The distressed (Type D) personality is independently associated with tinnitus: a case-control study.

BACKGROUND: Tinnitus is a common and disturbing condition, reported by 10% to 20% of the general population. OBJECTIVE: The authors sought to determine personality characteristics associated with tinnitus patients versus a control group of ear-nose-throat (ENT) patients without tinnitus. METHOD: Adult chronic tinnitus sufferers (N=265) and ENT patients without tinnitus (N=265) participated in a cross-sectional study. The authors evaluated personality characteristics with tests for distressed personality (Type D), neuroticism, extraversion, and emotional stability. RESULTS: As compared with control subjects, tinnitus patients had statistically significant and clinically relevant higher levels of neuroticism, negative affectivity, and social inhibition, on one hand, and lower levels of extraversion and emotional stability on the other hand. Also, tinnitus patients were more likely to have a type D personality. CONCLUSIONS: Neuroticism, reduced extraversion, and reduced emotional stability were associated with tinnitus, but the level of prediction of the model improved with the addition of type D personality to the single traits. This might indicate that personality characteristics, and type D personality, in particular, are associated with having tinnitus and might contribute to its perceived severity.

The impact of Type D personality on health-related quality of life in tinnitus patients is mainly mediated by anxiety and depression.

OBJECTIVE: To evaluate the impact of Type D personality on health-related quality of life (HRQoL) and self-reported tinnitus-related distress in chronic tinnitus patients and whether this relationship is mediated by indicators of psychological distress (i.e., vital exhaustion, anxiety, and depression). MATERIALS AND METHODS: Using a cross-sectional study design, 265 consecutive tinnitus patients were asked to complete the Hospital Anxiety and Depression Scale, the Maastricht Questionnaire, the Type D Scale (DS14), the Short-Form Health Survey 36, and the Tinnitus Reaction Questionnaire. RESULTS: The prevalence of Type D was 35.5%. Type D patients were significantly more anxious, depressed, and vitally exhausted, and experienced more impaired HRQoL and increased tinnitus-related distress compared with non-Type D patients. Structural equation modeling showed that Type D personality directly increased symptoms of depression and anxiety, but not vital exhaustion. Type D was also a direct predictor of poor mental and physical HRQoL and increased tinnitus-related distress, although this influence was mainly mediated by symptoms of depression and anxiety. Anxiety, depression, and vital exhaustion had a direct influence on HRQoL and self-reported tinnitus-related distress, with a higher impact on mental HRQoL (R2 = 0.74) compared with physical HRQoL (R2 = 0.33). Vital exhaustion was a predictor of HRQoL and self-reported tinnitus-related distress; however, its influence was moderated by enhanced levels of anxiety and depression. CONCLUSION: Tinnitus patients with a Type D personality were more likely to be anxious and depressed and to experience poor HRQoL and increased self-reported tinnitus-related distress, with the impact of Type D mainly being mediated by symptoms of anxiety and depression, although Type D also exerted a direct influence on these outcomes. These findings underline that to reduce the impact of tinnitus on HRQoL and self-reported tinnitus-related distress, treatment should be directed toward reducing anxiety and depression, especially in patients with a Type D personality.

Morphological changes in spiral ganglion cells after intracochlear application of brain-derived neurotrophic factor in deafened guinea pigs.

