitis media that had resolved by the time of testing had isolated prolongation of mean III-V interpeak latencies compared to normals (P < 0.01). These studies show that BAEP techniques are useful in estimating hearing loss in children with OME who are difficult to test by behavioral audiometry and show changes in rostral brainstem transmission in very young children with a history of OME.     

A hearing conservation program for Wisconsin youth working in agriculture

Adolescents working in agricultural settings may be exposed to noise levels that result in hearing loss. The article describes the design, implementation, and results of a four-year, hearing conservation program (HCP) conducted at school. Thirty-four schools (753 students) were randomly assigned to either an intervention or control group. The intervention included multicomponent educational strategies and employed features of an industrial HCP. Final compliance surveys indicated 87.5% of intervention students reported using hearing protection devices (HPD) at least some of the time, compared to 45% of control students. The HCP components with the greatest reported influence were distribution of HPDs for use on the farm and yearly hearing tests. Eighty percent of intervention students reported intention to use HPDs in the future. It is feasible to conduct a hearing conservation program with junior high school and senior high school students, and it appears possible to persuade teen-agers to protect themselves from exposure to loud noise while working on a farm.     

Neonatal sound deprivation affects brain stem auditory nuclei

CBA/J mice deprived of airborne sound stimulation during postnatal development have smaller globular cells in the ventral cochlear nucleus and smaller neurons in the medial nucleus of the trapezoid body than do normal control mice. The sound deprivation in these mice is similar to that experienced by persons with pure congenital conductive hearing losses. Even more profound central neural changes were found in auditory nuclei in the brain stem of a congenitally sensorineural deaf human.     

Functional mapping of the U3 small nucleolar RNA from the yeast Saccharomyces cerevisiae

The 2 f1-f2 distortion product otoacoustic emission (DP) was measured in 20 normal hearing subjects and 15 patients with moderate cochlear hearing loss and compared to the pure-tone hearing threshold, measured with the same probe system at the f2 frequencies. DPs were elicited over a wide primary tone level range between L2 = 20 and 65 dB SPL. With decreasing L2, the L1-L2 primary tone level difference was continuously increased according to L1 = 0.4L2 + 39 dB, to account for differences of the primary tone responses at the f2 place. Above 1.5 kHz, DPs were measurable with that paradigm on average within 10 dB of the average hearing threshold in both subject groups. The growth of the DP was compressive in normal hearing subjects, with strong saturation at moderate primary tone levels. In cases of cochlear impairment, reductions of the DP level were greatest at lowest, but smallest at highest stimulus levels, such that the growth of the DP became linearized. The correlation of the DP level to the hearing threshold was found to depend on the stimulus level. Maximal correlations were found in impaired ears at moderate primary tone levels around L2 = 45 dB SPL, but at lowest stimulus levels in normal hearing (L2 = 25 dB SPL). At these levels, 17/20 impaired ears and 14/15 normally hearing ears showed statistically significant correlations. It is concluded that for a clinical application and prediction of the hearing threshold, DPs should be measured not only at high, but also at lower primary tone levels.     

A modification of play audiometry to assess speech discrimination ability in severe-profoundly deaf 2- to 4-year-old children

OBJECTIVE: The aim was to develop an assessment procedure that was independent of language and speech production ability, to test speech feature discrimination in severe-profoundly deaf children 2 to 4 yr of age. DESIGN: The procedure being trialed was adapted from existing procedures. The child was required to respond with a game-like motor response to a "change" in a speech stimulus that was being presented repeatedly through a speaker. The change occurred at randomly determined times, and false alarm responses were measured during the waiting periods (while the child waited for the change). Two- to four-yr-old normally hearing children and hearing-impaired children using hearing aids and a group of 4-yr-old hearing-impaired children using cochlear implants were assessed on the task. RESULTS: More than 82% of the 3- and 4-yr-old normally hearing and hearing-impaired children were able to complete the testing for the eight speech sound contrasts within three 20 minute sessions. Fifty percent of the 2-yr-old normally hearing and hearing-impaired children were able to condition and complete the task. All of the normally hearing children who completed the task successfully discriminated all speech sound contrasts. The performance of the hearing-impaired children using hearing aids was influenced by the degree of hearing loss and the type of speech contrast being tested. Similarly, the average performance of the children using cochlear implants was better for easier contrasts such as /ba/bi/ with contrasting vowel formant cues. CONCLUSIONS: This procedure has potential for use as a reliable clinical and research tool for assessing the development of auditory discrimination ability in 2- to 4-yr-old severe-profoundly deaf children.     

