Planar Steering of a Single Ferrofluid Drop by Optimal Minimum Power Dynamic Feedback Control of Four Electromagnets at a Distance

Any single permanent or electro magnet will always attract a magnetic fluid. For this reason it is difficult to precisely position and manipulate ferrofluid at a distance from magnets. We develop and experimentally demonstrate optimal (minimum electrical power) 2-dimensional manipulation of a single droplet of ferrofluid by feedback control of 4 external electromagnets. The control algorithm we have developed takes into account, and is explicitly designed for, the nonlinear (fast decay in space, quadratic in magnet strength) nature of how the magnets actuate the ferrofluid, and it also corrects for electro-magnet charging time delays. With this control, we show that dynamic actuation of electro-magnets held outside a domain can be used to position a droplet of ferrofluid to any desired location and steer it along any desired path within that domain - an example of precision control of a ferrofluid by magnets acting at a distance.

[Universal newborn hearing screening--a silent revolution]

Significant hearing loss is one of the most frequent congenital diseases and present at birth in approximately one in 1000 newborns. During the first years of life, this number of children with permanent hearing loss rises by approximately the same amount. Hearing impairment is not an obvious condition in newborns in most cases and produces very few signs in infancy. Such hearing loss threatens normal speech and personality development. The longer the child is without auditory stimulation by speech, the more difficult it is to acquire the missed linguistic skills. Therefore, early detection and rehabilitation of such hearing loss is crucial. Universal newborn hearing screening is the most effective method to detect such impairment and is based on objective audiometric test methods that were recently developed and adapted for screening requirements. Useful tests are otoacoustic emissions and the auditory brainstem response. This article reviews this new screening tests in general and with special regard to the situation in Switzerland.

Influence of artifacts and pass/refer criteria on otoacoustic emission hearing screening

A screening device for otoacoustic emission (OAE) testing was evaluated via measurements of click evoked OAEs (CEOAEs) and/or distortion product OAEs (DPOAEs) obtained in normally hearing young adults and newborns. Moreover, measurements were performed in a passive cavity and in ears with severe sensorineural hearing loss, in which the occurrence of a pass result was assumed to indicate artifacts. Different parameter settings were investigated. In comparison to normally hearing young adults, overall pass rates in newborns were similar using CEOAEs (93 to 100%), but lower using DPOAEs (65 to 95% vs. 83 to 100%). Pass rates in ears with severe hearing loss were 10% at 2 kHz, 13% at 3 kHz, and lower at other frequencies. Pass rates in the test cavity were generally low. The influence of test frequency on pass rates and calculations using computer simulation indicated the presence of artifacts. The discrimination of such artifacts from biological signals is difficult or impossible, and they may represent a serious problem for efficient OAE screening.

Comparison of currently available devices designed for newborn hearing screening using automated auditory brainstem and/or otoacoustic emission measurements

OBJECTIVE

Suitability in clinical practise of three currently available devices designed for automated newborn hearing screening, one combining evoked otoacoustic emissions (EOAE) and automated auditory brain stem response (AABR), the Echoscreen-TDA from Fischer-Zoth, and two AABR screeners, the Algo 3 from Natus and the Beraphone MB11 from Maico, were tested prospectively.

METHODS

Transiently evoked otoacoustic emissions (TEOAE) and distortion product otoacoustic emissions (DPOAE) were measured in one ear of 150 healthy newborns using the Echoscreen-TDA. Three groups of 50 subjects each were tested additionally for AABR recordings either with Echoscreen-TDA, Algo 3 or Beraphone MB11. Measurements were performed after the second day of life. The following aspects were evaluated: (a) subject-instrumentation interface (b) test time (c) costs (unit price and costs for disposable material) and (d) pass rates.

RESULTS

Connecting the subjects to the device was the easiest for EOAE measurements with the Echoscreen-TDA, followed by AABR recordings with the Algo 3 and Echoscreen-TDA and were most difficult with the Beraphone MB11. The median test time on one ear was less than 30 s for EOAE measurements and 4-5 min for AABR recordings. Costs for the equipment and for disposable material were lowest for the Echoscreen-TDA and Beraphone MB11, respectively and highest for the Algo 3. Pass rates were highest with 98% for AABR recordings using the Algo 3 and lowest with 92% for AABR recordings using the Beraphone MB11, but differences were not statistically significant.

CONCLUSIONS

All tested devices can be used for universal neonatal hearing screening. It was easier to connect the subject to the device and measurements were quicker for OAE than for AABR measurements. Echoscreen-TDA combines the two techniques and had the lowest costs for the AABR equipment. Algo 3 had the highest costs for the equipment and for disposable material, but it was highly reliable, and both ears can be tested simultaneously. Connecting the subject was the most difficult with the Beraphone MB11, but there were no disposable supply costs.

