The clinical use of oto-acoustic emissions of cochlear distortion products

Otoacoustic emissions of cochlear distortion products (DPOAEs) were measured in normally hearing and hearing-impaired human ears. A total of 133 subjects (231 ears) were tested. Two puretone stimuli f1 and f2 were delivered to a sound probe fixed in the outer ear canal. The frequencies of the two primaries were chosen so that their geometric mean represented pure-tone audiometric frequencies. The otoacoustic emission was measured at the distortion product frequency 2f1-f2 by spectral averaging. For 199 ears, the levels of the primaries were 73 dBHL for L1 and 67 dBHL for L2. Statistical analysis was carried out in 77 ears of 46 subjects with normal hearing (average hearing levels at pure-tone audiometric thresholds less than or equal to 10 dBHL) and 36 ears of 25 subjects exhibiting near-normal hearing (average hearing levels at pure-tone audiometric thresholds less than or equal to 20 dBHL). The mean DPOAE amplitudes were similar in these two groups of ears. In 111 of these 113 ears (98.2%), DPOAEs were detected at three or more of the six tested frequencies between 1 and 6 kHz. DPOAEs were measured in more than 75% of ears at each frequency between 1-6 kHz and in more than 86% between 1-4 kHz. Eighty-six hearing-impaired ears of 44 subjects with sensorineural hearing loss formed the patient group. A highly significant correlation between pure-tone audiometric thresholds and DPOAE amplitudes was demonstrated in the frequency range of 1-4 kHz. Percentiles of DPOAE amplitudes were calculated in 22 ears with a mean pure-tone threshold less than or equal to 5 dBHL and in 12 specially selected pathological ears.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cochlear origin of early hearing loss in vestibular schwannoma

OBJECTIVE: To test whether early hearing loss (HL) is cochlear in origin in patients with vestibular schwannoma (VS). STUDY DESIGN: Retrospective case review in an academic tertiary referral center. METHODS: A group of 19 VS patients with normal/symmetrical hearing and a group of 20 VS patients with mild HL (threshold at any tested frequency better than 45 dB HL) on the tumor ear side. Differences of the amplitudes of the distortion products of otoacoustic emissions (DPOAEs) between the tumor ear and the nontumor ear were studied at frequencies of 1, 1.4, 2, 2.8, and 4 kHz. The Wilcoxon test was used to compare the ears for both groups and to test for possible differences in tumor size between groups. RESULTS: DPOAE amplitudes do not differ strongly between the ears in VS patients with normal/symmetrical hearing (two-sided P values: .050 at 1 kHz, .182 at 1.4 kHz, .378 at 2 kHz, .293 at 2.8 kHz, and .238 at 4 kHz) but are decreased compared with the nontumor ear at frequencies 1, 1.4, 2, and 2.8 kHz in VS patients with even mild HL (two-sided P values: .013 at 1 kHz, .007 at 1.4 kHz, .033 at 2 kHz, .010 at 2.8 kHz, and .156 at 4 kHz). Tumor size did not differ significantly between the two groups (P = .436). CONCLUSION: Amplitudes of DPOAEs begin to decrease even at the early stages of HL in VS patients, which suggests a cochlear origin of early HL in these patients. DPOAEs may be used in a clinical setting to monitor progression of cochlear damage at the early stages of hearing impairment in VS patients.     

Distortion product otoacoustic emissions in normal and hearing-impaired ears

Otoacoustic emissions of distortion products (DPOAE's) were recorded in normal and hearing-impaired human ears using relatively straightforward methods. Two pure-tone stimuli at fixed frequency levels of 73 dB HL for f1 and of 67 dB HL for f2 were used. The frequencies of the two primaries were chosen so that their geometric mean represented standard audiometric frequencies. Measurements of the emission amplitudes at 2f1-f2 and the adjacent noise floor were achieved by spectral averaging. A total of 101 subjects (199 ears) were tested. Seventy-seven ears in 46 subjects had normal hearing (hearing levels less than or equal to 20 dB at standard audiometric frequencies; average hearing levels, less than or equal to 10 dB). Thirty-six ears in 25 subjects had near-normal hearing (no hearing complaints, hearing levels less than or equal to 40 dB; average hearing levels, less than or equal to 20 dB). No significant differences in mean DPOAE values were apparent between these two groups of ears. All but two of these 113 ears (98%) showed emissions at three or more of the six frequencies tested between 1 and 6 kHz. Emissions were detected in more than 75% at each frequency between 1 and 6 kHz and in more than 85% between 1 and 4 kHz. A further 86 ears in 44 subjects exhibited varying degrees of sensorineural hearing loss caused by different pathologies. In general, emission amplitudes approximated the shapes of the audiograms, and a highly significant correlation between hearing thresholds and emission amplitudes was demonstrated in the frequency range of 1 to 4 kHz.(ABSTRACT TRUNCATED AT 250 WORDS)     

