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PubMed1993

Acoustic neuroma and non-tumour retrocochlear patients: audiological features.

Seventeen surgically confirmed acoustic neuroma subjects and seventeen radiologically confirmed non-tumour subjects with retrocochlear pathology of unknown aetiology were selected to investigate retrospectively the diagnostic yield of basic audiological test procedures. Puretone audiometry, tympanometry, reflexometry and auditory brainstem response audiometry were used in the identification of acoustic neuromas versus non-tumour retrocochlear disorders. All subjects had been referred originally for neuroaudiological assessment because of suspected acoustic neuroma and had been found to have a range of abnormal ABR findings consistent with retrocochlear pathology. Detailed retrospective analysis of audiological results following surgical and radiological classification showed subject similarities for most parameters of the individual audiological tests for both acoustic neuroma and non-tumour groups. A significant difference was noted, however, between the two clinical populations for the ABR Wave V absolute interaural latency difference parameter.

Acoustic Impedance Tests↗
PubMed1993

Effects of contralateral acoustic stimulation on otoacoustic emissions following vestibular neurectomy.

This study demonstrates that, following unilateral vestibular neurectomy, the inhibitory effect of contralateral acoustic stimulation on evoked otoacoustic emissions is absent. The patient acts as her own control in that the unoperated side shows normal suppression of otoacoustic emission amplitude with contralateral acoustic stimulation. The lack of interaural suppression of otoacoustic emissions on the sectioned side, in the presence of normal acoustic reflex threshold levels, provides evidence that observed phenomena are not merely a function of middle ear reflex activity. It is concluded that the lack of inhibition in the operated ear is due to the sectioning of the olivocochlear bundle within the inferior vestibular nerve, removing the efferent control of the receptor cells. Otoacoustic emissions recorded during contralateral acoustic stimulation may thus provide a rapid, non-invasive means of investigating the functional of the efferent auditory system.

Acoustic Stimulation↗
PubMed1998

A study of the acoustic reflex using fast-rate otoacoustic emissions.

Fast-rate otoacoustic emissions (OAEs) were used to determine the inward and outward transmission change produced by the stapedial muscle reflex. The subjects were otologically normal adult volunteers. Satisfactory recordings were obtained from a total of 16 ears. Runs of 16 click-evoked OAEs were recorded at a rate of 4282 clicks/s using the maximum length sequence (MLS) technique, with a contralateral tone presented at 10 dB above the contralateral acoustic reflex threshold during the recording of OAEs 5-12 in each run. The OAEs recorded with the contralateral tone were compared with those recorded without the tone to determine the effect of the acoustic reflex. An analysis of the OAEs in 0.5 kHz frequency bands suggested that the reflex produced significant attenuation of low frequency sound with smaller effects at high frequencies, which included amplification for some subjects. For eight of the 16 ears there was an increase in OAE amplitude with the acoustic reflex for at least one frequency band. At low frequencies (1, 1.5 kHz) the inward transmission change produced by the acoustic reflex appeared to be similar in magnitude to the outward transmission change.

Acoustic Stimulation↗
PubMed1977

Acoustic reflex measures of cochlear damage--a normative study.

It has been argued that certain reflex measures may indicate the presence of end-organ hearing loss. It has been noticed that the difference between wide band noise and pure tone thresholds is diminished, that the reflex threshold duration function is flattened and that the reflex relaxation index, as specified by Norris et al. (1974b), is reduced in cases of end-organ hearing loss. These aspects of the acoustic stapedial reflex, together with its growth with stimulus intensity, have been investigated in 25 normally hearing subjects. The overriding feature of the measures taken of the acoustic stapedial reflex, was the high inter-subject variability. The differences between the acoustic reflex thresholds for pure tone and WBN was found to be normally distributed about a mean value of 12 dB. The threshold-duration functions again were highly variable and encompassed the entire range of results from normal and end-organ impaired groups as reported by Woodford et al. (1975). The variability encountered in the RRI measures was found to increase with frequency. The growth of the acoustic stapedial reflex with intensity was found to be frequency dependent: the gradient of the function increasing with frequency for the long duration (500 ms) pulses and decreasing with the short duration (50 ms) pulses. It is concluded that considerable caution must be exercised in extrapolation from any one of these measures in isolation.

Acoustic Impedance Tests↗
PubMed1984

Acoustic-reflex adaptation: morphology and half-life data for subjects with normal hearing.

