[Unclear chronic vertigo syndromes-experiences with an interdisciplinary inpatient diagnostic concept]. / Unklare chronische Schwindelsyndrome ­ Erfahrungen mit einem interdisziplinären stationären Diagnostikkonzept.

Dizziness is a common leading symptom. Especially patients with chronic vertigo syndromes experience a significant impairment in quality of life up to a limitation of their ability to work in the case of employed persons. The consequences are financial and capacitive burdens on the health system due to frequently multiple examinations and sick leave up to occupational invalidity of the affected patient. In 150 patients with chronic vertigo syndromes and an unclear outpatient diagnosis, at least one diagnosis that justified the complaint was made in over 90% of cases on the basis of a structured interdisciplinary inpatient diagnostic concept. Chronic vertigo syndromes are often multifactorial. Psychosomatic (accompanying) diagnoses were found in more than half of the patients. Targeted therapy can only be recommended after establishing a specific diagnosis. This justifies an interdisciplinary inpatient diagnostic concept for persistently unclear cases.

[Acute vestibular syndrome in emergency departments : Clinical differentiation of peripheral and central vestibulopathy]. / Akutes vestibuläres Syndrom in der Notaufnahme : Klinische Differenzierung von peripherer vs. zentraler Vestibulopathie.

INTRODUCTION: The differentiation between central and peripheral vestibular disorders is difficult in some cases, especially during the clinical routine of an emergency department (ED) without otoneurological diagnostic equipment. This study evaluated the frequency of vestibular pseudoneuritis as distinguished from acute peripheral vestibular disorders in patients who were admitted to hospital with the suspicion of vestibular neuropathy (VN). METHODS: This retrospective study analyzed the results of anamnestic and clinical examinations of 315 patients admitted to the emergency department and the inpatient otoneurological examination results as well as the imaging of morphological alterations. In the ED, the clinical examination by a neurologist and an otorhinolaryngologist resulted in the characteristic signs of peripheral VN but no further evidence of a neurological disorder. Patients without signs of a peripheral vestibular disorder in the otoneurological diagnostics subsequently underwent cerebral magnetic resonance imaging scans (cMRI). RESULTS: Suspected isolated VN could be confirmed in 69% of the patients; however, in a further 29% of the patients neither the suspected isolated VN nor an ischemic pathology of the central nervous system as a cause of the vertigo could be confirmed. Additional cMRI scans revealed that 2% of patients suffered from an infarction of the mesencephalon, the pons, the medulla oblongata and the cerebellum. CONCLUSION: In rare cases central cerebral disorders mimic the pattern of a peripheral vestibular disorder. Despite thorough history taking, neurological and otolaryngological clinical examinations, it is not always possible to distinguish central and peripheral vestibular disorders of patients in emergency care suffering from acute vertigo. Video oculography-assisted caloric testing and the video head impulse test are recommended to confirm a peripheral VN. In cases without confirmation of suspected NV in otoneurological diagnostics, infarction of the mesencephalon, brain stem and cerebellum should be excluded by diffusion-weighted cMRI.

Listing's plane and the 3D-VOR in microgravity--the role of the otolith afferences.

The study addresses the question as to what extent the otolith-mediated gravity vector maintains the stability of the coordinate frames of the vestibulo-ocular reflex and the oculomotor system, described by Listing's Plane. Under normal 1 G conditions it has been demonstrated in the monkey that Listing's Plane (LP) and the 3D vestibulo-ocular response (3D-VOR) are close to collinear [10]. In the present study the coordinate frames of the oculomotor system and the three-dimensional vestibulo-ocular reflex (3D-VOR) system were measured under one-g gravity conditions and during a period of prolonged microgravity, on-board the International Space Station (ISS). To this end, the coordinate frame of the oculomotor system is described in Listing's coordinates and that of the 3D-VOR system by the minimal gain vector. The findings demonstrate that under Earthbound, one-g conditions the two coordinate frames diverge by approximately 20° in the human. In the absence of the gravity vector the radical loss in the otolith-mediated contribution to the dynamic VOR leads to a reduction of the torsional VOR component and in turn to a forward tilt of the oculomotor coordinate frame, described by the minimal gain vector. In contrast, the torsional component of LP during horizontal and vertical saccades was found to increase, resulting in a backward tilt of LP. Together with the backward tilt of LP a small but consistent change in LP vergence was observed. The thickness of LP did not appear to change in the absence of gravity. The changes in coordinate frame orientation persisted over the six-month periods spent in zero gravity. The postflight measurements demonstrate that re-adaptation to preflight values proceeds over several days to weeks. The findings demonstrate that the gravity vector represents a common reference for vestibular and oculomotor responses. They also support the idea that the gravity vector provides a central reference for the entire sensorimotor complex.

