Deneysel intratimpanik steroid uygulamasının koklea fonksiyonları üzerine etkisinin elektrofizyolojik ve ultrastrüktürel olarak değerlendirilmesi
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Tarih
2008
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info:eu-repo/semantics/openAccess
Özet
İntratimpanik yolla uygulanan deksametazonun, kobaylarda koklear fonksiyon ve yapı üzerindeki etkisinin elektrofizyolojik testler (Transient Evoked Otoakustik Emisyon ve İşitsel Beyinsapı Yanıtları) ve ultrastrüktürel (ışık ve elektron mikroskopik) olarak araştırıldığı çalışmamızda; elektrofizyolojik testler sonucunda, normal işitme eşiği ve emisyon varlığı saptanan toplam 20 kobayın 40 kulağı çalışma kapsamına alındı ve randomize olarak 6 gruba ayrıldı. Bu altı grubun dördü (I., II., IV. ve V. gruplar) çalışma grubu (her grupta 7'şer kulak), ikisi (III. ve VI. gruplar) kontrol grubu (her grupta 6'şar kulak) olarak planlandı. Çalışma grubundaki kulaklara, intratimpanik olarak deksametazon, kontrol grubundaki kulaklara serum fizyolojik enjekte edildi. I. ve IV. gruplara deksametazon 4 mg/ml dozunda, II. ve V. gruplara 2 mg/ml dozunda uygulandı. Enjeksiyonlar I., II., III. gruplarda 4 gün arayla 4 defa, IV., V., VI. gruplarda 2 gün arayla 4 defa şeklinde uygulandı. Enjeksiyonlar sonrası intakt timpan membran ve timpanometri testi ile "A" tipi timpanogram saptadığımız 37 kulağın elektrofizyolojik testleri tekrarlandı. Ölçümler sonunda her gruptan ultrastrüktürel incelemeler için 2'şer kulak randomize olarak ayrıldı. İntratimpanik enjeksiyonlar öncesi ve sonrası ölçümlerden elde edilen verilerin grup içi ve gruplar arası istatistiksel karşılaştırmaları yapıldı. Çalışma ve kontrol gruplarının tümünde, enjeksiyonlar sonunda emisyon parametrelerinde (reprodüktibilite, response ve S/N oranı) ve işitsel beyinsapı yanıtları eşiklerinde istatistiksel anlamlı değişiklik bulunmadı. Ayrıca, çalışmamızda gruplar arası (I. ile IV. grup, II. ile V. grup, III. ile VI. grup) karşılaştırmada enjeksiyonlar sonrasında emisyon parametrelerinde ve işitsel beyinsapı yanıtları eşiklerinde istatistiksel anlamlı değişiklik saptanmamıştır. Çalışmamızın ışık ve elektron mikroskobisi bulgularında; kontrol gruplarında ve çalışma gruplarının tümünde -doz ve uygulama sıklığından bağımsız olarak- normal koklear yapıların korunduğu görülmüştür. Ayrıca, deksametazonun 4 mg/ml uygulandığı çalışma gruplarında (I. ve IV. gruplar) -uygulama sıklığından bağımsız olarak- normal koklear yapının korunmasıyla beraber hücresel düzeyde metabolik aktivite artışını destekleyen elektron mikroskobisi bulguları saptanmıştır. Sonuç olarak, intratimpanik deksametazon enjeksiyonunun güvenli olduğunu, işitmesi normal kulaklarda olumsuz bir etkisinin bulunmadığını ve 4 mg/ml dozunda ultrastrüktürel olarak hücresel metabolik aktiviteyi artırdığını çalışmamızın bulguları doğrultusunda ileri sürebiliriz. Anahtar kelimeler: Otoakustik emisyonlar, spontan; Uyarılmış potansiyeller, işitsel; Guinea pig; Mikroskopi, elektron; Deksametazon.
