Biomedical subjects
Publications and source records attributed to W P Gibson.
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.
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.
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.
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.
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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.
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.
OBJECTIVE: Many reports have established that hearing-impaired children using the Nucleus 22-channel cochlear implant may show both significant benefits to lipreading and significant scores on open-set words and sentences using electrical stimulation only. These findings have raised questions about whether severely or severely-to-profoundly deaf children should be candidates for cochlear implants. To study this question, postoperative results for implanted children with different levels of preoperative residual hearing were evaluated in terms of speech perception benefits. STUDY DESIGN/SETTING: A retrospective study of the first 117 children, sequentially, to undergo implantation in the Melbourne and Sydney Cochlear Implant Clinics was undertaken. All children had been assessed by and received their implants in a tertiary referral centre. MAIN OUTCOME MEASURES: To assess aided residual hearing, the children were grouped into four categories of hearing on the basis of their aided residual hearing thresholds measured preoperatively. To assess benefits, the scores of children on standard speech perception tests were reviewed. As different tests were used for children with different ages and language skills, children were grouped into categories according to the level of postoperative speech perception benefit. RESULTS: The results showed that children in the higher categories of aided preoperative residual hearing showed significant scores on open-set word and sentence perception tests using the implant alone. For children in lower categories of aided residual hearing, results were variable within the groups. More than 90% of children with implants with aided residual hearing thresholds in the speech range above 1 kHz achieved open-set understanding of words and sentences. CONCLUSION: While the results of this preliminary study confirm previous findings of differential outcomes for children with different levels of preoperative residual hearing, they suggest that children with severe to profound hearing impairments should be considered for cochlear implantation.
Between April 1990 and June 1996, the extraosseous portion of endolymphatic sac has been removed from the affected ear in 77 patients suffering from Menière's disease. Removal of the extraosseous part of the endolymphatic sac without any drainage procedure did not increase the frequency or severity of the attacks of vertigo in any patient. The results of 43 patients with unilateral disease who had a follow-up period of two years are presented. Only eight of the patients had more than two recurrent attacks of vertigo lasting over two minutes within the two years after the surgery, and in three of these patients the severity of the attacks was greatly reduced. In 56 per cent of the operated ears, the hearing deteriorated at least 10 dBHL across five audiometric frequencies (250 Hz, 500 Hz, 1 kHz, 2 kHz and 3 kHz). To the author, endolymphatic sac removal appeared to provide better relief from vertigo than a simple drainage procedure with less tendency for recurrence several months or years after the initial surgery. At present, the statistical analysis of the results shows no significant difference between removal of the extraosseous portion of the endolymphatic sac and the "so called' endolymphatic sac drainage procedures.
A Cochlear Mini System 22 Channel cochlear implant extruded through the skin of a young girl. The implant was saved by use of a transposition flap. Extrusion appeared to be due to pressure necrosis from the implant on the overlying tissues. It is believed that this problem can be prevented by angulation of the implant before insertion so that it conforms to the curvature of the skull, so avoiding pressure on the tissues. The method of angulation is described.
The position of the jugular bulb (JB) is of great clinical significance to the otologist. A high and laterally situated jugular bulb may pose difficulties when dealing with the middle ear while a high and medially sited jugular bulb can create problems in neuro-otological surgery. This paper aims to study possible racial differences in the position of the jugular bulb. Fine-cut computed tomogram (CT) scans of temporal bones (in the axial plane) of 34 Caucasians and 34 Chinese were studied. The position of the jugular bulb was determined with reference to the midpoint of the lumen at the inferior limit of the cochlea (mpC). Of the 60 Caucasian and 58 Chinese temporal bones with identifiable jugular bulbs, 33 jugular bulbs of the Caucasian (55 per cent) and 34 jugular bulbs of the Chinese (58.6 per cent) were at the same height or higher than the mpC (p = 0.2; chi-squared test). The midpoint of the jugular bulb was 8.67 +/- 1.73 and 8.61 +/- 2.49 mm posterior to the mpC for the Caucasian and Chinese respectively (p = 0.2; t-test). However, the midpoint of the jugular bulb of eight Caucasian (24.2 per cent) and 22 Chinese (64.7 per cent) were medial to the mpC (p < 0.001; chi-squared test). Race does not influence the height of the jugular bulb nor its position in the sagittal plane but can influence whether a high jugular bulb is medially or laterally situated.
A straight, vertical post-aural incision for the 'Cochlear' multichannel cochlear implant has been evaluated in 52 patients (20 adults and 32 children). Nineteen of the children were under three years of age and five of these were under two years of age. The 7 cm long incision is placed approximately 3 mm behind the post-auricular crease and runs from the tip of the mastoid to a point 3 cm above the superior attachment of the pinna. The incision heals within several days. Because the incision is straight interruption of the blood supply to the flaps raised is the least possible. This also minimizes the possibility of scalp necrosis and implant extrusion. The likelihood of infection is reduced by the small size of the incision, minimal soft tissue dissection and small amount of dead space. Rapid healing has occurred in all cases despite infection in one.
Racial differences in the size, shape and structure of the cranium exist. This paper evaluates the importance of race in influencing the required sizes of craniotomies for gaining access to the lateral end of the internal auditory meatus without breaching the labyrinth via the retrosigmoid approach. Fine-cut CT scans of the temporal bones (axial cuts) of 34 Chinese and 34 Europeans were studied. The relevant distances and angles of the posterior cranial fossa and temporal bone were measured and statistically significant differences between the two races were found. This led us to the conclusion that a larger craniotomy is required in Europeans than in Chinese. In recommending an optimal size for a retrosigmoid craniotomy to remove acoustic neuromas completely and preserve hearing, the racial factor must be considered.
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A method of inserting a multielectrode cochlear implant into a cochlea that has become totally ossified following meningitis is described. The method, called the inlay technique, involves drilling a cleft so that the electrode array can be inserted along the position of the basal coil. First, the technique involves drilling along the scala tympani. Second, by drilling out the scala vestibuli, space is created to follow the basal turn of the cochlea without removing the overlying promontory. Five children have had this surgery, and between 12 and 15 electrodes were inserted. Two of the children have developed some open-set listening ability, with open-set sentence recognition scores of over 10%. One child has obtained open-set listening scores of over 50%.