[Laser stapedotomy]. / Laserstapedotomie.

In addition to hearing aids, stapesplasty represents the standard treatment of otosclerosis-induced hearing loss. In this procedure, the stapes superstructure is replaced by a prosthesis that is attached to the long process of the incus and communicates through a perforation in the footplate with the perilymphatic space of the inner ear. The removal of the stapes superstructure and perforation of the footplate are the critical steps of this surgical procedure. With the introduction of laser-assisted perforation techniques, the surgical safety of this method has been improved compared to conventional techniques. KTP, argon, as well as diode, Er:YAG and CO(2) lasers are used for stapedotomy. By using the CO(2) laser in conjunction with a scanner system, the number of laser applications required for the perforation of the footplate has been markedly reduced. In contrast to other systems, a more reproducible perforation diameter of the stapes footplate is achieved with a CO(2) laser equipped with a scanner. Complications such as uncontrolled leakage of perilymph, irradiation of inner ear structures or the occurrence of pressure waves with subsequent damage to the inner ear can be reduced by using a CO(2) laser. In this review, the surgical technique of CO(2) laser stapedotomy, including clinically established variants and paying particular attention to the one-shot technique, are described and discussed in comparison to other laser systems.

Testing utricular function by means of on-axis rotation.

CONCLUSIONS: Subjective visual vertical (SVV) estimation during on-axis rotation provides an efficient screening test of utricle function. The survey demonstrates that isolated disorders of peripheral utricular function can occur while SCC function appears normal. OBJECTIVE: The present study aimed to investigate estimation of SVV during constant velocity yaw rotation (with the head held on-axis--to enhance any asymmetry between right and left utricular responses), as a useful screening test. MATERIALS AND METHODS: In all, 230 patients were recruited from the dizziness clinic. For each patient, the SVV was estimated (a) while held stationary, and (b) during constant angular velocity (240 degrees/s), with the head centred on-axis. Bithermal caloric testing was also performed in 201 of the patients. RESULTS: Of those patients with normal SVV results during stationary testing, 18.3% were pathological during rotation testing. In those cases with pathological SVV during stationary testing, a significantly greater deviation from the norm was observed during rotation (p<0.001). Of those patients with normal caloric responses, 44.4% showed pathological SVV estimates; this increased to 54.3% for cases with unilateral weakness, and 56.5% for unilateral loss. No clear correlation was found between reports of tilt illusion and pathological SVV, respectively, between rotatory vertigo and pathological caloric responses.

["One shot" CO2 laser stapedotomy]. / "Ein-Schuss"-CO2-Laser-Stapedotomie.

BACKGROUND: In order to further optimize the surgical technique with CO(2) laser in stapes surgery, a scanner system was used to obtain a footplate perforation of 0.5-0.6 mm with only one laser application ("one-shot" stapedotomy). PATIENTS AND METHODS: A total of 255 patients with otosclerosis were submitted to primary CO(2) laser stapedotomy with a SurgiTouch scanner. This study discusses the surgical technique and clinical results. RESULTS: An adequately large perforation diameter could be achieved with a single shot in 68% of the patients treated. In 14% of the patients, a second laser application at the same site was necessary. In 18% the perforation had to be enlarged by several slightly overlapping laser applications without using the scanner. There was no evidence of laser dependent inner ear affections. CONCLUSION: CO(2) laser, combined with modern scanner systems, is well suited for application in stapes surgery.

CO2 laser stapedotomy with the "one-shot" technique--clinical results.