When guinea pigs are deafened with ototoxic drugs spiral ganglion cells (SGCs) degenerate progressively. Application of neurotrophins can prevent this process. Morphological changes of rescued SGCs have not been quantitatively determined yet. It might be that SGCs treated with neurotrophins are more vulnerable than SGCs in cochleae of normal-hearing guinea pigs. Therefore, the mitochondria and myelinisation of type-I SGCs were studied and the perikaryal area, cell circularity and electron density were determined. Guinea pigs were deafened with a subcutaneous injection of kanamycin followed by intravenous infusion of furosemide. Brain-derived neurotrophic factor (BDNF) delivery was started two weeks after the deafening procedure and continued for four weeks. Four cohorts of cochleae were studied: (1) cochleae of normal-hearing guinea pigs; (2) of guinea pigs two weeks after deafening; (3) six weeks after deafening; (4) cochleae treated with BDNF after deafening. The deafening procedure resulted in a progressive loss of SGCs. Six weeks after deafening the size of mitochondria, perikaryal area and cell circularity of the remaining untreated SGCs were decreased and the number of layers of the myelin sheath was reduced. In the basal part of the cochlea BDNF treatment rescued SGCs from degeneration. SGCs treated with BDNF were larger than SGCs in normal-hearing guinea pigs, whereas circularity had normal values and electron density was unchanged. The number of layers in the myelin sheath of BDNF-treated SGCs was reduced as compared to the number of layers in the myelin sheath of SGCs in normal-hearing guinea pigs. The morphological changes of SGCs might be related to the rapid loss of SGCs that has been reported to occur after cessation of BDNF treatment.

Intratympanic gentamicin therapy for control of vertigo in unilateral Menire's disease: a prospective, double-blind, randomized, placebo-controlled trial.

CONCLUSIONS: Intratympanic application of gentamicin is a relatively safe and efficient treatment for the reduction of complaints of vertigo attacks associated with Menière's disease. The treatment also reduces the severity of the perceived aural fullness. OBJECTIVE: To investigate the effectiveness of intratympanic gentamicin treatment in patients with unilateral Menière's disease. SUBJECTS AND METHODS: In a prospective, double-blind, randomized, placebo-controlled clinical trial subjects scored vertigo complaints, aural fullness and tinnitus, before, during and up to 1 year after treatment. Hearing loss was monitored with pure tone audiometry. RESULTS: Gentamicin treatment resulted in a significant reduction of the score for vertigo complaints and the score for perceived aural fullness. A small increase in hearing loss (average 8 dB) was measured in the gentamicin group.

A systematic review of diagnostic criteria for acute mastoiditis in children.

OBJECTIVE: To review systematically the literature for the current criteria and strategies used to diagnose acute mastoiditis in children. METHOD: A comprehensive literature search was performed in PubMed, Embase, and the Cochrane Library of studies on the diagnosis of acute mastoiditis in children published between January 1980 and September 2007. The study type and setting, diagnostic criteria for acute mastoiditis, disease-specific history, presenting otologic and systemic signs and symptoms, diagnostic procedures, and final diagnosis were identified. RESULTS: The initial search resulted in 1,057 articles. The inclusion criteria were met in 65; 44 were retrospective case series, and 21 were case reports. These studies included 2,109 children with a median age of 32 months (range, 0 mo-18 yr). Only 26 of 65 articles reported the criteria upon which the diagnosis of acute mastoiditis in children was based. The criteria most frequently used were the clinical signs of postauricular swelling, erythema, tenderness, and protrusion of the auricle. The most frequently used imaging modality was computed tomographic (CT) scanning (reported in 39 of 65 studies, performed in 68% of patients). The most frequently used laboratory test was white blood count (100% of patients in 45 of 65 studies). In 63 studies, the result of culturing from the otomastoid was reported: Streptococcus pneumoniae was the most frequently isolated bacterium. CONCLUSION: Acute mastoiditis in children is an entity that is poorly evaluated and understood in the modern literature. There is a lack of consensus regarding the criteria and strategies for diagnosing acute mastoiditis in the pediatric population. It is crucial that such criteria are established, and consensus is achieved so that prognostic and controlled studies can be initiated to identify risk factors and establish the most effective management of this condition in children.

Hippocampal volume measurement in patients with Ménière's disease: a pilot study.

