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Biomedical subjects

L G Duckert

Publications and source records attributed to L G Duckert.

At least 19 recordsLinked to original sources
PubMed1995

Magnetic resonance imaging of intratemporal facial nerve lesions in the animal model.

The facial nerve is often injured in head trauma. Computed tomography (CT) is the diagnostic study most frequently used to evaluate temporal bone fractures, but it does not demonstrate all soft tissues well. Recently, magnetic resonance imaging (MRI) has been used to evaluate certain soft tissues, including cranial nerves. Experience with MRI evaluation of temporal bone trauma is limited and consists primarily of anecdotal reports. This study assesses the accuracy of MRI in evaluating experimentally induced acute intratemporal facial nerve lesions. The tympanic segments of the right facial nerve in nine rabbits were contused, and MRI scans were performed without and with gadolinium-diethyl-triamine-pentaacetic acid (Gd-DTPA) at varying intervals after surgery. MRI with Gd-DTPA accurately identified the lesion site in eight of nine subjects. Gd-DTPA-enhanced MRI appears to be useful in the evaluation of traumatic facial nerve injuries.

Animals↗
PubMed1995

Ototoxicity of topical otomicrobial agents.

Topical antimicrobial solutions are used commonly for prevention or treatment of purulent otorrhea even though most solutions contain ototoxic agents. This study compares the cochlear and middle ear toxicity of cortisporin otic solution (COS), 0.3% gentamicin ophthalmic solution (GOS), benzalkonium chloride (0.026% and 0.05%), and 1.0% Ofloxacin, a new quinolone antibiotic. Saline 0.9% was used as a control. The agent was instilled daily for 7 days into the bulla of juvenile guinea pigs. The animals were sacrificed on the 14th day. The organ of Corti was examined using surface preparation light microscopy and scanning electron microscopy. The tympanic membrane (TM) and adjacent middle ear mucosa were examined with light microscopy. The average cochlear hair cell damage was 66% for COS, 6.5% for GOS, and 1% for Ofloxacin, benzalkonium and saline. COS and benzalkonium 0.05% produced moderate mucosal thickening and inflammation. However, this was not statistically different from the mild mucosal thickening produced by saline, GOS, Ofloxacin and 0.026% benzalkonium. There was statistically significant mild to moderate thickening of the TM for all agents compared to the saline control.

Animals↗
PubMed1992

Electrical evaluation of the facial nerve in acoustic neuroma patients: preliminary comparison between transcranial magnetic coil stimulation and electroneurography.

Subclinical involvement of the facial nerve by acoustic neuromas may be identified preoperatively using conventional electroneurography (ENoG). The clinical application of extratemporal stimulation distal to the stylomastoid foramen is limited in these cases by the more proximal site of the lesion. Transcranial magnetic coil stimulation (MCS) is a noninvasive means by which the facial nerve is stimulated at the level of the motor cortex or the brain stem, before it enters the internal auditory canal. Topographically such an assessment may have more diagnostic relevance than other forms of electrical stimulation in acoustic neuroma patients. To test this theory the facial nerves of 20 patients with acoustic neuromas were stimulated using ENoG and MCS preoperatively and 1 week postoperatively. Stimulation parameters were comparable and included threshold and suprathreshold levels of stimulation while compound action potential amplitudes and early and late response latencies were monitored. Facial nerve function was assessed clinically using the Stennert grading system. All the patients had clinically normal facial nerve function preoperatively. Normative data suggested a close correlation between threshold and suprathreshold amplitudes generated by both ENoG and MCS. To the contrary, in the pathologic ears there was a higher incidence of stimulus response abnormality determined by MCS than by ENoG. A comparison of these data, tumor size, and postoperative results promotes further evaluation of MCS as a prognostic index in acoustic neuroma patients.

Action Potentials↗
PubMed1991

[Electrophysiologic evaluation of the facial nerve in patients with acoustic neuromas. Preliminary results of a comparative study between conventional electroneurography and transcranial magnetic pulse stimulation].

Subclinical invasion of the facial nerve by acoustic neuromas may be identified preoperatively using conventional electroneurography (ENOG). The clinical application of extratemporal stimulation distal to the stylomastoid foramen is limited in these cases because of the more proximal site of the lesion. Transcranial magnetic coil stimulation (MCS) is a non-invasive means by which the facial nerve is stimulated at the level of the motor cortex or the brain stem before it enters the internal auditory canal. Topographically such an assessment may have more diagnostic relevance than other forms of electrical stimulation in acoustic neuroma patients. To test this theory the facial nerves of 20 patients with an acoustic neuroma were stimulated using ENOG and MCS before and 1 week after operation. Stimulation parameters were comparable and included threshold, double-threshold and supra-threshold levels of stimulation while compound action potential amplitudes and early and late response latencies were monitored. All the patients had clinically normal facial nerve function preoperatively. Using ENOG 65% of the patients showed amplitude reduction on the tumour side, whereas 70% of these patients had a reduction of amplitude to MCS. Combining both techniques, 88% of the patients had a significant amplitude reduction on the neuroma side. Comparison of the preoperative threshold measurements of both techniques showed that there was a significantly higher incidence of detection of lesions on the diseased side in neuromas larger than 2 cm by the use of MCS.