OBJECTIVE: To further optimize the surgical technique with the CO 2 laser in stapes surgery a scanner system was used to obtain a footplate perforation of 0.5 to 0.6 mm with only 1 laser application ("one-shot" stapedotomy). STUDY DESIGN: 188 patients with otosclerosis were submitted to a primary CO 2 laser stapedotomy with the SurgiTouch scanner. This study surveys the surgical technique and clinical results. RESULTS: An adequately large perforation diameter could be achieved with a single shot in 68% of the patients treated with the SurgiTouch scanner. In 11% of the patients, a second laser application at the same site was necessary. In 21% of the patients, the perforation had to be enlarged by several slightly overlapping laser applications without scanner. The clinical data of this study clearly documents that there is no evidence of laser depending inner ear affections. CONCLUSION: The CO 2 laser combined with modern scanner systems is well suited for application in stapes surgery.

Unilateral examination of utricle and saccule function.

Attention is directed towards the recently developed unilateral tests of saccular and utricular function. Together with the now widely used head-thrust test and the standard caloric test for semicircular canal function, these provide for a more comprehensive unilateral examination of labyrinth function. The efficacy of vestibular evoked myogenic potentials (VEMP) as a direct unilateral test of saccular function is currently being demonstrated in an increasing number of reports. Furthermore, the relevant neuronal pathways have been delineated in animal studies, so that all evidence points to the validity of the VEMP as a saccule-mediated response. Concerning utricular function, considerable headway has been made using the unilateral centrifugation paradigm. Testing is performed with a variable radius rotary chair with constant velocity rotation about the earth-vertical axis. Displacing the head by 3.5-4 cm from the rotation axis, the eccentrically positioned utricle is stimulated unilaterally by the resultant centrifugal force. This paradigm can be employed to elicit a utriculo-ocular response (UOR) or to permit measurement of the subjective visual vertical (SVV). More recently, it has also been demonstrated that testing during normal, on-centre yaw axis rotation is often sufficient to localise peripheral otolith dysfunction by means of SVV estimation. This test mode can be easily integrated into routine clinical testing. To illustrate the efficacy of such differential testing, the findings from two patients are presented that demonstrate for the first time an isolated unilateral utricular dysfunction.

Using high frame rate CMOS sensors for three-dimensional eye tracking.

A novel three-dimensional eye tracker is described and its performance evaluated. In contrast to previous devices based on conventional video standards, the present eye tracker is based on programmable CMOS image sensors, interfaced directly to digital processing circuitry to permit real-time image acquisition and processing. This architecture provides a number of important advantages, including image sampling rates of up to 400/sec measurement, direct pixel addressing for preprocessing and acquisition,and hard-disk storage of relevant image data. The reconfigurable digital processing circuitry also facilitates inline optmization of the front-end, time-critical processes. The primary acquisition algorithm for tracking the pupil and other eye features is designed around the generalized Hough transform. The tracker permits comprehensive measurement of eye movement (three degrees of freedom) and head movement (six degrees of freedom), and thus provides the basis for many types of vestibulo-oculomotor and visual research. The device has been qualified by the German Space Agency (DLR) and NASA for deployment on the International Space Station. It is foreseen that the device will be used together with appropriate stimulus generators as a general purpose facility for visual and vestibular experiments. Initial verification studies with an artificial eye demonstrate a measurement resolution of better than 0.1 degrees in all three components (i.e.,system noise for each of the components measured as 0.006 degrees H, 0.005 degrees V, and 0.016 degrees T. Over a range of +/-20 degrees eye rotation, linearity was found to be <0.5% (H), <0.5% (V), and <2.0% (T). A comparison with the scleral search coil technique yielded near equivalent values for the system noise and the thickness of Listing's plane.

[Otolith-ocular reflex in linear acceleration of low frequencies]. / Der otolith-okuläre Reflex bei linearen Beschleunigungen mit niedrigen Frequenzen.

BACKGROUND: During constant velocity rotation about the earth's vertical axis, eccentric displacement of the head can be used to generate adequate stimulation of the otolith organs. More recently, studies have been performed with a variable radius rotatory chair, which permits a controlled modulation of the centripetal or radial acceleration, to achieve linear acceleration frequencies much lower than with a conventional linear sled. METHODS: In the present study, frequency response and threshold testing was performed using sinusoidal modulation of the chair radius. Three-dimensional eye movements were recorded with binocular video-oculography. RESULTS: The gain (0.09 degree/degree at 0.03 Hz, 0.009 degree/degree at 1 Hz) and phase relationships of the otolith-ocular response (OOR) show a low-pass characteristic over the measured range of 0.03-1.0 Hz. In comparison to the flat response of neurophysiological recordings from the otolith afferent, our findings support the idea that any low-pass filtering of otolith afferents occurs at the level of the vestibular nuclei. CONCLUSION: The OOR could be detected at acceleration levels of 0.03 m/s2, much lower than the subjective threshold for the perception of 0.08 m/s2.