Distortion product otoacoustic emissions in sensorineural hearing loss

The measurement of distortion product otoacoustic emissions (DPOE), one of the types of otoacoustic emissions (OES) gives the possibility of frequency--specific, objective assessment of cochlear function. Data were collected from 67 ears with sensorineural hearing loss and 30 normally hearing ears as a control group. Percentage of DPOE response detected above the noise floor level was evaluated in relation to the pure-tone audiometric thresholds. Analysis of correlation coefficient between amplitude of DPOE and degree of hearing loss for respective frequencies was performed. DPOE were detected in significantly lower percentage in the group of ears with sensorineural hearing loss exceeding 60 dB HL. The amplitude of DPOE decreased with the degree of hearing loss detected in pure-tone audiometry. There was statistically significant correlation (r -0.65(-)-0.85) in all examined frequencies between DPOE and hearing loss (1-6 kHz).     

Distortion-product otoacoustic emissions in humans with high frequency sensorineural hearing loss

Distortion-product otoacoustic emissions (DPOAEs) and pure-tone behavioral thresholds were compared in 20 ears with normal hearing and in 20 ears with high-frequency sensorineural hearing loss. The purpose was to determine if DPOAE amplitude is associated with pure-tone behavioral threshold. Comparison of results from the two groups of ears indicated that DPOAEs were reduced in amplitude or were absent in ears with high-frequency hearing loss. The differences occurred at frequencies above 1,500 Hz. Comparing results from 750 to 8,000 Hz within the same ear revealed a frequency-related correspondence of elevated behavioral threshold to reduced DPOAE amplitude. When behavioral thresholds were better than 20 dB HL, DPOAE amplitude was within the range (+/- 2 SDs) determined for the ears with normal hearing. When pure-tone threshold was greater than 50 dB HL, DPOAEs were absent or were significantly attenuated in 16/17 subjects (94%). The association of emission level with behavioral threshold level was variable when threshold was between these two extremes. Results imply that the measurement of DPOAEs has clinical potential as a means of detecting hearing loss by frequency.     

Influence of nerve branch of origin and extracanalicular extension of the tumor on hearing after middle fossa removal of vestibular schwannoma

CONCLUSION: Neither nerve branch of origin nor extracanalicular (up to 1 cm) extension of a vestibular schwannoma (VS) influence the postoperative hearing outcome in patients operated via a middle cranial fossa (MCF) approach. OBJECTIVE: To test whether the nerve branch of tumor origin and an extracanalicular, up to 1 cm, tumor extension influences hearing outcome after MCF VS surgery. PATIENTS AND METHODS: This was a retrospective case review of 50 patients with postoperative pure-tone audiogram (PTA) performed later than 90 days after surgery. Twenty patients had a superior vestibular nerve (SVN) tumor and 27 patients had an inferior vestibular nerve (IVN) tumor. In three patients the nerve branch of origin of the VS could not be unequivocally determined. Thirty-four patients had a purely intracanalicular (IC) tumor and 16 patients had an extracanalicular extension in the cerebello-pontine angle. The differences between preoperative and postoperative air-conduction pure-tone hearing thresholds at 500, 1000, 2000, 3000, and 4000 Hz were compared between groups using the Mann-Whitney-Wilcoxon test. RESULTS: Neither vestibular nerve branch of origin nor extracanalicular tumor extension (up to 1 cm) caused any significant difference in the degree of postoperative hearing change at any of the tested PTA frequencies.     