[Subjective and objective audiometry]

Audiometry uses physically precisely defined acoustic stimuli. The response can be either a subjective reaction of the patient such as to press a button, or it can be a physiological reaction that can be measured objectively such as the acoustic reflex of the stapedial muscle. The aims of both types of audiometry, subjective and objective, are the assessment, the localization and the quantification of hearing loss. Specifically selected subjective or objective tests, and combinations of both, are being used to answer different clinical questions related to audiometric screening, audiological diagnosis, and quantitative description of the hearing loss. The selection of tests should be designed to answer the specific question most effectively.

Relationship of intraoperative electrically evoked stapedius reflex thresholds to maximum comfortable loudness levels of children with cochlear implants

Previous studies of the relationship between the intraoperatively obtained electrically evoked stapedius reflex threshold (ESRT) and the maximum comfortable loudness (MCL) values used to program the speech processor of cochlear implant (CI) patients have indicated that ESRTs provide an inexact estimate of MCL. In order to determine whether this estimate might be more exact for electrodes in different parts of the electrode array, we studied the electrode-specific relationships between ESRT and MCL in 29 Med-E1 Combi 40+ and 25 Nucleus CI 24 M patients after first fitting of the speech processor and 2 and 6 months later. The MCL values were mostly less than the ESRT values, but increased progressively over the first 6 months, reaching 83% and 72% of the ESRT values, on average, across all electrodes for the Med-E1 and Nucleus systems respectively. The population variation across electrodes decreased over the 6-month observation period and was least for the apical half of the array, for which the correlation coefficients of regressions between ESRT and MCL were around 0.65 for both systems. These results indicate that estimates of MCL values from the ERST are more accurate for the apical half of the intra-cochlear array and could then be described by an offset value plus an increase of MCL by 0.62 and 0.53 of ESRT for the Med-E1 and Nucleus systems, respectively.

Tetramethyltetrahydro-1,4-anthrachinonazobenzoesäure, ein 5-Lipoxygenase-Inhibitor mit zelldifferenzierender Aktivität.Untersuchungen an 1,4-Naphthochinonen, 28. Mitt. 1)

The combination of 5-lipoxygenase (5-LOX) inhibition and retinoid activity in one molecule could be a suitable too1 for the topical psoriasis therapy. The anellation of the 5-LOX inhibitor 1 with the tetramethylcyclohexane moity to the arotinoid structure 2 does not fullfil this expectation. This compound was not able to differentiate HL-60 cells to granulocytes. The exchange of the 3,5-di-tertbutyl-4-hydroxyphenyl substituent by benzoic acid and the synthesis of 8 resulted in the loss of 5-LOX inhibition also. The construction of 10 by the introduction of an azo spacer between the anthraquinone moity and benzoic acid of 8 finally led to the expected compound: 10 was potent 5-LOX inhibitor and concomitant differentiated HL-60 cells as measured by the NBT test.

[Partially hydrogenated aryl-1,2/1,4-anthraquinone derivatives, 5-lipoxygenase inhibitors with arotinoid structure]

The combination of 5-LOX inhibition and retinoid activity in one molecule could be an interesting pharmacological tool to influence psoriasis. Thus we synthesized compounds with arotinoid structure by anellation of the 5-LOX inhibitors 1 and 2 with 1,1,4,4-tetramethylcyclohexane. A key step was the CuCl-MeCN-O2 oxidation of tetrahydroanthracenol 13 to the corresponding 1,2-anthraquinone 14 which could be converted to the analogous 2-hydroxy-1,4-anthraquinone 19 by Thiele-Winter reaction followed by oxidation. The halogenated quinones 9 and 21 were arylated with 2,6-di-tertbutylphenol and demethylated or hydrolyzed to the target compounds 3 and 4 which were tested in comparison with the non-anellated 5-LOX inhibitors 1 and 2 for LOX inhibition in activated human granulocytes and for antioxidative activity by the method of Popov with the chemiluminometer Photochem. The results are discussed in relation to the corresponding logP values. The 1,2-quinones 1 and 3 are more potent 5-LOX inhibitors than their 1,4-analogues 2 and 4, the tetrahydroanthraquinon derivatives 3 and 4 are less potent than the naphthoquinones 1 and 2. All compounds are devoid of any activity in cell differentiation as compared to retinoic acid as indicated by the NBT test with HL-60 leukemia cells.

Mismatch negativity and psychoacoustic measures of gap detection in normally hearing subjects

Temporal auditory processing deficits are thought to play an important role in some pathologies of speech understanding difficulties. The purposes of the present study were to determine whether short silent gaps within a pure tone can be used to elicit mismatch negativity (MMN) as an objective measure of temporal resolution, and to investigate the relation between MMN and performance on a behavioral gap-detection task. The stimuli used for both tasks were 1-kHz sinusoids presented in a low-pass masking noise. Behavioral gap-detection thresholds were determined using an adaptive three-alternative forced-choice procedure. To elicit MMN, a series of deviant stimuli with varying gap durations was generated and presented in an oddball paradigm among standard stimuli without a gap. Only the gaps larger than the mean behavioral gap-detection threshold evoked a clear MMN. There was no clear relation between psychoacoustic and MMN thresholds.

