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Biomedical subjects

N J Coker

Publications and source records attributed to N J Coker.

At least 19 recordsLinked to original sources
PubMed2001

Histopathology of cochlear implants in humans.

The insertion of an intrascalar electrode array during cochlear implantation causes immediate damage to the inner ear and may result in delayed onset of additional damage that may interfere with neuronal stimulation. To date, there have been reports on fewer than 50 temporal bone specimens from patients who had undergone implantation during life. The majority of these were single-channel implants, whereas the majority of implants inserted today are multichannel systems. This report presents the histopathologic findings in temporal bones from 8 individuals who in life had undergone multichannel cochlear implantation, with particular attention to the type and location of trauma and to long-term changes within the cochlea. The effect of these changes on spiral ganglion cell counts and the correlation between speech comprehension and spiral ganglion cell counts were calculated. In 4 of the 8 cases, the opposite, unimplanted ear was available for comparison. In 3 of the 4 cases, there was no significant difference between the spiral ganglion cell counts on the implanted and unimplanted sides. In addition, in this series of 8 cases, there was an apparent negative correlation between residual spiral ganglion cell count and hearing performance during life as measured by single-syllable word recognition. This finding suggests that abnormalities in the central auditory pathways are at least as important as spiral ganglion cell loss in limiting the performance of implant users.

Aged↗
PubMed2000

Outcomes and quality of life in conductive hearing loss.

OBJECTIVE: The goal was to measure quality of life (QOL) and hearing-specific functional status before and after treatment of conductive hearing loss (CHL). STUDY DESIGN AND SETTING: A prospective, longitudinal, outcomes-based study was performed at an academic medical center. RESULTS: Mean baseline QOL scores in CHL patients were comparable with those of the general population. Audiometric studies indicated significant improvements in hearing threshold in all treated patients. There was no significant improvement in mean global QOL scores after treatment of CHL, although there was little room for improvement over baseline. The hearing-specific instrument did demonstrate significant improvements in emotional and social/situational hearing status after treatment. Patients treated with hearing aids had poorer baseline QOL and hearing status than patients treated with surgery and tended to show declines in QOL and only partial improvement in hearing-specific functional status after treatment. CONCLUSIONS: Treatment of CHL resulted in improvements in hearing-specific functional status, although changes were difficult to detect with a global QOL instrument.

Adolescent↗
PubMed2000

Harvesting human hair cells.

The sensory hair cells of the inner ear are responsible for converting balance and hearing stimuli into electrical signals. Until recently, all previous studies of hair cell physiology had been performed on tissue obtained from non-mammals and rodents. In primates, hair cells are difficult to access, because they rest within the densest structure of the body, the otic capsule of the temporal bone. In this report, we describe a technique that we have used in physiological studies to harvest living human hair cells. We collected vestibular and cochlear tissue specimens from adult humans undergoing translabyrinthine and transotic surgical approaches for resection of lateral skull base tumors. Viable hair cells were identified and visualized with light microscopy. The ability to study normal hair cells from humans may further the study of normal and pathological human sensation, hair cell regeneration, and genetic causes of balance and hearing disorders.

Adult↗
PubMed2000

Hearing preservation in conservation surgery for vestibular schwannoma.

OBJECTIVE: To evaluate preservation of hearing in the resection of vestibular schwannomas. STUDY DESIGN: A retrospective case review. SETTING: Tertiary-care medical center. PATIENTS: Forty-seven patients (25 men, 22 women) were studied; mean age was 46 years, mean tumor diameter 9.8 mm (range 3-30 mm.) INTERVENTIONS: All patients underwent resection of vestibular schwannomas by the middle cranial fossa (MCF) or the retrosigmoid (RS) approach. MAIN OUTCOME MEASURES: Hearing preservation was classified by the criteria outlined by the American Academy of Otolaryngology-Head Neck Surgery. Hearing was assessed preoperatively and postoperatively at 1 month and 1 year. Facial function was graded according to the House-Brackmann scale. Minimum follow-up was 18 months. RESULTS: Hearing was preserved in 69% of patients who underwent the MCF approach but in only 33% of patients for whom the RS approach was used. The RS approach was used for larger tumors (mean diameter 15 mm) and the MCF procedure for smaller tumors (mean diameter 9 mm). One hundred percent of patients had facial function H/B grade II or better, regardless of approach. CONCLUSION: Hearing function can be reliably preserved in a high percentage of selected patients undergoing resection of vestibular schwannoma.