CONCLUSION: No signs of chronic stress as in hippocampal atrophy were present in patients with Ménière's disease. OBJECTIVE: To evaluate the effect of chronic stress (allostatic load) by measuring hippocampal volume in patients with Ménière's disease. SUBJECTS AND METHODS: Ten patients with Meniere's disease and 10 healthy controls were evaluated for absolute and relative hippocampal volumes measured on MRI scans, saliva cortisol levels and frequency of daily stressors. The study was performed in a prospective, controlled setting with two raters who were blinded as to subject identity. RESULTS: Saliva cortisol levels and presence of daily stressor scores were similar in both groups. The first rater measured mean hippocampal volumes of 2.80 +/- 0.36 cm3 vs 3.15 +/- 0.52 cm3 (right) and 2.49 +/- 0.32 cm3 vs 3.06 +/- 0.46 cm3 (left), for the Ménière's disease and control group, respectively. The second rater measured 3.44 +/- 0.35 cm3 vs 3.60 +/- 0.52 cm3 (right) and 3.00 +/- 0.40 cm3 vs 3.42 +/- 0.45 cm3 (left), respectively. The volume of the left hippocampus was significantly smaller in patients with Ménière's disease compared with the controls for both raters (p < 0.05) and the right hippocampal volume was not different between the two groups. With correction for variation in head size (partial brain and partial intracranial volume) no significant differences in relative hippocampal volumes were observed between patients with Ménière's disease and the control group.

Functional sex differences in human primary auditory cortex.

BACKGROUND: We used PET to study cortical activation during auditory stimulation and found sex differences in the human primary auditory cortex (PAC). Regional cerebral blood flow (rCBF) was measured in 10 male and 10 female volunteers while listening to sounds (music or white noise) and during a baseline (no auditory stimulation). RESULTS AND DISCUSSION: We found a sex difference in activation of the left and right PAC when comparing music to noise. The PAC was more activated by music than by noise in both men and women. But this difference between the two stimuli was significantly higher in men than in women. To investigate whether this difference could be attributed to either music or noise, we compared both stimuli with the baseline and revealed that noise gave a significantly higher activation in the female PAC than in the male PAC. Moreover, the male group showed a deactivation in the right prefrontal cortex when comparing noise to the baseline, which was not present in the female group. Interestingly, the auditory and prefrontal regions are anatomically and functionally linked and the prefrontal cortex is known to be engaged in auditory tasks that involve sustained or selective auditory attention. Thus we hypothesize that differences in attention result in a different deactivation of the right prefrontal cortex, which in turn modulates the activation of the PAC and thus explains the sex differences found in the activation of the PAC. CONCLUSION: Our results suggest that sex is an important factor in auditory brain studies.

Intracochlear assessment of electrode position after cochlear implant surgery by means of multislice computer tomography.

The development of electrode arrays, the past years, has focused on modiolus-hugging cochlear implant electrodes. Besides, atraumatic implantation of electrodes is of importance for the use in hearing preservation, in cases of combined electric and acoustic stimulation. Intracochlear positioning of the individual electrodes by means of multislice computer tomography (CT) has not yet been shown. In this study we formulated and tested a CT imaging protocol for postoperative scanning of the temporal bone in cochlear implant subjects. Both a fresh human temporal bone and a fresh human cadaver head were implanted with a cochlear implant. Multislice CT was performed for adequate depiction of the cochlear implant. All scans were analyzed on a viewing workstation. After mid-modiolar reconstruction we were able to identify the intracochlear electrode position relative to the scala tympani and scala vestibuli. This was possible in both the implanted isolated temporal bone and the fresh human cadaver head. The feasibility of imaging the electrode position of the cochlear implant within the intracochlear spaces is shown with multislice CT. An imaging protocol is suggested.

Effectiveness of trimethoprim/sulfamethoxazole for children with chronic active otitis media: a randomized, placebo-controlled trial.

