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At least 487 records · Page 27Linked to original sources
PubMed2004

[The effects of DPPH on cochlear microcirculation].

OBJECTIVE: To investigate the effects of free radical, 1, 1-Diphenyl-2-picylhydrazyl(DPPH), on cochlear blood flow. METHOD: Twenty guinea pigs were divided into 3 groups at random, 6 for control group, 6 for 1 mmol/L of DPPH group and 8 for 0.1 mmol/L of DPPH group. 2 microliters vehicle or drugs were dropped into round window membrane. Cochlear microcirculation was monitored by laser Doppler flowmeter and the mean arterial blood flow(MABP), which transferred by pressure conductor sensor and preamplifier, was simutaneously recorded by a computer. RESULT: MABP was stable throught the experiment. Cochlear blood flow increased 12.49% (P < 0.05) in 1 mmol/L group, and decreased 3.02% (P < 0.05). In control group cochlear microcirculation had no significant changes. CONCLUSION: DPPH has effects on cochlear microcirculation. The mechanism still need to be explored later.

Animals↗
PubMed2004

[Round window area temporal bone section versus CT].

OBJECTIVE: To locate round window area and its related structure on auris transection and CT for anatomical evidence of image diagnosis and clinical operation. METHODS: Fifteen normal head specimen fixed with 10% dehyde were scanned by high-resolution computed tomography on canthomeatal line. CT image (depth 1.00 mm, thick 1.00 mm) was obtained. Temporal bone-centered tissues were taken, decalcified, desiccated and socked with collodion, then embedded and made into sequential transactions (thick 1.00 mm). Lower surface of section was observed by both naked eyes and microscope, then scanned and photographed. Versus CT image, auditory ossicle, osseous semicircular canals, vestibule, round window, niche, cochlea, pyramidal eminence, internal acoustic meatus and cochlear aqueduct were identified respectively. RESULTS: There were 18-22 layers of temporal transection on CT image. Round window and round window niche always appeared on the 10th layer (R) and the 11th layer (L). The mean of the depth of anterior wall was 0.92 mm (R) and 0.90 mm (L), and depth 1.89 mm (R) and 2.04 mm (L). The average distance from niche to jugular fossa wall was 2.10 mm (R) and 2.39 mm (L). No significant difference among of thickness, depth and distance from niche to jugular fossa wall. CONCLUSIONS: Temporal bone transection specimen had a clear picture of anatomical position between round window area and its related structure. Versus CT, the result contributed to image diagnosis and operation on auris diseases.

Adult↗
PubMed2005

[Dexamethasone pharmacokinetics in perilymph of guinea pig after different topical administrations].

OBJECTIVE: To determine pharmacokinetics profiles of dexamethasone (DEX) in perilymph of guinea pig with different intratympanic administrations, and to provide experimental evidence for clinical choice about administration. METHOD: Two different topical administrations placing a granule gelfoam soaked with DEX (10 g/L) in the niche of round window of guinea pig and infusing tympanic bulb with DEX solution (10 g/L) were conducted. Perilymph of the scala tympani was sampled 1-6 h after administration. DEX in the samples was assayed with high-performance liquid chromatography. RESULT: The concentrations of DEX in perilymph after placing a granule gel-foam soaked with DEX in the niche of round window were significantly higher than that after intratympanic infusing. The half-life time of DEX after placing a granule gelfoam was longer. CONCLUSION: DEX could effectively penetrate round window membrane into perilymph after different intratympanic administrations, and the method of placing a granule gelfoam soaked with DEX in the niche of round window is more effective than that of intratympanic infusing.

Administration, Topical↗
PubMed1992

Effect of round window membrane application of salicylate and indomethacin on hearing and levels of arachidonic acid metabolites in perilymph.

