Orbital ossifying fibroma: A case report. / Fibroma osificante orbitario, a propósito de un caso.

CLINICAL CASE: The case concerns a 34 year-old man, who presented with pain in the medial canthus in his left eye, with proptosis and diplopia. The examination showed exophthalmus and a palpable mass at the inner canthus. The computed tomography revealed a lesion, which was confirmed by biopsy to be a ossifying fibroma. DISCUSSION: Ossifying fibroma is a benign fibro-osseous lesion that mostly affects the jaw. Clinical presentation and complications vary according to its location. Clinical examination, imaging, and histopathology are essential for definitive diagnosis. Surgical treatment is multidisciplinary and long-term follow up is needed.

Maturation of the human cochlear amplifier: distortion product otoacoustic emission suppression tuning curves recorded at low and high primary tone levels.

The cochlear amplifier shows level-dependent function and works optimally at low levels. For this reason, manipulation of stimulus level is a route through which the human cochlear amplifier can be investigated in a noninvasive manner. Distortion product otoacoustic emissions (DPOAEs) evoked as a function of stimulus level provide a tool for exploration of human cochlear amplifier function and, when applied to neonates, for investigation of cochlear maturation. The current experiment generated 2f1-f2 DPOAE ipsilateral suppression tuning curves (STCs) at three primary tone levels and five f2 frequencies in a large group of premature and term neonates and adults. The differences between tuning generated with low- and high-level primary tones was measured to provide a gross estimate of the "tuning enhancement effect" attributed to the cochlear amplifier. Other features of the DPOAE suppression tuning curves were measured as well. Consistent with previous reports, at 1500 and 6000 Hz, STCs were narrower, with a steeper slope on the low-frequency flank of the tuning curve in premature neonates versus adults. Additionally, only DPOAE STCs from adults and term neonates became markedly broader and more shallow when recorded with high-level primary tones. It has been hypothesized that the excessive narrowness of suppression tuning and the absence of a level effect on DPOAE STCs recorded in premature neonates reflects a subtle immaturity in cochlear amplifier function just prior to term birth.

Cochlear receptor (microphonic and summating potentials, otoacoustic emissions) and auditory pathway (auditory brain stem potentials) activity in auditory neuropathy.

OBJECTIVE: To define both auditory nerve and cochlear receptor functions in subjects with auditory neuropathy (AN). DESIGN: We tested 33 AN subjects (66 ears) and compared them with 21 healthy subjects (28 ears). In AN subjects, the average pure-tone (1, 2, and 4 kHz) threshold loss was 57 dB HL. Click stimuli were used to elicit transient evoked otoacoustic emissions (TEOAEs), cochlear microphonics (CMs), and auditory brain stem responses (ABRs). Both cochlear and ABR potentials were recorded from surface electrodes (vertex-ipsilateral mastoid) using averaging procedures. The amplitudes and latencies of CMs and ABRs and the amplitude of the TEOAEs were analyzed. RESULTS: CM amplitudes recorded from normal ears decreased as a function of subject age. CMs recorded from AN subjects fell within the normal age-adjusted range in 60% of the subjects and were >2 SEEs (standard error of estimate) above the age-adjusted normal regression in 40% of the subjects. TEOAEs were absent in 19 (30%) AN ears (bilaterally in eight, and unilaterally in three subjects) and were present in 44 ears. In AN subjects, correlations among CM amplitude, TEOAE amplitude, and pure-tone average thresholds were not significantly related. CM amplitudes were not significantly different whether TEOAEs or ABRs were present or absent. The ABR was present in 21% of AN subjects and consisted of a low-amplitude Wave V without a preceding Wave I. Measures of CM amplitude and PTA hearing loss were not significantly different in those AN ears with a preserved ABR compared with ears with absent ABRs. Summating potentials to transient click stimuli were of small amplitude (<0.1 microV) and detectable in approximately 50% of the AN and healthy control subjects limiting formal analysis of summating potentials. CONCLUSIONS: In a significant proportion of AN subjects, we found abnormalities of cochlear receptor function, including elevated CM amplitudes and absence of TEOAEs. These two abnormalities occurred independently of each other. A low amplitude Wave V of the ABR was found in approximately one-fifth of AN subjects, evidence that neural synchrony can be partially preserved in some subjects with this disorder.