OBJECTIVE: The goal was to determine the clinical effectiveness of prolonged outpatient treatment with trimethoprim/sulfamethoxazole for children with chronic active otitis media. METHODS: We performed a randomized, placebo-controlled trial with 101 children (1-12 years of age) with chronic active otitis media (defined as otorrhea for > or =12 weeks). In addition to a short course of steroid and antibiotic eardrops, children were assigned randomly to receive 6 to 12 weeks of orally administered trimethoprim/sulfamethoxazole (18 mg/kg, 2 times per day) or placebo and were monitored for 1 year. RESULTS: At 6 weeks, 28% of children in the trimethoprim/sulfamethoxazole group and 53% of children in the placebo group had otomicroscopic signs of otorrhea. At 12 weeks, these values were 32% and 47%, respectively. At 1 year, the numbers of children with otorrhea were similar in the 2 groups (25% and 20%, respectively). One child in the trimethoprim/sulfamethoxazole group developed a skin rash. Vomiting or diarrhea was reported for 9% of the trimethoprim/sulfamethoxazole group and 2% of the placebo group. Pure-tone hearing levels and health-related quality of life improved during the study but did not differ between the trimethoprim/sulfamethoxazole group and the placebo group. Pseudomonas aeruginosa was the most frequently isolated bacteria in the otorrhea samples from both groups. CONCLUSIONS: A 6- to 12-week course of high-dose, orally administered trimethoprim/sulfamethoxazole therapy is beneficial for children with chronic active otitis media. The treatment effect is most pronounced with the shorter course and disappears if administration of the medication is discontinued.

Audiological performance after cochlear implantation: a 2-year follow-up in children with inner ear malformations.

CONCLUSIONS: Open-set speech perception in children with an inner ear malformation is equal to that of other congenitally deaf children after an average of 2 years follow-up. OBJECTIVE: To analyze audiological performance after cochlear implantation in a sample of children with radiographically detectable malformations of the inner ear compared to performance in prelingually deafened children at large. MATERIALS AND METHODS: Nine children with osseous inner ear malformations were compared to 22 congenitally deaf children, all of whom underwent cochlear implantation. All subjects were tested on their electrical evoked compound action potential. Speech perception tests were performed using the monosyllabic trochee polysyllabic test without visual support and the open-set monosyllabic wordlist. RESULTS: In all, 20% of the congenitally deaf children in our center study have inner ear abnormalities. Inner ear malformations were limited to incomplete partition of the cochlea; none of the subjects had common cavity malformations. Electrical compound action potentials were successfully recorded in both groups intraoperatively. Speech perception tests on open-set speech yielded an average of 48.8% (SD 21.2%) in the group of children with inner ear malformations vs 54.5% (SD 21.1%) in congenitally deaf children. In four of nine cases with an inner ear malformation we encountered a minor CSF leak.

Tinnitus and neural plasticity of the brain.

OBJECTIVE: To describe the current ideas about the manifestations of neural plasticity in generating tinnitus. DATA SOURCES: Recently published source articles were identified using MEDLINE, PubMed, and Cochrane Library according to the key words mentioned below. STUDY SELECTION: Review articles and controlled trials were particularly selected. DATA EXTRACTION: Data were selected systematically, scaled on validity and comparability. CONCLUSION: An altered afferent input to the auditory pathway may be the initiator of a complex sequence of events, finally resulting in the generation of tinnitus at the central level of the auditory nervous system. The effects of neural plasticity can generally be divided into early modifications and modifications with a later onset. The unmasking of dormant synapses, diminishing of (surround) inhibition and initiation of generation of new connections through axonal sprouting are early manifestations of neural plasticity, resulting in lateral spread of neural activity and development of hyperexcitability regions in the central nervous system. The remodeling process of tonotopic receptive fields within auditory pathway structures (dorsal cochlear nucleus, inferior colliculus, and the auditory cortex) are late manifestations of neural plasticity. The modulation of tinnitus by stimulating somatosensory or visual systems in some people with tinnitus might be explained via the generation of tinnitus following the nonclassical pathway. The similarities between the pathophysiological processes of phantom pain sensations and tinnitus have stimulated the theory that chronic tinnitus is an auditory phantom perception.

Differences in aerodynamic characteristics of new and dysfunctional Provox 2 voice prostheses in vivo.