Mixed effect modeling of sumatriptan pharmacokinetics during drug development. I: Interspecies allometric scaling

A sample of 22 subjects was studied from a population of adults who had suffered from bacterial meningitis in childhood. Audiovestibular, oculomotor and neuropsychological investigations were performed and quality of life was assessed. An age-matched control group of 20 subjects was recruited. In the meningitis group, nine subjects had abnormal pure tone audiograms. One was previously undiagnosed and a progression was found in four. There was an overrepresentation of subclinical vestibular pathology (6 out of 9 (67%)) in this group. Audiovestibular test results showed a peripheral pattern and oculomotor tests were normal. The quality of life scores of those with hearing loss were significantly higher than those in the control group. Neuropsychological tests of brain dysfunction were abnormal in six out of 22 (27%) who had recovered from meningitis. The prevalence of such dysfunctions was not related to audiovestibular disorder. The quality of life scores of those with brain dysfunctions were similar to those of the control group. The findings of reduced auditory memory and tone level perception in four out of 22 (18%), suggest that lesions of central auditory pathways may follow from bacterial meningitis. The results support the idea that inner ear damage is the major cause of hearing loss after bacterial meningitis. Despite the absence of brainstem involvement, central nervous system lesions with disturbed auditory processing and language functions can be of significance. The high frequency of discrete brain dysfunctions indicate that a thorough neuropsychological investigation is required after bacterial meningitis.     

Distortion product otoacoustic emissions for the assessment of auditory sensitivity

Distortion product otoacoustic emissions (DPOAEs) were evaluated in 494 normal and 506 cochlear-impaired human ears, to determine whether DPOAEs depend on factors such as background noise, the shape of the pure tone audiogram, sex and aging, and whether a DPOAE test can perform well in distinguishing normal-hearing from hearing-impaired ears. The amplitudes of DPOAEs were measured at the frequency of 2f1-f2 (f1 < f2, f2/f1 = 1.22, f2 at 1, 2 and 4 kHz) using as stimuli two pure tones at level of 70 dB from an ILO92 Otoacoustic Emission Analyzer. The correlation coefficients between the DPOAE level and the auditory threshold decreased as the background noise levels at 1 kHz and 2 kHz increased. Therefore, it appeared that ears with large background noise levels would be inadequate for the study of DPOAEs predicting the hearing state. The sensitivity (normal-hearing ears identified as normal hearing) and the specificity (hearing-impaired ears identified as hearing impaired) at the equal-sensitivity-specificity condition were 80.7-86.7% at 1, 2 and 4 kHz, and the areas under the receiver operating characteristic (ROC) curves, which were used to estimate the test performance, were 0.88 for 1 kHz, 0.91 for 2 kHz and 0.92 for 4 kHz. Since these results suggest that a DPOAE can be used as a reliable technique for objective auditory tests, it is thought that actual values (DPOAE level: 4.3 dB at 1 kHz, 5.0 dB at 2 kHz and 2.9 dB at 4 kHz) of false-positive (hearing-impaired ears identified as normal hearing) rates corresponding to 5% can be used in clinical evaluation to separate normal hearing from hearing-impaired ears. There was, however, a significant age effect at 4 kHz on DPOAEs in the ears with the same pure tone hearing thresholds, and the areas of the ROC curves in subjects ranging from 10 to 29 years old were larger than in subjects over 50 years (1 kHz: 0.88 to 0.94 versus 0.83 to 0.84, 2 kHz: 0.95 versus 0.89, 4 kHz: 0.95 to 0.96 versus 0.88 to 0.89). Therefore, it is thought that age-adjusted norms may be necessary for the accurate interpretation of DPOAE results.     

