[ASA and the inner ear. An old acquaintance in a new light].
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Animals↗
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[The Stennert antiphlogistic-rheologic infusion schema in treatment of cochleovestibular disorders].
The pathogenetic mechanisms of acute cochleo-vestibular lesions are still unknown, but viral infections and vascular phenomena with impairment of microvascular perfusion are thought to play a major role. Between 1 July, 1986 and 28 February 1998, 1501 patients were treated with an infusion protocol using cortisone, dextrane 40 and pentoxifylline. Group 1 contained 1001 patients with sudden hearing loss, group 2a 107 patients with isolated tinnitus and group 2b 393 patients with labyrinthine disorders (among which were 81 patients with cochleovestibular dysfunction). The records were evaluated retrospectively. In group 1 complete hearing recovery occurred in 44.8%, partially in 40.4%, no change in 12.1% and worsened in 2.6%. In group 2a with isolated tinnitus 17.9% had a complete recovery, 43.9% partial recovery, 35.5% no change and 2.8% worsened symptoms. In group 2b vertigo disappeared in 56.8%, had partial recovery in 21.0% and did not change in 7.4%. In the 1501 patients treated, no significant side-effects were found to the medical interventions used. From these results we conclude that the infusion protocol is safe and effective in the treatment of cochleo-vestibular disorders.
Adolescent↗
[Measuring beta-trace protein for detection of perilymph fistulas].
BACKGROUND: beta-trace protein is an immunological marker for cerebrospinal fluid or inner ear fluids. We present two initial cases in which a beta-trace protein nephelometric assay provided immunological proof of perilymph in samples taken from the nasopharynx. PATIENTS AND METHODS: Two cases are presented of an acute vestibulocochlear disorder following stapedotomy. Fluid samples, taken from the nasopharynx, were investigated using beta-trace protein laser nephelometry. The samples were collected using Merocel tamponades, which were left in place over night. RESULTS: In both cases, the samples were positive for beta-trace protein. Tympanoscopy was performed and the oval window was closed. After tympanoscopy a partial recovery of the hearing impairment was observed. CONCLUSION: Using beta-trace protein, it seems to be possible to diagnose a perilymphatic fistula by noninvasive means.
Adult↗
Functional and morphological effects of styrene on the auditory system of the rat.
The effect of inhaled styrene on the structure and function of the auditory organ of the male Wistar rat was studied. The animals were exposed either to 600, 300 or 100 ppm styrene (12 h/day, 5 days/week, for 4 weeks). Auditory sensitivity was tested prior to and after the exposure by auditory brain stem audiometry (ABR) at frequencies of 1.0, 2.0, 4.0 and 8.0 kHz. Inner ear morphological changes were studied by light- and electron-microscopy. Exposure to 600 ppm styrene caused a 3 dB hearing loss only at the highest test frequency (8 kHz). Quantitative morphological analysis of cochlear hair cells (cytocochleograms) showed that 600 ppm styrene caused a severe outer hair cell (OHC) loss particularly in the third OHC row of the upper basal and lower middle coil. The inner hair cells were usually intact. Exposure to lower styrene concentrations (100 and 300 ppm) caused no unequivocal functional deficit or hair cell damage. We conclude that there appears to be a concentration threshold for styrene ototoxicity in rats (between 300 and 600 ppm).
Administration, Inhalation↗
Secondary superficial siderosis of the central nervous system in a patient presenting with sensorineural hearing loss.
We present a 50-year-old man who was investigated for sensorineural hearing loss. On MRI of the brain superficial siderosis of the central nervous system was seen, while MRI of the spine revealed an ependymoma of the cauda equina. This case illustrates the importance of performing T2-weighted imaging of the brain and posterior fossa when sensorineural hearing loss is present. Spine imaging is mandatory when superficial siderosis of the brain is diagnosed without identification of a bleeding source in the brain.
Brain↗
Could vestibular evoked myogenic potentials (VEMPs) also be useful in the diagnosis of perilymphatic fistula?
