Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ACOUSTICS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,207 records · Page 67Linked to original sources
PubMed1997

Hearing preservation in the removal of intracanalicular acoustic neuromas via the retrosigmoid approach.

In a series of 514 consecutive operations for complete excision of acoustic neuromas, 94 procedures were performed via a retrosigmoid approach to preserve the patient's hearing. Twenty-six of these procedures (5.1%) were performed in cases of intracanalicular tumor and 68 (13.2%) were for larger lesions in which most of the tumor was located medial to the porus acusticus within the cerebellopontine angle. Preservation of useful hearing was achieved in 13 (50%) of 26 patients with intracanalicular tumors and in 20 (29%) of 68 with larger tumors. A trend toward higher success rates in intracanalicular tumors appears to be present, although the difference is not statistically significant (p = 0.09). Normal or near normal facial function (House and Brackmann Grades I and II) was present postoperatively in 25 (96%) of 26 patients. Indications for treatment of intracanalicular acoustic neuromas are considered and treatment alternatives are reviewed. Results from other series reporting removal of intracanalicular acoustic neuromas are considered with respect to hearing conservation and postoperative facial nerve function. Surgical excision of intracanalicular acoustic neuromas in otherwise healthy patients appears to be warranted if preservation of useful binaural hearing is considered a worthwhile objective and if perioperative morbidity can be maintained at an acceptably low level. The retrosigmoid approach is familiar to all neurosurgeons and offers a comparable success rate for hearing conservation and probably a superior outcome in terms of facial nerve function when compared with the middle fossa approach.

Action Potentials↗
PubMed2000

Microanatomical variations in the cerebellopontine angle associated with vestibular schwannomas (acoustic neuromas): a retrospective study of 1006 consecutive cases.

OBJECT: Great advances in neuroimaging, intraoperative cranial nerve monitoring, and microsurgical technique have shifted the focus of acoustic neuroma surgery from prolonging life to preserving cranial nerve function in patients. An appreciation of the vascular and cranial nerve microanatomy and the intimate relationship between neurovascular structures and the tumor is essential to achieve optimum results. In this paper the authors analyze the microanatomical variations in location of the facial and cochlear nerves in the cerebellopontine angle (CPA) associated with acoustic neuromas and, additionally, describe the frequency of involvement of surrounding neural and vascular structures with acoustic tumors of varying size. The authors base these findings on their experience with 1006 consecutive patients who underwent surgery via a retrosigmoid or translabyrinthine approach. METHODS: Between July 1969 and January 1998, the senior author (D.M.L.) performed surgery in 1022 patients for acoustic neuroma: 705 (69%) via the retrosigmoid (suboccipital); 301 (29%) via the translabyrinthine; and 16 (2%) via the middle fossa approach. Patients undergoing the middle fossa approach were excluded from the study. The remaining 1006 patients were subdivided into three groups based on tumor size: Group I tumors (609 patients [61%]) were smaller than 2.5 cm; Group II tumors (244 patients [24%]) were between 2.5 and 4 cm; and Group III tumors (153 patients [15%]) were larger than 4 cm. The senior author's operative notes were analyzed for each patient. Relevant cranial nerve and vascular "involvement" as well as anatomical location with respect to the tumor in the CPA were noted. "Involvement" was defined as adherence between neurovascular structure and tumor (or capsule), for which surgical dissection was required to free the structure. Seventh and eighth cranial nerve involvement was divided into anterior, posterior, and polar (around the upper or lower pole) locations. Anterior and posterior locations were further subdivided into upper, middle, or lower thirds of the tumor. The most common location of the seventh cranial nerve (facial) was the anterior middle third of the tumor for all groups, although a significant number were found on the anterior superior portion. The posterior location was exceedingly rare (< 1%). Interestingly, patients with smaller tumors (Group I) had an incidence (3.4%) of the seventh cranial nerve passing through the tumor itself, equal to that of patients with larger tumors. The most common location of the eighth cranial nerve complex was the anterior inferior portion of the tumor. Not surprisingly, larger tumors (Group III) had a higher incidence of involvement of fourth cranial nerve (41%), fifth cranial nerve (100%), ninth-11th cranial nerve complex (99%), and 12th cranial nerve (31%), as well as superior cerebellar artery (79%), anterior inferior cerebellar artery (AICA) trunk (91.5%), AICA branches (100%), posterior inferior cerebellar artery (PICA) trunk (59.5%), PICA branches (79%), and the vertebral artery (VA) (93.5%). A small number of patients in Group III also had AICA (3.3%), PICA (3.3%), or VA (1.3%) vessels within the tumor itself. CONCLUSIONS: In this study, the authors show the great variation in anatomical location and involvement of neurovascular structures in the CPA. With this knowledge, they present certain technical lessons that may be useful in preserving nerve function during surgery and, in doing so, hope to provide neurosurgeons and neurootologists with valuable information that may help to achieve optimum outcomes in patients.

