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At least 1,747 records · Page 97Linked to original sources
PubMed1990

Hearing conservation in acoustic neuroma surgery via the posterior fossa.

An increasing number of patients with an acoustic neuroma present with useful hearing in the tumour ear. Surgical removal of these tumours via the posterior fossa route may enable preservation of the cochlear nerve and otic capsule without increasing the morbidity to the facial nerve. The results of treating 51 cases of acoustic neuroma via the posterior fossa is presented. Forty four tumours measured less than 20 mm in diameter in the cerebellopontine angle and surgery was undertaken with hearing preservation as a principle objective. In 26 cases, the cochlear nerve was preserved anatomically and post-operative hearing at levels better than mean pure tone threshold of 50 dB or 50 per cent speech discrimination was recorded in 14 patients. The preservation of hearing represents a worthwhile surgical goal in selected patients with an acoustic neuroma without increasing the operative morbidity.

Cochlear Nerve↗
PubMed1991

Modifying the translabyrinthine approach to preserve hearing during acoustic tumour surgery.

Removing an acoustic schwannoma using the translabyrinthine approach has previously been considered incompatible with hearing preservation. By modifying the approach and preventing the loss of endolymph, we have successfully removed an intracanalicular acoustic schwannoma, which originated from the inferior vestibular nerve, and preserved hearing in the operated ear. This report represents the preliminary findings using this particular technique in the management of an intracanalicular acoustic tumour.

Audiometry↗
PubMed1991

Acoustic rhinometry used as a method to monitor the effect of intramuscular injection of steroid in the treatment of nasal polyps.

Acoustic rhinometry is a new method which describes the geometry of the nasal cavity and the epipharynx. The method, based on the reflection of an acoustic signal entered into the nasal cavity, can be used to evaluate the cross-sectional area of the nasal cavity as a function of distance from the nostril. The method has, together with nasal expiratory peak flow (NPF) and nasal index based upon a self assessment score, been used to evaluate, in an objective and dynamic way, the effect of systemic treatment of nasal polyps with steroids in a series of eight patients with recurrent nasal polyposis. The study shows a significant relationship between these three parameters before and after systemic treatment of nasal polyps with steroids. It is concluded that in this study acoustic rhinometry had an accurate and objective method for measuring the geometry of the nasal cavity before and after treatment for processes which block the nasal cavity.

Acoustics↗
PubMed1992

Criteria for hearing preservation in acoustic schwannoma surgery: the concept of useful hearing.

In the quest for hearing preservation in patients with acoustic schwannomas it is essential that surgeons do not lose sight of the concept of 'useful' hearing. There is an important difference between hearing preservation which pleases the surgeon and that which will be appreciated by the patient. Tumour size, pure tone audiogram average differences between ears and speech discrimination scores have been recorded in a series of 114 patients with unilateral acoustic schwannomas. Criteria for useful hearing are presented in terms of pure tone audiogram average difference and speech discrimination scores. There were 11 patients (10 per cent) with a speech discrimination score of 50 per cent or more, a pure tone audiogram average difference of 30 dB or better and a tumour size of no more than 2 cm. Only one patient (0.9 per cent) had a speech discrimination score of 50 per cent or more, a pure tone audiogram average difference of 20 dB or better and a tumour size of no more than 1 cm. It is concluded that hearing preservation techniques may be applicable to between 1 and 10 per cent of patients with unilateral acoustic schwannomas.

Audiometry, Pure-Tone↗
PubMed2006

Aerodynamic, acoustic and functional results of posterior transverse laser cordotomy for bilateral abductor vocal fold paralysis.

Bilateral abductor vocal fold paralysis (BAVFP) is a rare but life-threatening condition which may require an emergency tracheotomy procedure. The ideal surgical technique for this condition should improve quality of life by relieving the airway obstruction while preserving laryngeal functions such as phonation and deglutition. Posterior transverse laser cordotomy (PTLC) was first described by Dennis and Kashima as a technique for providing an airway at the posterior glottis without pre-operative tracheotomy; they reported it as a successful method with satisfactory functional results. The aim of this prospective study was to evaluate long term acoustic, aerodynamic and functional results of the primary bilateral PTLC technique in 22 BAVFP patients. Severity of dyspnoea was evaluated using a five-level subjective symptom scale graded according to the limitation in daily activity and level of respiratory difficulty. Aerodynamic and acoustic analyses were performed pre-operatively and prospective changes in aerodynamic and acoustic parameters were collected after one post-operative year.

Adult↗
PubMed1990

Comparisons of the clinical and radiological features and surgical management of posterior fossa meningiomas and acoustic neuromas.