Acoustic-reflex adaptation was studied in 35 subjects with normal hearing using nine pure-tone activators (250-6000 Hz) and a broadband-noise activator. The individual subject data generated by the 31-s activators presented 10 dB above the reflex threshold were digitized, corrected for baseline drift and ear canal volume, and analyzed in terms of the acoustic-admittance change in acoustic mmhos and in terms of the percentage of maximum-reflex magnitude. Reflex adaptation increased as a function of frequency. The adaptation functions for the lower frequencies (less than or equal to 1500 Hz) were essentially linear over the 31-s activator period, whereas the functions for the higher frequencies (greater than or equal to 2000 Hz) were curvilinear over the activator period. The experimental half-life data are compared with a theoretical half-life function that was generated to estimate normal acoustic-reflex adaptation as a function of activator frequency. Finally, the means and standard deviations are reported and discussed for (a) the onset time of adaptation, (b) the half-life time, and (c) the percentage of maximum reflex magnitude at 5-s intervals from 5 to 30 s.

Acoustic Stimulation↗
PubMedDate not supplied

Negative needle deflection of the acoustic reflex in otosclerotics.

The preoperative audiometric and electroacoustic impedance test results of 24 surgically confirmed otosclerotics are reviewed with special attention given to the direction of needle deflection during acoustic reflex testing. Information on the direction of needle deflection during acoustic reflex testing was gathered at 5 or 10 dB above reflex threshold. In 12 of the 24 patients acoustic reflexes were present, and in each case the response included negative needle deflections. The presence or absence of the acoustic reflex seemed to be related to the reported duration of the hearing loss.

Acoustic Impedance Tests↗
PubMed1983

Acoustic neuromas. Progression of hearing impairment and function of the eighth cranial nerve.

The results obtained by conventional otologic evaluation are reported for fifty-nine patients with acoustic neuromas, sixty-one patients primarily suspected of an acoustic neuroma but in whom Pantopaque cisternography had invalidated the diagnosis, and in seventy-one patients with Meniere's disease. The audiologic tests were confined to the following: pure-tone audiometry, speech audiometry, recruitment examination by ABLB and Metz recruitment tests, and examination for reflex decay a.m. Anderson. Nineteen patients had an audiogram taken at their initial visit with the otologist, and already at this examination--4.2 years before the diagnosis was made--a high-tone hearing impairment was present. Fourteen patients had anacusis in the tumor ear and one patient had an impairment of 90 dB. The audiologic evaluations are based only on patients with hearing equal to or better than 80 dB. There was no connection between preoperative hearing impairment and the age at operation, and anacusis was found in all age groups. Four patients had recruitment by the ABLB test and six patients by the Metz recruitment test. When these two tests were combined, two patients had recruitment by both tests. Twenty percent had pathologic stapedial reflex decay. Only one patient had a normal differential caloric test. It is concluded that the typical patient with an acoustic neuroma has a gradually increasing unilateral hearing impairment of eight years' duration. A pronounced high-tone impairment with PTA of 55 dB and a poor discrimination score are to be expected. The patient is uncertain at pure-tone threshold determination and displays a lack of recruitment at both ABLB and Metz recruitment tests. The patient has a decreased or nonexistent differential caloric reaction in the ear in question. A normal differential caloric test does in all probability exclude an acoustic neuroma; however, all possible audiometric and anamnestic configurations may be encountered, and deviation from the "typical" picture should not lure the investigator into excluding the presence of a neuroma.

Adult↗
PubMed1994

Acoustic neuroma in an adolescent without neurofibromatosis: case study.

When acoustic neuromas are found in younger age groups, they are typically bilateral and associated with neurofibromatosis (NF). A unilateral acoustic neuroma in a child or adolescent without NF is rare. We report audiometric, auditory brainstem response (ABR) and magnetic resonance imaging (MRI) data for a 15-year-old male with an acoustic neuroma but without associated NF. The patient was seen for audiologic assessment on three separate occasions over a period of 5 years. The first two assessments produced unremarkable audiometric and immittance data. The third assessment, subsequent to a failed school hearing screening, demonstrated a flat unilateral sensorineural hearing loss, unilateral absent acoustic reflexes, and abnormal bilateral ABR recordings. MRI with contrast demonstrated a unilateral mass extending out of the internal auditory meatus. Microscopic examination of the removed tumor confirmed a vestibular schwannoma. An enhanced MRI 3 years post neuroma removal demonstrated no evidence of tumor regrowth and no evidence of other neoplasms. ABR recordings for the uninvolved ear continued to demonstrate neural synchrony as evidenced by normal absolute wave latencies; however, the III-V and I-V interwave latencies remained extended beyond the 99th percentile. Postoperatively, the young man was fitted with a high gain in-the-ear hearing aid in the involved ear, which he has continued to wear on a daily basis for the past 3 years.