Adult↗
PubMed2001

Cerebrospinal fluid leak after acoustic neuroma surgery: influence of tumor size and surgical approach on incidence and response to treatment.

OBJECT: The aims of this study were to review the incidence of cerebrospinal fluid (CSF) leakage complicating the removal of acoustic neuroma and to identify factors that influence its occurrence and treatment. METHODS: Prospective information on consecutive patients who underwent operation for acoustic neuroma was supplemented by a retrospective review of the medical records in which patients with CSF leaks complicating tumor removal were identified. This paper represents a continuation of a previously published series and thus compiles the authors' continuous experience over the last 24 years of practice. In 624 cases of acoustic neuroma the authors observed an overall incidence of 10.7% for CSF leak. The rate of leakage was significantly lower in the last 9 years compared with the first 15, most likely because of the abandonment of the combined translabyrinthine (TL)-middle fossa exposure. There was no difference in the leakage rate between TL and retrosigmoid (RS) approaches, although there were differences in the site of the leak (wound leaks occurred more frequently after a TL and otorrhea after an RS approach, respectively). Tumor size (maximum extracanalicular diameter) had a significant effect on the leakage rate overall and for RS but not for TL procedures. The majority of leaks ceased with nonsurgical treatments (18% with expectant management and 49% with lumbar CSF drainage). However, TL leaks (especially rhinorrhea) required surgical repair significantly more often than RS leaks. This has not been reported previously. CONCLUSIONS: The rate of CSF leakage after TL and RS procedures has remained stable. Factors influencing its occurrence include tumor size but not surgical approach. The TL-related leaks had a significantly higher surgical repair rate than RS-related leaks, an additional factor to consider when choosing an approach. The problem of CSF leakage becomes increasingly important as nonsurgical treatments for acoustic neuroma are developed.

Cerebrospinal Fluid Otorrhea↗
PubMed2004

Predictive value of Kushida index and acoustic pharyngometry for the evaluation of upper airway in subjects with or without obstructive sleep apnea.

Acoustic pharyngometry is a relatively new noninvasive method that quantifies geometrically complexed pharyngeal dimensions. Our study aimed to investigate the predictability and usefulness of acoustic pharyngometry in diagnosis of obstructive sleep apnea (OSA), and we developed a prospective clinical trial in 16 subjects without apnea and 54 subjects with apnea. All seventy subjects received polysomnography (PSG) to assess the sleep architecture, including breathing and the degree of apnea hypopnea index. Acoustic pharyngometry was performed in four body positions (sitting, supine, right and left lateral) while awake with tidal breathing in addition to morphometric measurements (Kushida index) of oral cavity. This study shows that the cross-sectional area and volume of the upper airway is smaller in the supine position than any other positions. As well, the oropharyngeal junction area of the supine position is the most predictive parameter to discriminate between subjects with or without OSA. Acoustic pharyngometry can be a clinically useful tool for localizing the narrowed portion of the upper airway and predicting obstructive sleep apnea.

Acoustics↗
PubMed2000

Effects of training on attention to acoustic cues.