Classical conditioning modifies cytochrome oxidase activity in the auditory system

The effects of excitatory classical conditioning on cytochrome oxidase activity in the central auditory system were investigated using quantitative histochemistry. Rats in the conditioned group were trained with consistent pairings of a compound conditional stimulus (a tone and a light) with a mild footshock, to elicit conditioned suppression of drinking. Rats in the pseudorandom group were exposed to pseudorandom presentations of the same tone, light and shock stimuli without consistent pairings. Untrained rats in a naive group did not receive presentations of the experimental stimuli. The findings demonstrated that auditory fear conditioning modifies the metabolic neuronal responses of the auditory system, supporting the hypothesis that sensory neurons are responsive to behavioural stimulus properties acquired by learning. There was a clear distinction between thalamocortical and lower divisions of the auditory system based on the differences in metabolic activity evoked by classical conditioning, which lead to an overt learned behavioural response versus pseudorandom stimulus presentations, which lead to behavioural habituation. Increases in cytochrome oxidase activity indicated that tone processing is enhanced during associative conditioning at upper auditory structures (medial geniculate nucleus and secondary auditory cortices). In contrast, metabolic activation of lower auditory structures (cochlear nuclei and inferior colliculus) in response to the pseudorandom presentation of the experimental stimuli suggest that these areas may be activated during habituation to tone stimuli. Together these findings show that mapping the metabolic activity of cytochrome oxidase with quantitative histochemistry can be successfully used to map regional long-lasting effects of learning on brain systems.     

Identification des situations sociales à potentiel conflictuel chez les enfants: perspectives scolaire et familiale.

Studied specific situations in the home and at school in which children experience social conflicts. Human Ss: 674 normal Canadian school-age children (1st- and 2nd-grade students) (Study 1); 57 normal Canadian school-age children (1st- and 2nd-grade students) (aggressive-rejected [AR]) (Study 2); 57 normal Canadian school-age children (1st- and 2nd-grade students) (prosocial-popular [PP]) (Study 2). Study 1 was a validation of a home version of the Taxonomy of Social Problem Situations (TSPS) developed by K. A. Dodge et al (1985), in which questionnaire data from Ss' parents were subjected to factor analyses and a multivariate analysis of variance (MANOVA). In Study 2, parents and teachers rated the extent to which each S experienced specific social problem-solving difficulties, using the appropriate home or school version of the TSPS. Differences between the AR group and the PP group and between parents' and teachers' ratings were analyzed. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of profound hearing loss on a central auditory nucleus

The present study was designed to investigate the type and extent of degeneration occurring in the human central auditory system subsequent to profound hearing loss. The authors have examined the size of one population of neurons in the ventral cochlear nucleus in seven subjects with profound hearing loss (audiometric responses poorer than 90-100 dB HL). Six normal subjects, ages 35-78, were used as controls. Cell size in the hearing-impaired subjects ranged from normal to reduced by more than 50 percent. Two factors appear to contribute to the variability in cell size reduction. The correlation coefficient (Spearman rs) of cell size with duration of profound deafness was -0.48, indicating a moderate tendency for neurons to become smaller with longer periods of deafness. The correlation coefficient of cell size with number of surviving cochlear ganglion cells was 0.73, indicating a stronger tendency for neurons to be larger with greater eighth nerve innervation of the cochlear nucleus. Two cases of Scheibe degeneration showed the most severe degenerative change in the central auditory system.     