Adolescent↗
PubMed1995

Cranial nerve preservation after stereotactic radiosurgery for small acoustic tumors.

OBJECTIVE: To assess those factors associated with and predictive of cranial nerve preservation after stereotactic radiosurgery in patients with small acoustic tumors identified by magnetic resonance imaging. DESIGN: We performed a retrospective analysis of our experience with 31 patients with preserved hearing and acoustic tumors measuring 10 mm or smaller (pons-to-petrous dimension). All patients underwent clinical and audiologic evaluations varying from 6 to 48 months (mean, 20 months) after stereotactic radiosurgery performed with use of the 201 source cobalt 60 gamma unit. RESULTS: Stabilization or reduction in tumor volume was achieved in 29 of 31 patients. One patient required delayed microsurgical resection. Useful hearing (pure tone average < or = 50 dB and speech discrimination score > or = 50%) preservation was achieved in 10 of 10 patients immediately postoperatively, eight of 10 patients at 6 months, six of 10 patients at 1 year, and five of 10 at 2 years. Preservation of some measurable hearing was possible in all patients immediately after radiosurgery, in 84% and in more than half of patients at 2 years. Preoperative facial nerve function was preserved in 19 of 20 patients at 2 years after radiosurgery. All patients returned to their preoperative employment status within 2 to 5 days after radiosurgery. CONCLUSION: Stereotactic radiosurgery performed with current technology (multiple radiation isocenters and magnetic resonance imaging guidance) is a safe and effective management strategy for patients with small acoustic tumors. The risk of facial and trigeminal neuropathy after gamma knife radiosurgery is low, and useful hearing can be preserved in up to 50% of patients with useful preoperative hearing. Stereotactic radiosurgery is a valuable alternative strategy to surgical removal for many patients with newly diagnosed small acoustic tumors.

Adult↗
PubMed1986

Acoustic neurinoma diagnostic model evaluation using decision support systems.

Three acoustic neurinoma (hereafter called acoustic neuroma) diagnostic models (Jenkins, Le Liever, Kaseff) were implemented as rule-based decision support systems and evaluated from the perspective of sensitivity, specificity, and US dollar cost, using a data base of 95 case histories suggestive of acoustic neuroma. The specificities of the models were equivalent (.97). The Jenkins model had the highest sensitivity (.96) and the highest average cost ($1470.99). The sensitivities and average costs of the Le Liever and Kaseff models were comparable (.84 vs. .82, and $1092.38 vs $1114.17, respectively). We observed that omitting brain-stem evoked response and electronystagmography testing from the Le Liever model subjected four (4.2%) more patients without acoustic neuroma to air contrast computed tomography, increased sensitivity to .89, and decreased the average cost to $774.75, without affecting specificity. We discuss the reasons for the slightly improved sensitivity and the impact of decision support systems on the clinician.

Decision Making↗
PubMed1989

Acoustic tumor surgery. Prognostic factors in hearing conversation.

Preoperative selection criteria for hearing conservation surgery in patients with acoustic tumors continues to be unresolved. The level of hearing that is worth saving is still debatable. However, most acoustic tumor surgeons agree that hearing preservation is less likely the larger the tumor. We reviewed the results of 106 middle fossa acoustic tumor removals with attempted hearing preservation. Measurable postoperative hearing remained in 59% of 97 cases analyzed for postoperative hearing results. Tumor size, preoperative auditory brain-stem response, and preoperative electronystagmography were found to be useful in predicting successful postoperative hearing preservation. We found no correlation between the level of preoperative hearing and our ability to preserve measurable postoperative hearing. A new classification system is proposed for reporting hearing results after acoustic tumor surgery. It is based on functional hearing results and we believe it is simpler than previously proposed systems.

Audiometry↗
PubMed1990

Estrogen and progesterone receptors in acoustic neuromas.

