Observation of contrast enhancement in the cochlear fluid space of healthy subjects using a 3D-FLAIR sequence at 3 Tesla

In animals, the enhancement of perilymph in the cochlea has been reported using 1.25 mmol/kg of Gd-DTPA, allowing the separate visualisation of perilymph and endolymph for the diagnosis of Meniere's disease. The purpose of this study was three-fold: (1) to determine the optimal timing for detecting cochlear fluid enhancement using 3D-FLAIR (fluid-attenuated inversion recovery) after intravenous administration of 0.1 mmol/kg of Gd-DTPA in healthy human subjects; (2) to examine the reliability of enhancement in multiple healthy subjects; and (3) to investigate whether endolymph and perilymph space can be visually discriminated. In two healthy subjects, 3D-FLAIR images were obtained before, immediately after and 2 h, 4 h and 6 h after the injection. Three more healthy subjects were scanned before and 4 h after the injection. In all four ears of the initial two subjects, cochlear fluid was found to be most intensely enhanced 4 h after the injection. In all of the additional three subjects, the cochlear fluid signal had increased after 4 h from injection. However, visual differentiation of endolymph and perilymph fluid could not be achieved. Using 3D-FLAIR and Gd-DTPA, cochlear fluid enhancement can be observed in healthy human ears, even with a single dose of contrast-medium injection.

Management of the open labyrinth

Labyrinthine fistulas occur in approximately 5% of cholesteatoma cases, but the management of this difficult problem remains controversial. This study assessed the preoperative presentation and outcome in 37 patients operated on for cholestatoma complicated by labyrinthine fistula. Therapy involved removing the matrix from each fistula and reconstructing the bony wall of the labyrinth with bone dust, fibrin glue, and perichondrium. Corticosteroids were added to the management protocol in more recent cases. A fistula classification scheme was introduced to standardize the reporting of the extent of labyrinthine involvement and results of treatment. The most common preoperative symptoms, sensorineural hearing loss and vertigo, were notably lacking in more than 30% of patients. The fistula test was positive in only 32% of cases. Corticosteroids were seen to have a beneficial impact on postoperative outcome in those cases involving injury to the membranous labyrinth or removal of perilymph.

Whiplash, postural control, and the inner ear

Many patients with "whiplash syndrome" experience unrelenting neck stiffness and pain. This abnormal muscular tension is postulated to be causally related to a central disorder of postural control, which has evolved secondary to injury of the inner ear labyrinthine structures. Moving platform posturography was used to demonstrate the presence or absence of a static or dynamic equilibrium disorder in 48 patients who had experienced the oscillation forces induced by a rear-end automobile collision. Other vestibular tests were used to document dysfunction of the semicircular canals and the otolith structures. A high percentage of patients were found to have faulty inner ear functioning leading to inefficient muscular control of balance and erect posture. Active perilymph fistulas were identified at surgery in seven patients.

The Human Spiral Ganglion: New Insights into Ultrastructure, Survival Rate and Implications for Cochlear Implants

This study was based on high-resolution SEM assessment of freshly fixed, normal-hearing, human inner ear tissue. In addition, semiquantitative observations were made in long-term deafened temporal bone material, focusing on the spiral ganglia and nerve projections, and a detailed study of the fine bone structure in macerated tissues was performed. Our main findings detail the presence of extensive bony fenestrae surrounding the nerve elements, permitting a relatively free flow of perilymph to modiolar structures. The clustering of the spiral ganglion cells in Rosenthal's canal and the detailed and intricate course of postganglionic axons are described. The close proximity of fibers to cell soma is demonstrated by impression in cell surfaces, and presence of small microvilli-like structures at the contact regions, anchoring nerve fibers to the cell wall. Extensive fenestrae and the presence of a fragile network of endosteal bony structures at the surfaces guiding nerve fibers are described in detail for the first time. This unique freshly prepared human material offers the opportunity for a detailed ultrastructural study not previously possible on postmortem fixed material and more accurate information to model electrostimulation of the human auditory nerve through a cochlear implant. On the basis of this study, we suggest that the concentration and high density of spiral ganglion cells, and the close physical interaction between neural elements, may explain the slow retrograde degeneration found in humans after loss of peripheral receptors. Moreover, the fragile bony columns connecting the spiral canal with the osseous spiral lamina may be a potential site for trauma in (perimodiolar) electrode positioning.