Tracheoesophageal voice prostheses need to be replaced due to increased airflow resistance or retrograde leakage of fluid into the trachea as a consequence of biofilm formation. Previous in vitro studies show a change of aerodynamic features of biofilm covered voice prostheses after removal of the prostheses out of the patient. To assess these changes in an in situ situation, aerodynamic characteristics were measured within 45 patients at the beginning and at the end of the wearing process of the Provox 2 voice prosthesis. As a consequence, the influence of biofilm formation on aerodynamic characteristics can be evaluated. In the majority of cases, leakage through the prosthesis was the reason for replacement. No differences were found in the total flow, volume range and intratracheal pressure (ITP) of the voice prostheses measured. The airflow resistance of biofilm covered prostheses was significantly reduced compared to new clean prostheses. However, no correlation was found between the extent of biofilm and the different aerodynamic features measured. Biofilm formation on the Provox 2 is responsible for both reduction in airflow resistance and leakage through the prosthesis by deterioration of the silicone rubber material.

Evaluation of the relation between audiometric and psychometric measures of hearing after tympanoplasty.

The objective of this prospective study was to evaluate the relation between audiometric and psychometric measures after tympanoplasty from the perspective of preoperative selection of patients and postoperative assessment of the results of reconstructive middle ear surgery. Hearing (dis)ability was measured by means of pure-tone audiometry and a validated self-assessment questionnaire: the (modified) Amsterdam Inventory of Auditory Disability and Handicap (m)AIAD. Average hearing thresholds and (m)AIAD scores were evaluated for 80 patients, pre- and 12 months postoperatively. The average improvement of the air conduction threshold in the operated ear was 5.4 (+/-14.3) dB; the average improvement in the (m)AIAD score was 2.9 points (+/-12.1). Although not very strong, the audiometric improvement and increase in (m)AIAD score are significantly related. After the calculation of postoperatively measured mean scores on the (m)AIAD for different 10-dB intervals of postoperative hearing loss averaged over both ears, an interesting relation between the (m)AIAD score and hearing losses emerges. The (m)AIAD score is almost independent of hearing loss for postoperative hearing levels between 25 and 40 dB. Residual hearing loss has to become less than 25 dB before a smaller hearing loss corresponds with a higher (better) (m)AIAD score. For losses larger than 40 dB the (m)AIAD score clearly decreases with increasing hearing loss. Finally, even small residual hearing losses lead, on average, to (m)AIAD scores that are substantially lower than the score for normally hearing subjects. In general, the patient benefit seems related to the magnitude of improvement in the air-conduction thresholds, rather than to the achievement of a certain threshold level. In addition, even small residual hearing losses (less than 25 dB HL) still lead, on average, to (m)AIAD scores that are substantially lower than the scores for normally hearing subjects.

Analysis of cortisol and other stress-related hormones in patients with Ménière's disease.

OBJECTIVE: To evaluate cortisol and catecholamine levels in patients with Ménière's disease. STUDY DESIGN: Prospective, controlled study. SETTING: Tertiary referral center. PATIENTS: Thirty patients with Ménière's disease and 18 healthy controls. MAIN OUTCOME MEASURES: Serum and saliva cortisol, serum cortisol after the dexamethasone suppression test, urine free cortisol, and urine catecholamines. RESULTS: The serum and saliva cortisol levels were higher in Ménière's patients compared with their control group: 440 +/- 127 (n = 28) versus 366 +/- 90 (nmol/L) (n = 18) and 17.2 +/- 6.1 (n = 18) versus 11.6 +/- 4.6 (nmol/L) (n = 9), respectively. Both differences were significant (p < 0.05). There were no dissimilarities in urine cortisol or urine catecholamines for either group. Twenty-eight Ménière's patients were divided into two subgroups, namely, high- and low-cortisol groups, using a serum cortisol level cutoff point of 465 nmol/L (median). The total Ménière's disease time and the duration of tinnitus tended to be longer in the high-cortisol group (p = 0.07, two-tailed). The total Ménière's disease time was 13.5 +/- 9.9 years in the high-cortisol group and 7.1 +/- 7.4 years in the low-cortisol group (n = 14 for both). The subgroups were matched for age, gender, and unilaterally or bilaterally affected ears. CONCLUSION: Patients with Ménière's disease have higher serum cortisol levels. It is suggested that these higher cortisol levels are rather the result than the cause of this chronic disease, because patients affected longer seem to have higher cortisol levels. The exact impact of these higher cortisol levels on the inner ear and endolymph homeostasis is yet unknown.