In our study, the effect of dexamethasone injected by intratimpanically on cochlear function and structure in guinea pigs was investigated through electrophysiological tests (Transient Evoked Otoacoustic Emission and Auditory Brainstem Response) and ultrastructurally (light and electron microscopy). As a result of electrophysiological tests, 40 ears of 20 guniea pigs with normal hearing threshold and presence of normal emissions were included in the study. Six randomly chosen groups were formed. The study was conducted by organizing 4 of these 6 groups (Groups I, II, IV and V) as the study group (7 ears in each group), and 2 of them (Group III and VI) as the control group (6 ears in each group). Dexamethasone was injected intratimpanically to the ears in the study group, and physiological saline was injected to the ones in the control group. A dose of dexamethasone 4 mg/ml dose was injected in Groups I and IV; 2 mg/ml in Groups II and V. Injections were administered 4 times at 4-day intervals in Groups I, II and III; 4 times at 2-day intervals in Groups IV, V and VI. Following the injections, electrophysiological tests were repeated on 37 ears showing type A tympanogram after intact tympanic membrane and tympanometer tests. As a result of the measurements, 2 ears were randomized in each group in order to analyze ultrastructurally. The data were statistically compared in and between groups gathered following the measurements before and after the intratympanic injections. No statistical significant difference was found in all study and control groups, following the injections in emission parameters (reproducibility, response, S/N ratio) and auditory brainstem response thresholds. Moreover, there were no statistically significant differences between the groups (Groups I and IV; Groups II and V; Groups III and VI) following the injections in emission parameters and auditory brainstem response thresholds. In our study, light and electron microscopy findings showed that all study and control groups have preserved normal cochlear structures independently of dose and administration frequency. Furthermore, electron microscopy findings were found supporting metabolic activity rise at a cellular level along with the preservation of the normal cochlear structure in study groups (Groups I and IV) in which dexamethasone was administered at a 4 mg/ml dose- independent of application frequency. As a result, we have suggested that intratimpanically injected dexamethasone is reliable, has no negative effects in ears with normal hearing, and stimulates cellular metabolic activity at a 4 mg/ml dose. Key words: Autoacoustic emissions, spontaneous; evoked potentials, auditory; Guinea pig; Microscopy, electron; Dexamethasone.
In our study, the effect of dexamethasone injected by intratimpanically on cochlear function and structure in guinea pigs was investigated through electrophysiological tests (Transient Evoked Otoacoustic Emission and Auditory Brainstem Response) and ultrastructurally (light and electron microscopy). As a result of electrophysiological tests, 40 ears of 20 guniea pigs with normal hearing threshold and presence of normal emissions were included in the study. Six randomly chosen groups were formed. The study was conducted by organizing 4 of these 6 groups (Groups I, II, IV and V) as the study group (7 ears in each group), and 2 of them (Group III and VI) as the control group (6 ears in each group). Dexamethasone was injected intratimpanically to the ears in the study group, and physiological saline was injected to the ones in the control group. A dose of dexamethasone 4 mg/ml dose was injected in Groups I and IV; 2 mg/ml in Groups II and V. Injections were administered 4 times at 4-day intervals in Groups I, II and III; 4 times at 2-day intervals in Groups IV, V and VI. Following the injections, electrophysiological tests were repeated on 37 ears showing type A tympanogram after intact tympanic membrane and tympanometer tests. As a result of the measurements, 2 ears were randomized in each group in order to analyze ultrastructurally. The data were statistically compared in and between groups gathered following the measurements before and after the intratympanic injections. No statistical significant difference was found in all study and control groups, following the injections in emission parameters (reproducibility, response, S/N ratio) and auditory brainstem response thresholds. Moreover, there were no statistically significant differences between the groups (Groups I and IV; Groups II and V; Groups III and VI) following the injections in emission parameters and auditory brainstem response thresholds. In our study, light and electron microscopy findings showed that all study and control groups have preserved normal cochlear structures independently of dose and administration frequency. Furthermore, electron microscopy findings were found supporting metabolic activity rise at a cellular level along with the preservation of the normal cochlear structure in study groups (Groups I and IV) in which dexamethasone was administered at a 4 mg/ml dose- independent of application frequency. As a result, we have suggested that intratimpanically injected dexamethasone is reliable, has no negative effects in ears with normal hearing, and stimulates cellular metabolic activity at a 4 mg/ml dose. Key words: Autoacoustic emissions, spontaneous; evoked potentials, auditory; Guinea pig; Microscopy, electron; Dexamethasone.
Açıklama
Tıpta Uzmanlık Tezi
Anahtar Kelimeler
Kulak Burun ve Boğaz, Otorhinolaryngology (Ear-Nose-Throat), Otoakustik Emisyonlar, Spontan, Uyarılmış Potansiyeller
