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PubMedDate not supplied

Hearing preservation in unilateral acoustic neuroma surgery.

This paper reviews the principal English literature on hearing preservation in unilateral acoustic neuroma surgery. Seventeen case reports and 13 surgical series are included. In addition, we report ten cases of our own, two with successful hearing preservation. The purpose of this report is to study feasibility, success rate, and associated problems. Previous reports have been compared in terms of criteria that we have selected. A classification system similar to Silverstein's is used. The total number of cases under review is 621, with 221 reported successes. Cases limited to those having a unilateral acoustic neuroma, with valid supportive audiometry, were 394, with 131 successes. The approximate overall rate of success is 33%. There are five cases of hearing preservation with unilateral acoustic neuromas 3 cm or larger when supporting audiometric data are available, the largest being "4-5 centimeters." Problems included mixing of unilateral acoustic neuromas with other types of tumors and failure to include comprehensive data, particularly audiometry. We conclude 1) that hearing preservation is a reasonable goal in unilateral acoustic neuroma surgery, although the number of available candidates is relatively small and 2) that intelligent selection of patients and high quality surgical technique are the keys to success.

Deafness↗
PubMed1996

Acoustic rhinometry in the study of the acute nasal allergic response.

Acoustic rhinometry is a recently developed method for the objective assessment of nasal patency. In this study, acoustic rhinometry was used to measure changes in nasal cavity dimensions in the immediate response to nasal allergen challenge in eight pollen-sensitive subjects. Acoustic rhinometric changes were compared with subjective symptoms, as well as histamine in nasal secretions, cytology of nasal mucosal scrapings, and changes in olfactory function. A significantly greater decrease in nasal airway caliber occurred following allergen challenge as compared to buffer diluent challenge in the same individuals (70% +/- 7% versus 22% +/- 5%). During an allergic response, a strong correlation was found between the minimum cross-sectional area and the volume of the nasal cavity measured by acoustic rhinometry (r = .9). However, no correlation was observed between nasal airway caliber and concomitant subjective congestion reported by the subjects. A modest decrease in olfactory function was seen following allergen challenge (3.1 +/- 1.4 fewer odors identified correctly out of 20; p = .08). However, the alterations of olfactory function did not correlate with changes in nasal patency. The results presented in this study demonstrate that acoustic rhinometry has great potential as a reproducible method for the objective assessment of nasal obstruction occurring in nasal allergen challenge studies.

Acoustics↗
PubMedDate not supplied

An acoustical basis for universal phonotactic constraints.

Spectral characteristics of some selected phoneme sequences are investigated in an attempt to explain cross-linguistic tendencies in phonotactic constraints. A hypothesis is offered that some universal sequential constraints are acoustically motivated. Two acoustic factors are posited as determinants of favored/disfavored sequences: The magnitude of acoustic modulation within a sequence and the degree of acoustic difference between sequences. The hypothesis is tested experimentally for its applicability to some of the universal constraints. Trajectories of the first three formants are obtained for selected sequences of stop + liquid + vowel, stop + glide + vowel, stop + vowel, and vowel + stop. Standard Euclidean distance in frequency is computed as a measure approximating each acoustic factor. The results show that some universally rare or unstable phoneme sequences can be explained on the basis of their lack of spectral modulation and/or their spectral similarity to other sequences, suggesting that acoustic/auditory factors play a significant role in determining the phonetic shape of language.

Female↗
PubMed1995

Staged removal of acoustic tumors: techniques and lessons learned from a series of 83 patients.