Effect of dairy products on the lifetime of Provox2 voice prostheses in vitro and in vivo.

BACKGROUND: Reduction of biofilm formation on tracheoesophageal voice prostheses by certain dairy products might extend their clinical lifetime. The purpose of this study was to determine the influence of certain dairy products on voice prosthetic biofilms and lifetimes in vitro and in vivo. METHODS: The in vitro results were accomplished using an artificial throat. The lifetimes of Provox2 prostheses were evaluated in a patient group that daily consumed the evaluated products. RESULTS: Buttermilk and Yakult Light fermented milk decreased the amount of bacteria on voice prostheses but stimulated yeast prevalence in vitro. Concurrently, lifetimes of voice prostheses in patients consuming buttermilk were not significantly different, whereas patients consuming Yakult Light fermented milk drink had a significantly (p < .01) increased prosthesis lifetime by a factor of 3.76. CONCLUSION: Yakult Light fermented milk drink reduced biofilm formation on Provox2 prostheses in vitro and in vivo and significantly increased prosthesis lifetime. In vivo, no significant effects were observed for patients consuming buttermilk.

In vitro leakage susceptibility of tracheoesophageal shunt prostheses in the absence and presence of a biofilm.

Although leakage through a tracheoesophageal shunt prosthesis is the main cause of prosthesis failure in a laryngectomy patient, this has never been the subject of in vitro evaluation. The aim of this study was to compare three commercially available voice prostheses by comparison of their in vitro leakage patterns, in absence or presence of a biofilm. To compare in vitro leakage patterns, a model comprised of an artificial throat equipped with a single prosthesis coupled to a water reservoir was developed. By varying the height of the water reservoir, different pressures on the voice prosthesis can be obtained. Both in absence and presence of a biofilm, the Blom Singer voice prosthesis demonstrated the lowest leakage, followed by Groningen Low Resistance. The Provox2 showed significantly the most leakage, however, in presence of a biofilm the leakage of the Provox2 significantly decreased. Regular airflow during biofilm formation significantly increased leakage through the Provox2. Out of 746 clinical replacements, Provox2 showed 76% and Groningen Low Resistance 57% replacements due to leakage. The model used in this study showed significant differences in leakage of the three types of voice prostheses used. Leakage occurred more readily through Provox2 than through Groningen Low Resistance and Blom Singer prostheses, which is in line with clinical observations and enforces the model.

Prediction of survival and therapy outcome with 11C-tyrosine PET in patients with laryngeal carcinoma.

UNLABELLED: Choosing the optimal treatment for an individual with squamous cell carcinoma of the head and neck is a difficult challenge because of the unpredictable clinical behavior of this malignancy. A reliable method for assessing the clinical behavior and predicting the radiocurability of tumors would assist in the therapy strategy and prognosis. This study evaluated whether quantitative PET using l-[1-(11)C]-tyrosine (TYR) has predictive value for survival and therapy outcome in patients with primary squamous cell carcinoma of the larynx. METHODS: Thirty-four patients with histologically confirmed laryngeal carcinomas underwent dynamic (11)C-TYR PET before receiving definitive therapy. Various methods for quantification of tumor activity were used: assessment of protein synthesis rate (PSR), calculation of standardized uptake value, and estimation of tumor-to-nontumor ratio. Treatment consisted of radiotherapy (n = 20) or surgery (n = 14). The median follow-up was 40 mo. RESULTS: All malignancies were identified correctly, with no false-negative results. Cumulative survival was compared between patients with tumor PSR equal to or higher than the median (2.0 nmol/mL/min) and those with tumor PSR lower than the median and was found not to be significantly different (P = 0.07). When the radiotherapy group was evaluated separately, the difference in survival was significant (P = 0.03; 5-y survival, 30% vs. 73%) and high (11)C-TYR uptake correlated with poor prognosis. In multivariate analysis, PSR was an independent predictor for survival. Because differences (P = 0.08) between patients with and patients without recurrence were not significant, no predictive value of PSR for disease recurrence could be demonstrated. CONCLUSION: Prediction of survival of patients undergoing radiotherapy for laryngeal squamous cell carcinoma is feasible primarily by using (11)C-TYR PET to quantify activity before treatment.