The role of vestibular evoked myogenic potentials (VEMPs) is at this time indisputable in the study of vestibular disorders. Furthermore, VEMPs are widely accepted as a diagnostic tool when a superior semicircular canal dehiscence (SCD) is suspected, presenting in such cases a lowering of threshold values able to raise a recordable response due to increased inner ear immittance. According to the same principle, the possibility of another kind of alteration having the same effect on the inner ear might be considered when high-resolution computed tomography has excluded the presence of an SCD. In this paper four cases are described in which high-resolution computed tomography showed normal features without any labyrinthine dehiscence and VEMP threshold values were lowered; the appropriateness of suspecting a perilymphatic fistula in such cases and resorting to VEMPs in detecting a perilymphatic fistula is discussed.
Adult↗
The effect of promontorial bone on laser light transmission in measuring capillary blood flow in vivo.
Use of laser Doppler flowmetry (LDF) to assess cochlear blood flow (CBF) in experimental animals has elucidated the complex mechanisms in CBF regulation. Some attempts have been made to measure CBF in humans, although earlier studies produced confusing data about the physical possibility of LDF penetrating the human tympanic cavity promontory. In this study, we used LDF in an attempt to observe capillary blood flow in vivo through the intact human promontory in order to develop a method for measuring CBF in human patients. Temporal bones from six human cadavers were removed and the promontory overlying the basal turn of the cochlea was drilled off and fixed in 10% formalin. Perpendicular bone thickness was measured at the site of the stria vascularis. Seven young rats were anesthetized and the carotid artery was cannulated for blood pressure recording. Capillary flow was registered with LDF from two sites, the kidney and the plantar area of a hind limb, using a custom-designed probe with 632.8 nm and 780 nm wavelengths. Intravenous epinephrine was used to evoke blood flow changes. The same measurements were repeated through the promontorial bone. The light attenuation induced by the promontorial bone was 79+/-28% for the 632.8 nm wavelength, and 22+/-15 to 65+/-13% for the 780 nm wavelength, depending on the thickness of the bone. The sensitivity in detecting minute changes was 78% and 91-96%, respectively, for the 632.8 nm and 780 nm wavelengths. This study indicates that it is possible to detect minute changes in capillary blood flow through the intact human promontory at the site of the stria vascularis.
Adult↗
Recurrent meningitis and cerebrospinal fluid leak-two sides of the same vestibulocochlear defect: report of three cases.
Cochlear dysplasia is a rare congenital anomaly. However, early detection of this anomaly can prevent serious consequences. We describe three cases of cochlear dysplasia that presented with recurrent meningitis and cerebro-spinal fluid (CSF) leak in children in which early diagnosis prevented further complications.
Child, Preschool↗
Neurovascular compression syndrome of the eighth cranial nerve. What are the most reliable diagnostic signs?
Forty-three surgical cases were retrospectively analyzed to establish diagnostic criteria and operative indications for vertigo and tinnitus due to neurovascular compression (NVC) of the eighth cranial nerve (8th N). Many NVC syndromes were mistakenly diagnosed as Ménière's disease or benign paroxysmal positional vertigo. NVC was confirmed in 31 of the 43 patients. Neurovascular decompression (NVD) resulted in complete recovery or marked improvement of subjective symptoms in all 19 cases with vertigo (100%), and in 19 of 29 patients with tinnitus (65.5%). Multiple factor analysis revealed that abnormal caloric responses have high diagnostic value for vertigo due to NVC. Vertigo due to NVC is of short duration (a few sec to a few min.) in the early phase of the disease, which becomes longer and hearing becomes impaired as the history of NVC lengthens. Low pitch pulsatile and high pitch continuous tinnitus are probably due to NVC and are cured by NVD if hearing is still preserved. Tinnitus associated with hemifacial spasm is strongly indicative of NVD. Decompression of the 8th N should be performed in the early phase of disease, since cochlear and vestibular functions are irreversibly impaired if NVC continues for a long period of time.
Adult↗
Electrophysiological responses of the cochlea to transient asphyxia are influenced by arachidonate metabolites.