The removal of large acoustic tumors is associated with increased mortality and cranial nerve injury. One method for treating these difficult lesions is staged resection. Between 1972 and 1992, more than 600 acoustic tumors were resected at our institution. Of these, 83 were removed in stages. This represents the largest series of staged acoustic tumor resections reported to date. A review of available films and patient records was performed for all acoustic tumors resected in stages between 1972 and early 1993 to analyze demographic information, tumor size, operative technique, outcome, and complications. The information was collected on standardized data sheets and entered into a computer database. Virtually all tumors were large, with the average size being 4 cm in greatest diameter. The average patient age was 41 years, and there was a slight preponderance of female patients. Ten patients had neurofibromatosis Type 2. The suboccipital approach was used in most patients. Anatomic preservation of the VIIth cranial nerve was achieved in > 72% of patients, with an average House-Brackmann score of Grade 3 at the longest follow-up (mean, 43 mo). Facial reanimation was performed in 19 of 23 patients with transected VIIth cranial nerves. Complications included cerebrospinal fluid fistulas in 11 patients, with 8 of 11 fistulas resolving after lumbar drainage. Six patients had meningitis (bacterial in three and aseptic in three). Two patients developed wound infections, and 10 patients developed exposure keratitis. There were two documented recurrences. There were no operative deaths. In most series, the incidence of cranial nerve deficits as well as morbidity and mortality is directly related to tumor size. Our operative strategy involved debulking the lateral aspect of large tumors during Stage I. Second stage removal is performed after the remaining tumor is shown to decompress out of the pons on computed tomographic or magnetic resonance images. During the second procedure, the residual tumor is less vascular and no longer densely adherent to the brain stem. Although staged removal is not without risk, there seems to be no apparent increase in morbidity when these results are compared with the results of series from the literature. Although there remain no absolute indications for staged resection of acoustic tumors, we think that it may represent the safest option for these difficult lesions.

Adult↗
PubMed2005

Staged stereotactic irradiation for acoustic neuroma.

OBJECTIVE: Stereotactic radiosurgery has proven effective in the treatment of acoustic neuromas. Prior reports using single-stage radiosurgery consistently have shown excellent tumor control, but only up to a 50 to 73% likelihood of maintaining hearing at pretreatment levels. Staged, frame-based radiosurgery using 12-hour interfraction intervals previously has been shown by our group to achieve excellent tumor control while increasing the rate of hearing preservation at 2 years to 77%. The arrival of CyberKnife (Accuray, Inc., Sunnyvale, CA) image-guided radiosurgery now makes it more practical to treat acoustic neuroma with a staged approach. We hypothesize that such factors may further minimize injury of adjacent cranial nerves. In this retrospective study, we report our experience with staged radiosurgery for managing acoustic neuromas. METHODS: Since 1999, the CyberKnife has been used to treat more than 270 patients with acoustic neuroma at Stanford University. Sixty-one of these patients have now been followed up for a minimum of 36 months and form the basis for the present clinical investigation. Among the treated patients, the mean transverse tumor diameter was 18.5 mm, whereas the total marginal dose was either 18 or 21 Gy using three 6- or 7-Gy fractions. Audiograms and magnetic resonance imaging were obtained at 6-months intervals after treatment for the first 2 years and then annually thereafter. RESULTS: Of the 61 patients with a minimum of 36 months of follow-up (mean, 48 mo), 74% of patients with serviceable hearing (Gardner-Robinson Class 1-2) maintained serviceable hearing at the last follow-up, and no patient with at least some hearing before treatment lost all hearing on the treated side. Only one treated tumor (2%) progressed after radiosurgery; 29 (48%) of 61 decreased in size and 31 (50%) of the 61 tumors were stable. In no patients did new trigeminal dysfunction develop, nor did any patient experience permanent injury to their facial nerve; two patients experienced transient facial twitching that resolved in 3 to 5 months. CONCLUSION: Although still preliminary, these results indicate that improved tumor dose homogeneity and a staged treatment regimen may improve hearing preservation in acoustic neuroma patients undergoing stereotactic radiosurgery.

Adult↗
PubMed2005

Simultaneous measurement of metabolic and acoustic power and the efficiency of sound production in two mole cricket species (Orthoptera: Gryllotalpidae).