Our previous studies revealed that systemic salicylate-induced ototoxicity is associated with altered levels of arachidonic acid metabolites (AAMs) in the perilymph. In order to eliminate the possibility of systemic toxic effects of salicylate when it is given parenterally, an animal model of salicylate-induced ototoxicity was developed by applying it on the round window membrane (RWM). Using chinchillas as experimental animals, sodium salicylate (150 micrograms) or another nonsteroidal anti-inflammatory drug (NSAID), indomethacin (20 micrograms) was applied on the RWM, cochlear function was determined by auditory brainstem response (ABR) and perilymph assayed for AAMs both prostaglandins (PGs) and leukotrienes (LTs) by high performance liquid chromatography (HPLC) and radioimmunoassay (RIA) at different time intervals. When salicylate or indomethacin was applied on the RWM, dose-dependent ABR threshold losses of 20 to 50 dB was observed in 1 to 2 hours associated with decreased concentrations of 6-keto-PGF1 alpha and elevated levels of LTs. The hearing loss recovered to normal threshold over a period of 8 hours. The control group showed no hearing loss or any change in PG or LT-levels in the prilymph. The results of this study suggest that the method of inducing ototoxicity by applying salicylate or indomethacin on the RWM seems to be a reliable method for avoiding systemic toxicity of the parenteral treatment method and that ototoxicity induced by salicylate or indomethacin may be mediated by decreased PGs and elevated LTs.

Animals↗
PubMed1991

Effects of L-glutamine, glutaminase and glutamine synthetase on CAP threshold of cochlear nerve of guinea pig.

Negative direct current (-DC 300 microA) stimulation was applied to the round window of the guinea pig cochlea to exhaust the pre-synaptic intracellular reserves of the transmitter in hair cells, and then the scala tympani was perfused respectively with L-glutamine, glutamine synthetase and glutaminase. Experimental results showed that the negative DC electrical stimulation applied to the round window elevated the CAP threshold of the cochlear nerve in the basal turn of the cochlea, which recovered over a period of approximately 17-39 min. The perfusion of L-glutamine apparently elevated the CAP threshold. The recovery of the CAP threshold following electrical stimulation, however, was accelerated by the perfusion of 10 mmol/L L-glutamine. The time for recovery only took about 5-6 min. The perfusion of enzyme glutamine synthetase elevated the CAP threshold by 50 dB, while glutaminase had little effect. These results suggest that the effect of L-glutamine on the CAP threshold in the cochlea of the guinea pig appears to be that of a potent depolarizing agent which accelerates the recovery of the CAP threshold during the depletion of the transmitter, and L-glutamine may be the candidate for the afferent excitatory transmitter.

Animals↗
PubMed2006

The anatomy of the tympanic sinus.

The tympanic sinus is one of the most important structures of the human temporal bone. Located in its vicinity are the round window, posterior semicircular canal and facial nerve. The study was performed on 30 temporal bones taken from adult cadavers of both sexes. After the tympanic sinus had been identified, its morphological features were evaluated. The sinus was then measured using a graticule with an accuracy of 0.05 mm. Also measured were the shortest distances from the tympanic sinus to the neighbouring structures (the lateral and posterior semicircular canal, the facial nerve canal and the jugular fossa). The measurements were performed under a surgical microscope with eye-piece graduation of 0.05 mm accuracy. Four main morphological types of fossa of the tympanic sinus and two main developmental forms, a deep sinus and a shallow sinus, were distinguished. The existence of a deep sinus was associated with absence of the bridge and the sinus was shallower when the bridge was prominent. The very deep sinuses were located close to the facial canal, in some cases penetrating deep in its vicinity (in some cases even going beyond two thirds of the canal's circumference), which poses a real risk of facial nerve damage during surgical removal of a lesion located in close proximity to the nerve. In most cases the tympanic sinus is elliptical in shape and its long diameter lies in the vertical plane (mean value: 2.73 x 2.23 mm). The mean distances from the tympanic sinus to the facial nerve canal, lateral semicircular canal, posterior semicircular canal and jugular fossa were 1.5 mm, 2.1 mm, 1.59 mm and 5.5 mm respectively. No correlation was observed between the measurement results and either sex or side.

Adult↗
PubMed2006

[Use of intraoperative round window electrocochleography for assessment of cochlear implantation safety].