[Extended high-frequency audiometry--reproducibility of two type of earphones]

Auditory thresholds in the frequency range of 0.5-6 kHz and in the extended high-frequency range (8-16 kHz, according to ISO 389-5) were measured for one ear of 139 otologically healthy persons (77 females, 62 males, mean age 25 years, range 12-54 years) using insert earphones ER-2 of Etymotic Research and circumaural earphones HDA 200 of Sennheiser. For each subject, two measures of the thresholds were obtained for both types of transducers during the same test session. Repeatability was significantly worse in the 8-16 kHz region (repeated thresholds were within +/- 5 dB for 90% of the thresholds of each frequency and within +/- 10 dB for 98%), compared to that in the 0.5-6 kHz region (+/- 5 dB for 97%, +/- 10 dB for 100%), as determined by paired t-test and Wilcoxon signed rank test. Repeatability was similar for both transducer types.

[First results of a national hearing screening program in Switzerlans]

A Swiss study group was formed in summer 1998 with the aim of establishing a universal hearing screening programme in newborns following the recommendations of the "European Consensus Statement on Neonatal Hearing Screening" (Milan 1998). The aim of the group was to standardise and to introduce universal hearing screening in all infants born in Switzerland. Starting in June 1999, several hospitals in Switzerland began the screening programme using commercially available equipment for easy and highly automated measurement of transient evoked otoacoustic emissions. Up to March 2000, 6262 children were born in these hospitals and 5656 (90%) underwent neonatal hearing screening. 88 children of the 5656 did not pass the screening test. The measurement of otoacoustic emissions was repeated in a follow-up examination within 6 weeks. If otoacoustic emissions were again absent, evoked auditory brainstem potentials were measured. 48 children were found to have hearing within normal limits at the follow-up examination, 24 children have not been examined yet, 11 children were examined in other clinics or the follow-up examination was refused by the parents. 5 children were found to have bilateral hearing dysfunction and were referred to rehabilitation within the first 6 months of life.

Suppression of tone burst evoked otoacoustic emissions in relation to frequency separation

Tone burst evoked otoacoustic emissions (TBEOAEs) were measured for two tone bursts presented separately and as a two-tone burst complex to examine the linearity of TBEOAE generators for different frequency separations of the stimuli. The stimuli were: (a) tone bursts of 5-ms duration and center frequencies of 1, 1.5, 2 and 3 kHz; (b) complex stimuli with the 1-kHz tone burst combined digitally with each of the other specified tone bursts. Signals were delivered at 70 dB SPL using a non-linear processing method and at 60 dB SPL using a linear method to 21 ears of normally hearing adults. Spectra of TBEOAEs obtained with single-tone bursts were superimposed (composite) and compared to those of the two-tone burst complex. A close correspondence between the composite and complex spectra was present in all ears. However, the components on the higher-frequency slope of the 1-kHz spectral peak were reduced in the complex spectra obtained with a frequency separation of 0.5 kHz when compared to the corresponding composite spectra. The reduction was greater at a stimulus level of 70 dB SPL than with 60 dB SPL. The effect was smaller for a frequency separation of 1 kHz, and almost absent for the tone burst separation of 2 kHz. Thus, suppression leads to weak non-linear frequency superposition for higher-level, closely spaced stimuli.

Changes in collagen I and collagen III metabolism in patients with generalized atopic eczema undergoing medium-dose ultraviolet A1 phototherapy

Fourteen patients suffering from acute, exacerbated atopic eczema were screened for changes in collagen I and collagen III metabolism in serum (n = 11), urine (n = 11) and skin biopsies (n = 9) before and after medium-dose ultraviolet (UV) A1 phototherapy (15 exposures of 50 J/cm2 over a 3-week period, total dose 750 J/cm2). Mature collagen I and, to a lesser extent, mature collagen III were found to be decreased after the therapy in skin samples from the irradiated patients. As markers of collagen I degradation, the cross-links pyridoline and deoxypyridoline were analysed in urine using high-performance liquid chromatography. Both cross-links were found to be mildly increased after UVA1 phototherapy, without reaching statistical significance. As markers of de novo collagen synthesis we screened for the procollagen I-carboxyterminal peptide (PICP) and procollagen III-aminoterminal peptide (PIIINP) levels in serum and skin. The ratio of PICP to PIIINP in serum dropped significantly after the UVA1 phototherapy, suggesting a different impact of UVA1 on the two collagens. These findings were paralleled by a diminished ratio of PICP to PIIINP in tissue samples. Staining for matrix metalloproteinase 1 (MMP-1) and its specific counterpart, tissue inhibitor of MMP-1 (TIMP-1), showed slight increases for both proteins by therapeutic UVA1; this was also seen in serum for TIMP-1 but not MMP-1. In our study, high-energy UVA1 doses induced changes of the skin collagens in patients with atopic eczema which are measurable by their metabolites in serum and urine.