Adult↗
PubMed1999

Cost-effectiveness of the diagnostic evaluation of vertigo.

OBJECTIVE: To evaluate the cost-effectiveness of several diagnostic tests used in the evaluation of vertigo. STUDY DESIGN: Cost-effectiveness analysis, using data from retrospective case review. METHODS: Charts and test results were reviewed from 192 outpatients seen in an academic tertiary referral center for evaluation of vertigo. Cost-effectiveness analysis was performed using decision analysis software, data from office and hospital charges, and expert-based estimations of the utility of different test outcomes. Sensitivity analysis was performed using standard algorithms and wide variable ranges. RESULTS: We found that audiologic testing, posturography, and electronystagmography were the most cost-effective tests, and that magnetic resonance imaging and blood tests had the lowest cost-effectiveness. The analysis was sensitive to the effects of financial costs of tests but, with a few exceptions, was typically not sensitive to the utility of test outcomes or the distribution of test results. CONCLUSIONS: The use of cost-effectiveness analysis, the estimation of utility of test outcomes, and techniques of sensitivity analysis should help guide the clinician's decision making on appropriate testing for patients with vertigo.

Audiometry, Pure-Tone↗
PubMed1998

Ionic currents and electromotility in inner ear hair cells from humans.

The upright posture and rich vocalizations of primates place demands on their senses of balance and hearing that differ from those of other animals. There is a wealth of behavioral, psychophysical, and CNS measures characterizing these senses in primates, but no prior recordings from their inner ear sensory receptor cells. We harvested human hair cells from patients undergoing surgical removal of life-threatening brain stem tumors and measured their ionic currents and electromotile responses. The hair cells were either isolated or left in situ in their sensory epithelium and investigated using the tight-seal, whole cell technique. We recorded from both type I and type II vestibular hair cells under voltage clamp and found four voltage-dependent currents, each of which has been reported in hair cells of other animals. Cochlear outer hair cells demonstrated electromotility in response to voltage steps like that seen in rodent animal models. Our results reveal many qualitative similarities to hair cells obtained from other animals and justify continued investigations to explore quantitative differences that may be associated with normal or pathological human sensation.

Adult↗
PubMed1997

Use of an Internet-based journal club.

The on-line journal club is a useful example of the educational advantages created by the combination of current Internet technology with traditional journal club methods.

Communication↗
PubMed1997

Polyamines increase in the brain stem and cerebellum following labyrinthectomy.

The goal of this investigation was to test the hypothesis that unilateral damage to the vestibular end-organ (labyrinthectomy) stimulates polyamine synthesis in central vestibular neural structures that mediate the process of behavioral recovery (vestibular compensation). Pharmacological studies have shown that compensation can be altered by alpha-difluoromethylornithine (DFMO), a specific inhibitor of polyamine synthesis. Because polyamines are important in regeneration, development and modulation of N-methyl-D-aspartate (NMDA) excitatory amino acid receptors, which mediate vestibular synaptic plasticity, we investigated changes in polyamines in specific central vestibular structures after unilateral labyrinthectomy. The supernatant fraction of brain tissue homogenates was reacted with dansyl chloride. Dansylated polyamine derivatives were quantified in the vestibular nuclei, cerebellum, and inferior olive in both the control and the unilaterally labyrinthectomized guinea pig by high-performance liquid chromatography-fluorometric detection. No left-right differences in putrescine, spermidine, or spermine were detected in any brain parenchyma of controls. Polyamine imbalance, characterized by increased spermidine in the ipsilateral medial and lateral vestibular nuclei, was noted 12 and 24 h after unilateral labyrinthectomy (UL). In contrast, spermidine, spermine, and putrescine were elevated bilaterally in the cerebellum and inferior olive after UL. These biochemical changes may represent neuronal modifications to establish a balance between the vestibular nuclei after unilateral labyrinthectomy. Elucidation of the role of polyamines in central vestibular function and in vestibular compensation offers promise for the development of novel therapeutic strategies for treatment of vestibular disorders.

