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Biomedical subjects

W P Gibson

Publications and source records attributed to W P Gibson.

At least 19 recordsLinked to original sources
PubMed2001

Variation in speech perception scores among children with cochlear implants.

OBJECTIVE: The objective of this study was to identify common factors affecting speech perception scores in children with cochlear implants. DESIGN: Speech perception data for 167 implanted children were collected at two cochlear implant centres in Melbourne and Sydney. The data comprised audition-alone scores on open-set word and sentence tests. Children were selected on the basis that they had a Nucleus 22-electrode cochlear implant. The average age of the children was 5 yr. Information was also collected about 12 factors that may have influenced speech perception scores for each child. Analysis of covariance was used to identify factors that significantly affected speech perception scores. Pearson pairwise correlation coefficients were also calculated for all factors analyzed. RESULTS: The analyses in this study identified factors that accounted for 51%, 34%, and 45% of the variance in phoneme, word and sentence perception scores. Scores decreased by 1.4 to 2.4% per year of profound deafness prior to implantation. Children who normally use oral communication scored significantly higher than children normally using sign or simultaneous oral and sign communication. Children implanted in Sydney scored higher on average than children implanted in Melbourne. CONCLUSIONS: The results show that a significant part of the variation in speech perception scores is systematically related to audiological and environmental factors for each child. The reasons for significant differences between children using different communication modes or from different clinics were not identified.

Adolescent↗
PubMed2000

Electrocochleography in the diagnosis of Meniere's disease.

This study prospectively analyses electrocochleography (ECoG) recordings obtained from ears demonstrating symptoms highly suggestive of Meniere's disease. Comparison is made with ECoG recording from ears in which the diagnosis of Meniere's is considered unlikely (control ears). Electrocochleograph recordings were made through a transtympanic recording needle, situated in the round window niche. Analysis was made of the 1 kHz tone burst summation potential (SP) and the summation potential:action potential (SP/AP) ratio response to a 90 dB click. All patients were prospectively awarded a Meniere's score based on a 10-point scale, and comparison was made between ears awarded a score of 7 or greater (Meniere's ears; n > 500), and ears awarded a score 3 or less (control ears; n > 900). Results demonstrate a significant difference in the 1 kHz SP response, and the SP/AP ratio, between "control" and "Meniere's" ears. Furthermore, we show that SP negativity is proportional to the amplitude of the AP click response, and in patients producing an AP click amplitude exceeding 10 V, sensitivity of the tone burst test approaches 85%. This study provides further evidence suggesting the useful role of electrocochleography in determining a diagnosis of endolymphatic hydrops. and demonstrates improved sensitivity of the 1 kHz SP response, compared with SP/AP click ratio, in the diagnosis of Meniere's disease.

Action Potentials↗
PubMed2000

Performance after cochlear implantation: a comparison of children deafened by meningitis and congenitally deaf children.

The speech perception and speech production performance following cochlear implantation of congenitally deaf children and children deafened by meningitis were analysed. Three groups consisting of 70 congenitally deaf children, 22 children deafened by meningitis before two years of age and 14 children deafened by meningitis after two years of age were compared. The group deafened by meningitis after two years of age demonstrated significantly better speech perception than the other two groups. Their speech production appeared better but did not achieve statistical significance compared with the other two groups. There was no significant difference in either speech perception or speech production between the congenitally deaf group and the group deafened by meningitis before two years of age.

Child, Preschool↗
PubMed2000

The influence of residual high-frequency hearing on the outcome in congenitally deaf cochlear implant recipients.

OBJECTIVE: To show that congenitally deaf children who receive a cochlear implant between 10 and 15 years of age find it significantly more difficult to learn the new signal, and that a history of sound detection at high frequencies with hearing aids is predictive of better outcomes in these children. STUDY DESIGN: A retrospective study using a within-subjects design. SETTING: Children's Cochlear Implant Centre, Sydney (CCIC), Royal Prince Alfred Hospital, and the New Children's Hospital in Westmead are tertiary referral centers. PATIENTS: Forty-five congenitally deaf patients were grouped according to their age (in years) at implantation into group 1 (aged 10-15), group 2 (aged <10), group 2a (aged 6-9), and group 2b (aged 3-5). Within each group, individuals with previous hearing between 2 and 4 kHz before receiving a cochlear implant were identified, and their mean results were compared with those in their respective age-matched groups. INTERVENTIONS: Surgical implantation, intensive weekly habilitation at the CCIC. MAIN OUTCOME MEASURES: Speech perception, speech production, and language measures were compared. Questionnaires and telephone interviews were conducted. RESULTS: Group 2 (age <10 years) consistently outperformed group 1 (10-15 years) on all outcome measures, and most of them learned to converse without lipreading. In group 1, children with previous aided hearing at high frequencies displayed exceptional gains in speech perception and speech production, with reduced dependence on lipreading. Previous high-frequency hearing does not benefit group 2. CONCLUSIONS: Implant recipients aged 10 to 15 years experience more difficulty than younger children during the initial periods of device use. A history of high-frequency hearing before implantation in these individuals correlates with more rapid improvement.