A case of familial antithrombin III variant complicated by recurrent pulmonary infarction

This paper describes hearing loss and recovery as well as cochlear damage in chicks, after a 200-h exposure to an intense pure tone, and compares the results to similar data following a 48-h exposure to the same sound. The results revealed that the magnitude of initial hearing loss and the rate of recovery were nearly the same for both exposures. The initial cochlear damage produced by the 200-h exposure, however, was less severe than that seen after the 48-h exposure. In addition, new hair cells were observed in the lesion area immediately after the 200-h exposure. However, after the 48-h exposure, they were first identified after several days of recovery. These observations were consistent with the conclusion that cochlear repair began during the longer exposure itself. The fact that hearing loss and recovery was the same for the two exposure conditions, while the level of cochlear damage differed, suggests that functional recovery depended on processes other than the regeneration or repair of hair cells and supporting cells. These other processes are considered.     

A comparison of maximal bioenergetic enzyme activities obtained with commonly used homogenization techniques

A retrospective review was made of 719 primary stapedectomies and 48 re-operations carried out between 1975 and 1993. Preoperative and postoperative audiograms (6-12 months) were studied, analyzing 250, 500, 1000, 2000 and 4000 Hz, auditory gain and closure of the air-bone gap < or = 10 dB. Ninety percent had an auditory gain of > or = 10 dB at conversational frequencies. Age, the surgeon, and average preoperative pure tone did not influence the final result. Polyethylene prostheses (70.9%) and steel and teflon pistons (21.1%) were the prostheses used most often. Neurosensorial hearing loss (> 10 dB) occurred in 24 cases (3.3%). In revision stapedectomy, 66.6% of patients had air-bone gap closure of < or = 20 dB and 71% had a hearing gain of < or = 10 dB. Prosthesis displacement (43.7%) and incus necrosis (18.7%) were the most common findings in revision stapedectomy.     

Sarthran preserves cochlear microcirculation and reduces temporary threshold shifts after noise exposure

The cause of noise-induced hearing loss remains unclear despite years of both epidemiologic and experimental investigation. Among the many possible pathophysiologic mechanisms that may contribute to noise-induced temporary or permanent threshold shifts are insufficiencies in cochlear blood flow. Although the literature is inconsistent, several histologic and physiologic studies demonstrate signs of reduced circulation in the cochlea after noise exposure. Recent studies using computer-enhanced intravital microscopy complement these earlier findings. Evidence suggests that these microcirculatory events are mediated in part by several circulating factors, including the potent vasoactive peptide angiotensin. This study investigated this possibility by pretreating with the angiotensin receptor antagonist sarthran during noise exposure and examining both cochlear microcirculation and auditory sensitivity. The results of these experiments show noise-induced ischemia in the lateral wall of the cochlea and temporary threshold shifts. Treatment with sarthran prevented this noise-induced microcirculatory ischemia and preserved auditory sensitivity at the low frequencies tested. These findings support a role for the angiotensinergic system during noise exposure and suggest that preservation of cochlear blood flow is functionally related to auditory sensitivity.     

Continuous infusion of porcine factor VIII in the management of patients with factor VIII inhibitors

Increased detection thresholds for pure tones were observed in a large cohort of children exposed to lead environmentally while smaller studies in lead-exposed workers have reported conflicting results on assessments of auditory function. Pure tone detection thresholds were determined in a group of monkeys (Macaca fascicularis) dosed with 2 mg/kg/day of lead from birth through testing at 13 years of age. Blood lead concentrations were stable at about 30 micrograms/dl until monkeys were 10-11 years of age at which time they increased to between 50 and 70 micrograms/dl. Five age- and rearing-matched monkeys served as controls. Detection thresholds were determined at six frequencies between 0.125 and 31.5 kHz. Ear phones were fit over both ears, and thresholds were determined for each ear separately. The monkey signaled detection of the tone by breaking contact with a stainless steel bar. Three lead-exposed monkeys exhibited normal pure tone detection functions. Three monkeys had thresholds outside of the control range at some frequencies; there was a tendency for higher frequencies to be differentially more affected. These findings are consistent with reports of elevated pure tone thresholds in humans exposed to lead developmentally, although the effect is smaller than might have been predicted given the concurrent blood lead concentrations of these monkeys.