Cortical reorganization after acute unilateral hearing loss traced by fMRI

Unilateral acoustic stimulation produces a functional MRI (fMRI)-blood-oxygenation-level-dependent (BOLD) response mainly in the contralateral auditory cortex. In unilateral deaf patients, the BOLD response is bilateral. We studied a subject with sudden hearing loss after cochlear nerve resection before and repeatedly after surgery. During normal bilateral hearing, contralateral cortical BOLD responses were found. Progressing compensatory reorganization with bilateral representation of unilateral stimulation was detected over a period of approximately 1 year.

[Is there clinical evidence for the aging of the peripheral vestibular organ?]

The ageing process of hearing is well known. Age-dependent normative data are established for pure tone audiometry. It seems logical to suppose that the peripheral vestibular system undergoes a similar ageing process. To support this hypothesis we investigated subjects aged 50-82 with presbyacusis demonstrated by pure tone audiometry. Asymmetry of the peripheral vestibular system was ruled out by symmetrical thermal excitation rate. Slow-phase velocity of nystagmus induced by rotating-chair stimulation was compared with pure tone audiometry. We found no significant correlation and thus our approach failed to bear out the hypothesis.

[Instructor in the army and fortifications guard--risk occupations for acute acoustic trauma and for wearing a hearing aid]

In the Swiss army instructors and fortifications guards are exposed to firearms' noise which harms the ear. It was investigated whether the decline in the cases of acute acoustic traumas in non-professional soldiers serving in the army from 1987 to 1996 also was detectable in army instructors and fortifications guards (professional soldiers) and whether these persons were wearing hearing aids (as an indicator of hearing loss) more often than the average of the male Swiss population. First, we analyzed a historical time series of the incidence density of acute acoustic traumas in non-professional soldiers as well as in army instructors and fortifications guards. Second, we compared the prevalence rate of wearing a hearing aid in army instructors and fortifications guards with the male Swiss population. The incidence density for acute acoustic traumas in army instructors and fortifications guards observed over ten years showed no significant change whereas among non-professional soldiers a strong decline (-12% per year) was observed. The prevalence rate of wearing a hearing aid in army instructors and fortifications guards was significantly higher (RR 3.91 [95% CI 3.09-4.96]) than in the male Swiss population. These results suggest increased hearing impairment among army instructors and fortifications guards which is probably due to the high exposure to impulse noise events (occupational disease). It is recommended that these persons be subjected to a compulsory prevention program.

[The usefulness of intraoperatively registered, electrically evoked stapedius reflex for the programming of cochlear implants in children]

The programming of a cochlear implant speech processor used by young children is often difficult, especially when the stimulus level associated with maximum auditory loudness (MAL) needs to be determined. Excessively high stimulation should be avoided as this can have a traumatic effect. The aim of this study was to determine if a relationship exists between the intraoperatively determined electrical stapedius reflex threshold (ESRT) and the postoperatively determined MAL and hearing threshold for 27 patients, each having one of three implant types. The question of whether the ESRT provides a practical technique to simplify, improve and accelerate speech processor programming was investigated. For the monopolar stimulation mode used for the Med-El and Clarion implant systems, the average MAL and threshold was expressed as a percentage of the average ESRT across all electrodes. For the "common ground" stimulation mode used for the Nucleus implant system, a parabolic transformation was used to relate MAL and ESRT to one another. These transformations between MAL values calculated from the ESRT and the actual MAL values, determined psychoacoustically, diverged considerably from one another. Therefore, it was not possible to determine the MAL from the ESRT with certainty. The ESRT does, however, provide a means to estimate an approximate upper boundary for the MAL, apart from its use to control implant function. The determination of the exact MAL will still need to be determined using behavioural techniques.

Intensity discrimination, temporal integration and gap detection by normally-hearing subjects with weak and strong otoacoustic emissions

It is unlikely that the overall status of a cochlea and middle ear which produces strong otoacoustic emissions (OAEs), i.e. high-level evoked emissions (EOAEs) and spontaneous emissions (SOAEs), has a generalized effect on peripheral auditory processing if the sensitivity is normal. Current data do not support the hypothesis that a weak OAE profile (low-level EOAEs and no SOAEs) is indicative of subclinical damage to the cochlea. Nevertheless, the ability of a subject to perform some psychoacoustical tasks may be influenced by the interaction between OAEs and test signals. The present experiments investigated the influence of strong or weak OAEs on: (1) intensity just-noticeable differences for pure tones; (2) temporal integration in the vicinity of SOAEs; (3) gap detection thresholds for broad-band noise bursts. The results show that OAEs can influence performance on these psychoacoustical tasks, especially for low-level stimuli with spectral components in the vicinity of high-level SOAEs.

Premeatal and retromeatal cerebellopontine angle meningioma. Two distinct clinical entities

OBJECTIVE

Meningiomas represent the second most common type of neoplasm of the cerebellopontine angle (cpa). Their relationship to critical neural or vascular structures of the cpa is variable and they present with different signs and symptoms.