DPOAE suppression tuning: cochlear immaturity in premature neonates or auditory aging in normal-hearing adults?

Previous work has shown that distortion product otoacoustic emission (DPOAE) suppression tuning curves (STCs) recorded from premature neonates are narrower than adult STCs at both low and high frequencies. This has been interpreted to indicate an immaturity in cochlear function prior to term birth. However, an alternative explanation for this finding is that adult DPOAE STCs are broadened and reflect cochlear hair cell loss in normal-hearing adults due to aging, and natural exposure to noise and ototoxins. This alternative hypothesis can be tested by studying suppression tuning in normal-hearing school-aged children. If normal-hearing children, who have not aged significantly or been exposed to noise/ototoxins, have DPOAE suppression tuning similar to adults, the auditory aging hypothesis can be ruled out. However, if children have tuning similar to premature neonates and dissimilar from adults, it implicates aging or other factors intrinsic to the adult cochlea. DPOAE STCs were recorded at 1500, 3000, and 6000 Hz using optimal parameters in normal-hearing children and adults. DPOAE STCs collected previously from premature neonates were used for age comparisons. In general, results indicate that tuning curves from children are comparable to adult STCs and significantly different from neonatal STCS at 1500 and 6000 Hz. Only the growth of suppression was not adultlike in children and only at 6000 Hz. These findings do not strongly support the auditory aging hypothesis as a primary explanation for previously observed neonatal-adult differences in DPOAE suppression tuning. It suggests that these age differences are most likely due to immaturities in the neonatal cochlea. However, nonadultlike suppression growth observed in children at 6000 Hz warrants further attention and may be indicative of subtle alternations in the adult cochlea at high frequencies.

Distortion product otoacoustic emission (2f1-f2) amplitude growth in human adults and neonates.

Distortion product otoacoustic emissions (DPOAEs) are thought to be by-products of an active amplification process in the cochlea and thus serve as a metric for evaluating the integrity of this process. Because the cochlear amplifier functions in a level-dependent fashion, DPOAEs recorded as a function of stimulus level (i.e., a DPOAE growth function) may provide important information about the range and operational characteristics of the cochlear amplifier. The DPOAE growth functions recorded in human adults and neonates may provide information about the maturation of these active cochlear processes. Two experiments were conducted. Experiment I included normal-hearing adults and term-born neonates. The 2f1-f2 DPOAE growth functions were recorded for both age groups at three f2 frequencies. Experiment II was an extension of the first experiment but added a subject group of premature neonates. The results of these studies indicate that DPOAE growth functions most often show amplitude saturation and nonmonotonic growth for all age groups. However, premature neonates show monotonic growth and the absence of amplitude saturation more often than adults. Those premature neonates who do show saturation also show an elevated threshold for amplitude saturation relative to adults. In contrast, term neonates are adultlike for most measures except that they show a larger percentage of nonsaturating growth functions than adults. These results may indicate immaturity in cochlear amplifier function prior to term birth in humans. Outer hair cell function and/or efferent regulation of outer hair cell function are hypothesized sources of this immaturity, although some contribution from the immature middle ear cannot be ruled out.

Distortion product otoacoustic emission suppression in subjects with auditory neuropathy.

