Cochlin isoforms and their interaction with CTL2 (SLC44A2) in the inner ear.

Choline transporter-like protein 2 (CTL2) is a multi-transmembrane protein expressed on inner ear supporting cells that was discovered as a target of antibody-induced hearing loss. Its function is unknown. A 64 kDa band that consistently co-precipitates with CTL2 from inner ear extracts was identified by mass spectroscopy as cochlin. Cochlin is an abundant inner ear protein expressed as multiple isoforms. Its function is also unknown, but it is suspected to be an extracellular matrix component. Cochlin is mutated in individuals with DFNA9 hearing loss. To investigate the CTL2-cochlin interaction, antibodies were raised to a cochlin-specific peptide. The antibodies identify several cochlin polypeptides on western blots and are specific for cochlin. We show that the heterogeneity of the cochlin isoforms is caused, in part, by in vivo post-translational modification by N-glycosylation and, in part, caused by alternative splicing. We verified that antibody to CTL2 co-immunoprecipitates cochlin from the inner ear and antibody to cochlin co-immunoprecipitates CTL2. Using cochlear cross-sections, we show that CTL2 is more widely distributed than previously described, and its prominent expression on cells facing the scala media suggests a possible role in homeostasis. A prominent but previously unreported ribbon-like pattern of cochlin in the basilar membrane was demonstrated, suggesting an important role for cochlin in the structure of the basilar membrane. CTL2 and cochlin are expressed in close proximity in the inner sulcus, the spiral prominence, vessels, limbus, and spiral ligament. The possible functional significance of CTL2-cochlin interactions remains unknown.

Absent semicircular canals in CHARGE syndrome: radiologic spectrum of findings.

BACKGROUND AND PURPOSE: This paper describes the CT findings that characterize the middle and inner ear anomalies in coloboma, heart defects, choanal atresia, mental retardation, genitourinary, and ear anomalies (CHARGE) syndrome. With this information, neuroradiologists will be better prepared to provide clinically relevant information to their referring physicians regarding this rare syndrome. MATERIALS AND METHODS: CT studies from 13 patients were reviewed by 2 neuroradiologists with Certificate of Additional Qualification. Each ear was counted separately for a total of 26 ears. Middle and inner ear anomalies associated with CHARGE syndrome were categorized. Investigational review board approval was obtained. RESULTS: Twenty of 26 (77%) ears demonstrated cochlear aperture atresia. Four of these ears were evaluated with MR imaging and were found to lack a cochlear nerve. Twenty-one of 26 (81%) cochlea had some form of dysplasia. Six of 26 (23%) round windows were aplastic. Three of 26 (12%) round windows were hypoplastic. Twenty-one of 26 (81%) oval windows were atretic or aplastic. Fifteen of 26 (58%) vestibules were hypoplastic or dysplastic. There were 5 of 26 (19%) enlarged vestibular aqueducts. Twelve of 26 (46%) vestibular aqueducts had an anomalous course. All cases demonstrated absent semicircular canals. Twenty-three of 26 (88%) facial nerve canals had an anomalous course. Four of 26 (15%) tympanic segments were prolapsed. Three of 26 (12%) temporal bones had an anomalous emissary vein referred to as a petrosquamosal sinus. Twenty-one of 26 (81%) middle ear cavities were small. Twenty-three of 26 (93%) ossicles were dysplastic with ankylosis. Three of 26 (12%) internal auditory canals were small. CONCLUSION: The CT findings that correlate to the anomalies of CHARGE syndrome affect conductive as well as sensorineural hearing. Stenosis of the aperture for the cochlear nerve aperture on CT is suggestive of hypoplasia or absence of the cochlear nerve, which has been demonstrated in some cases by MR. Absence of the cochlear nerve would be a contraindication to cochlear implantation.

Pediatric cochlear implant patient performance as a function of age at implantation.