Dominance, Cerebral↗
PubMed1991

Management of middle third facial fractures.

In the management of fractures of the middle third of the face, it should be apparent to the surgeon that the more sophisticated fixation techniques carry increased liability, and their incorrect and imprecise application mandates identification and correction of any contributing factors if malunion is to be avoided. A less sophisticated stabilization technique that, by convention, generally is reliable, less complicated, less expensive, and less intimidating may be preferred. Given the complexity and diversity of midfacial injuries and the variety of available fixation and stabilization techniques, it is unlikely that any one method precisely suits every situation.

Facial Bones↗
PubMed1990

Ultrastructural observations on regenerating hair cells in the chick basilar papilla.

This experiment was designed to investigate cellular and subcellular maturational changes in regenerated immature sensory cells and support cells of the chick basilar papilla following gentamycin treatment. Scanning and transmission electron microscopy were used. The experimental animals received one subcutaneous injection of gentamycin sulfate daily (50 mg/kg) for five or 10 days. The animals receiving five days of injection were sacrificed the following day. The remaining animals were allowed to survive either seven or 28 days before sacrifice and preparation for electron microscopy. The initial lesion consisted of total degeneration of hair cells within 500 microns of the proximal tip providing the opportunity to study a 'pure' population of regenerating sensory cells. Sensory cell regeneration could be identified by one day after terminating gentamycin treatment. Early in development sensory cell precursors were morphologically very similar to supporting cells. A density gradient, based on cytoplasmic staining characteristics, was established which increased from cells displaying low density at the base of the supporting cell layer to high density cells at the luminal surface. These changes in density were equated to increase in number of and types of cytoplasmic organelles. In contrast to the empty appearing cytoplasm of the support cell, the cytoplasm of the hair cell precursor contained numerous mitochondria, clusters of ribosomes, and vesicles. As the cell approached the surface, mitochondria became more numerous as did smooth and coarse endoplasmic reticulum and Golgi apparatus. This gradient suggested that determination of the cellular phenotype occurred at the level of the basal membrane followed by migration to the surface, during which time differentiation was characterized by an increase in number and complexity of cellular organelles. Luminal surface modifications occurred as soon as the cell erupted. The development of stereocilia, rootlet, cuticular plate and cellular polarization followed the normal embryogenetic pattern. At 28 days, stereocilia organization was still incomplete as was the orientation of the bundle. To the extent that proper orientation of hair cells or bundles is necessary for normal transduction, mature function at 28 days would not be anticipated. Innervation of the presumptive hair cell precursors could be observed one day after treatment, early in the course of hair cell differentiation. Synaptogenesis followed the normal embryogenetic sequence; however, afferent and efferent nerve terminals remained immature appearing at 28 days. This observation may have physiological implications manifested by delay of hearing

Afferent Pathways↗
PubMed1989

Relationship of hearing impairment to dementia and cognitive dysfunction in older adults.

We conducted a case-control study in 100 cases who had Alzheimer's-type dementia and 100 age-, sex-, and education-matched, nondemented controls to evaluate the hypothesis that hearing impairment contributes to cognitive dysfunction in older adults. The prevalence of a hearing loss of 30 dB or greater was significantly higher in cases than in controls (odds ratio, 2.0; 95% confidence interval, 1.2 to 3.4), even when adjusted for potentially confounding variables. In addition, we observed a dose-response relationship in which greater hearing loss was associated with a higher adjusted relative odds of having dementia. Hearing loss was also significantly and independently correlated with the severity of cognitive dysfunction, as measured by the Mini-Mental State Examination, in nondemented as well as demented patients. These results demonstrate an association between hearing impairment and dementia and lend support to the hypothesis that hearing impairment contributes to cognitive dysfunction in older adults.

Aged↗
PubMed1989

Intraocular pressure as an index of ocular injury in orbital fractures.