Next to acoustic neuromas, meningiomas are the most common benign tumour of the posterior fossa. This paper reviews the personal experience of one of the authors with the management of 26 posterior fossa meningiomas and 212 acoustic neuromas. The aim was to compare the clinical and radiological features of these two types of posterior fossa tumours to determine whether they can be differentiated preoperatively. The study also aimed at analysing the surgical treatment of posterior fossa meningiomas. The results showed that posterior fossa meningiomas can usually be differentiated from acoustic neuromas on the basis of clinical and radiological features. Preoperative differentiation aids surgical management, especially for selection of surgical approach. In most instances, posterior fossa meningiomas can be totally resected with minimal morbidity and mortality.

Adult↗
PubMed1998

Stereotactic radiosurgery for acoustic neuroma: a Canadian perspective.

Stereotactically delivered radiation is now an accepted treatment for patients with acoustic neuroma. In some cases, patient preference may be the reason for its selection, while in others neurosurgeons may select it for patients who are elderly or have significant risk factors for conventional surgery. The majority of patients with acoustic neuroma treatment with stereotactic radiosurgery have been treated with the Gamma Knife, with follow ups of over 25 years in some instances. Other radiosurgery modalities utilizing the linear accelerator have been developed and appear promising, but there is no long-term follow up. Canada does not possess a Gamma Knife facility, and its government-funded hospital and medical insurance agencies have made it difficult for patients to obtain reimbursement for Gamma Knife treatments in other countries. We review the literature to date on the various forms of radiation treatment for acoustic neuroma and discuss the current issues facing physicians and patients in Canada who wish to obtain their treatment of choice.

Canada↗
PubMed2001

Guided shear horizontal surface acoustic wave sensors for chemical and biochemical detection in liquids.

The design and performance of guided shear horizontal surface acoustic wave (guided SH-SAW) devices on LiTaO3 substrates are investigated for high-sensitivity chemical and biochemical sensors in liquids. Despite their structural similarity to Rayleigh SAW, SH-SAWs often propagate slightly deeper within the substrate, hence preventing the implementation of high-sensitivity detectors. The device sensitivity to mass and viscoelastic loading is increased using a thin guiding layer on the device surface. Because of their relatively low shear wave velocity, various polymers including poly(methyl methacrylate) (PMMA) and cyanoethyl cellulose (cured or cross-linked) are investigated as the guiding layers to trap the acoustic energy near the sensing surface. The devices have been tested in biosensing and chemical sensing experiments. Suitable design principles for these applications are discussed with regard to wave guidance, electrical passivation of the interdigital transducers from the liquid environments, acoustic loss, and sensor signal distortion. In biosensing experiments, using near-optimal PMMA thickness of approximately 2 microm, mass sensitivity greater than 1500 Hz/(ng/mm2) is demonstrated, resulting in a minimum detection limit less than 20 pg/mm2. For chemical sensor experiments, it is found that optimal waveguide thickness must be modified to account for the chemically sensitive layer which also acts to guide the SH-SAW. A detection limit of 780 (3 x peak-to-peak noise) or 180 ppb (3 x rms noise) is estimated from the present measurements for some organic compounds in water.

Acoustics↗
PubMed2005

Enzyme kinetics in acoustically levitated droplets of supercooled water: a novel approach to cryoenzymology.

The rate of the alkaline phosphatase-catalyzed hydrolysis of 4-methylumbelliferone phosphate was measured in acoustically levitated droplets of aqueous tris (50 mM) at pH 8.5 at 22 +/- 2 degrees C and in supercooled solution at -6 +/- 2 degrees C. At 22 degrees C, the rate of product formation was in excellent agreement with the rate observed in bulk solution in a cuvette, indicating that the acoustic levitation process does not alter the enzyme activity. The rate of the reaction decreased 6-fold in supercooled solution at -6 +/- 2 degrees C. The acoustic levitator apparatus is described in detail.

Acoustics↗
PubMed2006

In situ evaluation of density, viscosity, and thickness of adsorbed soft layers by combined surface acoustic wave and surface plasmon resonance.