OBJECTIVE: The objective of this study was to examine the effect that age at implantation has on performance of children who received multichannel cochlear implants. STUDY DESIGN: This is a retrospective study of 295 children who were broken down into 5 age groups based on age at implantation: 1-3 years, 3-5 years, 5-7 years, 7-9 years, and 9-11 years. Speech perception test scores obtained 12, 24, and 36 months postactivation were compared for the 5 groups using repeated-measures analysis of variance. SETTING: This study was carried out at a tertiary academic medical center. PATIENTS: Subjects consisted of 295 children who ranged in age from 12 months to 10 years 11 months at the time they obtained their cochlear implant. INTERVENTION: All patients received their cochlear implant at a single implant facility. MAIN OUTCOME MEASURES: Performance on several speech perception tests was compared 12, 24, and 36 months postactivation. Performance was evaluated as a function of age at implantation. RESULTS: Patients in all 5 groups demonstrated improved scores when compared with scores obtained preoperatively with hearing aids. Repeated-measures analysis of variance (ANOVA) revealed a significant group by time interaction for 3 of the 5 measures. For all three of these measures, children implanted at younger ages demonstrated greater gains in speech perception over time than children implanted at older ages. CONCLUSIONS: These results are in agreement with those of previous studies indicating that early implantation facilitates improved development of speech perception skills in profoundly deaf children.

Antibodies to HSP-70 in normal donors and autoimmune hearing loss patients.

OBJECTIVE: To evaluate serum antibody to heat shock protein (HSP) 70 as a marker for autoimmune sensorineural hearing loss (AISNHL). DESIGN: Sera from 20 patients with rapidly progressive sensorineural HL and 20 control volunteers without HL were tested for antibody reactivity against multiple HSP 70 substrates. Substrates included recombinant human HSP (rHuHSP) 72, purified bovine brain heat shock cognate (HSC) 73 and HSP 72, as well as heat-shocked and non-heat-shocked protein extracts from bovine kidney (MDBK) cells. All serum donors were previously tested for antibody to guinea pig inner ear supporting cells; 17 of 20 patients but none (0 of 20) of the controls were positive. METHODS: Sera were tested using Western blots. RESULTS: Reactivity with rHuHSP 70 was observed in 16 patients and 17 controls. Similarly, 15 of 20 patients and 17 of 20 controls stained for both HSP 72 and HSC 73 from the bovine brain. When tested against the heat-shock-induced and control MDBK extracts, six patients and nine controls had greater reactivity with the induced HSP 72. CONCLUSION: The frequency of antibodies to HSP substrates did not differ in patients and controls. Prior studies reported that HSP 72 is the 68 kD antigen commonly detected by AISNHL sera. However, we show that HSP 72 antibodies are no more prevalent in patients than in normal controls. Thus, it is unlikely that the 68 kD protein is HSP 72. Therefore, HSPs are not appropriate substrates for serodiagnosis of AISNHL.

Implantation of the malformed cochlea.

OBJECTIVE: This study assesses the results of cochlear implantation in children with cochlear malformations. STUDY DESIGN: Retrospective, matched-pairs analysis of prospectively collected data. SETTING: University-based regional cochlear implant center. PATIENTS: Seventeen children with osseous cochlear malformations who had undergone implantation were matched and compared with a group of children with normal cochleae who had undergone implantation. INTERVENTIONS: All subjects received a multichannel cochlear implant and habilitation. MAIN OUTCOME MEASURES: All subjects were tested with the Early Speech Perception test, and the Glendonald Auditory Speech Perception tests for words and sentences. Patients were classified in a standardized speech perception category based on performance on the Early Speech Perception test. RESULTS: All subjects demonstrated improving performance on all measures of speech perception over time. Overall, the two groups showed no statistically significant differences in performance at 6 and 24 months. However, subjects with malformed cochleae evidenced slower rates of improvement than did their matched control subjects. Subjects with more severe malformations demonstrated poorer performance, but this may have been attributable to preoperative factors rather than to implant performance. CONCLUSIONS: Children with radiographic cochlear malformations benefit from cochlear implantation with multichannel devices. They ultimately perform as well as their matched counterparts with normal cochleae, although they may improve more slowly over time.

Labyrinthectomy versus vestibular neurectomy: long-term physiologic and clinical outcomes.

