The effects of keratinocyte growth factor on healing of tympanic membrane perforations.

Tympanic membrane (TM) perforations heal by reepithelialization and fibrous layer proliferation. The rat TM model may be used to study growth factors that promote epithelialization and fibroblast proliferation, such as epidermal growth factor (EGF) and fibroblast growth factor (FGF). The authors previously evaluated the effects of FGF on tympanic membrane perforations and showed an enhanced rate of wound healing with preservation of normal structure and function. The same model was used to test keratinocyte growth factor (KGF, also called FGF-7). This growth factor has been shown to stimulate the migration and proliferation of keratinocytes. This is the first study investigating KGF in the tympanic membrane perforation model. Our results show that in contrast to FGF and EGF, KGF does not enhance the rate of wound healing, but rather results in a more organized wound repair process.

An investigation of acute facial paralysis in animals induced by exposure of the tympanic membrane to cold air.

The goal of this investigation was to test the hypothesis that tympanic membrane exposure to cold air is a cause of acute facial palsy. A series of acute invasive experiments and a series of chronic noninvasive experiments were conducted in both cats and dogs. In the acute studies, stimulation was applied intracranially to the facial nerve root through a stereotaxically placed microelectrode and recordings of compound action potentials obtained extracranially from the facial nerve. Nerve conduction was monitored continuously during the application of cold air to the tympanic membrane. Nerve conduction disturbances were observed in all animals tested (8), and reduction in compound action potential amplitude ranged from 33% to 96%. Histologic analysis of the intratemporal portion of the facial nerve was performed in the animal exhibiting the greatest block in conduction, representative of a near-total paralysis. Axon swelling, demyelinization, and degeneration (Bungner's bands) without inflammation were apparent along the entire tympanic membrane segment. Interstitial swelling of nerve endoneurium was also present at the second genu and vertical segment. In the chronic studies, animals were exposed to cold air and monitored daily for facial paralysis after recovery from anesthesia. None of the animals demonstrated any detectable behavioral facial paralysis.

Transmastoid labyrinthectomy in older patients.

Transmastoid labyrinthectomy is an effective procedure for the control of episodic vertigo due to unilateral peripheral vestibular dysfunction. However, its application in older patients has been limited, primarily because of concerns that older patients may not compensate well postoperatively. Poor vestibular compensation results in constant disequilibrium, motion intolerance, and visual symptomatology. The purpose of this report is to review our results with transmastoid labyrinthectomy in patients over the age of 65. Complete records were available for 22 patients operated on between July 1984 and June 1994. Patient's records were reviewed for age, preoperative duration of symptoms, coexistent medical conditions, vertigo control, and postoperative disequilibrium. Advanced age need not be a contraindication to transmastoid labyrinthectomy.

Evaluation of basic fibroblast growth factor in tympanic membrane repair.

Basic fibroblast growth factor (bFGF) has been shown to enhance speed of wound repair at a number of anatomic sites. This study presents an evaluation of bFGF in a model of acute tympanic membrane (TM) perforation in order to assess rate of healing as well as structural and functional outcome. Perforations were created in the tympanic membranes of rats, then allowed to heal in the presence of topically applied bFGF with the opposite ear serving as a control. The growth factor was applied in repeated doses beginning 2 days after creation of the TM defect. The treated ears healed faster by an average of 4.0 days. The healed tympanic membranes were assessed using tympanometry and light microscopy. Structurally and functionally, the healed tympanic membranes were similar to the controls. The observed results indicate that bFGF promotes accelerated healing and restoration of normal architecture in acute TM defects.

Lipocortin I immunolocalization in normal and hydropic guinea pig ears.

Annexins are a family of eight highly conserved proteins that bind phospholipids in the presence of calcium. One of these proteins, lipocortin I, has restricted distribution in adult and developing tissues, suggesting regulatory function. Among the protean roles theorized are regulation of inflammation by influencing eicosanoid production, participation in endo- and exocytosis, and control of membrane permeability. Such processes could have important roles in the inner ear; therefore, we investigated the patterns of lipocortin I expression in the normal guinea pig ear. Lipocortin I appeared at high levels in nonsensory, endolymph-facing tissues. Perilymph-facing cells had little lipocortin I activity. Lipocortin I was minimally expressed, or is absent, in sensory cells of the cochlea and vestibular systems. In the kidney, changes in quantity and distribution of lipocortin I have been seen during recovery from acute tubular necrosis. In an attempt to gain insight into the role of lipocortin I, the authors investigated its response to an experimental insult. Surgically created endolymphatic hydrops was chosen as an insult involving the endolymph-producing epithelia that richly express lipocortin I. Comparing unilaterally created hydrops, for up to 3 weeks' duration, to contralateral control ears demonstrated no quantitative or distribution changes in lipocortin I.