OBJECTIVE: The objective of this experiment was to address: 1) whether normal efferent system function is required for normal cochlear tuning as measured by distortion product otoacoustic emission (DPOAE) suppression in humans and 2) whether cochlear function, assessed by DPOAE suppression tuning, is normal in a small group of patients with auditory neuropathy. DESIGN: DPOAE suppression tuning curves (STCs) are similar to other physiologic measures of tuning. They are generated by evoking a DPOAE with two simultaneously presented pure tones and then suppressing the distortion product with a third tone of varying frequency and level. In this study, DPOAE STCs were generated with f2 frequencies of 1500, 3000, and 6000 Hz in 15 normal-hearing adults and four subjects with documented auditory neuropathy. Tuning curve width, slope and tip characteristics, as well as rate of suppression growth were measured in each group. Contralateral suppression of otoacoustic emissions (OAEs) was also recorded as an index of medial efferent function. RESULTS: Results show that the four subjects with auditory neuropathy lacked efferent suppression of OAEs. However, these four subjects showed normal estimates of cochlear tuning as measured by DPOAE suppression results. CONCLUSIONS: This finding suggests that normal efferent system function is not required at the time of test for normal DPOAE suppression tuning. It also suggests that cochlear function as evaluated by detailed measures of DPOAE suppression, is normal in these "typical" patients with auditory neuropathy.

Maturation of medial efferent system function in humans.

Otoacoustic emissions are typically reduced in amplitude when broadband noise is presented to the contralateral ear. This contralateral suppression is attributed to activation of the medial olivocochlear system, which has an inhibitory effect on outer hair-cell activity. By studying the effects of contralateral noise on cochlear output at different stages of auditory maturation in human neonates, it is possible to describe the timecourse for development of medial efferent system function in humans. The present study recorded 2 f1-f2 distortion product otoacoustic emissions (DPOAE) in human adults, term and premature neonates at three f2 frequencies: 1500, 3000, and 6000 Hz, using fixed primary tone frequency ratio (f2/f1 = 1.2) and level separation (10 dB, L1 > L2). Average DPOAE growth functions were recorded with and without contralateral broadband noise. Results indicate that contralateral suppression of DPOAEs is absent at 6000 Hz, but present at 1500 and 3000 Hz for all ages. However, DPOAE amplitude from premature neonates was not altered by noise in an adult-like manner; in this age group, DPOAE amplitude was equally likely to by suppressed or enhanced by noise presented contralaterally. Contralateral enhancement may reflect a temporary stage of immaturity in outer hair cell-medial efferent fiber synapses just prior to term birth.

A developmental study of distortion product otoacoustic emission (2f1-f2) suppression in humans.

Suppression of the 2f1-f2 distortion product otoacoustic emission (DPOAE) provides an effective paradigm for the study of functional cochlear maturation in humans. DPOAE iso-suppression tuning curves (STCs) represent some aspect of peripheral filtering, probably related to the boundaries of distortion generation. Studies conducted thus far suggest that the cochlear tuning assessed by this technique is adult-like in humans by term birth (Abdala et al., Hear. Res. 98 (1996) 38-53; Abdala and Sininger, Ear Hear. 17 (1996) 374-385). However, there have been no studies of cochlear tuning in premature human neonates. DPOAE STCs and suppression growth functions were measured from 14 normal-hearing adults, 33 term and 85 premature neonates to investigate the developmental time course of cochlear frequency resolution and non-linearity. Premature neonates showed non-adult-like DPOAE suppression at f2 of 1500 and 6000 Hz: (1) STCs were narrower in width (Q10) and steeper in slope on the low-frequency flank of the tuning curve; (2) suppressor tones lower in frequency than f2 produced atypically shallow growth of DPOAE suppression. The influence of immature conductive pathways cannot be entirely ruled out as a factor contributing to these results. However, findings may indicate that an immaturity exists in cochlear frequency resolution and non-linearity just prior to term birth. The bases of this immaturity are hypothesized to be outer hair cell in origin.

Gender distinctions and lateral asymmetry in the low-level auditory brainstem response of the human neonate.