Transtympanic versus sustained-release administration of gentamicin: kinetics, morphology, and function

OBJECTIVES/HYPOTHESIS

Transtympanic gentamicin therapy has become a popular treatment modality for Meniere's disease, but questions regarding the ideal dose of medicine, the best administration paradigm, and the safest treatment end-point remain unanswered. The goal of this study is to examine the inner ear kinetics of transtympanic gentamicin and compare this with the kinetics of sustained-release delivery in a basic science model. In addition, we plan to examine the relationship of these kinetics curves to the effect of the two treatment modalities on inner ear function and morphology. It is hoped that this analysis will help clinicians to better apply local medical therapy to the ear.

STUDY DESIGN

The study is a basic science project designed to examine perilymph gentamicin concentrations, hearing results, and inner ear morphology in an animal model.

METHODS

Gentamicin was applied to the right ear of chinchillas either through a transtympanic approach or in a sustained-release device. The left ear remained untreated as an internal control. At set time points the animals' hearing and balance function was studied and the perilymph was harvested, after which the animal was killed and preserved for histological evaluation. Kinetics curves were constructed for each of the two treatment paradigms and compared with histological and functional outcomes.

RESULTS

The two groups yielded dramatically different kinetics curves. The transtympanic curve had a high peak level at 24 hours with rapid fall-off and almost total elimination by 48 hours, whereas the sustained-release curve was characterized by a long, flat plateau phase with a peak that was approximately one-third that of the transtympanic curve. In addition, the variability seen in perilymph concentrations was significantly higher in the transtympanic group than in the sustained-release group. Immunohistochemical analysis using antibodies against cleaved caspase-3 and cleaved caspase-7 demonstrated early damage in the spiral ganglion of both groups, before any obvious morphological change in the hair cells. The staining was significantly more dense in animals with transtympanic delivery. Cochlear and vestibular hair cell damage was seen at late time points in animals from both groups. Hearing loss (HL) progressed in an orderly fashion in the sustained-release group of animals, with no HL seen in the early time points and universal significant threshold shifts present by 72 hours. In the transtympanic group, the HL was more variable, with significant threshold shifts occurring as early as 4 hours after treatment, but with some animals demonstrating preserved hearing at the 72-hour time point. All animals demonstrated profound HL at the 6-day time point.

CONCLUSIONS

There is a significant difference in the shape and variability of the perilymph kinetics curve when comparing sustained-release delivery to transtympanic delivery of gentamicin. High early peak levels of gentamicin seen with transtympanic therapy may have a profound effect on the spiral ganglion and produce early HL before obvious hair cell damage. Sustained delivery of gentamicin produces universal HL at 72 hours. The reliability of sustained-release delivery to the ear reduces functional and morphological variations between animals.

The perilymph fistula syndrome defined in mild head trauma

Neurological and neuro-otological studies were carried out on 102 adults with mild cranio-cervical trauma productive of positional vertigo and perilymph fistula as confirmed by laboratory tests, and by the finding of perilymph fistula at tympanotomy in the surgically managed group. In this patient group, all other neurological and neuro-otological diagnoses were excluded, e.g. epilepsy, cerebral palsy, multiple sclerosis, retardation; and for the neuro-otological group those with a history of ototoxicity, labyrinthitis, Meniere's disease, chronic ear infections, or developmental or familial disorders. Emphasis in this study was on mild trauma: fewer than half of the sample had been rendered unconscious in the injury of record, and a third of the cases were of whiplash type, with no loss of consciousness (LOC) and no remembered headstrike. These concomitant lesions comprise the perilymph fistula syndrome (PLFS) with a unique profile of neurological, perceptual, and cognitive deficits resembling a post-concussion injury. A complete description of the clinical picture is given, including psychological, cognitive and diagnostic tests, and the outcome of bedrest vs. surgical management. PLFS can arise from minor trauma, fistula are frequently bilateral (71/102), a mild sensorineural hearing loss is of variable occurrence (53%), secondary hydrops is not uncommon, and women appear more vulnerable than men for developing the syndrome. As based upon combined laboratory techniques and clinical symptomology, fistula were correctly predicted in 61 of 65 laser-operated ears. The positional vertigo component of PLFS was in all cases managed according to a special physical therapy program utilizing exercises for vestibular symptom habituation. Even when diagnosed late, a good-to-excellent outcome was achieved in 70% of treated patients.