An improved method of screening for ocular injuries in patients sustaining orbital fractures is proposed. We performed a retrospective study of 107 patients who sustained orbital fractures. Intraocular pressures were measured on presentation in 17 patients and were found to be elevated on the side of the injury in eight patients, five (63%) of whom had significant ocular injury. No patient with normal intraocular pressure was found to have an ocular injury. In a prospective study, the intraocular pressures of 30 patients sustaining orbital fractures were measured. Twelve patients (40%) had normal (less than 22 mm Hg) and bilaterally symmetric (less than 3 mm Hg difference) intraocular pressures. One (8%) of these patients sustained ocular injury. In contrast, 18 patients (60%) had either an elevated intraocular pressure (greater than 22 mm Hg) or a difference between eyes of greater than or equal to 3 mm Hg. Eleven (61%) of these patients were found to have sustained an ocular injury. We conclude that intraocular hypertension or significant interocular pressure differences should alert the physician to a potential ocular injury.

Adolescent↗
PubMed1989

Possible precursors of regenerated hair cells in the avian cochlea following acoustic trauma.

Hair cell regeneration following acoustic trauma to the avian cochlea has been documented using DNA labeling with tritiated thymidine. The goal of this study was to identify potential precursor cell populations for regenerating hair cells. Chicks were exposed in pairs to a 1500 Hz pure tone at 120 dBSPL for 18 h. The animals received repeated injections of 3H-thymidine over a survival period of 6, 15, or 24 h, 3 days or 30 days after the completion of noise exposure. One cochlea from each animal was processed for autoradiography and the other for scanning electron microscopy. Labeled, regenerated hair cells were present by 3 days after exposure and recovery from injury was nearly complete by 30 days. Examination of animals in short survival groups suggest that two precursor populations may exist. For inferior sensory epithelial damage, cuboidal or hyaline epithelial cells appear to serve as the precursor cell population for the regeneration of both hair cells and supporting cells. With isolated superior damage, however, supporting cells may be the precursor population.

Animals↗
PubMed1988

The effect of cochleostomy on the development of endolymphatic hydrops--morphologic changes in the rabbit cochlea.

The present study was designed to examine the effects of cochleostomy on the development of endolymphatic hydrops in the rabbit. Fistulization of the cochlear partition and simultaneous obstruction of the endolymphatic duct was performed in one group of animals (n = 13). Rabbits in two other groups underwent either cochleostomy (n = 6) or endolymphatic duct obstruction (n = 6) alone. Animals were terminated at 1-, 4-, and 6-week intervals and the cochleas were examined with the light microscope to document the presence or absence of hydrops, or were evaluated with the scanning electron microscope to assess sensory-cell damage. Hydrops was observed in 67% of the animals in the combined duct-obstruction/cochleostomy group, in 100% of the duct-obstruction alone group, and in 0% of the cochleostomy alone group. Widespread sensory-cell degeneration was observed with the scanning electron microscope in the combined and the cochleostomy alone groups.

Animals↗
PubMed1988

Chronic perilymphatic fistula: experimental model in the guinea pig.

Chronic perilymphatic fistulas were created in guinea pig cochleas using silicone rubber tubing placed into the scala tympani through the round window. Fistula patency was determined by fluorescein perfusion into cerebral spinal fluid. Fistula were found to be patent in 6 of 6 animals at 7 days and 8 of 13 animals at 28 days. Analysis of ABRs revealed threshold increases of 10 to 15 dB across all frequencies at 1 hour and 7 days. However, thresholds returned to pre-fistula levels by 28 days. Animals with acute fistulas (simple laceration of the round window) had similar threshold increases at 1 hour; however, recovery to baseline levels occurred by day 7. Control animals with intact round windows did not have threshold shifts. Scanning electron microscopy revealed hair cell loss localized to the apical and basal turns of the cochlea. The morphologic changes observed occurred acutely (within 7 days) and were not progressive, despite the presence of a fistula. Hair cell loss or degeneration did not correlate with hearing loss.

Animals↗
PubMed1987

Single-point stabilization of zygomatic fractures with the minicompression plate.

Unstable zygomatic fractures frequently require stabilization at two points. A new "mini" dynamic compression plating system designed specifically for zygomatic fractures permits single-point stabilization. We used a minicompression plating system with a series of patients at the University of Washington Affiliated Hospitals, Seattle. Satisfactory single-point stabilization of displaced zygomatic fractures was consistently achieved with this method. The plate and screws are substantially smaller than commonly used in mandibular fractures facilitating cosmetic concealment. There are theoretical advantages of this plating system as they apply to the unique geometry of the zygomatic fracture.

Bone Plates↗
PubMed1986

Reversible mechlorethamine-associated hearing loss in a patient with Hodgkin's disease.

Mechlorethamine, when administered in massive doses (0.6-1.5 mg/kg) to cancer patients in several early studies, caused severe irreversible hearing loss. There have been no reports of ototoxicity with doses of 0.4 mg/kg or less. The authors describe a 36-year-old man who developed profound sensorineural hearing loss during his first cycle of MOPP chemotherapy for Hodgkin's disease. Cyclophosphamide was substituted for mechlorethamine in subsequent cycles and his hearing deficit resolved. This is the first reported case of reversible ototoxicity associated with currently recommended doses of mechlorethamine.