We show the theoretical and experimental combination of acoustic and optical methods for the in situ quantitative evaluation of the density, the viscosity, and the thickness of soft layers adsorbed on chemically tailored metal surfaces. For the highest sensitivity and an operation in liquids, a Love mode surface acoustic wave (SAW) sensor with a hydrophobized gold-coated sensing area is the acoustic method, while surface plasmon resonance (SPR) on the same gold surface as the optical method is monitored simultaneously in a single setup for the real-time and label-free measurement of the parameters of adsorbed soft layers, which means for layers with a predominant viscous behavior. A general mathematical modeling in equivalent viscoelastic transmission lines is presented to determine the correlation between experimental SAW signal shifts and the waveguide structure including the presence of the adsorbed layer and the supporting liquid from which it segregates. A methodology is presented to identify from SAW and SPR simulations the parameters representatives of the soft layer. During the absorption of a soft layer, thickness or viscosity changes are observed in the experimental ratio of the SAW signal attenuation to the SAW signal phase and are correlated with the theoretical model. As application example, the simulation method is applied to study the thermal behavior of physisorbed PNIPAAm, a polymer whose conformation is sensitive to temperature, under a cycling variation of temperature between 20 and 40 degrees C. Under the assumption of the bulk density and the bulk refractive index of PNIPAAm, thickness and viscosity of the film are obtained from simulations; the viscosity is correlated to the solvent content of the physisorbed layer.

Acoustics↗
PubMed1997

Antibody binding to a functionalized supported lipid layer: a direct acoustic immunosensor.

A direct immunosensor has been developed using an acoustic wave device as a transducer. The device is based on an acoustic waveguide geometry that supports a Love wave. The biorecognition surface, formed on a gold layer, consisted of a biotinylated supported lipid layer which specifically bound streptavidin and, subsequently, biotinylated goat IgG. The modified surface was used as a model immunosensor and successfully detected rabbit anti-goat IgG in the concentration range 3 x 10(-8) - 10(-6) M. Using the anti-goat IgG binding isotherm and the time-resolved measurements of antibody binding, both the binding and rate constants of the reaction were determined. The specificity of each binding step was studied with the acoustic wave device, and it was concluded that the phospholipid bilayer showed a good suppression of nonspecific binding. Comparative measurements using surface plasmon resonance allowed the response of the immunosensor to be quantitatively correlated with mass binding to the surface.

Acoustic Stimulation↗
PubMed1999

Operation of acoustic plate mode immunosensors in complex biological media.

Acoustic wave based immunosensors have proven to facilitate the in situ detection of marker-free proteins in real time. However, the vast majority of these studies focuses on the interaction of a single type of antigen with immobilized receptors in pure buffer solutions. In an effort to evaluate the potential of acoustic plate mode immunosensors for operation in more complex biological environments, antigen/antibody reactions have been studied in pure buffer solution, in the presence of cells, and in human serum. It has been observed that the devices do not respond to cell adsorption and that antigen/antibody reactions can successfully be detected even if a thick layer of cells is deposited on the sensing surface. By varying the frequency of operation, it was shown that the sensitivity of the devices toward nonspecific protein adsorption is reduced at high frequencies of operation. Thus, spurious immunosensor response caused by non-specific adsorption processes can be suppressed by appropriately selecting device frequency. Using immunoglobulin G with minimum cross reactivity with human serum proteins, antigen/antibody reactions have also been monitored in human serum. While the observed frequency shifts are comparable to those measured in pure buffer solutions, the binding process is accompanied by additional acoustic loss, indicating changes in the viscoelastic properties of the interfacial layer.

Acoustics↗
PubMedDate not supplied

Retroviral transduction of adherent cells in resonant acoustic fields.

Ultrasound-induced cavitation has been extensively used to enhance the efficiency of nonviral-based gene delivery. Although such unique mechanical force could possibly augment the efficacy of retrovirus-mediated gene transfer, we harnessed an alternative approach, a resonant acoustic field, to facilitate the retroviral transduction rate. NIH 3T3 fibroblast cells suspended in a culture well and mixed with ecotropic retroviruses were co-treated with megahertz resonant acoustic fields (RAF). Suspended NIH 3T3 cells under RAF treatment agglomerated at acoustic nodal planes by primary radiation force within a short exposure time. These first arrived and agglomerated cells formed bands as nucleating sites for nanometer-sized ecotropic retroviruses circulated between nodal planes to attach on and thereby increased cell-virus encounters. According to the neomycin-resistant colony assay, 2-fold increment of retroviral transduction rate was obtained by exposing cells and retroviruses in the RAF for 6 min in the presence of 8 microg/mL Polybrene.

3T3 Cells↗
PubMed2000

Differential effects of cohort removal stress on the acoustic startle response of the Roman/Verh rat strains.