Acoustic neuromas are more frequent, larger, and more vascular in women, and their growth rate increases during pregnancy. Estrogen receptors were claimed to be demonstrated in these neoplasms for the first time in 1981. Since then, numerous diverging studies, using various biochemical and histochemical methods, have been published on the contents of estrogen and progesterone receptors in acoustic neuromas. We determined the content of estrogen and progesterone receptors by means of an immunohistochemical method, using monoclonal antibodies, which has proved to be reliable, reasonably sensitive, and clinically relevant in other tissues, especially in breast carcinomas. No estrogen or progesterone receptors could be found in 18 consecutive acoustic neuromas from 7 men and 11 women, ranging in age from 26 to 73 years. The results do not support preoperative hormone treatment of acoustic neuromas.

Adult↗
PubMed1999

Cochlear ablation alters acoustically induced c-fos mRNA expression in the adult rat auditory brainstem.

Expression of c-fos mRNA was studied in the adult rat brain following cochlear ablations by using in situ hybridization. In normal animals, expression was produced by acoustic stimulation and was found to be tonotopically distributed in many auditory nuclei. Following unilateral cochlear ablation, acoustically driven expression was eliminated or decreased in areas normally activated by the ablated ear, e.g., the ipsilateral dorsal and ventral cochlear nuclei, dorsal periolivary nuclei, and lateral nucleus of the trapezoid body and the contralateral medial and ventral nuclei of the trapezoid body, lateral lemniscal nuclei, and inferior colliculus. These deficits did not recover, even after long survivals up to 6 months. Results also indicated that neurons in the dorsal cochlear nucleus could be activated by contralateral stimulation in the absence of ipsilateral cochlear input and that the influence of the contralateral ear was tonotopically organized. Results also indicated that c-fos expression rose rapidly and persisted for up to 6 months in neurons in the rostral part of the contralateral medial nucleus of the trapezoid body following a cochlear ablation, even in the absence of acoustic stimulation. This response may reflect a release of constitutive excitatory inputs normally suppressed by missing afferent input or changes in homeostatic gene expression related to sensory deprivation. Instances of transient, surgery-dependent increases in c-fos mRNA expression in the absence of acoustic stimulation were observed in the superficial dorsal cochlear nucleus and the cochlear nerve root on the ablated side.

Acoustic Stimulation↗
PubMed2006

Spatial and acoustic pressure dependence of microbubble-mediated gene delivery targeted using focused ultrasound.

BACKGROUND: Ultrasound/microbubble-mediated gene delivery has the potential to be targeted to tissue deep in the body by directing the ultrasound beam following vector administration. Application of this technology would be minimally invasive and benefit from the widespread clinical experience of using ultrasound and microbubble contrast agents. In this study we evaluate the targeting ability and spatial distribution of gene delivery using focused ultrasound. METHODS: Using a custom-built exposure tank, Chinese hamster ovary cells in the presence of SonoVue microbubbles and plasmid encoding beta-galactosidase were exposed to ultrasound in the focal plane of a 1 MHz transducer. Gene delivery and cell viability were subsequently assessed. Characterisation of the acoustic field and high-resolution spatial analysis of transfection were used to examine the relationship between gene delivery efficiency and acoustic pressure. RESULTS: In contrast to that seen in the homogeneous field close to the transducer face, gene delivery in the focal plane was concentrated on the ultrasound beam axis. Above a minimum peak-to-peak value of 0.1 MPa, transfection efficiency increased as acoustic pressure increased towards the focus, reaching a maximum above 1 MPa. Delivery was microbubble-dependent and cell viability was maintained. CONCLUSIONS: Gene delivery can be targeted using focused ultrasound and microbubbles. Since delivery is dependent on acoustic pressure, the degree of targeting can be determined by appropriate transducer design to modify the ultrasound field. In contrast to other physical gene delivery approaches, the non-invasive targeting ability of ultrasound makes this technology an attractive option for clinical gene therapy.

Acoustics↗
PubMed1978

Immunologic detection of acoustic neuroma: preliminary report.

In an attempto to provide preoperative histologic identification of internal auditory canal and cerebellopontine angle tumors, and to attempt to detect small tumors and recurrent tumors, immunologic aspects of acoustic neuroma patients and control subjects were studied. Reactions based upon the interaction of patients' fresh lymphocytes in contact with acoustic neuroma antigens were studied by a leukocyte migration inhibition (LMI) assay and a locally developed refinement, the plasma effect assay. These were performed either preoperatively, postoperative, or both, in 17 patients with surgically confirmed acoustic neuromas and in 24 controls subjects. Preoperative tumor patients had a higher likelihood of having elevated LMI and plasma effect assay values than normals. False positive results were rare and the combination of the LMI and plasma effect assay decreased false negative responses to 20%. Meaningful conclusions must await more extensive testing but it has been demonstrated that tumor associated antigens do exist on the membranes of schwannoma cells and that most patients with an acoustic neuroma mount a cell-mediated immune response against these antigens.