Labyrinthine fistulae: pathobiology and management

PURPOSE OF REVIEW

This article reviews literature on three manifestations of these pathologic mechanisms: leakage of perilymph from the inner ear into the middle ear, disruption of the bone of the labyrinth caused by cholesteatoma or other manifestations of chronic otitis media, and superior semicircular canal dehiscence syndrome.

RECENT FINDINGS

Labyrinthine fistulae are caused by abnormal communications between the inner ear and surrounding structures. Under normal circumstances, the fluid-filled spaces of the membranous labyrinth are encased in the dense bone of the otic capsule with only two places of increased compliance: the oval window and the round window. Disruption of the labyrinthine bone can lead to areas of increased compliance, with symptoms and signs that can be understood based upon abnormal pressure transmission in the system. Communication between the endolymphatic and perilymphatic spaces of the labyrinth or passage of perilymph from the labyrinth into the middle ear or mastoid can lead to hearing loss and/or vestibular disturbances.

SUMMARY

Findings on clinical examination as well as CT imaging of the temporal bone can be useful in making the diagnosis. Management is based upon the specific pathological factors and the impact of the symptoms and signs on the patient.

Spontaneous Intracranial Hypotension: A Rare Cause of Labyrinthine Hydrops

Spontaneous intracranial hypotension should be considered as a possible cause of cochlear hydrops. We report a case of unilateral hearing loss attributed to spontaneous intracranial hypotension on the basis of characteristic abnormalities seen on magnetic resonance imaging. The diagnostic gold standards for intracranial hypotension are lumbar measurement of cerebrospinal fluid pressure and magnetic resonance imaging. The usual treatment is an autologous blood injection into the peridural spaces. The mechanism of hearing loss is thought to involve secondary perilymph depression due to a patent cochlear aqueduct. This perilymph depression would induce a compensatory expansion of the endolymphatic compartment, with a subsequent decrease in basilar or Reissner's membrane compliance. Endolymphatic hydrops can occur in the course of intracranial hypotension, and not only because of abnormal endolymph production or resorption. Hydrops can thus be classified into 1) syndromes of endolymphatic origin and 2) syndromes of perilymphatic origin, in which loss of perilymph induces compensatory expansion of the endolymphatic space.

Sudden or fluctuating hearing loss and vertigo in children due to perilymph fistula

Five cases are presented of children with rapid onset of sensorineural hearing loss, disequilibrium, or both, who were found at exploratory tympanotomy to have a perilymph fistula. Four of the children had histories suggesting that antecedent barotrauma or physical exertion contributed to the development of the fistula. One child with congenital unilateral craniosynostosis had a residual temporal bone abnormality on the same side as the perilymph fistula. Two children had identifiable anatomic abnormalities in the middle ear. A classification of perilymph fistula is proposed that describes a congenital, an acquired, and a combined type of fistula. Inner ear fluid dynamics and patency of the cochlear aqueduct appear to be important factors in pathogenesis. Children with unexplained fluctuating or sudden onset of sensorineural hearing loss, and children with unexplained disequilibrium or vertigo should be suspected of having a perilymph fistula. The history can be singularly important in raising the suspicion that a perilymph fistula may be present. Although audiometric, vestibular, and radiographic studies can be helpful, there is no way to prove the presence or absence of a fistula without directly viewing the middle ear. Tympanotomy with repair of the fistula does not assure improvement in hearing.

Deaf animal models for studies of a multichannel cochlear prosthesis

Pathological alterations of the cochlea were studied in three different deaf animal (cat) populations. The ototoxic drug neomycin sulfate, was administered in one experimental series by direct infusion into the cochlear perilymph; a second group was given a series of intramuscular injections of the drug; and in a third experiment a mechanical lesion was made in the basilar membrane of the basal turn and the animals subsequently deafened by systemic neomycin. Hearing losses were tracked by monitoring thresholds of auditory brainstem responses to click stimulation. These deaf cat preparations fairly efficiently model pathologies recorded in man and are highly predictable over an acceptable time frame. Such preparations are of practical value for experiments involving intracochlear electrical stimulation (e.g., with model cochlear prosthesis electrodes).