We here report the first simultaneous measurement of metabolic cost of calling, acoustic power and efficiency of sound production in animals--the mole crickets Scapteriscus borellii and S. vicinus (Gryllotalpidae). We measured O(2) consumption, CO(2) production and acoustic power as the crickets called from their burrows in an open room. We utilized their calling burrow as the functional equivalent of a mask. Both species had a respiratory quotient near 0.85, indicative of metabolism based on a mix of carbohydrates and fats. The metabolic rate was significantly higher in S. borellii (11.6 mW g(-1)) than in S. vicinus (9.0 mW g(-1)) and averaged about eight- to fivefold greater, respectively, than resting metabolism. In some individuals, metabolic rate decreased by 20% during calling bouts. Costs of refurbishing calling burrows in S. borellii were less than calling costs, due to the behavior's short duration (ca. 15 min) and its relatively low average metabolic rate (4 mW). Acoustic power was on average sevenfold greater in S. borellii (21.2 vs 2.9 microW) and was more variable within individuals and across species than the metabolic rate. The efficiency of sound production was significantly higher in S. borellii (0.23 vs 0.03%). These values are below published estimates for other insects even though these mole crickets construct acoustic burrows that have the potential to increase efficiency. The cricket/burrow system in both species have an apparent Q(ln decrement) of about 6, indicative of significant internal damping caused by the airspaces in the sand that forms the burrow's walls. Damping is therefore an important cause of the low sound production efficiency. In field conditions where burrow walls are saturated with water and there is less internal damping, calls are louder and sound production efficiency is likely higher. File tooth depths and file tooth-to-tooth distances correlated with interspecific differences in metabolism and acoustic power much better than with wing stroke rates and plectrum-to-file tooth strike rates. To further investigate these correlations, we constructed two models of energy input to the tegminal oscillator. A model based on transfer of kinetic energy based on differences in tegminal velocity and file tooth spacing showed the most promise. Related calculations suggest that if there are no elastic savings, the power costs to accelerate and decelerate the tegmina are greater than the predicted power input to the tegminal oscillator, and that they are similar in the two species even though S. vicinus has a nearly threefold higher wing stroke rate.

Acoustics↗
PubMed1999

Directional acoustic radiation in the strut display of male sage grouse Centrocercus urophasianus.

We present evidence that the acoustic component of the strut display of male sage grouse Centrocercus urophasianus is highly directional and that the nature of this directionality is unique among measured vertebrates. Where vertebrate acoustic signals have been found to be directional, they are most intense anteriorly and are bilaterally symmetrical. Our results show that sage grouse acoustic radiation (beam) patterns are often asymmetric about the birds' anterior-posterior axis. The beam pattern of the 'whistle' note is actually strikingly bilobate with a deep null directly in front of the displaying bird. While the sage grouse display serves to attract potential mates, male sage grouse rarely face females head on when they call. The results of this study suggest that males may reach females with a high-intensity signal despite their preference for an oblique display posture relative to those females. We characterized these patterns using a novel technique that allowed us to map acoustic radiation patterns of unrestrained animals calling in the wild. Using an eight-microphone array, our technique integrates acoustic localization with synchronous pressure-field measurements while controlling for small-scale environmental variation in sound propagation.

Acoustics↗
PubMed1990

[Behavioral characteristics associated with acoustic stimulation and the neurochemical alterations of monoaminergic systems in rat brain at the steady state of repeated methamphetamine administration].

Behavioral characteristics associated with acoustic stimulation and the neurochemical alterations of monoaminergic systems in rat brain at the steady state of repeated methamphetamine administration were investigated. We confirmed that reverse tolerance in stereotyped behavior was constructed up to the 28th day after repeated intermittent pretreatment with increasing doses of MAP (2.5, 5, and 7.5 mg/kg x 3 and 10 mg/kg x 2, every other day). During acoustic stimulation, locomotor activity in the saline group was significantly increased, but the activity after the stimulation was completely suppressed. In contrast to the saline group, locomotor activity was not influenced by the acoustic stimulation in the MAP group, suggesting that behavioral hyporesponsiveness to acoustic stimulation was induced by MAP treatment. Two days after the last injection, the contents of 5-hydroxytryptamine (5-HT) and 5-hydroxyphenylacetic acid (5-HIAA) in the cerebral cortex, midbrain + thalamus, hypothalamus and striatum were significantly decreased. These changes were maintained up to the 28th day after the drug withdrawal in the cerebral cortex and the midbrain + thalamus. From these results, the persistence of behavioral hyporesponsiveness to acoustic stimulation might be associated with long-lasting reduction of 5-HT synthesis.

Acoustic Stimulation↗
PubMed1981

Radiological techniques for small acoustic tumors--a re-evaluation.