Threshold measures of auditory brainstem response (ABR) were generated in 72 full-term newborn infants in response to clicks and tone burst stimuli between 500 and 8000 Hz as detailed in a previous study. These results were further analyzed for differences in response related to ear (lateral asymmetry) and subject gender. Thresholds obtained in male infants were significantly lower than those of females (P = 0.0485). The greatest differences in threshold between male and female infants occurs in the right ear (7.45 dB) as opposed to the left ear (1.56 dB). Both male and female infants have significantly larger wave V amplitude elicited from the right ear than the left (P = 0.0002) using low-level stimuli. Also, as has been noted in adults, female infants have larger amplitude ABRs than males (P = 0.0018), but amplitude differences across gender are significant only in the right ear (ear by gender interaction P = 0.0278). Results of this study indicate that gender differences and lateral asymmetry in auditory function are not a result of gender bias for or unbalanced auditory trauma, but a biologically significant phenomenon that is present at birth. The argument is made that superior right ear performance may be part of cerebral laterality in auditory function.

Auditory threshold sensitivity of the human neonate as measured by the auditory brainstem response.

The absolute auditory sensitivity of the human newborn infant was investigated using auditory brainstem response thresholds (ABR). ABRs were elicited with clicks and tone-bursts of 0.5, 1.5, 4.0 and 8.0 kHz, embedded in notched noise, in healthy, full-term human neonates and young adults with known, normal-hearing sensitivity. Stimuli were calibrated using a probe microphone positioned near the tympanic membrane in the ear canal of each subject to control for differences in resonance characteristics of infant and adult ear canals. ABR thresholds were also characterized relative to group psychophysical thresholds (nHL) and relative to individual psychophysical threshold or sensation level (SL) for the adult subjects. Infant ABR thresholds measured in p.e. SPL for all stimuli are elevated by to 3-25 dB relative to adult thresholds. Threshold elevation is greatest for the high-frequency stimuli. Result are consistent with neural immaturity for high-frequency stimuli in the auditory system of human neonates.

Distortion product otoacoustic emission (2f1-f2) amplitude as a function of f2/f1 frequency ratio and primary tone level separation in human adults and neonates.

Distortion product otoacoustic emission (DPOAE) (2f1-f2) amplitude is dependent upon both the frequency ratio and level separation of the eliciting primary tones. In adults it has been established that, on average, a f2/f1 ratio of 1.22 is optimal for evoking the most robust DPOAE; DPOAE amplitude is systematically reduced when f2/f1 ratio is either increased or decreased, thus forming a bandpass function (Harris et al., 1989). The frequency ratio function (DPOAE amplitude x f2/f1 ratio) is thought to reflect the filtering properties of the cochlea (Allen and Fahey, 1993; Brown et al., 1993). Primary tone level separation also influences DPOAE amplitude, with a 10- to 15-dB level difference between the primary tones (L1 > L2) typically generating largest amplitude in adults. Equivalent studies have not been conducted in neonates. The present study evoked the 2f1-f2 DPOAE in adults, term and premature neonates to define the optimal f2/f1 ratio and L1-L2 level separation and to investigate the filtering properties of the developing cochlea. Two f2 frequencies were investigated: 1500 and 6000 Hz. F2 was held constant while f1 was varied to produce 13 frequency ratios. Primary tone level separation varied from 15 to 0- in 5-dB intervals. ANOVA were conducted on the resulting f2/f1 frequency ratio and level separation data. Results showed that the mean optimal frequency ratio for DPOAE generation is comparable in adults and neonates. Also, either a 15- or 10-dB level separation (L1 > L2) produced the largest DPOAE amplitude for adults and term neonates whereas DPOAEs from premature neonates appeared to be relatively insensitive to primary tone level separation. The f2/f1 frequency ratio functions were similar in shape, slope, and bandwidth for adults and neonates, suggesting adult-like cochlear filtering prior to term birth. This finding is in agreement with previous work from our laboratory reporting adult-like DPOAE suppression tuning curves in term-born neonates [Abdala et al., Hear. Res. (1996)].