The effects of inhibition of the strial Na+-K+-activated ATPase by perilymphatic ouabain in the guinea pig

The endolymphatic effects of perilymphatic ouabain (2 X 10(-3) M) were followed in 3 guinea pigs using ion-sensitive micro-electrodes, enabling a Na+-related permeability increase to be identified. Investigation of the strial ultrastructural changes in 11 more animals revealed early swelling of the marginal cells, while the intermediate and basal cells became shrunken with characteristically dark-staining cytoplasm. The subsequent cellular alterations were complex. The findings suggest that a major function of the Na+-K+-activated ATPase is preservation of the normal intracellular environment, inhibition resulting in widespread indirect effects. General measures of strial function, consequently, do not document just ATPase inhibition.

Effects of perilymphatic perfusion with neomycin on the cochlear microphonic potential in the guinea pig

The effects of three concentrations of neomycin, administered by a method of acute perilymphatic perfusion of the guinea pig cochlea, on the cochlear microphonic potential (CM) at 4 kHz and 500 Hz are described. A concentration-dependent reduction in CM occured during the 60 minute perfusion period. Neomycin at 10-4 M did not change the CM magnitude, while at 10-3 and 102 M it caused 4 kHz (and 500 Hz) CM reductions which began within 24 (for both frequencies) minutes and 10 (and 12) minutes of drug application respectively. CM reduction proceeded at a higher rate for greater neomycin concentration. The perfusion technique, the implication of the frequency indifference, and the potential of the perfusion technique for inner ear biochemical analysis are discussed.

Sources of error in use of beta-2 transferrin analysis for diagnosing perilymphatic and cerebral spinal fluid leaks

Beta-2 transferrin is a protein found in cerebral spinal fluid and inner ear perilymph, but not in blood, nasal, or ear secretions. The clinical use of this test has been previously demonstrated, but sources of test error have not been addressed. The purpose of this study was to evaluate sources of error related to this test in order to improve its clinical use. We reviewed the specimens submitted for beta-2 analysis over the first 12 months of test availability at our institution to identify potential factors leading to test error. Sources of error were categorized into the following groups: sample collection, delivery, and extraction factors; assay factors; physician-related factors; and patient-related factors. The test for beta-2 transferrin is a valuable diagnostic tool for the management of difficult clinical problems, provided the physician is aware of potential factors that can lead to test error and clinical mismanagement.

Perilymph fistulas in infants and children

During the years 1975 through 1981 we performed exploratory tympanotomies on 33 infants and children (44 ears) to verify the presumptive diagnosis of perilymph fistula (PLF). A PLF was identified at the round window, oval window, or both in 29 (66%) of the 44 ears explored. After surgery hearing was unchanged in 86%, improved in 5%, and worsened in 9% of the ears in which PLFs had been observed. Complaints of vertigo subsided in all children in whom a PLF was repaired. Preoperative factors determined to be highly suggestive of the presence of a PLF included the following: sudden onset of sensorineural hearing loss (SNHL), congenital deformities of the head, and abnormal findings on tomograms of the temporal bones, especially Mondini-like inner ear dysplasias. Middle ear abnormalities (primarily congenital) were observed in 20 of the 44 ears. Abnormal results of preoperative vestibular function studies, which included a fistula test, and sex were not consistently found to be associated with an observed PLF at tympanotomy.

Morphometric comparison of endolymphatic and perilymphatic spaces in human temporal bones

To measure the endolymphatic and perilymphatic spaces, we used human temporal bones (horizontal serial sections) under two selection criteria: absence of otological pathology, and absence of artifact in the membranous labyrinth (boundary between endolymphatic and perilymphatic spaces) maintaining an intact structural integrity. Under magnified projection, the area of scala tympani, scala vestibuli, scala media, vestibular endolymphatic space, and vestibular perilymphatic space were measured separately, using a microcomputer digitizing tablet. Three repeated measurements were obtained and averaged. The mean total labyrinthine fluid space was 204.5 mm3; the mean total endolymphatic space was 38.1 mm3 and mean total perilymphatic space 166.4 mm3. The mean total vestibular fluid space was 120.9 mm3 and mean total cochlear fluid space 83.6 mm3. In the vestibule, the perilymphatic space occupied 74.8%, and the endolymphatic space, 25.2%, whereas 90.8% of the cochlear fluid space was occupied by perilymph.