Small acoustic neuromas are not detected on conventional, computed tomography (CT) brain scans. Eighteen patients with proven acoustic tumors and negative CT brain scans were studied retrospectively to re-evaluate current radiological techniques. We found that the conventional mastoid plain film or thin section tomography is an accurate, cost effective, screening test for acoustic tumors. When these screening studies are positive and agree with the clinical and audiometric examinations, a CT brain scan should then be performed. If the latter is negative, Pantopaque myelography or air-CT should follow. The decision to proceed to invasive studies has been helped by such tests as brain stem audiometry. Since no single, noninvasive X-ray test currently exists to diagnose the small acoustic tumor, screening X-ray studies are indicated before the use of invasive, expensive studies. A protocol for the radiological work-up of small acoustic tumors is suggested.

Adult↗
PubMed1991

The treatment of small acoustic tumors: now or later?

Prior to the advent of microneurosurgery, the operative mortality for acoustic tumor removal was high and management often consisted of observation until sufficient symptoms warranted removal. The treatment of these tumors has evolved, and recent introduction of gadolinium-enhanced magnetic resonance imaging (MRI) allows the diagnosis of very small intracanalicular acoustic tumors before hearing has been significantly affected. For such tumors, some surgeons advocate the premicrosurgical philosophy of observation rather than removal. Our results of small acoustic tumor removal with attempt at hearing preservation were reviewed. From 1961 to June 1989, 39 acoustic tumors 0.5 cm or less were removed by the middle fossa approach. Measurable hearing was preserved in 67%, and facial function 1 year postoperatively was normal or nearly normal in 97%. There was no other permanent operative morbidity. Given our results, early surgical removal of small acoustic tumors is advocated.

Adolescent↗
PubMed1995

Patterns of evoked otoacoustic emissions associated with acoustic neuromas.

Evoked otoacoustic emissions (OAEs) are assumed to reflect healthy outer hair cell function. Over the past few years, evoked OAEs have been shown to be useful as indicators of cochlear hearing loss. Because basic studies have shown that OAEs are extremely sensitive to cochlear anoxia and hypoxia, as well as to the adverse effects of many inner ear diseases, it is possible that these objective tests can provide some insight into the fundamental basis of the hearing loss exhibited by patients with acoustic neuromas. The primary aim of the present study was to examine the effects of acoustic neuromas on the amplitudes of evoked OAEs and to compare these findings with tumor-induced hearing levels. To this end, tests of behavioral audiometry, distortion-product otoacoustic emissions and transiently evoked otoacoustic emissions were performed on 44 patients with verified acoustic neuromas. The results demonstrated that the majority of ears with acoustic neuromas displayed one of two distinct patterns of evoked OAEs: a cochlear pattern or a noncochlear pattern. Although behavioral hearing thresholds were higher with larger tumors, OAE levels exhibited no clear relationship to tumor size. The present findings support the notion that acoustic neuromas may cause hearing impairment according to two types of influence that act at different levels of the peripheral auditory system. The tumor's cochlear effect on evoked OAE activity is most likely caused by an indirectly mediated compromise of the organ of Corti's vascular supply. It is probable that the direct pressure of the tumor on the eighth cranial nerve is responsible for the observed noncochlear effects.

Audiometry↗
PubMed2006

Intense acoustic bursts as a signal-enhancement mechanism in ultrasound-modulated optical tomography.

Biophotonic imaging with ultrasound-modulated optical tomography (UOT) promises ultrasonically resolved imaging in biological tissues. A key challenge in this imaging technique is a low signal-to-noise ratio (SNR). We show significant UOT signal enhancement by using intense time-gated acoustic bursts. A CCD camera captured the speckle pattern from a laser-illuminated tissue phantom. Differences in speckle contrast were observed when ultrasonic bursts were applied, compared with when no ultrasound was applied. When CCD triggering was synchronized with burst initiation, acoustic-radiation-force-induced displacements were detected. To avoid mechanical contrast in UOT images, the CCD camera acquisition was delayed several milliseconds until transient effects of acoustic radiation force attenuated to a satisfactory level. The SNR of our system was sufficiently high to provide an image pixel per acoustic burst without signal averaging. Because of the substantially improved SNR, the use of intense acoustic bursts is a promising signal enhancement strategy for UOT.