OBJECTIVE: To determine whether long-term vestibular compensation (VC) and clinical outcomes differ after transmastoid labyrinthectomy (TML) versus retrolabyrinthine vestibular neurectomy (RVNS). STUDY DESIGN: Prospective, observational study. SETTING: Tertiary care, university hospital. PATIENTS: Twenty-one subjects were studied several years after they were relieved of spontaneous episodic vertigo caused by peripheral vestibular disease by TML or RVNS. INTERVENTIONS: All patients had undergone TML or RVNS more than 2.5 years before the study and returned for physiologic and functional studies of vestibular compensation. MAIN OUTCOME MEASURES: Completeness of physiologic VC, as assessed by electronystagmography and rotational chair testing; performance on computerized dynamic posturography; pure-tone and speech audiometry; self-assessment of balance and hearing function with validated survey instruments. RESULTS: There were no differences in the incidence of physiologic VC or functional recovery between the TML and RVNS subjects. Although a majority of subjects in each group had evidence of incomplete vestibular compensation, there was no difference in self-assessment of balance or hearing handicap at long-term follow-up. CONCLUSIONS: Long-term clinical balance and hearing outcomes are equivalent when TML and RVNS successfully cure spontaneous, episodic vertigo. There is a high incidence of incomplete VC after both procedures, though this does not usually produce a significant balance handicap.

Multichannel cochlear implantation in visually impaired patients.

OBJECTIVE: To evaluate the outcome of cochlear implantation in patients with severe to profound hearing loss and visual impairment. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center with a large cochlear implant program. PATIENTS: Six adults and two children with severe or profound hearing loss and significant visual impairment underwent multichannel cochlear implantation. Follow-up period ranged from 6 months to 9 years. Case history, etiology of visual and hearing loss, and benefit from cochlear implant were evaluated. INTERVENTIONS: Cochlear implantation and subsequent rehabilitation. MAIN OUTCOME MEASURES: Speech perception measures were selected based on the patient age and cognitive abilities. Identical measures were used in each patient before and after implantation. RESULTS: As a group, patients did well after cochlear implantation. There was significant improvement in speech perception when compared with the score before implantation. CONCLUSIONS: Cochlear implants can play a significant rehabilitative role in patients with severe visual and auditory impairment. Additional skills are required by the implant team for rehabilitation of patients with multiple sensory deficits.

Diagnosis and initiating treatment for peripheral system disorders: imbalance and dizziness with normal hearing.

Disorders affecting the peripheral vestibular system commonly involve the peripheral auditory system causing hearing loss. There are a number of disorders, however, that selectively involve the peripheral vestibular system causing dizziness without hearing loss. These disorders include benign paroxysmal positional vertigo, vestibular neuritis, recurrent vestibulopathy, familial vestibulopathy, and bilateral idiopathic vestibulopathy. This article reviews these disorders and their diagnosis and management.

Recurrence of acoustic neuroma after incomplete resection.

OBJECTIVE: To determine the risk of recurrent tumor in patients after incomplete resection of acoustic neuroma. STUDY DESIGN: Retrospective case review. SETTING: A tertiary referral center. PATIENTS: Thirty-nine patients were identified who underwent incomplete resection of acoustic neuroma between January 1988 and December 1993, and had a minimum follow-up of 3.5 years, at a mean of 6.2 years (range 3.5-10.2 years). INTERVENTION: Regular follow-up. using either computed axial tomography or magnetic resonance imaging yearly. MAIN OUTCOME MEASURES: Growth of residual tumor as determined by the increase in its greatest dimension on follow-up imaging studies and the necessity for additional treatment. RESULTS: Tumor regrowth occurred in 17 patients (44%). Ten patients (26%) required additional treatment during the follow-up period. CONCLUSION: This study suggests that incomplete resection of acoustic neuroma is associated with a significant risk of recurrent tumor requiring subsequent intervention.

Minimizing wound complications in cochlear implant surgery.

OBJECTIVE: An extended postauricular incision has replaced the standard C-shaped scalp flap for cochlear implant surgery at our institution. The postoperative wound complication rates of the two incisions were evaluated. STUDY DESIGN: This study was a retrospective case review. SETTING: This study was performed in a tertiary referral center. PATIENTS: A total of 256 adult and pediatric patients who underwent cochlear implantation during a 10-year period (1986 to 1996) were reviewed. MAIN OUTCOME MEASURE: Postoperative wound complications were identified. Major complications included flap necrosis, wound dehiscence with or without implant exposure, and wound infection requiring hospitalization. Hematoma, seroma, or superficial wound infections were considered minor complications. RESULTS: There were 6 major and 6 minor complications among 116 patients with the standard scalp flap (complication rate, 10.3%). There was only 1 minor complication among 140 implants using the postauricular incision (0.7%). CONCLUSION: The extended postauricular incision appears to significantly reduce the incidence of wound complications in cochlear implant surgery.