Quantitative diagnostic test for perilymph fistulas

Clinically, the definitive diagnosis of perilymph fistulas can only be made by tympanotomy. Results of various fistula tests based upon the vestibulo-ocular reflex have not correlated well with findings during tympanotomy. A new fistula test has been developed based upon vestibulo-spinal responses. By systematic removal of both visual and support-surface orientation references from the subject--leaving only vestibular control of postural reflexes--patients with perilymph fistulas demonstrated an increased (sometimes phase-locked) postural sway in response to sinusoidal changes in external auditory canal pressures. Results from 100 consecutively operated ears (64 patients)--77 of whom underwent preoperative and postoperative moving-platform fistula tests--indicate that the test sensitivity is 97 percent for this highly selective patient population. Absolute specificity could not be determined because, on patients without clinical indications for surgery, tympanotomy is contraindicated.

Perilymph fistulas. Diagnostic criteria and therapy

Fifty-one patients suspected of having a perilymph fistula were evaluated. We postulated that many patients with predominantly vestibular complaints had unrecognized perilymph fistulas. An analysis was made of symptoms, physical findings, vestibular and audiometric test results in order to determine appropriate diagnostic criteria for the presence of perilymph fistulas. The patient population was divided into two groups, those with and without fistulas. Data from both groups were compared by mean values of variables, step-wise discriminant analysis, and factor analysis. A history of trauma with sudden onset of dizziness and/or hearing loss should alert the physician to a fistula. Findings of significance were positional nystagmus of short latency and long duration without import of nystagmus direction, canal paresis and reduced speech reception threshold with poor speech discrimination scores. Discriminant analysis correctly classified 19 fistula and 10 nonfistula cases explored operatively and identified two error judgments in 22 nonoperated cases. Bed rest for the first five days proved to be the most effective means of therapy. Surgical intervention with repair of the fistula by perichondrial graft provided effective control of vertigo more frequently than restoration of hearing.

Novel 3D-printed hollow microneedles facilitate safe, reliable, and informative sampling of perilymph from guinea pigs

BACKGROUND

Inner ear diagnostics is limited by the inability to atraumatically obtain samples of inner ear fluid. The round window membrane (RWM) is an attractive portal for accessing perilymph samples as it has been shown to heal within one week after the introduction of microperforations. A 1 µL volume of perilymph is adequate for proteome analysis, yet the total volume of perilymph within the scala tympani of the guinea pig is limited to less than 5 µL. This study investigates the safety and reliability of a novel hollow microneedle device to aspirate perilymph samples adequate for proteomic analysis.

METHODS

The guinea pig RWM was accessed via a postauricular surgical approach. 3D-printed hollow microneedles with an outer diameter of 100 µm and an inner diameter of 35 µm were used to perforate the RWM and aspirate 1 µL of perilymph. Two perilymph samples were analyzed by liquid chromatography-mass spectrometry-based quantitative proteomics as part of a preliminary study. Hearing was assessed before and after aspiration using compound action potential (CAP) and distortion product otoacoustic emissions (DPOAE). RWMs were harvested 72 h after aspiration and evaluated for healing using confocal microscopy.

RESULTS

There was no permanent damage to hearing at 72 h after perforation as assessed by CAP (n = 7) and DPOAE (n = 8), and all perforations healed completely within 72 h (n = 8). In the two samples of perilymph analyzed, 620 proteins were detected, including the inner ear protein cochlin, widely recognized as a perilymph marker.

CONCLUSION

Hollow microneedles can facilitate aspiration of perilymph across the RWM at a quality and volume adequate for proteomic analysis without causing permanent anatomic or physiologic dysfunction. Microneedles can mediate safe and effective intracochlear sampling and show great promise for inner ear diagnostics.