Feasibility Studies↗
PubMed1997

Respiratory and arousal responses to acoustic stimulation.

STUDY OBJECTIVES: Although sleep-related obstructive apnea is most often associated with transient arousal, the impact of this arousal on respiratory control remains unclear. We tested the hypotheses that acoustic arousing stimulation can generate a significant respiratory response during sleep in healthy subjects and that the magnitude or timing of this response is affected by the presence of electrocortical arousal or inhaled carbon dioxide. DESIGN: We employed binaural tone bursts (0.5-s duration, 4-KHz center frequency, 99-s interstimulus interval) to elicit repetitive transient arousals from sleep during nocturnal polysomnographic recordings beginning at 10 PM and ending at 6 AM. PARTICIPANTS: Recordings were conducted in five healthy adult volunteers aged 24 to 37 years. INTERVENTIONS: Inspired gas was alternated between room air and 3% to 7% CO2 (titrated to yield an approximate 50% increase in minute ventilation) at 1-h intervals. MEASUREMENTS AND RESULTS: Each 30-s epoch was scored for sleep/wake stage according to standard criteria. Only results obtained during nonrapid eye movement sleep are presented herein. Tone-evoked arousals were detected by computer analysis as increased EEG frequency occurring within 3 s of acoustic stimulation. For each tone, respiratory parameters for each of three prestimulus and four poststimulus breaths were normalized to the overall mean of prestimulus breaths measured during room air breathing for each subject. Tone bursts elicited repetitive transient arousals with a mean duration of approximately 10 s from all stages of sleep. With respect to the three prestimulus breaths, acoustic stimulation was associated with increased tidal volume and decreased inspiratory duration for at least four breaths. These respiratory responses to acoustic stimulation were not significantly influenced by either presence of transient arousal from sleep or inspired gas. CONCLUSIONS: We conclude that transient EEG arousal may be repeatedly evoked from nonrapid eye movement sleep by transient acoustic stimulation in normal sleepers. This sensory stimulation is associated with augmented ventilation, a response that is not significantly affected by inspired hypercapnia or the presence of generalized EEG arousal.

Acoustic Stimulation↗
PubMedDate not supplied

Brainstem auditory evoked response in adolescents with acoustic mycotic neuroma due to environmental exposure to toxic molds.

Indoor air contamination with toxic opportunistic molds is an emerging health risk worldwide. Some of the opportunistic molds include: Stachybotrys chartarum, Aspergillus species (A. fumigatus, A. flavus, A. niger, A. versicolor etc.), Cadosporium, Alternaria, Penicillium, Trichoderma, Fusarium graminearum etc. These molds flourish in homes that are moist and damp. Reports of floods are now evident in many parts of the world. With these global changes in climatic conditions that favor the opportunistic mode of living among these molds, some health authorities are beginning to feel concerned about the diversity and the extent to which opportunistic molds can cause adverse health effects in humans. Mycotoxicosis is the collective name for all the diseases caused by toxic molds. Frequently, we have cases of acoustic neuroma due to mycotoxicity in our Center. Mycotic neuroma probably has not been reported before and the application of brainstem auditory evoked response (BAER) techniques in acoustic mycotic neuroma have not been reported either. The aim of this study, therefore, was to report cases and measurements of acoustic mycotic neuroma in adolescents using the brainstem auditory evoked response. The patients' case history, clinical neurological and neurobehavioral questionnaires were assessed. Then, the BAERs were recorded between Cz and Ai, with a second channel, Cz-Ac. The case histories and the questionnaires were analyzed in conjunction with the outcome of the objective brainstem auditory evoked response measurements. The prevalent subjective findings in the patients were headaches, memory loss, hearing loss, lack of concentration, fatigue, sleep disturbance, facial swelling, rashes, nosebleeds, diarrhea, abdominal pains and respiratory difficulties. Objective BAER showed overall abnormalities in all the patients. Although the waveform abnormalities varied, 1-3 interpeak latencies were abnormal in all the patients. Overall results showed the presence of acoustic mycotic neuroma and confirmed the sensitivity and usefulness of BAER in screening acoustic mycotic neuroma and sensorineural auditory dysfunction.