Learning new phonetic categories in a second language may be thought of in terms of learning to focus one's attention on those parts of the acoustic-phonetic structure of speech that are phonologically relevant in any given context. As yet, however, no study has demonstrated directly that training can shift listeners' attention between acoustic cues given feedback about the linguistic phonetic category alone. In this paper we discuss the results of a training study in which subjects learned to shift their attention from one acoustic cue to another using only category-level identification as feedback. Results demonstrate that training redirects listeners' attention to acoustic cues and that this shift of attention generalizes to novel (untrained) phonetic contexts.

Adolescent↗
PubMed1992

[Normal structure of stereocilia and recovery from ciliary damage in the organ of Corti after acoustic overstimulation].

The normal structure of outer hair cell (OHC) stereocilia in the organ of Corti, as well as damage and the recovery of OHC stereocilia after acoustic overstimulation, were demonstrated using scanning electron microscopy and tannic acid-osmium staining techniques. The highest row of OHC stereocilia is known to show an orderly gradation in height along the length of the cochlea. The present study demonstrated that the middle and lower rows of stereocilia possess a similar height gradation pattern. These findings suggest that the orderly gradation of stereocilia may play an important role in the tuning capability of the organ of Corti sensory cell. To investigate the mechanisms of recovery from ciliary acoustic damage, guinea pigs were exposed to a 4.00 kHz pure tone at an intensity of 120 dB for 120 minutes. All animals showed temporarily elevated hearing thresholds, which had returned to normal one week later. The first detectable change after acoustic overstimulation was a derangement of the cilia with a loss of ciliary interconnections. The tip links connecting the tips of the stereocilia to their taller neighbours were also affected showing elongation or disappearance. In comparing ciliary damage immediately after and one week after acoustic overstimulation, no signs of recovery in hair cell cilia which had been already lost, could be detected, while stereocilia with slight damage seemed to recover in the early post-sound exposure stage. Some lost tip links also seem to reappear in surviving cilia. In addition side links have the possibility of recovery.

Acoustic Stimulation↗
PubMed1992

[Susceptibility of organ of Corti with or without melanin to acoustic overstimulation].

Albino and pigmented guinea pigs were compared in terms of susceptibility to acoustic trauma. The animals were exposed to a 4 kHz pure tone of 120 dB for 60 min. N1 thresholds of CAP were measured before and after the acoustic exposure. Changes in the outer hair cell and stria vascularis were studied using SEM and TEM. After acoustic trauma, N1 thresholds were more elevated in the albino than in the pigmented guinea pigs. Also, pathological changes in the outer hair cell and stria vascularis were more severe in the albino animals. A noteworthy finding in the stria vascularis was that the melanin in intermediate cells had moved into marginal cells. This melanin migration may be possibly involved in mechanisms underlying prevention of acoustic trauma.

Acoustic Stimulation↗
PubMed2003

Interlaboratory acoustic power measurement.

OBJECTIVE: This article describes an American Institute of Ultrasound in Medicine-sponsored intercomparison of the results of acoustic power measurements performed by several laboratories. METHODS: Two primary calibration techniques, namely, planar scanning and radiation force balance, were used in the frequency range typical of that in which sonographic imaging devices operate. The same reference source, the National Institute of Standards and Technology (Gaithersburg, MD) standard ultrasonic power source, capable of producing acoustic fields in the frequency range from approximately 1 to 21 MHz, was circulated to 3 laboratories. RESULTS: The results of the calibrations indicate that the overall uncertainty in acoustic power measurements depends on the target and the measurement method. In the case of radiation force balance measurements with an absorbing target, the largest discrepancy between the available National Institute of Standards and Technology-calibrated results and the reported data was 10.6% at approximately 2.5 MHz. At higher frequencies, beyond 10 MHz, the largest discrepancy reported with an absorbing target was 8.4%. For a reflecting target, the largest discrepancies were 16.2% at approximately 3.7 MHz and 15.4% at about 10 MHz. The largest discrepancy identified for the planar scanning technique below 10 MHz was 7.4% at 3.7 MHz. CONCLUSIONS: The results obtained suggest that an absorbing target may be preferable for acoustic power measurements with radiation force balance. In a group that consists of 2 research laboratories and 1 manufacturer, the power measurements agreed within 16%.