The development of cochlear frequency resolution in the human auditory system.

OBJECTIVE: The objectives of this study were: 1) to evaluate the maturity of cochlear frequency resolution in human neonates, and 2) to further elucidate the differential time course for development of frequency resolution at the cochlear and auditory-neural levels of the auditory system. DESIGN: This paper describes a relatively new technique using distortion product otoacoustic emision (DPOAE) suppression to study cochlear tuning. DPOAE suppression tuning curves (STCs) were generated in 15 normal-hearing adults and 26 healthy, term-born neonates at 1500, 3000, and 6000 Hz. The 2f1-f2 DPOAE was measured in all subjects with primary tones of 65 and 50 dB SPL (L1 > L2) and a 1.22 f2/f1 frequency ratio. Initially, an unsuppressed DPOAE was recorded. After this, a suppressor tone was introduced, and its level varied until DPOAE amplitude was reduced by 6 dB. By plotting the suppressor level required to achieve criterion amplitude reduction by suppressor frequency (for many tones), a DPOAE STC was generated. DPOAE STC shape, width, slope, and tip characteristics were analyzed for both adults and neonates. RESULTS: General shape and appearance of DPOAE STCs were comparable for adults and neonates, as was STC tip frequency and level. Statistical analyses of tuning-curve width (Q) and slope (dB/octave) failed to show age effects, further confirming the similarity between adults and neonates. DPOAE STCs were stable, show minimal intra- and intersubject variability, and closely resemble and behave like physiologic measures of tuning from the VIIIth nerve. CONCLUSIONS: Results suggest that: 1) cochlear tuning and related active processes are basically mature by term birth in the human auditory system, 2) tuning immaturities reported in infants as old as 6 mo of age probably involve auditory-neural immaturities, and 3) suppression of the 2f1-f2 DPOAE seems, to provide an indirect measure of cochlear frequency resolution in humans.

Hearing threshold as measured by auditory brain stem response in human neonates.

OBJECTIVES: This article evaluates the concept of auditory threshold and discusses the limitations of assessing threshold in human neonates. The advantages and limitations of assessing neonatal threshold by means of auditory brain stem response (ABR) are discussed, and data from several studies of newborn ABR threshold are compared. The authors report data from their own study designed to compare adult and neonatal ABR threshold using tonal stimuli. EXPERIMENTAL DESIGN: Several studies are compared. Data from the authors are ABR thresholds for tone bursts of 0.5, 1.5, 4, and 8 kHz, determined from 2-channel recordings in full-term neonates and adults. Stimuli were calibrated in SPL by means of a probe microphone inserted into the ear canal along with the insert transducer of each subject. RESULTS: All studies find a degree of threshold elevation in neonates relative to adult threshold. Neonatal ABR thresholds from our laboratory for stimuli from 500 through 8000 Hz are elevated relative to adult thresholds by 5 to 25 dB. Threshold elevation in our data and in other studies has found that neonatal ABR thresholds to high-frequency stimuli show the largest elevation relative to adults and low-frequency stimuli the most mature. CONCLUSIONS: Thresholds of neonates, as measured by the ABR, are immature especially for high-frequency stimuli. Proper stimulus calibrations, which removes the influence of ear canal resonance, are important for comparisons of data across age groups. Developmental differences in the conductive mechanism and neural immaturity are the most harmonious explanations for elevation of neonatal ABR thresholds.

Distortion product otoacoustic emission suppression tuning curves in human adults and neonates.