Spatial hearing disability after acoustic neuroma removal

OBJECTIVES/HYPOTHESIS: Previous studies on hearing loss (HL) after acoustic neuroma removal concentrate mainly on pure-tone hearing results rather than hearing disability. Our objectives were to use the Speech, Spatial and Qualities of Hearing scale (SSQ), a comprehensively validated questionnaire, to characterize and quantify the auditory disabilities that patients experience with a profound unilateral HL after acoustic neuroma removal. STUDY DESIGN: Forty-four patients with profound unilateral HL after acoustic neuroma surgery completed the SSQ. Their findings were compared with those of a control population sample matched for age, sex, and hearing level in the better hearing ear. RESULTS: In comparison with controls, with use of analysis of variance, acoustic neuroma patients scored poorly on all items except for the identification of sounds and objects (P = .123). The greatest difficulties involved speech in the presence of noise, situations of multiple speech-streams and switching (such as listening to someone speaking and the television at the same time), the location of unseen objects, and increased listening effort (P < .05). CONCLUSION: This study demonstrates that, compared with a control population, these patients experience a significant range of auditory disabilities. It is important that clinicians be aware of the impact of such a profound unilateral HL and its potential to affect daily life. Patient counseling prior to surgery is essential, especially in patients whose loss of binaural hearing could constitute a major disability.     

An objective method of analyzing cochlear versus noncochlear patterns of distortion-product otoacoustic emissions in patients with acoustic neuromas

OBJECTIVES: To objectify the effects of retrocochlear disease on distortion-product otoacoustic emissions (DPOAEs) by developing a computer-based software strategy for classifying DPOAE patterns as cochlear or noncochlear and to evaluate the sensitivities of these techniques in a large series of patients with unilateral acoustic neuromas. STUDY DESIGN: Development of a novel, software-based method of DPOAE analysis, which was evaluated with data obtained from a retrospective review of the results from audiometric tests performed in a series of patients. METHODS: A computer-based software strategy was developed, using frequency-specific data from normal-hearing adults, for the purpose of distinguishing cochlear from noncochlear patterns of hearing loss, by determining the discrepancies between DPOAEs and behavioral audiometry. Preoperative pure-tone thresholds and DPOAEs from 97 patients with surgically confirmed acoustic neuroma were compared using an objective method and a standard, subjective technique that was considered to be the gold standard. The effects of bilateral hearing losses, such as noise-induced hearing loss and presbycusis, were accounted for during the analysis to isolate the effects of the tumors on hearing thresholds and DPOAEs. RESULTS: Overall, 55 (57%) of the tumor ears were assigned to the cochlear group (i.e., DPOAEs consistent with hearing thresholds), 40 (41%) to the noncochlear group (i.e., DPOAEs inconsistent with hearing thresholds), and 2 (2%) to an indeterminate group, using the subjective technique for classifying DPOAEs. There was no significant difference in the categorization of the patients with acoustic neuroma when employing the objective strategy. The objective algorithm, when modified to maximize the number of noncochlear identifications, led to assignments of 36 (37%) to the cochlear, 57 (59%) to the noncochlear, and 4 (4%) to the indeterminate categories. CONCLUSIONS: Subjective analysis of a large series patients with acoustic neuromas showed that the majority of ears with tumors demonstrated cochlear (57%), rather than non-cochlear (41%), patterns of DPOAEs. The computerized, software-based algorithm developed for differentiating cochlear from noncochlear patterns of DPOAEs in patients with retrocochlear disease had a maximum sensitivity of 59%. This value was significantly higher than that reported in previous studies.     

Risk factors for distortion product otoacoustic emissions in young men with normal hearing

The purpose of this study was to evaluate the possible effects of risk factors on distortion product otoacoustic emissions (DPOAEs) in young adult men with normal hearing. Four hundred thirty-six United States Marine recruit men (mean age = 19.2 years +/- 1.8 years; age range = 17-29 years) participated in this study. Questionnaires were given to each recruit to obtain demographic data and history of noise exposure, solvent exposure, smoking history, and hearing-related histories. Otoscopy, tympanometry, pure-tone air-conduction audiometry (2.0-8.0 kHz) and DPOAEs (2.3-8.0 kHz) were measured. DPOAE levels were lower in Not Hispanic or Latino recruits, in heavy smokers, in recruits who reported loud live music exposure and ringing in their ears after noise exposure. These differences were not statistically significant at all frequencies. Recruits with multiple risk factors had the lowest DPOAEs as compared to recruits with fewer, or no, risk factors; these differences were not statistically significant. Obtaining risk factor data as part of an audiometric evaluation is important even though the individual may have normal hearing.     