MATERIALS AND METHODS

A retrosigmoid craniotomy was performed in 31 cpa-meningiomas from January 1981 to February 1997. The mean age of the 25 women (81%) and the 6 men (19%) was 53 +/- 13 years. According to their location within the posterior fossa and with special reference to the internal auditory canal (IAC), they were classified in 17 cases (55%) as retromeatal (posterior to the iac) and in 14 cases (45%) as premeatal (anterior to the iac).

RESULTS

The retromeatal group showed a significantly larger tumour size (21 +/- 15 vs 29 +/- 20 mm) and the diagnosis was made later (2.7 +/- 3.2 vs 1.1 +/- 0.9 years) compared to premeatally located meningiomas. Before the operation, a reduction of the facial nerve function (64% vs 0%) and hearing function (100% vs 25%) was present significantly more often in premeatal meningiomas. The clinical appearance of the retromeatal group was dominated by cerebellar symptoms (44% vs 0%). Both preoperative and postoperative impairment of facial nerve and auditory function prevailed in the premeatal group.

CONCLUSION

The topological classification of CPA-meningiomas according to their location anterior or posterior to the ICA is important, because the clinical presentation, the surgical strategy to be applied, and the functional outcome of critical neural structures differ between the two subtypes. Our results provide substantial evidence for the paradoxical observation that premeatal meningiomas have a significantly worse postoperative functional outcome compared to retromeatal meningiomas although premeatal meningiomas become symptomatic earlier and at smaller sizes.

Intracochlear acoustic pressure measurements: transfer functions of the middle ear and cochlear mechanics

Direct intracochlear acoustic pressure recordings (from 20 to 20,000 Hz) are used to measure the middle-ear transfer functions (forward and reverse) and to better understand the cochlear mechanics in the guinea pig. In the forward direction, the middle-ear transfer function is strongly dependent on the frequency and presents a maximum of +30 dB at 1,000 Hz (bulla open). In the reverse direction, the middle-ear transfer function looks like an ideal reverse middle-ear pressure transformer with -35 dB gain and 0 degrees phase lag from 20 to 8,000 Hz (bulla open, closed ear canal). Passive cochlear mechanics is studied with the help of intracochlear pressure measurements and differential cochlear microphonic potential recordings in the different turns.

Trigeminocardiac reflex during surgery in the cerebellopontine angle

OBJECT

In different experimental studies authors have analyzed the autonomic responses elicited by the electrical, mechanical, or chemical stimulation of the trigeminal nerve system. The trigeminocardiac reflex (TCR) is a well-recognized phenomenon that consists of bradycardia, arterial hypotension, apnea, and gastric hypermotility. It occurs during ocular surgery and during other manipulations in and around the orbit. Thus far, it has not been shown that central stimulation of the trigeminal nerve can also cause this reflex.

METHODS

The TCR was defined as clinical hypotension with a drop in mean arterial blood pressure (MABP) of more than 20% and bradycardia lower than 60 beats/minute. Pre-, intra-, and postoperative heart rate (HR) and MABP were reviewed retrospectively in 125 patients who underwent surgery for tumors of the cerebellopontine angle (CPA), and they were divided into two groups on the basis of the occurrence of the TCR during surgery. Of the 125 patients, 14 (11%) showed evidence of the TCR during dissection of the tumor near the trigeminal nerve at the brainstem. Their HRs fell 38% and their MABPs fell 48% during operative procedures as compared with preoperative levels. After cessation of manipulation, the HRs and the MABPs returned to preoperative levels. Risk factors for the occurrence of the TCR were compared with results from the literature.

CONCLUSIONS

The authors' results show the possibility of occurrence of a TCR during manipulation of the central part of the trigeminal nerve when performing surgery in the CPA.

Direct evidence of cubic difference tone propagation by intracochlear acoustic pressure measurements in the guinea-pig

The fine tuning mechanisms involved in the normal processing of sound in the cochlea are non-linear, hence combination tones are generated inside the cochlea when a pair of low-level pure tones with neighbouring frequencies f1 and f2 is used as a stimulus. Their detection as sounds in the ear canal proves that they undergo backward propagation in the cochlea and through the middle ear, and the non-invasive measurement of the combination tone at 2f1-f2, called the cubic difference tone (CDT), has become a routine method of monitoring cochlear function. In order to gain information on the hypothetical places where CDTs are generated, on their intracochlear levels and propagation velocities, direct measurements of CDT pressure waves were carried out in scala vestibuli and tympani of the first and second turn of the guinea-pig cochlea. Cubic difference tones at 2f1-f2 varied from 0.75 to 9 kHz and were measured with a miniature piezoresistive transducer. Its high sensitivity allowed the detection of CDTs whenever their levels exceeded 5 dB SPL in the ear canal, i.e. 40 dB SPL (re: 20 microPa) inside the cochlea. The levels of CDTs were similar in scala vestibuli of the first and second turn. Phase comparisons between measurements at 2f1-f2 in the first and second turn allowed determination of the place where the CDT phase was minimum. It provided an estimation of the generation site of the CDT, which appeared to be close to the place tuned to f2 for stimulus levels lower than 70 dB SPL. Forward and backward travel times from one turn to the other were assessed at several frequencies, and both values were shorter than 0.2 ms. In contrast, the overall 'round-trip' delay of CDTs, measured in the ear canal, was about five times larger, suggesting that local filtering processes rather than propagation delays account for the overall CDT delay.