Clinical application of otoacoustic emissions: what do we know about factors influencing measurement and analysis?

Three electrophysiologic audiologic procedures-aural immittance measurement, auditory brainstem response (ABR), and otoacoustic emissions (OAE)- were first described in the 1970's. Immittance measurement and ABR have contributed importantly for years to the assessment of auditory function in children and adults, whereas OAEs have not yet been incorporated into the everyday audiology test battery. In this article, we argue that the transition from OAE measurement by hearing scientists in laboratory settings to routine application by audiologists in the clinic will be greatly facilitated by (1) comprehensive, large-scale studies of the effects of subject characteristics, such as gender and age (from infancy to advancing adulthood), on both transient evoked (TEOAE) and distortion product (DPOAE) otoacoustic emissions; (2) clinical investigations of TEOAE and DPOAE in sizeable patient populations with specific neurotologic diagnoses; (3) guidelines for OAE test protocols in clinical environments; and (4) clear criteria for OAE analysis in clinical populations.

Dynamic sensorineural hearing loss: implications for audiologists: case reports.

Although many persons with sensorineural hearing loss (SNHL) seeking hearing care do not have active ear disease, audiologists must appreciate the potentially dynamic and treatable nature of some etiologies of SNHL. This is particularly important now as audiologists are increasingly employed in private practice or other clinical settings that may serve as the point of entry for hearing care. In this paper, we review a variety of clinical entities affecting newborn infants, children, and adults that are associated with dynamic SNHL. Using a case report format, we illustrate treatment-related changes in SNHL, emphasizing the audiologist's role in patient management.

Neuroplasticity of the adult primate auditory cortex following cochlear hearing loss.

Tonotopic organization is an essential feature of the primary auditory area (A1) of primate cortex. In A1 of macaque monkeys, low frequencies are represented rostrolaterally and high frequencies are represented caudomedially. The purpose of this study was to determine if changes occur in this tonotopic organization following cochlear hearing loss. Under anesthesia, the superior temporal gyrus of adult macaque monkeys was exposed, and the tonotopic organization of A1 was mapped using conventional microelectrode recording techniques. Following recovery, the monkeys were selectively deafened for high frequencies using kanamycin and furosemide. The actual frequencies deafened were determined by the loss of tone-burst elicited auditory brainstem responses. Three months after deafening, A1 was remapped. Postmortem cytoarchitectural features identifying A1 were correlated with the electrophysiologic data. The results indicate that the deprived area of A1 undergoes extensive reorganization and becomes responsive to intact cochlear frequencies. The region of cortex that represents the low frequencies was not obviously affected by the cochlear hearing loss.

Dermoid tumor of the middle ear: case report and literature review.

Dermoids and teratomas are frequently described in the head and neck, but are rarely found in the middle ear or temporal bone. We have recently managed a case of an extensive middle ear dermoid occurring in a 14-month-old female. The purpose of this article is to report the presentation and management of this case and to review the literature with respect to this entity.

Cochleovestibular nerve compression syndrome. I. Clinical features and audiovestibular findings.

Cochleovestibular nerve compression syndrome (CNCS) is the term used to describe a group of audiovestibular symptoms thought to be due to a vessel compressing the cochleovestibular nerve. These symptoms include recurrent vertigo, continuous disequilibrium and acquired motion intolerance. Recently, Moller reported that CNCS can be diagnosed based on abnormalities in the auditory brainstem response (ABR). After specifically excluding all other vestibular disorders, 63 patients with symptoms suggestive of CNCS were identified. These patients were systematically evaluated with a standard neurotologic test battery, and the results were reviewed retrospectively. Hearing loss was found in 51 (81%) of 63 cases, including 33 cases of unilateral high-frequency loss and 14 cases of middle-frequency loss. ABR data were interpreted with respect to Moller's criteria, and abnormal studies were found in 42 (75%) of 56 cases. Abnormal electronystagmograms were found in 57 (93%) of 61 cases. Thirteen of the patients subsequently underwent a posterior fossa procedure for vertigo and, vessels were found in contact with the cochleovestibular nerve in 11 of 13 cases. The results of this study suggest that the majority of CNCS patients have neurotologic test findings that suggest an abnormality of the cochleovestibular nerve. The results and their implications are discussed.