Vestibular investigations in acoustic neuroma

Forty-eight patients with surgically proven acoustic neuroma were examined preoperatively with a comprehensive battery of vestibular tests. In 87% of the patients, reduced caloric responses were measured on the side of the lesion. In 60% of the patients a non-responsive labyrinth was found. Spontaneous nystagmus was observed in 29% of the patients. A significant correlation with the size of the tumour was found in the occurrence of abnormal saccades in the calibration test, pathological smooth pursuit movements and the occurrence of gaze nystagmus, respectively. There was no correlation between the magnitude of the caloric response reduction and the mean hearing loss, which suggests that the hearing loss and the vestibular function loss do not occur synchronously. This study shows that in most cases of acoustic neuroma, the peripheral part of the vestibular system is severely disturbed. Abnormalities in the central and peripheral part of the vestibular system are more easily recognized with increasing tumour size. We conclude that a complete battery of vestibular tests is essential in combination with audiometric, neurologic and radiologic analysis for the early clinical diagnosis of acoustic neuroma.     

Hearing loss evaluation of Sjögren's syndrome using distortion product otoacoustic emissions

Sj?gren's syndrome (SS) is a cell-mediated immune disorder primarily affecting the exocrine glands and hearing loss may be the first otological manifestation of this autoimmune disease. In order to assess the degree of sensorineural hearing loss in SS, 22 female patients were examined by means of standard audiometric tests (pure-tone audiometry, acoustic reflexes and impedance testing) and using distortion product otoacoustic emissions (DPOAEs). The results indicated that only 36.3% of the patients had mild sensorineural hearing loss. Hearing level and distortion product threshold estimates were found to be significantly correlated. No relationship was found between the duration of the disease and the DPOAE and hearing threshold variables. The data suggest that SS may not directly cause sensorineural hearing loss.     

Influence of nerve branch of origin and extracanalicular extension of the tumor on hearing after middle fossa removal of vestibular schwannoma

Conclusion. Neither nerve branch of origin nor extracanalicular (up to 1 cm) extension of a vestibular schwannoma (VS) influence the postoperative hearing outcome in patients operated via a middle cranial fossa (MCF) approach. Objective. To test whether the nerve branch of tumor origin and an extracanalicular, up to 1 cm, tumor extension influences hearing outcome after MCF VS surgery. Patients and methods. This was a retrospective case review of 50 patients with postoperative pure-tone audiogram (PTA) performed later than 90 days after surgery. Twenty patients had a superior vestibular nerve (SVN) tumor and 27 patients had an inferior vestibular nerve (IVN) tumor. In three patients the nerve branch of origin of the VS could not be unequivocally determined. Thirty-four patients had a purely intracanalicular (IC) tumor and 16 patients had an extracanalicular extension in the cerebello-pontine angle. The differences between preoperative and postoperative air-conduction pure-tone hearing thresholds at 500, 1000, 2000, 3000, and 4000 Hz were compared between groups using the Mann–Whitney–Wilcoxon test. Results. Neither vestibular nerve branch of origin nor extracanalicular tumor extension (up to 1 cm) caused any significant difference in the degree of postoperative hearing change at any of the tested PTA frequencies.     

Hearing Loss Evaluation of Sjo¨gren's Syndrome Using Distortion Product Otoacoustic Emissions

Sjögren's syndrome (SS) is a cell-mediated immune disorder primarily affecting the exocrine glands and hearing loss may be the first otological manifestation of this autoimmune disease. In order to assess the degree of sensorineural hearing loss in SS, 22 female patients were examined by means of standard audiometric tests (pure-tone audiometry, acoustic reflexes and impedance testing) and using distortion product otoacoustic emissions (DPOAEs). The results indicated that only 36.3% of the patients had mild sensorineural hearing loss. Hearing level and distortion product threshold estimates were found to be significantly correlated. No relationship was found between the duration of the disease and the DPOAE and hearing threshold variables. The data suggest that SS may not directly cause sensorineural hearing loss.     