Analysis of Variance↗
PubMed1997

Development of a new outcomes instrument for conductive hearing loss.

OBJECTIVE: The objective was to design and validate a disease-specific outcomes instrument for use in conductive hearing loss (CHL). STUDY DESIGN: The study was a retrospective survey of 47 patients recently treated for CHL with either a hearing aid or surgery. Patients were tested with the newly designed instrument (the Hearing Satisfaction Scale [HSS]), previously validated hearing-specific instruments, and a generic quality-of-life instrument. SETTING: The study was performed in an academic tertiary referral center. MAIN OUTCOME MEASURES: These included test-retest reliability, internal consistency reliability, content validity, criterion validity, and construct validity of the HSS. RESULTS: Test-retest reliability (r = 0.72, p < 0.001) and internal consistency reliability were adequate (Cronbach's alpha was 0.83 and 0.74 for the two subscales of the HSS). Criterion validity for individual items was adequate (r = 0.45, p = 0.02) using audiometric data as the criterion standard. Construct validity was also high using results from other instruments; both convergent and divergent validity of the HSS was demonstrated. In addition, the HSS demonstrated the ability to differentially discriminate between subgroups when grouped by level of hearing loss. CONCLUSIONS: The HSS is a valid and reliable instrument for use in outcomes research on conductive hearing loss.

Adult↗
PubMed1996

Update on facial nerve disorders.

Many issues involving the diagnosis and treatment of facial nerve disorders continue to engender controversy and debate. This article examines the theory that Bell's palsy is a herpes simplex neuritis and proposes facial nerve decompression for recurrent palsies. The contemporary management of herpes zoster oticus, temporal bone fractures, otogenic facial paralysis, and hemifacial spasm is reviewed.

Decompression, Surgical↗
PubMed1996

Barotrauma after stapes surgery: a survey of recommended restrictions and clinical experiences.

OBJECTIVE: To identify a consensus on the postoperative barorestrictions after stapes surgery and to examine the clinical barotrauma experience within this patient population encountered by the surveyed physicians. DATA SOURCE: A 34-item survey was developed, allowing for detailed analysis of physician demographic data, practice characteristics, surgical experience, and clinical experience with barotrauma after stapes surgery. The postoperative restrictions addressed by the survey included those for air travel, snorkeling, and scuba diving. Recommendations for the use of ventilation tubes and hyperbaric oxygen therapy were investigated as well. STUDY SELECTION: Surveys were mailed to 419 active members of the American Otological Society and the American Neurotology Society as listed in the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) 1994-1995 Conjoint Directory. A total of 284 (67.8%) surveys were returned, of which 53 were not sufficiently completed and were excluded in the statistical analysis. DATA EXTRACTION: The demographic data and clinical experience were analyzed to determine statistical association with the postoperative recommendations using chi 2 or Fisher's exact tests. The kappa statistic was used as a measure of consistency between physicians' recommended restriction for a specific activity after a stapedectomy or stapedotomy. CONCLUSION: No consensus was demonstrated as to restrictions from activities such as air travel, snorkeling, or scuba diving. Despite this lack of consensus, no significant difference was demonstrated in the prevalence of barotrauma reported within the responding physicians' practices based on their individual recommendations for these activities.