Adolescent↗
PubMed2000

Abnormal positive potentials in round window electrocochleography.

OBJECTIVE: To describe an atypical waveform, termed an abnormal positive potential (APP), on round window electrocochleograms (RW ECochG) of children and to relate its occurrence to clinical history. STUDY DESIGN: APPs were identified prospectively, and a retrospective analysis was made of these patients' clinical histories, audiograms, and auditory outcomes (hearing aid, cochlear implant, or nonauditory communication) SETTING: Tertiary referral teaching hospital, day surgery and clinics. PATIENTS: All 431 children <110 months of age suspected of a severe to profound hearing loss who underwent RW ECochG from January 1993 to August 1997. INTERVENTION: Diagnostic RW ECochG for auditory threshold estimation. MAIN OUTCOME MEASURE: The presence on the RW ECochG of the APP: an early positive potential in the absence of a compound action potential (CAP). RESULTS: An APP was observed in 34 children. The APP was most marked in response to clicks and 8-kHz tones. The APP click threshold averaged 70 dB hearing loss. The brainstem evoked potential of these children showed an absence of waves, or a broad positive wave with no subsequent waves. Twenty-nine of 30 behavioral audiograms obtained were indicative of severe to profound hearing loss. Auditory outcomes were available from 26 children; 45% of them derived no help from a hearing aid, and 8 children received a cochlear implant. Clinical factors frequently associated with APP were prematurity in combination with kemicterus or hypoxia. CONCLUSIONS: APP thresholds were lower than neural thresholds or behavioral thresholds. Children with APP need close follow-up, because half of those studied needed nonauditory strategies to develop effective communication.

Audiometry, Evoked Response↗
PubMed1999

Positioning of the receiver-stimulator for the CI-24M cochlear implant in infants.

A new cochlear implant (CI-24M) has recently been released by Cochlear Ltd. The shape and size of the receiver-stimulator differs from that of the CI-22M. Infants as young as one year of age are now receiving cochlear implants. We have examined the likely effect of skull growth following the implantation of a CI-24M cochlear implant in an infant of this age.

Child↗
PubMed1999

Surviving cochlear function in the presence of auditory nerve agenesis.

This case reports electrophysiological evidence for cochlear function in a child with radiological evidence of bilateral auditory nerve agenesis or severe hypoplasia. The diagnosis of auditory nerve agenesis was supported by a bilateral atresia of internal auditory canals on computed tomography (CT) scan and magnetic resonance imaging (MRI) absent auditory brainstem responses and absent behavioural responses to sound. Despite the apparent absence of an auditory nerve or spiral ganglion, electrocochleography revealed surviving cochlear function at 70-80 db HL and an abnormal electrocochleographic waveform. This case demonstrates that cochlear function may develop without afferent, or efferent innervation. It also emphasizes that cochlear function may occur in the presence of profound deafness.

Abnormalities, Multiple↗
PubMed1999

Hearing loss associated with large internal auditory meatus: a report of five paediatric cases.

This paper describes the abnormality of a large internal auditory meatus (LIAM). Computed tomography (CT) scans show the otic capsule to be affected by a widened, bulbar internal auditory meatus with loss of or reduction of the bony wall dividing the lateral fundus of the meatus from the cochlea. The vestibule is abnormally dilated. We report five cases of children with LIAM and profound hearing loss. Three of these children are girls and two children were boys. Three had congenital progressive hearing loss, one of these had an accompanying large vestibular aqueduct and dysplasia of the cochlea. Two patients had had meningitis resulting in profound loss.

Child, Preschool↗
PubMed1999

Meniere's disease: the incidence of hydrops in the contralateral asymptomatic ear.