Acoustics↗
PubMed1998

[Voice acoustic analysis in patients with a hearing aid or cochlear implant].

The subject of our study was two groups of patients with hearing disorders: 23 cases implanted with multi-channel cochlear device (Nucleus Mini System 22) and 10 patients with perceptive hypoacusis who used hearing aids. The voice acoustic analysis was performed before cochlear implantation or application of a hearing aid and after a 6-month rehabilitation period. The acoustic analysis was carried out by means of a laryngophone connected to KAY 4300 instrument. The estimation of acoustic parameters of a laryngeal tone during rehabilitation process as well as parameters of spectrographic analysis was presented with the use of MDVP and CSL. Voice acoustic analysis can be an objective evaluation of progress in voice and speech rehabilitation process of patients with hearing disorders, particularly small children.

Adolescent↗
PubMedDate not supplied

[Hypothesis on acoustic receptive fields].

A hypothesis of acoustic receptive fields is studied, which is based on the fact that the cochlea of the internal ear is a wave guide with traveling waves and the resonance in the critical layer. When a harmonic sound influences the ear, the traveling wave reaches the critical layer for the corresponding frequency and generates there a train of decaying waves about 25 periods in duration, which form a steep slope of the envelope. The funnel-shaped convergence of all neurones innervating the acoustic receptors of the Corti organ along the slope of the envelope gives rise to acoustic receptive fields. The hypothesis is consistent with some other experimental data. Such an acoustic receptive field makes it possible to use the whole train of waves in the critical layer to measure the frequency of the acting sinusoidal sound with the greatest possible accuracy. Similarly, a high accuracy of recognition of short-time sound pulses is provided, which could not be explained earlier.

Acoustic Stimulation↗
PubMed1999

Acoustic neuroma surgery in geriatric patients.

Patients older than 65 years who develop acoustic neuromas have the same signs and symptoms as younger patients. Age limits beyond which surgery for acoustic neuroma is currently not recommended are unreasonable. Untreated vertigo in older patients frequently results in falls that can cause fracture of the femur and significant morbidity and mortality. Surgical removal of acoustic neuromas in patients older than 65 produces results that are as good as those seen in younger patients. The patient's general medical condition, life expectancy, and factors other than chronological age should be considered when surgery is being contemplated. Acoustic neuroma surgery for the older patient can provide gratifying results and should not be withheld strictly on the basis of age.

Aged↗
PubMedDate not supplied

[Auditory evoked potentials from brain stem determined in acoustic nerve neurinomas].

An analysis of the studies of Brain Stem Electric Response Audiometry of patients operated on Bachaumont Clinic or in Cochin hospital in Paris, because of acoustic neurinoma, was carried out. The studies comprised 88 patients divided into groups according to the size of tumour. A group of small intrameatal tumours, a group of up to 2 cm tumours, a group of between 2 and 3 cm tumours and a group of above 3 cm tumours. A control group of examined patients consisted of 20 persons with one-side acoustic impairment or two-side impairment but predominant on one side and patients with one-side tinnitus or two-side tinnitus but predominant on one side. Examinations of these patients made with CT and NMR did not show presence of acoustic neurinoma. BERA's tests did not show a response in case of 22 patients with acoustic neurinoma. In 71% of cases BERA's tests showed an extrahelix type, for which in 50% of cases a prolonged latency on the side of the tumour was found. In 4% of cases Brain Stem Electric Response Audiometry gave results within normal range both with respect to morphology and latency time of each wave. A slight correlation between the size of tumour and type of BERA change was found.

Adolescent↗
PubMed1999

Assessment of dysequilibrium after acoustic neuroma removal.

