Endolymphatic Hydrops Impair The Frequency Sensation Function Of The Guinea Pig Vestibule

Part oneThe establishment of guinea pigs model of endolymphatic hydropsObjective:The goal of the present study was to develop a guinea pig model of endolymphatic hydrops, providing basis for the experiments afterwards. Methods: Thirty guinea pigs were randomly divided into three groups (group1,2and control group).Groupl and2guinea pigs were made as a model of ELH by resection of the right endolymphatic sac and obliteration of partial right duct for the study of Meniere’s disease.Control group performed fake operation.The animals of group1or2were sacrificed at1month or2month after the surgery, respectively. The animals of control group were sacrificed at2month. Results:We found there are no hydrops in the control group or in the left ears of treated groups. There are different degrees of distension of Reissner’s membrane to the scala vestibuli after operation.The distension of Reissner’s membrane is more apparent in groupl than in group2. Conclusions: The resection of the right endolymphatic sac and obliteration of partial right duct can lead to endolymphatic hydrops. The posterior cranial fossa approach to obstruct endolymphatic sac is a method of establishing animal model of endolymphatic hydrops stably. Part twoThe Electronystagmography (ENG) recording of guinea pigsObjective:The goal of the present study was to develop the electronystagmography (ENG) recording of guinea pigs and to explore the frequency sensation function damage of the periphery vestibule induced by endolymphatic hydrops. Methods:Thirty guinea pigs were randomly divided into three groups (treated group and control group1and control group2, n=10). The animals of treated groups were made as a model of ELH by resection of the right endolymphatic sac and obliteration of partial right duct. The animals of control group2performed vestibular destruction. Electronystagmography (ENG) evoked by ice water and rotation test preoperatively or postoperatively. Nystagmus frequency and duration were recorded. Results:In ENG examination after ice water stimulation, obvious nystagmus was observed in the animals of control group2, lasting for a long time; and there was no response in the animals of treated group and control group1. After rotation tests, no obvious nystagmus was yet observed in the animals of control group2; and there were no significant differences in the nystagmus speed of the ENG waves to the left or right in treated group and control group1(P>0.05). After Head Thrust Test (HTT), no obvious eye movement was yet observed in the animals of control group2; and there were no significant differences in the eye movement speed of the ENG waves to the left or right in treated group and control group1(P>0.05). Conclusions:These results show endolymphatic hydrops selectively induces low frequency rotation sensation function damage of the periphery vestibule. There is no obvious influence to the high frequency or acceleration rotation sensation function. Part threeThe Electronystagmography (ENG) recording of endolymphatic hydrops guinea pigs in different periodsObjective:The goal of the present study was to observe nystagmus of endolymphatic hydrops guinea pigs in different periods and to explore the damage endolymphatic hydrops do to the guinea pig vestibule in different periods. Methods: Forty guinea pigs were randomly divided into four groups (group1,2,3and control group, n=20). The animals of group1,2,3were made as a model of ELH by resection of the right endolymphatic sac and obliteration of partial right duct. Electronystagmography (ENG) evoked by ice water and rotation test at normaltime (group1) or postoperatively after2week (group2),4weeks (group3) and8weeks (group4), respectively. Nystagmus frequency and duration were recorded. The animals of control group were administered with equal volume of saline subcutaneously. The guinea pigs were sacrificed at each time. The vestibular end organs were prepared for scanning and transmission electron microscopy. Results: In ENG examination after ice water stimulation, weak nystagmus was observed in four guinea pigs of group2. There was no response in the animals of other treated groups. After rotation tests, no significant differences in the nystagmus speed of the ENG waves to the left or right in every group(P>0.05). After Head Thrust Test(HTT), no significant differences in the eye movement speed of the ENG waves to the left or right in every group(P>0.05). Electron microscopy was used to observe the hair cells of the four groups. In group2, the hair cells were normal. In group3, hair cells in some period were not arranged in perfect order, and the hair became short even fallen, with edema of the type II hair cells and intact of the Type I hair cells. In group4, some hair cells disappeared in some places and the type II hair cells were badly damaged. Conclusions:These results show endolymphatic hydrops selectively influence low frequency rotation sensation function of the periphery vestibule. The damage is concentrated on the type II hair cells. It can be inferred that the type II hair cells are involved in low frequency rotation vestibular perception.