Measuring unilateral otolith function via the otolith-ocular response and the subjective visual vertical.

In the present study, attention is directed to the unilateral response of the otolith system to static and dynamic tilt, as reflected by subjective estimation of the visual vertical (oculogravic perception). Measurements were performed with a variable radius rotary chair, which permits controlled modulation of the centripetal, or radial, acceleration. By limiting the radius, i.e. eccentric displacement of the head by 3.5 cm during constant-velocity rotation about the earth-vertical axis, adequate unilateral stimulation of the otolith organ--predominantly the utricle--is generated, without involving the semicircular canals. This paradigm has been employed to measure the unilateral utriculo-ocular response. In contrast to the otolith-ocular response (OOR), the subjective visual vertical (SVV) reflects the processing of otolithic information in the higher brain centres (thalamus, vestibular cortex). Exploitation of these two complementary approaches provides useful information for both experimental and clinical scientists. The findings also reveal that centripetal acceleratory stimulation during constant angular velocity with the subject centred on axis is sufficient to localize peripheral otolith dysfunction by means of SVV estimation. This represents a novel test of otolith function that can be easily integrated into routine clinical testing.

Influence of pulsed laser irradiation on the morphology and function of the guinea pig cochlea.

Recent experimental and clinical studies have demonstrated that several pulsed laser systems are also suitable for stapedotomy. The aim of the study was to investigate morphological and functional inner ear changes after irradiating the basal turn of the guinea pig cochlea with two pulsed laser systems of different wavelengths. The Er:YSGG (lambda=2.78 mcm) and Ho:YAG (lambda=2.1 mcm) lasers were used applying the laser energies necessary for perforating a human stapes footplate. The cochleas were removed 90 min, 1 day, 2 weeks, or 4 weeks after laser application. Acoustic evoked potentials (compound action potentials) were measured before and after laser application and at the above times immediately before removal of the cochleas. The organ of Corti was examined by scanning electron microscopy. Application of Er:YSGG laser parameters effective for stapedotomy had no adverse effects on Corti's organ in the guinea pig cochlea. On the other hand, effective Ho:YAG laser parameters cause damage to the outer hair cells with fusion of stereocilia and formation of giant cilia leading to partial or total cell loss. The inner hair cells and supporting cells were usually normal. These morphological data show a good correlation with the electrophysiological measurements. Our results clearly demonstrate that, besides achieving efficient bone management, the Er:YSGG laser has high application safety. On the other hand, the Ho:YAG laser is not well tolerated in our animal study. Its use in stapedotomy would be unreliable and dangerous for the inner ear.

[Experimental and clinical experiences with the Er:YAG laser otoscope]. / Experimentelle und klinische Erfahrungen mit dem Er:YAG-Laserotoskop.

BACKGROUND AND OBJECTIVE: Laserotoscopes are suitable for low-pain outpatient surgery of otitis media with effusion (OME) under topical anesthesia. The myringotomy perforations should have a diameter greater than 2 mm to ventilate the middle ear for approximately 3 weeks. PATIENTS/METHODS: In this study, the clinical applicability of a prototype of an Er:YAG laserotoscope (Baasel Lasertechnik, Starnberg, Germany) was tested. Formalin-fixed human tympanic membranes yielded the parameters suitable for clinical application of an Er:YAG laserotoscope in patients. With a focussed laser beam (beam diameter 500 microns), one is able to achieve perforations of 50-micron diameter with one single laser pulse applying pulse energies of 70 mJ (energy density 36 J/cm2). The ablation rate, i.e., the tissue layer that is ablated per laser pulse, is 100 microns using pulse energies of 70 mJ. This means that formalin-fixed human tympanic membrane can be perforated with one single laser pulse. RESULTS: Ten patients with OME (otitis media with effusion) were treated under topical anesthesia of the tympanic membrane (8% tetracainbase in Isopropanol for 15 min) with focussed laser pulses (beam diameter 500 microns) with energies of 100 mJ (energy density 52 J/cm2). A sufficient perforation diameter of 2 mm could be achieved with an average of 15 juxtaposed laser applications. The enlargement of the perforations was made difficult by extruding middle ear secretions and slight bleeding of the tympanic membrane. Between laser applications, the target tissue had to be cleaned by suctioning using the operation microscope. The healing of the tympanic membrane was verified and compared in postoperative clinical follow-ups. With a perforation diameter of 2 mm, the Er:YAG laser myringotomies healed within 14 days. The used parameters did not generate side effects such as inner ear hearing loss. CONCLUSIONS: An effective, easy, and practical performance of laser myringotomy is not currently possible with the Er:YAG laserotoscope.