Audiometric patterns in ototoxicity of intra-arterial Cisplatin chemoradiation in patients with locally advanced head and neck cancer

This study describes audiometric patterns of ototoxicity in a consecutive series of patients uniformly treated with intra-arterial high-dose cisplatin chemoirradiation for advanced cancer of the head and neck. Air conduction thresholds were measured from 0.125 to 16 kHz and bone conduction thresholds were measured from 0.5 to 4 kHz. The overall audiometric pattern was characterized by maximum threshold shifts after the 2nd cisplatin infusion and a maximum total threshold shift at 8 kHz, irrespective of gender, age, pretreatment sensorineural hearing loss (SNHL) or subjective complaints during therapy. A hearing deterioration gradient was observed from (ultra-) high to low frequencies, worse with increasing pre-existent SNHL and with increasing cumulative dose of cisplatin chemoradiation. Cisplatin chemoradiation-induced hearing loss seemed to reach a plateau at higher levels (75-80 dB HL) for frequencies above 8 kHz compared to frequencies up to 8 kHz (45-60 dB HL). Recovery of SNHL was found after therapy in 27 ears characterized by extensive hearing loss at frequencies 1, 2 and 4 kHz.     

Hearing Preservation in Acoustic Neuroma Surgery

Introduction An acoustic neuroma (AN) is a neurinoma arisingfrom the vestibular branch of the VIIIth cranial nerve,thereby also termed “vestibular schawnnomas (VS)”.The histo-pathologically benign nature of this tumorgives the possibility for neuro-otologists to preserve thecochlear nerve and hearing in tumor resection sur-geries. Advances in imaging technology have greatlyimproved early diagnosis of ANs with very small sizesand made tumor removal without significantly insultinghearing. …     

High-frequency hearing influences lower-frequency distortion-product otoacoustic emissions

OBJECTIVES: The primary goal of this study was to test the ability of 2f1-f2 distortion-product otoacoustic emissions (DPOAEs) to detect reduced cochlear function in the presence of normal behavioral sensitivity. DESIGN: A prospective study was performed in normal-hearing young adults using simple and complex regression analyses to clarify the relationship between ultra-high frequency (UHF) hearing and DPOAE levels at lower frequencies, as well as the influence of hearing levels for frequencies within the conventional test range and subject age on this association. METHODS: Average DPOAE levels between 4 to 8 kHz, which were elicited by equilevel primary tones of low to moderate levels, were measured as level-frequency functions, or distortion-product (DP) grams, and related to the mean UHF hearing levels from 11.2 to 20 kHz. The median hearing level for the UHF hearing was used to separate subjects into good and poor UHF hearers. This distinction was then used to compare DPOAE levels from 4 to 8 kHz for the 2 groups to determine if UHF hearing status influenced DPOAE levels at lower frequencies. RESULTS: Simple regression analysis revealed that the 4-to 8-kHz DPOAE levels were significantly correlated with the pure-tone average (PTA) from 11.2 to 20 kHz. However, the PTA for 4 and 8 kHz was also significantly correlated with the PTA for UHF hearing. Further multiple regression analyses revealed that UHF hearing significantly and uniquely accounted for approximately 14% of the variance in DPOAE levels from 4 to 8 kHz for most of the primary-tone level combinations. In contrast, neither the PTA for the conventional hearing range nor subject age contributed significantly to the DPOAE variance. CONCLUSIONS: The findings suggest that UHF hearing influences DPOAEs at significantly lower frequencies because emissions are sensitive to subtle changes in outer hair cells not yet detected by pure-tone thresholds in this region or because alterations in the basal cochlea affect the generation of lower-frequency DPOAEs originating from more apical cochlear regions.     

Distortion product otoacoustic emissions in children at school entry: a comparison with pure-tone screening and tympanometry results

This study examined the test performance of distortion product otoacoustic emissions (DPOAEs) when used as a screening tool in the school setting. A total of 1003 children (mean age 6.2 years, SD = 0.4) were tested with pure-tone screening, tympanometry, and DPOAE assessment. Optimal DPOAE test performance was determined in comparison with pure-tone screening results using clinical decision analysis. The results showed hit rates of 0.86, 0.89, and 0.90, and false alarm rates of 0.52, 0.19, and 0.22 for criterion signal-to-noise ratio (SNR) values of 4, 5, and 11 dB at 1.1, 1.9, and 3.8 kHz respectively. DPOAE test performance was compromised at 1.1 kHz. In view of the different test performance characteristics across the frequencies, the use of a fixed SNR as a pass criterion for all frequencies in DPOAE assessments is not recommended. When compared to pure tone plus tympanometry results, the DPOAEs showed deterioration in test performance, suggesting that the use of DPOAEs alone might miss children with subtle middle ear dysfunction. However, when the results of a test protocol, which incorporates both DPOAEs and tympanometry, were used in comparison with the gold standard of pure-tone screening plus tympanometry, test performance was enhanced. In view of its high performance, the use of a protocol that includes both DPOAEs and tympanometry holds promise as a useful tool in the hearing screening of schoolchildren, including difficult-to-test children.     