Successful cochlear implantation in a patient with MELAS syndrome.

OBJECTIVE: To describe methods of assessing cochlear implant candidacy in patients with potentially significant peripheral and central nervous system (CNS) degeneration. STUDY DESIGN: A patient with a degenerative CNS disease (MELAS syndrome) undergoing evaluation for cochlear implantation is described. SETTING: This study took place at a tertiary care center. PATIENT: A patient with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) who had cortical blindness and profound sensorineural hearing loss was evaluated and rehabilitated with cochlear implantation. INTERVENTIONS: Pure-tone audiogram, behavioral responses to promontory stimulation electrical auditory brainstem response, and electrically evoked middle-latency responses (MLRs) were used to assess eighth nerve, auditory brainstem, and cortical auditory pathways. Cochlear implantation with Cochlear Corporation mini 22 implant was performed. RESULTS: Repeatable electrically evoked MLRs and behavioral responses to promontory stimulation documented the presence of auditory cortical responses. Successful implantation resulted in open set speech recognition and communication using the auditory/oral mode. CONCLUSION: This report describes successful implantation in a patient with MELAS syndrome and demonstrates the ability to preoperatively confirm the integrity of brainstem and cortical auditory pathways despite significant CNS degeneration.

Familial Mondini dysplasia.

OBJECTIVES/HYPOTHESIS: To determine the mode of inheritance of familial nonsyndromic Mondini dysplasia. STUDY DESIGN: Correlative clinical genetic analysis of a single kindred. METHODS: Clinical history, physical examination, audiologic analysis, computed tomography of the temporal bones, and cytogenetic analysis. RESULTS: The male proband, three affected sisters, and an affected brother are offspring of unaffected parents. The mother and an unaffected brother have audiologic findings suggestive of heterozygous carrier status for a recessive hearing loss gene. CONCLUSIONS: Pedigree analysis indicates autosomal recessive inheritance in this family. The observed inheritance and clinical, audiologic, and radiologic findings are different from those previously described for another family with nonsyndromic Mondini dysplasia. The phenotype in this study family therefore represents a distinct subtype, indicating clinical and genetic heterogeneity of this disorder. This information should facilitate future molecular linkage analyses and genetic counselling of patients with inner ear malformations.

Hearing improvement after resection of cerebellopontine angle meningioma: case study of the preoperative role of transient evoked otoacoustic emissions.

In a retrospective case study of a patient with a right-sided cerebellopontine angle mass lesion, transient evoked otoacoustic emissions were robustly present despite a severe to profound sensorineural hearing loss and abnormal auditory brainstem response. These results were interpreted as suggestive of a neural site of lesion, and the potential for planned, preserved, or improved hearing by a suboccipital surgical craniotomy was considered. A gross total resection was successful. Three years postoperatively, the patient has normal hearing sensitivity and word recognition ability.

AP30, a differential protein marker for perilymph and cerebrospinal fluid in middle ear fluid, has been purified and identified as human apolipoprotein D.

Using two-dimensional (2-D) gel electrophoresis, human perilymph and cerebrospinal fluid have been shown to be highly enriched for an acidic protein with MR 30,000, we designated it as AP30. The protein exhibits charge heterogeneity, with at least eight isoforms visible between pI 4.5 to 5.5 on 2-D gels. Purification of the protein was carried out by ammonium sulfate precipitation, polybuffer exchanger column chromatofocusing, and acetone fractional precipitation. The resulting preparation also contains eight spots in the acidic area of 2-D gels, and one broad band located at Mr 30,000 by SDS-PAGE. Digestion of AP30 with neuraminidase causes the isoforms to shift to a more basic position and to consolidate into two primary spots, indicating that AP30 is a variably sialylated glycoprotein. Amino acid analysis of AP30 revealed an amino acid content very similar to that of human apolipoprotein D. Attempts to determine the amino acid sequence demonstrated that the N-terminus is blocked. Edman sequencing of two peptide fragments, generated by cyanogen bromide cleavage of AP30, both revealed sequences having 100% identity to human apolipoprotein D. Western blot analysis of AP30 with the antibody against authentic human apolipoprotein D demonstrated a high degree of cross-reactivity. These studies indicate that AP30 from human perilymph and cerebrospinal fluid is a member of the apolipoprotein D family.