OBJECTIVE: Published data evaluating the rate of dysequilibrium after acoustic neuroma removal are inconsistent. The purpose of this investigation was to determine the incidence and severity of dysequilibrium and quality of life in a group of patients after acoustic neuroma surgery. STUDY DESIGN: The study design was a retrospective chart review and survey that included demographic and medical history questions, the Dizziness Handicap Inventory (DHI), the UCLA Dizziness Questionnaire (UCLA-DQ), and the Health Status Questionnaire (HSQ). SETTING: The study was conducted in a multispecialty tertiary care clinic. PATIENTS: Two hundred thirty-seven subjects who underwent initial surgical removal of an acoustic neuroma between January 1990 and June 1997 were studied. MAIN OUTCOME MEASURES: Correlation of dysequilibrium with age, gender, and tumor size was measured. Survey analysis including DHI, UCLA-DQ, and HSQ scores. RESULTS: Sixty-five percent of patients reported persistent dysequilibrium after surgery. A majority of those with dysequilibrium had DHI, UCLA-DQ, and HSQ scores that suggested minimal impact on the quality of life. The HSQ scores were statistically significantly poorer for the patients with dysequilibrium than for those without dysequilibrium. CONCLUSIONS: Sixty-five percent of patients reported dysequilibrium after acoustic neuroma removal. The quality-of-life impact was mild.

Cranial Nerve Neoplasms↗
PubMed2000

Tumor-associated hemorrhage in patients with acoustic neuroma.

OBJECTIVE: To describe the clinical significance of tumor-associated hemorrhage in patients with acoustic neuromas. STUDY DESIGN: Retrospective chart review. SETTING: University-based, tertiary care teaching hospital. PATIENTS: Three patients with acoustic neuromas who experienced symptomatic tumoral bleeding. INTERVENTIONS: Radiographic imaging, surgical removal of tumors, and pathologic analysis. MAIN OUTCOME MEASURES: Patient histories, radiologic characteristics, surgical results, and pathologic findings. RESULTS: Tumoral hemorrhage can occur in patients with acoustic neuromas. These three cases and a review of the world literature suggest that tumor size may be the most important risk factor for tumor-related hemorrhage. CONCLUSION: These findings have implications for those patients with acoustic neuromas who choose not to have surgical removal.

Aged↗
PubMed1999

Radiosurgery for acoustic neurinomas (vestibular schwannomas).

BACKGROUND: Radiosurgery is a therapeutic technique characterized by the delivery of a single high dose of ionizing radiation from an external source to a precisely defined intracranial target. The application of radiosurgery to the treatment of acoustic neurinomas has increased substantially in the last decade. Most of the published experience pertains to the use of the gamma knife. OBJECTIVES: To report the experience at the first Israeli Linear Accelerator Radiosurgery Unit in the management of 44 patients with acoustic neurinomas. METHODS: We analyzed the clinical records and imaging studies of all patients undergoing radiosurgery for acoustic neurinomas between 1993 and 1997, and quantified the changes in tumor volume, hearing status, and facial and trigeminal nerve function. The contribution of radiation dose and original tumor volume upon those variables was also studied. RESULTS: At a mean follow-up of 32 months (range 12-60), 98% of the tumors were controlled (75% had shrunk; 23% had stable volume). The actuarial hearing preservation rate was 71%. New transient facial neuropathy developed in 24% of the patients, persisting in mild degrees in 8%. Neuropathy correlated primarily with tumor volume. Tumors with volumes > 4 ml were at high risk when marginal radiation doses were > 1,400 cGy. Dose reduction to a maximum of 1,400 cGy produced no neuropathies in the last 20 patients, still preserving tumor control rates. CONCLUSIONS: Radiosurgery is an effective and cost-efficient therapeutic modality for newly diagnosed acoustic neurinomas in the elderly or medically infirm population, and for all residual or recurrent tumors after conventional surgery.

Adult↗
PubMed2000

Acoustic reflex threshold and loudness discomfort.