Distortion product otoacoustic emission (DPOAE) iso-suppression tuning curves (STC) were generated in 15 normal-hearing adults and 16 healthy term-born neonates for three f2 frequencies. The 2f1-f2 DPOAE was elicited using f2/f1 = 1.2, LI = 1.2, LI = 65 and L2 = 50 dB SPL. A suppressor tone was presented at frequencies ranging from 1 octave below to 1/4 octave above f2 and varied in level until DPOAE amplitude was reduced by 6 dB. The suppressor level required for 6 dB suppression was plotted as function of suppressor frequency to generate a DPOAE STC. Forward-masked psychoacoustic tuning curves (PTC) were obtained for three of the adult subjects. Results indicate that DPOAE STCs are stable and show minimal inter- and intra-subject variability. The tip of the STC is consistently centered around the f2 region and STCs are similar in shape, width (Q10) and slope to VIIIth-nerve TCs. PTCs and STCs measured in the same subject showed similar trends, although PTCs had narrower width and steeper slope. Neonatal STCs were recorded at 3000 and 6000 Hz only and were comparable in shape, width and slope to adult STCs. Results suggest: (1) suppression of the 2f1-f2 DPOAE may provide an indirect measure of cochlear frequency resolution in humans and (2) cochlear tuning, and associated active processes in the cochlea, are mature by term birth for at least mid- and high-frequencies. These results provide significant impetus for continued study of DPOAE suppression as a means of evaluating cochlear frequency resolution in humans.

The development of frequency resolution in humans as revealed by the auditory brain-stem response recorded with notched-noise masking.

Studies of tuning in infants have reported that auditory brain-stem response (ABR) tuning curves generated using low-frequency probes are adultlike by 3 months of age while high-frequency tuning curves remain immature [Folsom and Wynne, J. Acoust. Soc. Am. 81, 412-417 (1987)]. Behavioral studies have similarly reported adultlike low-frequency psychoacoustic tuning curves by 3 months with high-frequency tuning curves immature until approximately 6 months of age [L. Olsho, Infant Behav. Dev. 8, 371-384 (1985); Spetner and Olsho, Child Dev. 61, 632-652 (1990); Schneider et al., J. Exp. Psych.: Human Percept. Perform. 16, 642-652 (1990)]. Prior to this experiment, there have been no ABR studies of the development of frequency resolution for infants older than 3 months. In this study, notched-noise tuning functions were constructed from wave-V amplitude data for 3-month-old, 6-month-old, and adult subjects. Tone-pip stimuli at 1000, 4000, and 8000 Hz (50 dB nHL) were presented simultaneously with notched-noise masking centered at frequencies related to the tone-pip frequency (1/3-oct intervals above and below the probe frequency). By plotting wave-V amplitude across notched-noise center frequency, isointensity tuning functions were generated for the three subject groups at the three probe frequencies. Auditory filter width (Q) and slope (dB/oct) were measured from each notched-noise tuning function in order to qualify degree of tuning. Consistent with previous studies, results showed that 3-month-old infants do not have adultlike tuning for high-frequency stimulation (8000 Hz). In contrast, by 6 months of age, tuning-function width (Q) is adultlike for both high- and low-frequency probes. These results, combined with previously reported evidence that the human cochlea is fully tuned at birth [Abdala et al., submitted to Hear. Res. (1995); Bargones and Burns, J. Acoust. Soc. Am. 83, 1809-1816 (1988)], suggest that immaturities in the auditory-neural system contribute to the broad high-frequency tuning consistently observed in 3-month-old human infants.

Frequency contribution to the click-evoked auditory brain-stem response in human adults and infants.