Cochleovestibular nerve compression syndrome. II. Vestibular nerve histopathology and theory of pathophysiology.

The present study was undertaken to systematically examine and characterize pathological changes in vestibular nerve specimens obtained at surgery in patients with symptomatic cochleovestibular nerve compression syndrome (CNCS). Vestibular nerves were obtained in six cases of CNCS and were intermingled with vestibular nerves obtained in cases of Meniere's disease. All of the nerve specimens were coded and reviewed microscopically in a blind-study fashion by the neuropathologist. The vestibular nerves obtained from CNCS cases showed significant endoneurial fibrosis, compared to controls (specimens from patients with Meniere's disease). Based on observations in this study, as well as the clinical symptoms and audiovestibular test findings in these patients, a theory of pathophysiology in CNCS of the cochleovestibular nerve is proposed. The implications of this theory are discussed with respect to the diagnosis of CNCS.

An investigation of the potential for laser nerve welding.

Suture repair of a severed peripheral nerve is cumbersome, presents a focus for infection and neuroma formation, and does not always produce adequate stump alignment. An alternative form of repair is laser nerve welding, which is attractive because it does not introduce foreign material into the anastomotic site, it forms a circumferential seal, and it can be performed in difficult-to-reach areas. Laser repair has not been widely accepted both because the effect of laser irradiation on intact nerves is not well documented, and the anastomotic strength of the weld has been inferior to suture repair. In the first part of the present study, rat sciatic nerves were exposed and irradiated with increasing intensities from a Sharplan CO2 and KTP laser to document nerve damage as recorded by decreases in the peak compound action potential. A new technique of laser repair (S-Q weld) was then developed that involved harvesting subcutaneous tissue from the adjacent dermis, wrapping it around the two opposed nerve stumps, and lasering it to the epineurium to effect a weld. The strength of the S-Q weld (6.1 grams) was considerably greater than that produced by laser welding alone. The third phase of the study compared regeneration at 2 months in severed rat sciatic nerves repaired by either microsuture or S-Q weld. Analysis of the compound action potential values indicated that the number of regenerating fibers after laser repair was greater than that after suture repair, although a significant difference could not be demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)

Management of flap necrosis in cochlear implantation.

Skin flap complications are the most commonly reported problems in cochlear implant surgery when the anteriorly based C-shaped flap is used for the incision. If the prosthesis is exposed by flap necrosis, local skin flaps may be used to obtain coverage. Unfortunately, the long-term viability of such flaps may be compromised by the pressure exerted by the transmitter. Two cases of flap necrosis severe enough to expose the prosthesis have been successfully managed by relocating the device to a position superior to the auricle, under healthy skin. In one case the receiver was removed owing to infection and reimplanted at a later date. In this case, the electrode array was left in place at explantation in order to stent the cochlea. The surgical techniques and flap designs for this procedure are presented. No further surgical complications have developed in either case. The devices are performing well for both patients at this time. We have found relocation of the implant a useful technique in the management of major flap necrosis. This technique may also be useful to prevent flap necrosis should excessive flap thinning occur during the implant operation.

Complications of skull base surgery.

As skull base resections have increased in complexity and magnitude, so have the complications associated with the procedures. In this paper, we have reviewed the major complications of skull base surgery, including CSF leak, bleeding, stroke, meningitis, cranial nerve deficits and recurrent disease. This report summarizes the factors that lead to these complications, as well as measures to prevent them. We have also discussed our approach to the management of these complications, with particular emphasis on CSF leak and vagal nerve paralysis.

Gadolinium-enhanced magnetic resonance imaging in Bell's palsy.

Inflammation of the facial nerve in Bell's palsy can be demonstrated on gadolinium-enhanced magnetic resonance imaging. We have studied a series of 17 Bell's palsy patients with gadolinium-enhanced magnetic resonance imaging, and the purpose of this paper is to report our findings and discuss their significance. Most acute Bell's palsy cases demonstrate facial nerve enhancement, usually in the distal internal auditory canal and labyrinthine/geniculate segments. Other segments demonstrate enhancement less often. Gadolinium enhancement occurs regardless of the severity of the paralysis and can persist after clinical improvement of the paralysis. The findings of this study corroborate other evidence that the segments of the facial nerve most often involved in Bell's palsy are the only segments that are most often enhanced with gadolinium-enhanced magnetic resonance imaging. The role of gadolinium-enhanced magnetic resonance imaging in the management of Bell's palsy patients is discussed.