Adult↗
PubMed1995

Nontuberculous mycobacterial mastoiditis.

Although nontuberculous mycobacterial (NTM) infections are recognized as an important cause of cervicofacial lymphadenopathy in children, NTM mastoiditis is rare. Further, NTM mastoiditis may be difficult to distinguish clinically from tuberculous mastoiditis since both may present with chronic, painless otorrhea and exuberant middle ear granulation tissue. The treatment of tuberculous mastoiditis is antituberculosis chemotherapy; however, most NTM infections are resistant to antituberculous agents, and the preferred treatment of NTM mastoiditis is mastoidectomy. We report a recent case of mastoiditis caused by Mycobacterium avium complex in an infant who presented with a temporal bone mass.

Child↗
PubMed1995

Progressive hearing loss after transverse temporal bone fracture.

Transverse fractures often violate the otic capsule and commonly, although not invariably, result in immediate and profound sensorineural hearing loss. The pathogenic mechanisms producing sensorineural hearing loss include direct trauma to the cochlear nerve, disruption of the membranous labyrinth, vascular compromise or hemorrhage into the inner ear, perilymphatic fistula, and endolymphatic hydrops. The last two mechanisms account for the occasional patient who develops progressive sensorineural hearing loss after the initial insult. On early posttraumatic evaluation three patients were discovered to have transverse fractures and residual auditory function. Deterioration of hearing led to middle-ear exploration with closure of perilymphatic fistulas. Hearing was preserved in two patients. Diagnosis of posttraumatic perilymphatic fistulas requires early audiometric assessment, high-resolution computed tomographic scanning of the temporal bones to detect fracture of the otic capsule and pneumolabyrinth, and a high index of clinical suspicion.

Accidental Falls↗
PubMed1995

Localization of ornithine decarboxylase (ODC) in the cochlea of the immature rat.

Ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine synthesis, is important in cochlear development. Whereas tissue specific differences in cochlear ODC activity have been demonstrated, cellular localization of ODC protein in the inner ear of the immature rat has not. ODC was localized in inner ear structures using an ODC polyclonal antibody and the effects of cycloheximide on ODC immunoreactivity and enzymatic activity were determined. Tissues demonstrating elevated enzymatic activity contained cells with the strong immunoreactivity. ODC activity was highest in the organ of Corti and lateral wall followed by the cochlear nerve. Immunoreactivity was demonstrated throughout the cochlea with intense staining of the hair cells, pillar cells, Deiter's cells, inner sulcus cells, basilar membrane, stria vascularis, spiral ganglion cell bodies and cochlear nerve fibers. Cycloheximide rapidly diminished cochlear ODC activity and expression of ODC protein. The half-life of cochlear ODC was 30 min. Localization of cellular sites of ODC is important in understanding the role of the ODC-polyamine pathway in cochlear development and will be a valuable marker for tissue damage from ototoxic agents.

Animals↗
PubMed1995

Radiation therapy in the management of paragangliomas of the temporal bone.

The use of radiation therapy for the treatment of paragangliomas of the temporal bone remains controversial. Few studies exist that provide sufficient information on staging the long-term follow-up to clarify this issue. A retrospective study was undertaken of 38 patients with temporal bone paragangliomas treated with radiation therapy between 1956 and 1991. All patients received radiation therapy, either as a primary modality (14 patients), in combination treatment with surgery (13 patients), or as salvage therapy (11 patients). Mean disease stage (Fisch classification system) for each group was C2, B, and C1, respectively. The follow-up period ranged from 1 to 27 years (median 11.5 yr). Local control was achieved in 79% of the primary radiation therapy group, 100% of the combined treatment group, and 91% of the salvage therapy group. Complications resulting from radiation therapy were few and minor. This study demonstrates that the use of radiation therapy for temporal bone paragangliomas offers effective local control as a primary treatment modality, in combination with surgery, and as salvage therapy with few long-term complications.

Adult↗