The influence of a transient asphyxia on cochlear potentials, i.e. endolymphatic potential (EP), summating potential (SP) and cochlear microphonics (CM) was investigated in guinea pigs when pretreating the animals with various substances interacting with the arachidonic acid (AA) cascade at the level of thromboxane. The controls showed the well-known decline of the EP, CM and the SP increase. When infusing a thromboxane synthetase inhibitor (dazoxiben) or two different thromboxane receptor blockers (daltroban or sulotraban) before the 3-minutes' period of asphyxia was started, the electrophysiological responses of the inner ear (cochlea) could significantly be influenced. The results indicate that a shift of the thromboxane (TXA2)/prostacyclin (PGI2)-balance in favour of the last improve the metabolic conditions for a survival of the cochlea when it is challenged.
Analysis of Variance↗
Evoked otoacoustic emissions and pure tone threshold audiometry in patients receiving cisplatinum therapy.
Eight children and young adults with cancer were evaluated serially using pure tone audiometry as well as registration of click-evoked otoacoustic emissions (EOAE) 1 day prior to therapy as well as after various numbers of doses of cisplatinum. A reduction of EOAE-amplitudes following cisplatinum therapy was observed in all patients. This reduction tended to recover after the end of cisplatinum administration. Since EOAE are believed to result from cochlear bio-mechanical processes, the reduced emissions are interpreted as signs of cochlear dysfunction. We conclude, that EOAE testing may be a simple, non-invasive method that may detect early, transient functional impairment of hearing due to ototoxic agents such as cisplatinum, even in children. Further controlled trials are needed.
Acoustic Stimulation↗
Influence of click polarity on the brain-stem auditory evoked response (BAER) revisited.
Brain-stem auditory evoked responses (BAERs) were recorded both to rarefaction and condensation click stimuli in 92 normal hearers and 78 patients with varying degrees of cochlear hearing loss (N = 340 ears). Frequency distributions of rarefaction minus condensation (R - C) latency and amplitude differences revealed clinically significant polarity effects in a substantial percentage of the patients studied. Bivariate plots of R - C latency and amplitude differences versus average high frequency hearing loss (PTA 3) demonstrated that the magnitude of the R - C latency and amplitude differences also seemed to be influenced by degree of high frequency hearing loss. Results are discussed relative to the phase-locking properties of the afferent auditory nerve fibers and the possible electrodiagnostic consequences of recording the BAER either to alternating or condensation clicks.
Acoustic Stimulation↗
Cochlear histopathology in Paget's disease.
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Cochlea↗
Extensive otosclerosis and endolymphatic hydrops: histopathologic study of temporal bones.
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Cochlear Diseases↗
Effects of organic acids on the edema of the stria vascularis induced by furosemide.
Furosemide is a loop diuretic which is ototoxic. Investigations have shown the stria vascularis to be the target tissue of this ototoxic drug. The purpose of the present study was to investigate the effects of furosemide on the stria vascularis in chinchillas, in controls and in animals pretreated with the above organic acids. Control animals were injected with 0.5 ml alkalinized saline followed by furosemide IV 30 min later. Experimental animals received probenecid, penicillin or sodium salicylate IV. Thirty minutes later, furosemide was injected in the same dose as in the controls. The basal turn of the stria vascularis was rapidly removed at various times from 10 to 30 min after furosemide administration and processed for transmission electron microscopy. Control animals were found to have reversible edema of the stria vascularis. Experimental animals had variable findings. Those animals pretreated with penicillin had virtually no edema of the stria vascularis at any time. Salicylate and probenecid pretreated animals had significantly less edema from one to 10 min after furosemide injection, but more edema than controls at later times. These findings suggest a discrepancy between ultrastructural pathology and functional status of the cochlea in experimental animals pretreated with probenecid or sodium salicylate followed by furosemide. On the other hand, good structure function correlations were seen in controls and in experimental animals pretreated with penicillin.
Acids↗
Cochlear blood flow measured by averaged laser Doppler flowmetry (ALDF).