Antigens, Neoplasm↗
PubMed1990

Irradiation of pigmented melanoma cells with high intensity pulsed radiation generates acoustic waves and kills cells.

Photokilling of pigmented mouse melanoma cells (B-16) was investigated using pulsed high intensity visible radiation. Melanin acts as an endogenous chromophore, and 694 nm radiation with 40 nsec pulse duration and 0.5-3 X 10(7)w/cm2 intensity causes cell death. Irradiation of non-pigmented human melanoma cells (U1) or human squamous carcinoma cells (FaDu) under similar conditions did not kill the cells. Also, irradiation of B-16 cells with 300 microsec laser pulses (10(3)W/cm2) or with continuous wave (CW) radiation (10(-3)W/cm2) did not kill the cells. These data indicate that pigmented cell killing is due to absorption of radiation by melanin and that the pulsewidth and intensity of radiation play important roles in cell killing. The generation of acoustic waves due to absorption of the pulsed radiation by pigmented cells and by isolated melanosomes was demonstrated at 532 and 625 nm and 8.5 nsec pulse duration (10(7)-10(8) W/cm2); the amplitudes of the acoustic signals were approximately 2.5-3.0-fold higher at 532 nm compared with 625 nm, and they increased with increasing fluence. In contrast, irradiation of U1 or FaDu cells with comparable fluences and intensities did not generate acoustic waves. A possible correlation between the generation of photoacoustic waves and pigment cell death is proposed. Since the thermal relaxation time of melanosomes is 0.5-1.0 microsec, the mechanism proposed is that thermal confinement of high intensity, short-pulse visible radiation generates acoustic waves by thermal expansion, leading to mechanical damage to the cells.

Acoustics↗
PubMed1997

Unilateral brain damage, prosodic comprehension deficits, and the acoustic cues to prosody.

Stimuli from two previously presented comprehension tasks of affective and linguistic prosody (Pell & Baum, 1997) were analyzed acoustically and subjected to several discriminant function analyses, following Van Lancker and Sidtis (1992). An analysis of the errors made on these tasks by left-hemisphere-damaged (LHD) and right-hemisphere-damaged (RHD) subjects examined whether each clinical group relied on specific (and potentially different) acoustic features in comprehending prosodic stimuli (Van Lancker & Sidtis, 1992). Analyses also indicated whether the brain-damaged patients tested in Pell and Baum (1997) exhibited perceptual impairments in the processing of intonation. Acoustic analyses of the utterances reaffirmed the importance of F0 cues in signaling affective and linguistic prosody. Analyses of subjects' affective misclassifications did not suggest that LHD and RHD patients were biased by different sets of the acoustic features to prosody in judging their meaning, in contrast to Van Lancker and Sidtis (1992). However, qualitative differences were noted in the ability of LHD and RHD patients to identify linguistic prosody, indicating that LHD subjects may be specifically impaired in decoding linguistically defined categorical features of prosodic patterns.

Affect↗
PubMed2003

MRI analysis of hydrocephalus associated with acoustic neurinoma.

We investigated the hydrocephalus in 24 patients associated with acoustic neurinoma. We found the high incidence of homo-lateral ventricular dilatation to the side of the acoustic neurinoma. Utilizing magnetic resonance imaging, the diameter of the tumor parallel to the pyramidal bone, diameter of the tumor perpendicular to the pyramidal bone, grade of the 4th ventricle deviation, and the shape of the tumor (round or oval) were analyzed. Ten (42%) of the 24 patients with acoustic neurinoma were found to have hydrocephalus. Seven (70%) of the 10 patients with hydrocephalus exhibited asymmetrical lateral ventricle dilatation: in all cases the lateral ventricle in the hemisphere homolateral to the acoustic neurinoma was larger than that of the contralateral side. The hydrocephalus was not related to the grade of the 4th ventricle deviation but rather to the diameter of the tumor parallel to the pyramidal bone (p < 0.01). The diameter of the tumor parallel to the pyramidal bone was also related to the asymmetrical lateral ventricular dilatation (p < 0.05).

Adult↗