Hearing loss in vestibular schwannomas: analysis of cochlear function by means of distortion-product otoacoustic emissions

Objective

We investigated cochlear function in a group of patients affected by vestibular schwannoma (VS), by means of recording distortion-product otoacoustic emissions (DPOAEs).

Methods

Between January 1996 and January 2007, we observed 183 patients affected by unilateral VS. DPOAEs, compared to the corresponding hearing thresholds, were subjectively classified into three categories: “compatible” with hearing function, “cochlear” and “retro-cochlear”. We also related the responses to some clinical variables (tumor size, intracanalicular tumor and radiologic appearance of the internal auditory canal). Statistical analysis was performed.

Results

In 137 cases (74.9%), DPOAEs were as expected based on audiometry responses, while in 11 patients (6%) a “cochlear” DP-gram was recorded and in 35 patients (19.1%) DPOAEs evidenced a “retro-cochlear” pattern. In eight cases we detected acoustic responses despite a profound hearing loss. No statistically significant data merged from the comparison between “cochlear” and “retro-cochlear” responses and the clinical variables.

Conclusion

Our results confirm that sensorineural hearing loss due to VS can be of sensory and/or neural origin. DPOAEs still remain just a complementary auditory test; nevertheless, in case of severe or profound unilateral hearing loss, recorded acoustic responses may be suspicious for the presence of a vestibular schwannoma.     

Early detection of ototoxicity using 1/6th-octave steps

The National Center for Rehabilitative Auditory Research has developed a protocol to provide early identification of ototoxicity for patients receiving ototoxic medications. The initial work involved patients with relatively good high-frequency hearing and resulted in the use of an individualized, sensitive frequency range separated by 1/6th-octave intervals. This protocol tested pure-tone frequencies at 1/6th-octave steps above 9 kHz, but only conventional audiometric frequencies were tested below 9 kHz. More recently, the testing protocol was expanded to include 1/6th-octave testing below 9 kHz. The primary question of interest was to determine whether adding 1/6th-octave test frequencies below 9 kHz would increase the ototoxicity detection rate for patients with poorer hearing. Results indicated 76 of the 210 (36.2%) ears that demonstrated initial ototoxic hearing change would have been missed or detected later if only conventional frequency testing was conducted.Therefore, for individuals with poorer hearing, expanding the use of the 1/6th-octave test protocol provides earlier identification of ototoxicity.     

Cochlear implantation in patients with neurofibromatosis type 2 and bilateral vestibular schwannoma.

OBJECTIVE: To investigate the results of cochlear implantation in patients with neurofibromatosis Type 2 (NF2) and bilateral vestibular schwannoma. STUDY DESIGN: Retrospective case review. SETTING: Three academic tertiary referral centers. PATIENTS: Seven patients with NF2 and bilateral vestibular schwannoma who lost hearing in at least one ear after treatment of their tumor (surgery or radiation therapy). INTERVENTION: Cochlear implantation after treatment of their vestibular schwannoma. MAIN OUTCOME MEASURE: Postimplantation audiometric scores (pure-tone average thresholds, consonant-nucleus-consonant (CNC) words/phonemes, Central Institute for the Deaf (CID) sentences, Hearing in Noise Test (HINT) quiet/noise, and Monosyllable, Trochee, Spondee (MTS) recognition/category tests), patient satisfaction, and device use patterns. RESULTS: The average age at implantation was 40 years (range, 16-57 yr). Follow-up ranged from 6 to 88 months after implantation. Three patients were implanted with residual useful hearing in the contralateral ear, whereas four patients had no hearing in the contralateral ear. Hearing loss was due to surgical excision of tumor (n=5) or gamma-knife radiotherapy (n=2). Postactivation pure-tone average thresholds in the implanted ear ranged from 30 to 55 dB (average, 32.5 dB), although speech reception testing varied considerably among subjects. Despite this variability, all patients continue to use the device on a daily basis. CONCLUSION: In selected cases of deafness in patients with NF2 where there has been anatomic preservation of the auditory nerve after acoustic neuroma resection or radiation therapy, cochlear implantation may offer some improvement in communication skills, including the possibility of open-set speech communication in some patients. These results compare favorably to the auditory brainstem implant offering an alternative for hearing rehabilitation in patients with NF2.