Direct measurement flow resistance of cochlear aqueduct in guinea pigs.

OBJECTIVE: The cochlear aqueduct connects the scala tympani to the subarachnoid space and is the main pressure equalization canal for the inner ear. Increases in inner ear volume and pressure are thought to cause clinical symptoms such as vertigo, tinnitus and fluctuating hearing loss. In this study the flow resistance of the cochlear aqueduct was determined and its relation with inner ear pressure was studied. MATERIAL AND METHODS: Inner ear pressure was measured in the scala tympani through the round window using a micropipette. Through a second micropipette, artificial perilymph was infused into, or withdrawn from, the scala tympani at various constant rates. From the infusion rate and the change in perilymphatic pressure during infusion the flow resistance of the cochlear aqueduct was calculated. RESULTS: The flow resistance was found not to be constant but to depend on the position of the round window membrane and possibly on the magnitude and direction of fluid flow through the aqueduct. Measured flow resistance values were in the range 11-45 Pa s/nl. For very small flow values the flow resistance averaged over 6 animals was 21 Pa s/nl. CONCLUSIONS: The flow resistance of the cochlear aqueduct is not a constant value. The cochlear aqueduct is a canal with dynamic properties and may play a role in the complicated process of inner ear pressure regulation.

Prevention of biofilm formation by dairy products and N-acetylcysteine on voice prostheses in an artificial throat.

OBJECTIVE: To evaluate the preventive effect of buttermilk, Yakult Light fermented milk drink and N-acetylcysteine on biofilm formation on voice prostheses in vitro. MATERIAL AND METHODS: Groningen button and Provox 2 voice prostheses were inoculated with a mixture of bacteria and yeasts isolated from previously explanted Groningen button voice prostheses. After 5 h, separate throats were flushed with buttermilk, Yakult Light fermented milk drink, N-acetylcysteine or phosphate-buffered saline, which served as a control. After 7 days, the microflora on each voice prosthesis was determined. RESULTS: On Groningen button voice prostheses, buttermilk, Yakult Light fermented milk drink and N-acetylcysteine all reduced the amount of both bacteria and yeasts. On Provox 2 voice prostheses, buttermilk, Yakult Light fermented milk drink and N-acetylcysteine reduced the amount of bacteria but, conversely, increased the amount of yeasts. CONCLUSION: These in vitro experiments demonstrate that biofilm formation on voice prostheses is reduced in an artificial throat by the use of buttermilk, Yakult Light fermented milk drink and N-acetylcysteine. However, the structural differences between the type of voice prostheses may influence the ultimate effects.

Evaluation of cochlear function in an acute endolymphatic hydrops model in the guinea pig by measuring low-level DPOAEs.

During and after microinjection of artificial endolymph into scala media of the guinea pig, the 2f1- f2 -DPOAE at 4.5 kHz generated by low-level primaries was recorded. Reproducible changes were measured when 1.1 microl of artificial endolymph was injected at a rate of 1.65 nl/s (1.53-1.83). This volume corresponds with an acute endolymphatic hydrops of 23%. After the onset of injection the inner ear pressure immediately increased to a mean higher level of 22 Pa, whereas the 2f1- f2 -amplitude and -phase did not change for about 1 min. Thereafter, the amplitude decreased 2.6 dB (+/- 0.7) on average and slowly regained almost its initial value, with recovery frequently starting within the period of injection. In an attempt to explain the observed changes in 2f1- f2 -amplitude the basilar membrane displacement towards scala tympani at the 2f1- f2 generation site is estimated to be 19 nm for a 1.1 microl increase of endolymph volume. A small deflection of the outer hair cell stereocilia and as a consequence a change in cell conductance may explain the 2f1- f2 -amplitude changes. However, the precise mechanism of cochlear function change caused by endolymph volume increase (hydrops) remains to be elucidated.