Adolescent↗
PubMed2002

The perceived urgency of speech warnings: semantics versus acoustics.

The relationship between the semantics of words and the acoustics of the way they are spoken is explored. Actors spoke warning signal words in an urgent, nonurgent and monotone style, and participants rated the urgency of the words. Results showed effects for signal word and style of presentation. Acoustic analysis showed that the urgent words were spoken at higher frequency with a broader pitch range and were louder than the nonurgent or monotone words. These acoustic differences were used to synthesize artificial versions of signal words in urgent and nonurgent formats. The urgent words were rated as more urgent than the nonurgent words, a finding attributable to their differing acoustics. Within each speaking style the words were acoustically the same, yet effects for signal word were found, suggesting that semantics is also important in urgency perception. This research has implications for the design and implementation of speech warning systems, particularly those in which urgency mapping is required.

Adolescent↗
PubMed2000

Acoustic schwannoma and arachnoid cyst colocated in the cerebellopontine angle--case report.

A 50-year-old female presented with a right acoustic schwannoma colocated with a cerebellopontine angle arachnoid cyst. The arachnoid cyst was distinct from the arachnoid cap surrounding the acoustic schwannoma. Initial excision of the arachnoid cyst created the space required to excise the schwannoma. The acoustic schwannoma had surprisingly dense adhesions to the brainstem, probably due to the constant pressure exerted by the cyst displacing the tumor towards the brainstem. The acoustic schwannoma was excised by meticulous dissection. Such a coexisting lesion should be suspected when a large cystic collection surrounds an acoustic schwannoma. Initial excision of the arachnoid cyst will prevent excessive cerebellar retraction.

Arachnoid Cysts↗
PubMed2003

Cost comparison of auditory brainstem response versus magnetic resonance imaging screening of acoustic neuroma.

The cost-effectiveness of current diagnostic approaches employed in patients with suspected acoustic neuroma was evaluated. Currently, patients with signs and symptoms suggestive of acoustic neuroma, such as sudden unilateral hearing loss and/or tinnitus, undergo auditory brainstem response (ABR) screening tests to rule out this condition. If the ABR is normal, acoustic neuroma can be ruled out. However, if the ABR is abnormal, magnetic resonance imaging (MRI) or computed tomography is necessary to confirm the diagnosis. When one considers the total costs of this screening approach, one can ask whether straight MRI screening of all of these patients would be a more cost-effective approach to diagnosing this condition. A retrospective chart review of patient records obtained from the acoustic diagnostics laboratory at Hotel Dieu Hospital, Kingston, Ontario, was performed. A database of patients who have undergone ABR testing over the past 2 years was compiled and analyzed to assess how many of them went on to receive MRI. The total costs (based on Ontario Health Insurance Plan [OHIP] fee schedule rates) of this approach were compared with the estimated costs of straight MRI screening performed on the same patient population. By making such an analysis, decisions regarding the most cost-effective approach to screening for acoustic neuroma can be objectively assessed.

Adult↗
PubMed1996

Measurement of endocochlear DC potentials in ears with acoustic neuromas: a preliminary report.

The pathogenesis of hearing loss in acoustic neuromas remains to be elucidated. To obtain more detailed information about inner ear damage in this disease, especially that dealing with the possibility of ischemia of the inner ear due to compression of the blood supply in the internal auditory canal by acoustic neuromas, measurement of endocochlear DC potential (EP) was attempted in three ears with acoustic neuromas during surgical removal of the tumors by the translabyrinthine approach. The size of each tumor was 3.0, 0.8, and 1.8 cm, respectively. An EP with a positive value was recorded in each of the three ears, i.e., 54, 57, and 38 mV, respectively, although the first and third patients were profoundly deaf on the side with a tumor. These findings were interpreted as being evidence of retention of function by the stria vascularis and the existence of blood supply to the inner ear in spite of the presence of tumors. Measurement of the EP seems to provide a new tool with which to analyze the causes of hearing loss in acoustic neuromas. Relatively low EP values may suggest mild dysfunction of the stria vascularis with acoustic neuromas.

Aged↗