Spontaneous chronic epidural pneumocephalus resulting from hyperpneumatization of the cranium causing mass effect: case report.

OBJECTIVE AND IMPORTANCE: We report a rare case of spontaneous epidural pneumocephalus resulting from an unusual boney defect caused by hyperpneumatization of the cranium. The pneumocephalus was also unusual for its chronicity and significant mass effect. CLINICAL PRESENTATION: A 49-year-old man presented with a 3-year history of diffuse headaches and sensation of air movement in his sinuses on the right side. An evaluation for suspected sinusitis using computed tomography determined extensive pneumatization of most of the cranium, a large accumulation of epidural air, and a critical degree of brain shift. INTERVENTION: A right frontoparietal-temporal craniotomy with an osteoplastic bone flap was performed. The floor of the middle cranial fossa and the inner table of the bone flap were extensively debrided of air cells. A large pericranial flap was turned down over the floor of the middle cranial fossa and was held in place by a fat graft. After closing the craniotomy, a tympanostomy tube was placed into the right tympanic membrane. CONCLUSION: The incidence of hyperpneumatization of the cranium seems to be very low. Hyperpneumatization when present, however, can cause spontaneous intracranial pneumocephalus. Based on the literature and the success of this case, the optimal management is surgical obliteration of the involved air cells.

Performance with the 20 + 2L lateral wall cochlear implant.

OBJECTIVE: The purpose of this study was to investigate the operating characteristics of the Nucleus 20 + 2L lateral wall cochlear implant including speech recognition results. STUDY DESIGN: This was a prospective randomized study involving five different modes of stimulation. SETTING: This study was carried out in an academic, tertiary referral center. PATIENTS: The patients included in this study were adult cochlear implant candidates ages 44-74 years. Length of deafness ranged from 1 to 58 years with a variety of etiologies. INTERVENTIONS: All patients were implanted with a 20 + 2L implant, which includes an intrascalar electrode array and an apically placed extracochlear, titanium encased ball electrode in contact with the endosteum of the apical turn. All patients underwent psychophysical and speech recognition testing in five different modes of electrode configuration. MAIN OUTCOME MEASURE(S): The main outcome measures included thresholds, comfort levels, dynamic ranges, and speech recognition results obtained in five electrode configuration modes. RESULTS: Thresholds were significantly lower (repeated measures ANOVA) in both monopolar conditions when compared to bipolar mode of stimulation. A binomial statistical analysis indicated that in five of nine patients activated in all five modes of stimulation, the monopolar modes of stimulation resulted in improved speech recognition scores. CONCLUSIONS: The results of the study demonstrate the feasibility of the use of an apical lateral cochlear wall electrode in conjunction with an intrascalar electrode array. It further demonstrated the superiority of monopolar stimulation in selected patients.

Evaluation of clinical measures of equilibrium.

OBJECTIVE: Evaluate the clinical utility of several simple measures of static and dynamic equilibrium in human subjects. In particular, one proposed clinical measure, the Clinical Test of Sensory Integration and Balance (CTSIB) was compared with dynamic posturography for the measurement of postural control capabilities. STUDY DESIGN: Cross-sectional study of normal subjects and prospective observational study of the same performance measures in vestibular disorder patients. SETTING: Academic tertiary care referral center. PARTICIPANTS: Data were collected for all test measures from a group of normal subjects (ages, 20 to 79 years), as well as for a group of patients undergoing treatment for vestibular dysfunction. RESULTS: Data suggest that several semiquantitative clinical tests of static and dynamic equilibrium can be helpful in evaluating and monitoring patients with chronic vestibular dysfunction. The CTSIB results seem to correlate well with dynamic posturography, suggesting that this measure may be useful in identifying patients with abnormal postural control. Formal dynamic posturography testing appears to be more sensitive in detecting abnormal postural control and more exact in defining the specific pattern of dysfunction. CONCLUSION: Simple clinical measures of static and dynamic equilibrium can reliably distinguish vestibular disorder patients from normal subjects. Dynamic posturography continues to play an important role in the functional evaluation and management of vestibular disorder patients.