OBJECTIVE: This study analyzes the incidence of endolymphatic hydrops in the asymptomatic contralateral ear of patients with classic Meniere's disease. STUDY DESIGN: A retrospective study of 3000 subjects who underwent electrocochleography (ECOG) from 1988 to 1998. METHODS: The presence of endolymphatic hydrops was determined by use of ECOG recordings, which were made through a transtympanic recording needle situated in the round window niche. Analysis was made of the 1-kHz toneburst summation potential (SP), and comparison was made between asymptomatic contralateral "Meniere's ears" (n = 144) and asymptomatic normal "control ears" (n = 114). RESULTS: Results demonstrated that more than 10% of the contralateral asymptomatic Meniere's ears have an ECOG recording that is highly suggestive of the presence of endolymphatic hydrops. In contrast, less than 2% of the control population demonstrate abnormal ECOG recordings. Furthermore, 15% of the population of contralateral Meniere's ears lie above the 95th percentile of the control population for 1-kHz tone-burst (100 dB) SP negativity. CONCLUSIONS: This study suggests that a high percentage of patients who have what appears to be unilateral Meniere's disease have evidence of endolymphatic hydrops in the contralateral asymptomatic ear. This finding has important clinical relevance for the management of patients in whom destructive surgery is planned and further highlights the importance of electrocochleography in the diagnosis and management of this disease process.

Audiometry, Evoked Response↗
PubMed1998

Cochlear origin of hearing loss in MELAS syndrome.

There have been few studies investigating the mechanism and nature of the hearing loss that occurs in the mitochondrial disorders. We studied 18 patients with the MELAS A3243G point mutation from four different kindreds. Pure tone audiometry, speech discrimination testing, acoustic reflexes, tympanometry, and brain stem auditory evoked responses were performed to localize the site of pathology in the auditory pathways. In 12 patients, we performed electrocochleography and otoacoustic emissions to assess cochlear involvement. Neuroimaging and promontory nerve stimulation were performed to exclude retrocochlear pathology. Audiological testing confirmed sensorineural hearing loss in 14 of the 18 patients studied; hearing loss was usually gradual in onset, was symmetrical, and initially affected the higher frequencies. In some patients, there were features that distinguished the hearing loss from presbyacusis, including a young age at onset, asymmetrical involvement, stepwise progression, and partial recovery. We treated one patient who had profound bilateral hearing loss with cochlear implantation; this restored good functional hearing. Hearing loss in MELAS syndrome appears to be due to dysfunction of the cochlea, probably resulting from metabolic failure of the stria vascularis and outer hair cells. Cochlear implantation is a therapeutic option worth considering in those patients who become deaf.

Adolescent↗
PubMed1997

Further experience with a straight, vertical incision for placement of cochlear implants.

Experience with a straight, vertical incision for cochlear implantation in 168 patients of all ages is reported and comparison made with previous experience using a 'C' shaped incision in 173 patients with regard to complications encountered. With the straight incision the only complication was a wound infection which settled in one week; this is in contrast to the 'C' shaped incision, which was associated with a number of serious complications. The straight incision also compared favourably with the other incisions commonly used for cochlear implantation and appears to offer advantages over them.

Adolescent↗
PubMed1997

Use of transtympanic round window electrocochleography for threshold estimations in children.

OBJECTIVE: This study aimed to evaluate the efficacy of round window electrocochleography for the estimation of hearing thresholds in difficult-to-test children. STUDY DESIGN: The study was a retrospective analysis. SETTING: A standard day-stay operating room was used. PATIENTS: Round window electrocochleography was performed on 198 children between January 1993 and January 1996. INTERVENTION: The intervention was diagnostic. MAIN OUTCOME MEASURE: Clinically reliable pure-tone audiograms were obtained in 101 patients (50.9%) for comparisons of electrocochleography and behavioral thresholds. RESULTS: The mean differences between electrocochleography and behavioral thresholds at 0.5, 1, 2, and 4 kHz were less than 6 dB. Ninety-seven percent of the results were within +30 to -30 dB, and approximately 86% of the results were within +20 to -20 dB. Good correlation coefficients of 0.83, 0.84, 0.91 and 0.88 were found between electrocochleography and behavioral thresholds at 0.5, 1, 2, and 4 kHz, respectively. Only 2 of 395 ears were complicated postoperatively by suppurative otitis media. There were no anesthetic complications. CONCLUSION: Round window electrocochleography can be used in conjunction with other audiometric methods for threshold estimations in the difficult-to-test children and as part of the preoperative assessment for cochlear implantation.

Adolescent↗
PubMed1997

Pathophysiologic theories in the etiology of Meniere's disease.

The etiology of the attacks of vertigo that occur in Meniere's disease is discussed in this article. None of the current theories remain tenable in view of recent findings concerning the physiology and pathophysiology of the cochlea and endolymphatic sac. A new theory suggests that a narrowed duct becomes obstructed by debris that is cleared by a combination of the secretion of hydrophillic proteins within the sac and a hormone, saccin, that increases the volume of endolymph within the cochlea. It is proposed that the sudden restoration of longitudinal flow initiates the attacks of vertigo.

Endolymphatic Sac↗