The influence of disappearing and reappearing spontaneous otoacoustic emissions on one subject's threshold microstructure

The effects of a consistently disappearing and reappearing spontaneous otoacoustic emission (SOAE) at around 2280 Hz on microstructure for pure tones of varying durations in a 33 year-old woman with normal hearing was studied. The SOAE began to appear after 10-15 min in a quiet test room and increased in level by up to 22 dB over a 30-40-min period. The SOAE was measured every 12 to 15 min. Between measurements, the subject performed a signal detection task for pure tones with total durations varying from 20 to 320 ms. The signal frequencies were within a +/- 30-Hz range relative to the SOAE frequency. For signal durations of 40-320 ms, there was a local dip at the target SOAE frequency when it was either not detectable or its level was lower than -14 dB SPL. Subjective threshold levels were as much as 12 dB better than those obtained when the SOAE was -6 dB SPL or greater. The results suggest that a region of the cochlea with high sensitivity and instability can be put into self-oscillation producing an SOAE, possibly by a change of efferent activity. Hearing threshold is affected possibly due to adaptation or masking.

Quantification of the neuromuscular blocking agent rocuronium and its putative metabolite 17-desacetylrocuronium in heparinized plasma by capillary gas chromatography using a nitrogen sensitive detector

We have developed a sensitive and specific capillary GC (cGC) assay for the quantification of the quarternary aminosteroidal compound rocuronium (roc), a neuromuscular blocking agent, and its putative metabolite 17-desacetylrocuronium (17OH-roc), using 3-desacetylvecuronium (3OH-vec) as an internal standard (I.S.). This novel method has been applied to a pharmacokinetic study with roc, monitoring sixty patients who were classified according to four different body mass index (BMI) groups. The isolation of these drugs from plasma was carried out using a dichloromethane liquid-liquid extraction after ion-pairing of the positively charged ammonium compounds with iodide. To achieve thermal stability, tert.-butyldimethylsilyl-ethers were formed at the 3OH- and 17OH-steroidal positions by reaction with N-methyl-N-(tert.-butyldimethylsilyl)-trifluoroacetamide at 70 degrees C overnight. An automated cGC system fitted with a nitrogen sensitive detector with a specially prepared glass phase bead and a computer controlled data handling system was used to analyze and quantify the compounds, which were separated on a DB1 capillary column with helium as the carrier gas and a temperature program ranging from 120 to 300 degrees C. The method is linear for 50-6400 ng/ml for roc and 80-6400 ng/ml for 17OH-roc. The detection limits were 10 ng/ml for roc and 50 ng/ml for 17OH-roc. The lower limit of quantification was 50 ng/ml for roc and 80 ng/ml for 17OH-roc. Intra-assay coefficients of variation (C.V.s) were 10% and 15% and the inter-assay C.V.s 8-18% and 16-21% for roc and 17OH-roc, respectively.

Evaluation of electrically elicited stapedius reflex threshold measured through three different cochlear implant systems

OBJECTIVE

To evaluate intraoperative electrically elicited stapedius reflex thresholds (ESRTs) measured through three different cochlear implant systems: the Nucleus Mini 22, the Clarion Enhanced Bipolar, and the Med-El Combi-40.

SUBJECTS AND METHODS

Relations between intraoperative ESRT and postoperative maximum comfort level (MCL) were examined in seven children (4 Nucleus, 2 Clarion, and 1 Med-El) and one adult (Clarion).

RESULTS

Preliminary results indicated most ESRTs were either higher or both higher and lower (across the electrode array within a subject) than MCLs. All systems provided satisfactory means for measuring ERSTs.

CONCLUSION

It is recommended that hand-held systems have a direct readout to the programming station and that audio and visual feedback be improved for all units.

A non-invasive patient registration and reference system for interactive intraoperative localization in intranasal sinus surgery

A basic problem common to all systems for computer assisted surgery (CAS) is patient referencing, or the transfer of preoperative image data to the intraoperative pathology. The authors describe a highly precise CAS system with non-invasive referencing that can be used in ear, nose and throat (ENT) surgery of the paranasal sinuses. It is based on optical digitizing with several custom-made self-localizing surgical instruments. The accuracy of the system was tested in an experimental model using a plastic head. Measurements of repositioning the reference bow had a mean error of 0.81 mm +/- 0.31 mm. The system was evaluated clinically with 11 patients who received surgery for different pathologies of the paranasal sinuses. These trials met with a high rate of success and specific results are reported.