The results of previous research reports have led some investigators to hypothesize that frequency contribution to the infant click-evoked auditory brain-stem response (ABR) is low-frequency dominated and derived primarily from the apical cochlea. This is in contrast to latency and morphology of the adult click-evoked ABR which reflects contributions from the basal cochlea. Recent research, however, has suggested that a simple low-frequency first model of development does not adequately describe the infant auditory brain-stem response. This experiment was conducted as a carefully controlled comparison of infant and adult click-evoked ABRs restricted to narrow frequency ranges with notched-noise masking. The primary objective of this experiment was to define frequency contribution to wave I and V click-evoked ABR latency and morphology in adults and 3-month-old infants. Results indicate that 3-month-old infants have adultlike latency shifts (re: unmasked latency) when the ABR is recorded in the presence of notched-noise masking with center frequencies ranging from 500-8000 Hz. With high-frequency centered notches, latency, and morphology change are similar to the unmasked response, while low-frequency centered notches induce an average latency shift of approximately 3.5 ms for wave I and V of both infant and adult subjects. These data suggest that by 3 months of age, in normal hearing infants, ABR latency and appearance are determined by high-frequency spectral components in the broadband click which activate the basal cochlea. The adultlike pattern of latency shift observed in the ABR of these infants suggests that relatively mature tonotopic organization is established by 3 months of age.

Perceptual features from normal-hearing and hearing-impaired children's errors on the NST.

Perceptual features for consonants contained in the nonsense syllable test, were evaluated from normal-hearing and hearing-impaired children's errors. One group consisted of 30 normal-hearing children between 6:0 and 12:8 years of age; the other group consisted of 7 hearing-impaired children between 8:0 and 14:8. The subjects provided verbal responses to list A of the nonsense syllable test which was presented at 25, 35, 45, and 55 dB sensation levels regarding each subject's speech reception threshold. Responses were phonetically transcribed, pooled across sensation levels, converted to confusion matrices, and submitted to Symmetric Individual Differences Scaling. Consonants were analyzed for pre- and inter-vocalic positions. Results revealed that features differed across subject groups and consonant positions. Salient features related to place of articulation, voicing, nasality, sonorancy, and sibilancy.

Statistical models for predicting Edgerton-Danhauer NST scores from pure-tone thresholds.

Pure-tone thresholds (PTTs) and phonemic-scored responses to the Edgerton and Danhauer (1979) Nonsense Syllable Test (NST) at 25, 35, 45, and 55 db SL re each S's SRT, were taken from 97 Ss of 4 earlier studies of Danhauer and colleagues. All studies had used the same stimuli and procedures. Among the 97 Ss were heterogeneous subpopulations of normally-hearing and sensorineural hearing-impaired Ss, aged 6-81 yrs. PTTs at octaves from .25-8 kc/s, singly and in various weighted combinations, were explored by step-wise multiple linear regression analyses for the best equation to predict an individual's NST score at each SL. Included were the two weighted PTT averages (over .5, 1, and 2 kc/s) proposed by Butts, Schoney and Ruth (Asha, 1984, 26, 64). PTT2 kc/s was the single most predictive datum. The most predictive equation at one NST SL was not necessarily the best at another SL. At each NST SL, the most predictive equation was always one or other of the equations of Butts et al, and at the higher levels the best equations incorporated in addition certain weighted PTTs at .5 and 1 kc/s. The results indicated that it is possible to predict a S's NST scores from PTTs with reasonable accuracy: from 86-91% of Ss' NST scores were predicted within +/- 10%. Further validation and refinement of these models on larger and different subject samples may result in equations predicting NST scores from PTTs with those difficult-to-test patients in whom speech recognition capacity cannot well be tested directly.

A survey of speech and other auditory perception assessment materials used by cochlear implant centers.

A questionnaire assessing the various auditory perception materials used by cochlear implant centers in evaluating cochlear implant candidates and patients was developed, pilot tested, and mailed in August, 1985, to 135 cochlear implant centers. After a follow-up, there was a 45% return rate. The questionnaire sampled responses pertaining to the respondents' demographics, the types of assessment materials they used, and their opinions about speech and other auditory perception tests for evaluating cochlear implant patients. The data revealed that most centers use the same tests repeatedly for both pre- and post-implant assessments. Several factors relating to the tests and their administration were identified. Only 36% of the centers expressed satisfaction with the currently-used materials. The tests most frequently used were not necessarily considered to be the best or most appropriate for evaluating cochlear implants. Most respondents stated a need for the development of new test materials, and some suggestions were provided.