OBJECTIVE: To objectively evaluate whether cochlear implantation surgery made damage to cochlear basal membrane or not through analyzing the change of the threshold of cochlear microphonic (CM) of round window electrocochleography before and after inserting electrode during cochlear implantation surgery. METHOD: Round window electrocochleography was performed on 40 cases with profound sensorineural deafness under general anesthesia in the standard operating room in order to analyze the change of the threshold of cochlear microphonic (CM) of round window electrocochleography before and after inserting electrode during cochlear implantation surgery. RESULT: Among the 40 cases, thresholds of cochlear microphonic (CM) before and after inserting electrode during cochlear implantation surgery were similar in 39 cases. The thresholds of cochlear microphonic (CM) after inserting electrode decreased about 5 dB at certain frequency. The thresholds of cochlear microphonic (CM) after inserting electrode increased 20-50 dB in only one case. There was a sense of resistance in implanting the electrodes in this patient. CONCLUSION: Use of round window electrocochleography may objectively evaluate whether cochlear implantation surgery make damage to cochlear basal membrane or not.

Adolescent↗
PubMed1991

Physiologic measures of electrically evoked auditory system responsiveness: effects of pathology and electrical stimulation.

During the past years we have addressed issues of implant application in children related to candidate selection and time of implantation. The studies have incorporated an assessment of the utility of the electrically evoked middle latency response (EMLR) as a measure of responsiveness of the central auditory pathways elicited by electrical stimulation. We have demonstrated that the EMLR in the guinea pig is similar in waveform characteristics to the acoustically elicited MLR, that it is equal in sensitivity to the electrically evoked auditory brainstem response (EABR) and can be used to reflect the sensitivity of different sites of stimulation. Because of its longer latency, the EMLR shows far less sensitivity to electrical artifact than the EABR. While suprathreshold characteristics of the EMLR are affected by anesthesia (ketamine and xylazine), threshold is not. In the ototoxically deafened animal we have found a decrease in the amplitude input/output function slope with decreasing density of spiral ganglion cell survival and that moderately high intensity of electrical stimulation produces a temporary threshold shift (eTTS) in the EMLR. These data suggest that this measure may be useful in assessing surviving spiral ganglion cell populations for the selecting of candidates for implantation and establishing safe, functional, upper-limits of electrical stimulation for young children. Finally, we have found that early electrical stimulation can reduce the progress of spiral ganglion cell degeneration secondary to ototoxic-induced hair cell loss.

Acoustic Stimulation↗
PubMed1986

[Sudden deafness caused by rupture of the round window membrane. Surgical indications, course and prognosis].

Tympanotomy was performed on 39 of 247 patients with sudden hearing loss between 1980 and 1982. In 23 cases a round window membrane defect was found. Evaluation of the indications, intraoperative findings and postoperative course allows the following conclusions to be drawn. Only in patients treated in the second week was the rate of success significantly higher than the spontaneous remission rate in patients without perilymphatic fistula. If there is no improvement in the hearing level in the first week after covering a round window membrane defect the prognosis is poor. Stabilization of the hearing is complete in the first three weeks after treatment. Prognosis in extensive membrane defects with large perilymphatic fistulas is definitely worse than in small round window membrane defects. The best results were achieved for the following groups: physical exertion/barotrauma, sudden deafness, progressive hearing loss despite drug therapy.

Aprotinin↗
PubMed1989

Pre-operative cochlear implant assessment using a round window ball electrode.

Placement of a round window electrode allows far superior electrical assessment of a cochlear implant candidate than promontory stimulation. The approach to the round window necessitates either a tympanomeatal flap, which requires a certain amount of time and nursing support, or a myringotomy which may raise worries about possible iatrogenic perforations as well as about technical difficulties of access to the round window. We have used a myringotomy incision in 20 cases. The technique and results are discussed, both in terms of electrical data obtained and of access to the round window. There were no cases of persistent perforation.

Acoustic Stimulation↗
PubMed1989

[Personal experiences with audiometric detection of perilymph fistulas].

Rupture of the round window membrane is thought to be important in the pathogenesis of sudden hearing loss. In 1982 Fraser and Flood proposed an audiometric test to improve the indication for tympanoscopy which, in their experience, verified the diagnosis of perilymph fistulae in a high percentage of cases. Between 1 January 1986 and 30 June 1988 the above test was carried out on 74 patients at the ENT Department of the University of Hamburg. In 41 cases a tympanoscopy was performed. In 13 cases with a positive test result not a single perilymphatic fistula could be found intra-operatively, while in 3 cases of rupture the test was negative. In our experience this test is not helpful for the pre-operative assessment of tympanotomy in sudden hearing loss.

Audiometry↗