Influence of CO2 laser application to the guinea-pig cochlea on compound action potentials.

HYPOTHESIS: Experiments in guinea pigs were performed to clarify which, if any, of the CO2 lasers in different modes (continuous wave [cw] and superpulse) can damage the inner ear on application of the laser parameters required for stapedotomy and to determine their application safety. METHODS: The laser effect connected with perforating the basal convolution of the guinea-pig cochlea (cochleostomy) was examined. Acoustic evoked potentials (compound action potentials [CAPs]) yielded information on inner-ear function. RESULTS: In cw mode, even single applications of an approximately four times higher power density (60,000 W/cm2) than necessary for stapedotomy at a pulse duration of 50 msec (energies up to 1 J) and 20-fold applications of effective parameters for a footplate perforation (power density 16,000 W/cm2; energy 0.2 J) did not cause CAP changes. Experimental studies with the CO2 superpulse laser used (peak pulse powers: ca. 300 W) have demonstrated that irreversible CAP alterations already occur in the effective laser range in > 40% of the animals. CONCLUSIONS: Because damage is expected only at much higher energies (> 2 J) than those used clinically, the CO2 laser in cw mode has a high application safety for laser stapedotomy. The application of the CO2 laser in superpulse mode with peak pulse powers of approximately 300 W in stapedotomy appears to be more unreliable and dangerous for the inner ear.

[The CO2 laser otoscope. A new application device for paracentesis]. / Das CO2-Laserotoskop. Ein neues Applikationssystem für die Parazentese.

The CO2 laser myringotomy is a current low-pain procedure for middle-ear ventilation for secretory otitis media (SOM) that can be performed under topical anesthesia, even in children. The duration of middle-ear ventilation is essentially determined by the size of the perforation created. Perforations with a diameter greater than 2 mm ventilate the tympanic cavity for approximately 3 weeks, thus avoiding tympanic ventilation tubes. To date, the CO2 laser beam can only be reliably applied to the tymapanic membrane via a micromanipulator system coupled to an ear microscope. The CO2 laser otoscope is a new application system that markedly reduces the technical complexity of surgery and improves the mobility and availability of the system. The incorporation of a small inexpensive CO2 laser in the otoscope represents a significant development in SOM therapy.

Extended high frequency audiometry in pre-school children.

Since adequate and reliable earphones are now available and standards have been established, clinical audiometry can be performed at extended high frequencies (EHFs). In the present study, 47 preschool children (aged 4-7 years) were examined with EHFs (8-16 kHz) using the new Sennheiser HDA 200 earphone. The hearing thresholds correspond to those of other studies; the median thresholds and range increase with increasing frequency. The medians and quartiles were: 10 kHz: 25 (5-35) dB(SPL), 11.2 kHz: 35 (20-40) dB(SPL), 14 kHz 40 (30-50) dB(SPL) and 16 kHz: 50 (40-60) dB(SPL). The hearing thresholds could be more reliably determined in the older children (> 5 years) and were 5 dB better than in the younger ones (< 5 years). Thresholds in the 10-12.5 kHz range correspond to those of adults but are more sensitive by 5-12 dB in the 14-16 kHz range.

Thermic effects in the "vestibule" during laser stapedotomy with pulsed laser systems.