Concurrent platinum-based chemotherapy and hyperfractionated radiotherapy with late intensification in advanced head and neck cancer

PURPOSE

To determine whether a course of hyperfractionated radiation therapy concomitant with escalated radiosensitizing platinum compounds can be administered with acceptable morbidity and achieve a high rate of loco-regional control for Stage III and IV head and neck cancer and whether the patients can be tumor free at the primary site after initial therapy and cured by the additional chemoradiation without radical resection of the primary tumor.

METHODS AND MATERIALS

Patients with Stage III/IV head and neck cancer were treated in this multicenter Phase II Study with 1.8 Gy fraction radiotherapy for 2 weeks, with escalation to 1.2 Gy b.i.d. hyperfractionation to 46.8 Gy. Concomitant continuous infusion cisplantinum (CDDP) 20 mg per meter square on day 1 to 4 and 22 to 25 was given. Reassessment by biopsy of primary and nodes was done. Patients with a complete response continued with hyperfractionated radiotherapy to 75.6 Gy with simultaneous carboplatinum (Carbo), 25 mg per meter square b.i.d. for 12 consecutive treatment days. Patients with residual disease at 46.8 Gy required curative surgery. Seventy-four patients were treated at the three institutions; 20 were Stage III and 54 were Stage IV. All patients had daily mouth care, nutritional, and psychosocial support.

RESULTS

This regime was well tolerated. Eighty-five percent of toxicities were Grade 1 or 2 and there was only one Grade 4 hematologic toxicity. Late toxicities included xerostomia in 25 patients, dysphasia in 18, and mild speech impediment in 11. Biopsies of primary site were done after the first course of treatment in 59 patients. Neck dissections were performed in 35 patients. Forty-four of 59 (75%) primary sites and 16 of 35 (46%) lymph nodes had pathologically complete response (CR). Of the 74 patients, only 12 required surgical resection of the primary site. Thirty-five of the 50 node positive patients had neck dissections, 16 of these were CRs at surgery. At 4 years (median follow-up of 26 months), disease-specific survival is 63%. The actuarial survival for all patients is 51%. Patients with pathological CR after initial treatment have disease specific survival of 73% at 4 years vs. 48% of patients with partial response (PR) only.

CONCLUSION

This study, developed on the basis of radiobiological and cell kinetic precepts, produced results that compare favorably with other reports of management of patients with advanced head and neck cancer. In comparison with our previous study, these results are comparable, not impressively better. The associated morbidity was somewhat worse.

The role of transient-evoked otoacoustic emission testing in the evaluation of elderly persons

OBJECTIVE

The purposes of this study were: To determine the quantitative and qualitative changes that occur in transient-evoked otoacoustic emissions (TEOAEs) in older individuals without addressing the effect of aging alone and without correction for hearing loss of the subject selection. To investigate the clinical value of measuring TEOAEs in the routine audiological evaluation of older people reasoning that a finding of hearing loss in the presence of TEOAEs could indicate a form of presbycusis with a primary central component.

DESIGN

Click-evoked otoacoustic emissions (CEOAEs) were measured in 201 subjects without middle ear problems aged 60 yr and older (range 60 to 97 yr) who volunteered for the study because of complaints concerning their hearing. Audiological procedures included a pure-tone audiogram, modified Speech Perception in Noise test (German version: Basler Satztest), and the Hearing Handicap Inventory for the Elderly (German version). Results from ears with a pure-tone average (PTA) at 0.5, 1, and 2 kHz of < or = 30 dB HL were further analyzed with respect to the presence or absence of CEOAEs. In addition, tone burst evoked otoacoustic emissions (TbOAEs) were tested in ears with responses to click stimuli. The test consisted of a paradigm used previously in our laboratory to assess superposition and suppression of frequency within the cochlea (see Xu, Probst, Harris, & Roede, 1994).

RESULTS

CEOAEs were not detectable in ears with a PTA > 30 dB HL. The prevalence of CEOAEs in ears with a PTA < or = 30 dB HL was 60%. Response levels decreased as hearing thresholds became poorer, but there was no apparent influence on TEOAE level due to age alone. The audiological measures from ears with and without CEOAEs and with PTAs < or = 30 dB HL were similar with the exception of small between group differences at lower frequencies. The TbOAE results showed no differences in linear superposition and suppression when results were compared with those of younger subjects tested previously.

CONCLUSIONS

The lower overall amplitudes of TEOAEs and the lower prevalence of 60% in comparison to results from younger subjects with normal hearing imply that cochlear changes do occur with aging. However, the preservation or loss of TEOAEs does not separate subjects with presbycusis into distinct audiological categories or handicaps. Tone burst results suggest that frequency processing within the cochlea is not affected by age alone. We conclude that TEOAEs add no relevant information in the routine clinical evaluation of elderly persons with hearing problems.