Disability from vestibular symptoms after acoustic neuroma resection.

OBJECTIVE: This study aimed to evaluate the recovery of balance function after acoustic neuroma resection. STUDY DESIGN: This study was a retrospective case review with patient survey. SETTING: The surgery was conducted at a tertiary referral center. PATIENTS: Patients who underwent surgical resection of acoustic neuroma and had preoperative vestibular function testing were eligible for entering the study. INTERVENTIONS: All patients received surgical resection of acoustic neuroma. Patients treated since 1990 received postoperative vestibular habituation exercises. MAIN OUTCOME MEASURES: These included postoperative symptom and disability scores, dizziness handicap inventory (DHI) total and subset scores, time after surgery at which patients were able to walk independently, whether patients returned to their usual professional responsibility, and time to return to full activities at work. RESULTS: Significant correlation was found between several preoperative symptoms and vestibular testing results and the resulting postoperative disability from dizziness. CONCLUSIONS: This information may be helpful in counseling patients before surgery with respect to the degree of postoperative dysequilibrium and may suggest that the clinician should initiate more aggressive vestibular rehabilitation exercises in patients who may be at greater risk of having persistent dysequilibrium develop after surgery.

Electrically evoked auditory potentials: current clinical applications in children with cochlear implants.

OBJECTIVE: To summarize the current applications of auditory evoked potential in children with cochlear implants and candidates for implantation. PATIENTS AND METHODS: Perioperative transtympanic EABR is used routinely for ear selection and to establish the electrical stimulability of the ear intended to be implanted. The perioperative transtympanic EABR is supplemented with EABR obtained immediately following the insertion of the electrode array and the seating of the implant's receiver. Postoperatively, EABR and averaged electrode voltages are used effectively to properly adjust the implant stimulus parameters and to determine whether the implant is functioning adequately. Postoperatively, cognitive evoked potentials to speech and tonal stimuli may also be obtained. RESULTS: EABR results have contributed to effective implant placement and function. There were several significant correlations between speech recognition and cognitive evoked potential. CONCLUSION: These measures help assure proper implant function and effective stimulus delivery.

Cochlear implantation of children with minimal open-set speech recognition skills.

OBJECTIVE: The purpose of this study was to evaluate the postoperative performance of 12 children who demonstrated some open-set speech recognition skills before receiving a Nucleus multichannel cochlear implant with a view toward expanding the selection criteria for cochlear implant candidacy to include children who derive minimal benefit from amplification. DESIGN: Pre- and postoperative performance of two groups of children were compared. Group 1 consisted of 12 children who demonstrated some open-set speech recognition skills before receiving a Nucleus multichannel cochlear implant (Borderline group). Group 2 consisted of 12 children who demonstrated no open-set speech recognition skills before implantation with a Nucleus device (Traditional group). In all children, candidacy was determined based on preimplant binaural aided performance. For most subjects, the poorer ear was selected for implantation. Mean pre- and postoperative speech recognition scores of the Borderline subjects were compared to determine the benefit provided by their cochlear implants. Secondly, matched-pair analyses were used to compare the mean speech recognition scores obtained by the Borderline and Traditional subjects. RESULTS: The scores of the Borderline group improved significantly on five of six speech recognition measures when 6 mo postoperative scores obtained with the implant were compared with preoperative test scores obtained with hearing aids. By the 12 mo postoperative interval, the scores of the Borderline group had improved significantly (p < 0.05) on all six measures. In contrast, scores obtained by the Traditional group had improved significantly on three of six measures at both the 6 and 12 mo postoperative intervals. Comparison of postoperative test scores revealed that the Borderline group scored significantly higher than the Traditional group on three of six measures at the 6 mo test interval and on six of six measures at the 12 mo test interval (p < 0.05). CONCLUSIONS: The findings of this study indicate that both groups derive significant benefit from their cochlear implants. Although the mean preoperative audiograms for the implanted ears did not differ significantly for the two groups of subjects, members of the Borderline group exhibited significantly better speech recognition skills than the Traditional group during the first year after implantation. These findings suggest that the increased auditory experience of the Borderline subjects positively influenced their performance with a cochlear implant. The authors advocate that the selection criteria used to determine pediatric cochlear implant candidacy be broadened to include consideration of children who demonstrate minimal open-set speech recognition skills.