BACKGROUND AND OBJECTIVE: Apart from the ablation properties at the stapes footplate, the degree of thermic loading in the inner ear is important in determining the suitability of pulsed lasers for stapedotomy. The aim of the study is to compare the thermic effects in the vestibule with different pulsed laser systems. STUDY DESIGN/MATERIALS AND METHODS: Temperature increases and heat exchange processes in the fluid (physiological saline) were examined in a calorically and physiologically approximated cochlea model for applying the laser parameters effective in creating footplate perforations. RESULTS: With all systems, increases in the energy density, number of pulses, and thus resultant total energy lead to higher temperatures. In the effective energy density range, the highest temperature increases achieved with the requisite number of pulses at a distance of 2 mm behind the perforation are 26 degrees C with the Ho:YAG laser. The lowest temperature maxima are 5.5 degrees C with the Er:YAG and <5 degrees C with the Er:YSGG laser. The excimer laser, investigated at only one energy density, showed maximal temperatures of 10 degrees C. CONCLUSION: The Er:YSGG and Er:YAG laser can be applied in laser stapedotomy in a relatively broad energy density range without a risk of inner ear damage by thermic loading. On the other hand, the Ho:YAG laser is not recommended for stapedotomy because of the higher energy density and pulse rate required for sufficient perforation and the resultant higher temperature increases in the perilymph. Though likewise achieving perforations with only slight temperature increases in the fluid of the cochlea model, the excimer laser does not seem appropriate for stapedotomy because of the long period of heat exposure (ca. 60 s) due to the lower ablation rate at the stapes necessitating a longer application time.

[Effect of the pulsed Er:YSGG and Ho:YAG laser on the organ of Corti of the guinea pig cochlear--a scanning electron microscopy study]. / Wirkung des gepulsten Er:YSGG- und Ho:YAG-Lasers auf das Corti-Organ der Meerschweinchen-Cochlea--eine rasterelektronenmikroskopische Studie.

BACKGROUND: Recent experimental studies have demonstrated that, apart from the continuous wave lasers, several pulsed laser systems are also suitable for stapedotomy. The aim of this study was to clarify whether irradiation of the basal convolution of the guinea pig cochlea could cause morphological inner-ear changes using the Er:YSGG and Ho:YAG laser with laser parameters required for stapedotomy. METHODS: After opening the bulla, the basal convolution of the guinea pig cochlea, whose thickness is similar to that of the human stapes footplate, was irradiated with the Er:YSGG and Ho:YAG laser. The laser parameters used were those necessary for an adequate perforation of a human stapes footplate (500-600 microns). The cochleae were removed 90 minutes, 1 day, 2 weeks, or 4 weeks after laser application. The organ of Corti was examined by scanning electron microscopy in all convolutions. RESULTS: Application of Er:YSGG laser parameters effective for stapedotomy (5 pulses, energy: 85 J/pulse, energy density: 36 J/cm2, total energy: 0.425 J) had no adverse effects on the organ of Corti in the guinea pig cochlea. On the other hand, effective Ho:YAG laser parameters (10 pulses, energy: 210 J/pulse, energy density: 90 J/cm2, total energy: 2.1 J) caused damage to the outer hair cells with fusion of stereocilia and formation of giant cilia leading to partial or total cell loss. The inner hair cells and supporting cells were usually normal. CONCLUSION: Our results clearly demonstrate that the Er:YSGG laser has high application safety. It could prove to be a viable alternative to the thermically acting CO2 laser for stapedotomy. The Ho:YAG laser is not well tolerated in animals and has low application safety. Its use in stapedotomy would be unreliable and dangerous for the inner ear.

[Hearing tests in extended high frequency range in pre-school age children. Initial results]. / Höruntersuchungen im erweiterten Hochtonbereich bei Kindern im Vorschulalter. Erste Ergebnisse.

Since reliable headphones are now available, clinical audiometry can also be performed in extended high frequencies (EHF). Hearing in frequencies over 10 kHz is more influenced by age, noise and toxicity. Thus it is useful to take additionally results in children to establish the normal hearing threshold. In the present study, 35 pre-school children (ages 4-7 years) were tested by EHF (8 kHz-16 kHz) using a new Sennheiser HDA-200 headphone. The hearing thresholds recorded corresponded to those of other studied. Median and standard deviations for 10 kHz were 25 dB(SPL) +/- 12 dB(SPL), 35 dB(SPL) +/- 12 dB(SPL) for 12.5 kHz and 50 dB(SPL) +/- 15 dB(SPL) for 16 kHz. In the older children (> 5 years), hearing thresholds could be more reliably determined and were 10 dB(SPL) better than in the younger children (< 5 years). Thresholds at 10 kHz-12.5 kHz corresponded to those found in adults, but were more sensitive by 5 dB(SPL)-15 dB(SPL) in the 14 kHz-16 kHz range.