This report describes a new approach to estimate the hydromechanical properties of a vascular system. Averaged laser Doppler flowmetry (ALDF) was developed by averaging the flux signal of a laser Doppler flowmeter (LDF) synchronized to the heart cycle. The usefulness of this method was verified by manipulation of the cochlear microvasculature. Twelve pigmented guinea pigs under pentobarbital/fentanyl anesthesia were used. The cochlea was surgically exposed and the LDF probe placed on the bony surface of the first turn to monitor cochlear blood flow (CBF). The LDF flux signal (0.2 s time constant) was sampled by an A/D board at 2 kHz for 255 ms and averaged with synchronization to the heart beat. The mean blood flow, peak to peak amplitude, and time (phase) delay of pulsatile flow were measured from the averaged signal. According to a transmission line model of the vascular system, under a given perfusion pressure, mean flow reflects resistance while amplitude and time delay of the pulsatile flow are related to the reactance component of the impedance of the vascular system. During the formation of photochemically-induced thrombosis in the cochlear microvasculature, there was a dramatic mean flux decrease (90.1 +/- 3.4% from baseline (BL), N = 6). Additionally, a time-dependent decrease in amplitude and time delay of pulsatile flow were indicated by ALDF. These results suggest a large increase in vascular resistance and significant decrease in compliance.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
A reversible ischemia model in gerbil cochlea.
A completely reversible cochlear-ischemia animal model was developed, and an initial study of ischemia/reperfusion-induced cochlear function change is presented. The bulla of the anesthetized gerbil was opened through a ventral approach and the anterior inferior cerebellar artery and its branches were exposed. Cochlear blood flow (CBF) from the basal turn of the cochlea was monitored with a laser Doppler flowmeter. An electrically isolated microclamp was used to occlude the labyrinthine artery (LA). During LA clamping, the cubic distortion product (DP) was continuously recorded. The LA was repeatedly clamped for different durations in all animals, and CBF consistently showed full recovery after clamp release. No obvious change in vessel diameter or flow pattern was observed under a stereomicroscope. Mean blood pressure did not show significant change during clamping. Immediately upon LA clamping, CBF decreased rapidly nearly to zero. After clamp release, CBF demonstrated an immediate rapid increase, followed by a secondary gradual recovery to baseline. CBF recovery patterns were clamp duration-related. Within a few seconds of occlusion, DP decreased and reached a minimum of approximately 24% of the initial level in less that 30 s. Following reperfusion of the cochlea, DP gradually increased, decreased again, then slowly recovered. Time delay between CBF reperfusion and the first increase of DP was proportional to clamping duration, and the increased amplitudes demonstrated a negative relationship to clamp duration. We assume that the first decrease in DP during clamping was caused by ischemia in the cochlea; the second decrease, during the cochlear reperfusion, could be a form of reperfusion-induced change in cochlear function. This ischemia/reperfusion model in gerbil cochlea demonstrates excellent repeatability and reversibility. Since DP and other measurements can be used to dynamically monitor cochlear or hair cell functions, this model is useful in studies of auditory physiology and pathophysiology.
Animals↗
Extracochlear electrically evoked otoacoustic emissions: a model for in vivo assessment of outer hair cell electromotility.
Cochlear outer hair cell (OHC) motion in response to changes in membrane potential (electromotility) has been extensively studied in vitro. Electromotility is thought to actively control the micromechanical properties of the sensory epithelium. In order to understand how OHC electromotility contributes to normal cochlear responses, its role must be assessed in vivo. We have developed a novel animal model for the study of electromotility in vivo. Alternating current is delivered by an electrode to the round window (RW) of gerbil cochlea and the electrically evoked otoacoustic emission (EEOE) is measured from the external ear canal. As much as 45 dB SPL sound could be generated by about 200 micro A RMS extracochlear current delivered to the RW. Except for the fine structure of EEOE transfer function curves, the magnitude of the EEOE has a bandpass appearance ranging from about 4 to 32 kHz and shows a positive linear relationship to the current intensity. The phase has a linear relationship with frequency and shows no significant change with current intensity. Local intracochlear perfusion of 4% paraformaldehyde caused EEOE to decrease by approximately 20 dB. These results indicate that the EEOE is probably generated by OHCs near the electrode location and propagates to the external ear canal. In addition, the force generated by OHCs in vivo is a linear function of the electrical stimulus. The major advantages of our model include: (1) non-invasive procedure and normal cochlea; (2) wide dynamic range of the measurement; (3) simple and easy preparation. With these features this model has potential applications in basic hearing research and in the diagnosis and treatment of otological patients.
Animals↗