Adult↗
PubMed1986

Preliminary observations after facial rehabilitation with the ansa hypoglossi pedicle transfer.

Facial paralysis is a very disabling condition, both functionally and cosmetically. Despite the different methods of facial reanimation that have been described, there is no single method that will restore normal facial tone and motion. Of the methods available, primary neurorrhaphy is probably the most effective. The recovery period, however, is prolonged and, as a result, muscle tone and bulk may be lost. The hypoglossal-facial anastomosis is also a very reliable and effective technique but requires necessary interruption of both major cranial nerve trunks. Transfer of a neuromuscular pedicle (based on the ansa hypoglossi) has been offered as a method of facial reanimation that involves neither prolonged recovery nor interruption of the major cranial nerve functions. The application of this technique for reinnervation of a paralyzed larynx was first described by Tucker in 1970, and the technique was applied to facial muscle (in animal models) in 1977. The effectiveness of this technique--and its application in the management of facial paralysis in the human patient--remains controversial. We report our experience with a series of six patients who underwent neuromuscular pedicle transfer in conjunction with other more conventional methods of facial reanimation. The function of the pedicle and its contribution to the overall facial rehabilitation were assessed clinically and electromyographically. Factors influencing the success of the procedure and clinical and experimental evidence to support its application are discussed. While our experience with this technique is limited, it would appear that the neuromuscular pedicle transfer may play a useful adjunctive role in reanimation of the face in selective cases of facial paralysis.

Adult↗
PubMed1985

Morphologic changes in the guinea pig cochlea following cochleostomy--a preliminary scanning electron microscope study.

Fistulization of the membranous labyrinth via a surgically created endolymphatic-perilymphatic shunt (cochleosacculotomy) is currently being advocated as a treatment for endolymphatic hydrops. As a preliminary study to the investigation of the effects of labyrinthine fistulization on the hydropic condition, we sought first to reproduce the cochleosacculotomy procedure in a series of normal animals. Fistulization of the cochlear duct was performed in 15 normal animals using a tungsten wire directed via the round window through the cochlear partition in the region of the organ of Corti. The animals were sacrificed at regular intervals and the cochleas examined for histopathologic changes with the scanning electron microscope. Observations suggest that discrete permanent fistulization of the cochlear duct in the normal guinea pig results in progressive sensory cell degeneration. The implication of these observations and the apparent difference between these results and the experience thus far reported in humans are discussed.

Animals↗
PubMed1984

Placebo effect in tinnitus management.

Masking devices, lidocaine, and analog oral forms of lidocaine have all been reported as being effective forms of therapy to relieve tinnitus. Many studies, however, have used single-blind protocols and were possibly biased by placebo effects. To investigate the contributions of a placebo effect in clinical tinnitus studies, 25 tinnitus patients who had received a placebo injection in a previous double-blind lidocaine study were contacted on the pretense that they would receive a test dose of lidocaine; the 20 who responded were included in this study. A 5 cc bolus of placebo saline solution instead of lidocaine was then administered to each patient. Forty percent of the patients reported a change in their tinnitus following the placebo injection. The results of this study serve to point out the inherent flaws in straight clinical trials, and that the success rates achieved in such uncontrolled clinical investigations may be biased by the placebo effects.

Clinical Trials as Topic↗
PubMed1984

Morphological changes following cochlear implantation in the animal model.

Examination of the effects of cochlear implantation in the animal model has made it increasingly clear that biological changes may be induced by the device. In a preliminary study we established a damage threshold at 400 microA RMA (70 microCoul/cm2/phi) after a single three-hour exposure to continuous 1 kHz sinusoidal stimulation. By systematic modification of stimulation parameters in the present study we have sought to establish damage thresholds and patterns of histological change in the chronically stimulated animal and further elucidate the mechanisms underlying the histopathological change in a second acute animal preparation. In part one, chronic stimulation at 1 000 Hz for a total of 12 hours distributed over a four-week period resulted in a lower damage threshold at 15-20 microCoul/cm2/phi, the lowest value tested. In addition to sensory and supporting cell degeneration osteoneogenesis and spiral ganglion cell degeneration were also observed. These findings are of some relevance under conditions of prolonged implantation and stimulation in the human. In part two of the study, acute stimulation for a three-hour period at 100 Hz reduced the damage threshold from 400 microA to 200 microA RMS. This inverse relationship between threshold and frequency suggests that electrophoretic effects are, at least in part, responsible for the histological changes observed. The threshold shift was less than predicted, however, making it less likely that a single factor is responsible for the stimulation-induced damage.

Acoustic Stimulation↗