OBJECTIVE: Trying to find an accurate relation between loudness discomfort level and acoustic reflex threshold. METHODS: Seventy patients were involved in this study. Ten normal patients, 30 patients of unilateral conductive hearing loss and 30 patients of unilateral or bilateral, mild to moderate sensorineural hearing loss were tested by 1, 2, KH2 pure tones, 0.5, 1, 2, 4, 8 KHz narrow band noise, wide band noise and speech noise stimuli to get loudness discomfort level and acoustic reflex threshold in each ear for each stimulus. RESULTS: Ninety two percent of predicted loudness discomfort levels occurred within +/-6 of acoustic reflex threshold rescaled data, when least squares regression method was applied. CONCLUSION: It is apparent that predicted results are statically significant. They are not constant value, but vary according to the acoustic reflex threshold change, stimulus used and hearing situation (normal, conductive or perceptive loss).

Audiometry, Pure-Tone↗
PubMed2000

Acoustic neuroma: postoperative quality of life.

OBJECTIVE: Evaluating patients who have had surgical management of acoustic neuroma has relied heavily on the surgeon's viewpoint for determining success. However, the perspective of the surgeon may be different from that of the patient. Thus, a recent increased interest in terms of quality of life has been documented by the literature on this specific topic essentially through the use of a questionnaire. The objective of this paper was to review this topic in our series of patients operated on for acoustic neuroma to ascertain the personal and social impact that surgery has had on their lifestyle. DESIGN: This retrospective study was devoted to increasing statistics to provide more detailed and valid information during the counselling phase. METHODS: This study was carried out on 82 patients who underwent surgery for acoustic neuroma between 1988 and 1997. Each patient was recalled and assessed for his/her postoperative quality of life. Detailed information was requested on the initial postoperative facial, vestibular, and hearing functions; their evolution; and their social consequence. Finally, at the end of the interview, each patient was invited to give a final comment on his/her opinion regarding the outcomes of surgery and preoperative information. RESULTS: Facial function showed a grade I-III in 85.4% of cases, with postoperative neurovegetative dysfunction (taste and lacrimation) in 43%. Audiologic abnormalities (worsening hearing and tinnitus) were complained of in 90% and 57% of the cases, respectively. Twenty-three percent of the patients had various degrees of gait instability; 6% reported postoperative headache at 1-year follow-up. Social consequence (reduced work ability, vocational change, new education, state pension, etc.) was not influenced by surgery in 80%. CONCLUSIONS: Our experience is in general agreement with previously reported statistics. It is interesting to note that our patients exhibited more disturbances linked to the sensory component of facial nerve. In contrast, dysequilibrium had a less negative influence. These outcomes suggest the importance of thorough preoperative counselling in candidates for surgery for acoustic neuroma in order to motivate them and, at the same time, to reduce their psychological discomfort.

Adult↗
PubMed1998

[The study on the acoustic-phonetic features of marginal velopharyngeal closure].

OBJECTIVE: To study the acoustic-phonetic features of the cleft patients with marginal velopharyngeal closure. METHODS: The acoustic-phonetic features of 17 cleft patients with marginal velopharyngeal closure were analyzed with USSA sound spectrograph, contrasted by the features of 28 cleft patients with velopharyngeal incompetence and 18 patients with velopharyngeal competence. RESULTS: The manifestations of single vowel spectrum differ from that of the same vowel in sentence for MVPC patients. There are extra formants or strong nasal formants in a number of vowels spectrums in sentence, while they do not occur on single vowel spectrum. The spike and stop gap in the spectrograms of stops and affricatives may be absent or existing occasionally, and the noise energy in the lowest frequency area in the spectrograms of aspirated consonants may be watched or not. CONCLUSION: Acoustic analysis is very valuable to evaluate the state of marginal velopharyngeal closure. Analyzing the acoustic features of multiple vowels and consonants, and comparing the resonance characteristics of single vowel with the same vowel in continuous speech simultaneously are emphasized.

Acoustics↗