ECoG results in perilymphatic fistula: clinical and experimental studies

Patients with perilymphatic fistula have been described as having symptoms similar to Meniere's disease and endolymphatic hydrops. Direct clinical or experimental evidence linking the two inner ear disorders has been lacking. An enhancement of the summating potential observed with electrocochleography suggests a diagnosis of ELH in both of these inner ear disorders. In this study, ECoG results of 27 patients with surgically confirmed PLF are reported. Fourteen patients with surgically confirmed spontaneous PLF had abnormal ECoG. Six of these 14 patients had normal hearing. The ECoG changes in patients with Meniere's disease and those with surgically confirmed PLF are identical, indicating the underlying pathologic change in both is hydrops. But there is no specific diagnostic abnormality on ECoG that differentiates these two inner ear disorders. Also, an experimental model of PLF was developed and studied in guinea pigs. "Inactive" PLF is defined as "an opening was made into the cochlea, but if no perilymph moved out through the fistula, it was defined as inactive" An "active" PLF occurs when perilymph actually moves from the inner ear out to the middle ear. ECoGs were recorded before and after creation of an "active" PLF. ECoG abnormalities were seen in "active" PLF and correlated with histologic data demonstrating ELH. An abnormally enhanced summating potential was demonstrated after active removal of perilymph through the experimentally created fistula. Cochlear duct histology showed hydropic distention of Reissner's membrane in the experimental ears and no changes in the membranous labyrinths of the unoperated, control ears.(ABSTRACT TRUNCATED AT 250 WORDS)

Inner ear fluid volumes and the resolving power of magnetic resonance imaging: can it differentiate endolymphatic structures?

Magnetic resonance imaging (MRI) can accurately recognize minute volumes as small as 1 mm3. The volumes of the utricle and saccule of the inner ear are within the resolving power of MRI, but these structures cannot be recognized because the endolymph and perilymph signals are identical. To clarify the interpretation and description of inner ear structures on MRI, we measured and calculated the volumes of the perilymphatic and endolymphatic spaces of the human ear. We found the total volume of the bony labyrinth to be approximately 192.5 mm3 (endolymph, 34.0 mm3; perilymph, 158.5 mm3).

Perilymph fistula: the Stanford experience

Seventy-eight tympanotomies were performed to determine the presence of perilymph fistulas (PLFs); of these, 51% were found. The oval and round windows of all patients were grafted, whether PLFs were present or not. Of those patients with PLFs, 64% had resolution of their major symptom; when no PLF was found, 44% had a similar outcome. We concluded that 1) PLFs often behave as if they are epiphenomena in relation to hearing and balance, 2) PLFs can be intermittent, 3) PLF surgery is disappointing for restoration of hearing in sudden hearing loss when compared to the rate of spontaneous recovery, 4) stabilizing a fluctuating or progressive loss is a more realistic goal, and 5) establishing preoperative criteria for exploration is still a problem.

The gene for X-linked progressive mixed deafness with perilymphatic gusher during stapes surgery (DFN3) is linked to PGK

A linkage analysis has been performed in a large Dutch kindred with progressive mixed deafness with perilymphatic gusher during stapes surgery (DFN3) using a panel of X-chromosomal RFLPs. Tight linkage (zmax = 3.07 at 0 = theta = 0.00) was demonstrated with the locus for phosphoglycerate kinase (PGK), which is located at Xq13. Tight linkage was excluded for DXS9 (probe RC8) and DXS41 (probe 99.6) on Xp and for blood clotting factor 9 (FIX) on distal Xq. Deafness is one of the predominant clinical features in males with deletions of the Xq21 band. Our results suggest that this association may be due to involvement of the DFN3 gene.

Diagnosis of perilymph fistula using ENG and impedance

The presence of perilymph fistula has been difficult to determine because of the lack of efficient and reliable testing methods. The condition is suspected on the basis of history alone and confirmed by surgery. This paper details a quick, reliable procedure called the ENG fistula test, using impedance bridge for pressure change and electronystagmography to aid the establishment of nystagmus and dizziness. To evaluate this procedure, a combination of tests were performed, including Valsalva maneuver, tragal compression, and pneumatic otoscopy, which were previously considered helpful in the diagnosis of fistula. Of them, Valsalva maneuver and tragal compression proved inconclusive; pneumatic otoscopy proved to be helpful. In comparison, however, the ENG fistula test proved most valuable, with results surgically confirmed in 90.8% of cases in this series. This study involved 74 patients whose primary complaint was dizziness. Only some patients simultaneously experienced hearing lows. Included are 5 patients whose positive ENG fistula test results and 15 whose negative test results were confirmed by surgery. Selected case histories are presented.