[Antibiotic prophylaxis in laterobasal fractures]

A retrospective study over 5 years evaluated the medical records of 78 patients who had suffered lateral skull base fractures. The purpose of the present study was to answer the question of whether antibiotic prophylaxis reduced the risk of meningitis. Fifty-five of 78 patients (71%) were given no antibiotics, among whom four developed meningitis. In 29% of patients treated with antibiotics, two developed meningitis. This difference was not significant. Even when cases with uncomplicated ("simple") lateral skull base fractures were separated from those with severe additional lesions related to their injuries, no significant correlation was found in the occurrence of meningitis despite the use of an antibiotic. Eight of 14 patients with initial otoliquorrheas were treated with antibiotics, with two of these 8 patients developing meningitis. None of the patients who did not receive antibiotics developed meningitis. Our findings shows that it is not advisable to treat patients who have suffered from lateral skull base fractures with prophylactic antibiotics. Instead, these patients should be examined frequently and appropriate antibiotic therapy prescribed at the first clinical symptoms of meningitis.

Reverse middle-ear transfer function in the guinea pig measured with cubic difference tones

Otoacoustic emissions are increasingly useful for determining cochlear function noninvasively. It is widely agreed that these acoustic signals reflect micromechanical processes in the cochlea. However, their quantitative interpretation requires knowledge of the ways in which vibrations travelling back to the ear canal from the cochlea are shaped by the middle ear. An intracochlear source is needed to derive the reverse middle-ear transfer function (rMETF) by comparing pressure in the external ear canal to the corresponding pressure in scala vestibuli. In the present study, the rMETF was obtained in vivo in the guinea pig using as intracochlear sound source the cubic difference tones (CDTs) generated by a pair of external pure tones. With a closed ear canal and open bulla, the rMETF was found to be flat (-35 dB) over a broad frequency range (1.5-8 kHz). The differences between forward and reverse METF could be explained by different loads acting on the middle ear network, which depends on the direction of signal transmission. With knowledge of the rMETF, it becomes possible to quantify CDTs within the cochlea by measuring them noninvasively in the ear canal.

Noninvasive tracking of patient's head movements during computer-assisted intranasal microscopic surgery

A noninvasive system designed for patient tracking during image-guided intranasal sinus surgery is described. It is based on optical digitizing with a custom-made registration and reference system, locatable surgical instruments, and a self-localizing operating microscope. Experimental and clinical results reveal a high degree of accuracy for the system. A mean spatial error of 0.82 +/- 0.31 mm was determined for repositioning of the reference system in a plastic model of the skull. For the positioning of the microscope, a mean error of 2.3 +/- 0.83 mm was calculated. Measurements of repositioning accuracy in 24 patients who received surgery for various sinus diseases had a mean spatial error of 1.56 +/- 0.76 mm. The 95% error interval for locating intranasal structures using the surgical instrument was 2.05 mm, and it was 4.92 mm using the microscope. These results suggest that the use of our noninvasive registration and reference system may be effective, accurate, and useful for noninvasive tracking of patient movements in computer-assisted intranasal surgery.

[Follow-up of caloric test response after acute peripheral vestibular dysfunction]

This study examined retrospectively the spontaneous recovery of patients with an acute peripheral vestibular deficit in order to determine whether the caloric test response and with it vestibular function improves over time. The caloric bithermal was tested three times on 79 patients who were hospitalised with an acute deficit. The first test was recorded on emergency admission by observing nystagmus beats under the Frenzel glasses. Two to five days later a complete electronystagmus (ENG) examination was performed. A second ENG was performed, on average, 4 months later. 46% of the patients recovered a normal caloric canal paresis value (less than 32%). By comparing the canal paresis values in the first and second ENG an improvement exceeding 30% was demonstrated in 50% of the patients and there was no correlation between the extent of the canal paresis deficit and the amount of recovery. A simultaneous cochlear deficit had no influence on the recovery of vestibular function.

[Speech audiometry with logatomes]

BACKGROUND

Logatomes are nonsense syllables used for analyzing the confusion of phonemes by hearing impaired listeners. They can provide a precise differentiation of phonemic confusions which may be useful in the exact adjustment of programmable hearing aids.

METHODS

In this study, two lists of logatomes with 108 three-sound combinations with a structure of consonant-vowel-consonant (c-v-c) and vowel-consonant-vowel (v-c-v) were recorded on a compact disk. Twenty normally hearing adults and 28 patients with a sensorineural hearing loss were tested at a comfortable listening level of about 25 +/- 5 dB above the mean audiometric thresholds at 0,5. 1,0 and 2,0 kHz. An index of reduction of speech perception was calculated.

RESULTS

A significant relationship between reduction of logatome perception and pure-tone audiometric thresholds at 1,2,3, and 4 kHz was demonstrated. Moreover, it was possible to distinguish between different groups of hearing impairment.

CONCLUSIONS

The logatome test helps to analyze specific effects that hearing loss can have on the recognition of acoustic speech signals. The logatome test may become a valuable addition to speech audiometric tests with further standardization.