Male and female rats of the inbred Roman/Verh strains, which have been psychogenetically selected and bred for good (RHA-I/Verh) and extremely poor (RLA-I/Verh) two-way avoidance acquisition, were evaluated in an acoustic startle response test. One half of the rats of each strain and sex were previously subjected to 30 min of isolation by removal of their cage partners ("cohort removal"). During the testing session each animal received 40 acoustic stimuli at interstimulus intervals of 30 seconds. The hyperemotional RLA-I/Verh rats (especially the males) showed stronger acoustic startle responses than did their RHA-I/Verh counterparts. Startle amplitudes of the RLA-I/Verh males were further enhanced by the stress of 30 min isolation, whereas cohort removal did not significantly affect startle response amplitudes in RHA-I/Verh rats of either sex or in females of the RLA-I/Verh strain.

Acoustic Stimulation↗
PubMed2000

The temporal unfolding of local acoustic information and sentence context.

The purpose of this study was to investigate the temporal unfolding of local acoustic information and sentence context using both cross-modal interference (CMI) and word-monitoring tasks. The timing of sentence context effects have important theoretical implications for models of language processing (e.g., initial context independence vs. initial interaction). Yet, different tasks tend to yield different results. For both experiments, stimuli from an acoustically manipulated "goat-to-coat" continuum were embedded in sentences whose interpretation was biased toward either "goat" or "coat." In experiment 1 (CMI), the primary task was listening to sentences for comprehension; the interference task was a word/nonword decision to an unrelated visual probe that appeared at one of three positions within the sentence. Results showed immediate effects of the acoustic manipulation, but only delayed effects of sentence context. These results were interpreted to indicate that phonological processing is initially context-independent but is followed by rapid context integration. Experiment 2 used a word-monitoring task: Response times were significantly longer when sentence context was incongruent with the monitoring target, showing an immediate effect of context. The apparently contradictory results of the two experiments together support an account of language processing in which phoneme categorization is initially independent of sentence context unless an explicit judgment about the identity of the target is required.

Adult↗
PubMed1983

Invariances in the acoustic expression of emotion during speech.

An experiment was designed to test whether different individuals produce similar voice patterns when they read the same emotional passage. Quantitative scoring criteria were developed that reflect the extent to which different individuals consistently produce similar constellations of acoustic attributes in response to the same emotional context. The scoring procedure was applied to the voice tracks of standard utterances produced by 11 subjects reading 10 different emotionally evocative scripts. The results supported the hypothesis that different individuals produce standard acoustic configurations to express emotions. Because acoustic properties reflecting contrastive stress consistently varied with emotional context over syntactically and semantically identical utterances, some factor related to emotional context other than syntax or semantics must account for the variations. An evolutionary argument that emotion communication can be seen as intention communication is presented to account for these variations. Implications for theories of emotions and of intentional generative semantics are discussed.

Emotions↗
PubMed1976

Modification of the rat's acoustic startle response by antecedent visual stimulation.

Male hooded and albino rats were exposed to a light flash followed at various temporal intervals by a startle-eliciting 117 db. (re 20 muN/m2) burst of white noise. The visual stimulus engendered startle response inhibition (maximally when the lead time was 64-250 msec) as well as startle response latency reduction (maximally when the lead time was 2-8 msec). The temporal functions for the effects of visual stimuli paralleled those previously reported for startle modification by acoustic events. Further study revealed that, given optimal lead times, inhibition is produced reliably by weaker visual stimuli (3 X 10-6 cd-sec/cm2) than latency reduction (3 X 10-4 cd-sec/cm2). This differential sensitivity to visual stimuli is also analogous to previously reported findings for events in the acoustic environment. It reveals that the neural mechanisms that mediate latency reduction and inhibition can be engaged by either acoustic or visual stimulation.

Acoustic Stimulation↗
PubMed1991

Medial cerebellum and long-term habituation of acoustic startle in rats.

Three experiments assessed the effects of damage to the medial cerebellum on long-term habituation (LTH) of the acoustic startle response. Experiment 1 replicated previous results. Lesions of the cerebellar vermis blocked LTH without affecting initial response levels or short-term habituation (STH). The lesions did not disrupt LTH of a simultaneously measured lick-suppression response. In Experiment 2, vermal lesions again blocked LTH of acoustic startle. Control lesions of the cerebellar hemispheres did not affect LTH. In Experiment 3, lesions to the medial (fastigial) cerebellar nuclei blocked LTH. Lesions to the lateral (dentate and interpositus) nuclei did not affect LTH. It is concluded that the medial cerebellum (cortex and nuclei) is part of the essential circuitry for LTH of acoustic startle, whereas the lateral cerebellum is not involved in the basic habituation process.

Acoustic Stimulation↗