Macroscopic description of the external and middle ear of paca (Cuniculus paca Linnaeus, 1766) / Descrição macroscópica da orelha externa e media da paca (Cuniculus paca Linnaeus, 1766)

Paca (Cuniculus paca), one of the largest rodents of the Brazilian fauna, has inherent characteristics of its species which can conribute as a new option for animal experimantation. As there is a growing demand for suitable experimental models in audiologic and otologic surgical research, the gross anatomy and ultrastructural ear of this rodent have been analyzed and described in detail. Fifteen adult pacas from the Wild Animals Sector herd of Faculdade de Ciências Agrárias e Veterinárias, Unesp-Jaboticabal, were used in this study. After anesthesia and euthanasia, we evaluated the entire composition of the external ear, registering and ddescribing the details; the temporal region was often dissected for a better view and detailing of the tympanic bulla which was removed and opened to expose the ear structures analyzed mascroscopically and ultrastructurally. The ear pinna has a triangular and concave shape with irregular ridges and sharp apex. The external auditory canal is winding in its path to the tympanic mebrane. The tympanic bulla is is on the back-bottom of the skull. The middle ear is formed by a cavity region filled with bone and membranous structures bounded by the tympanic membrane and the oval and round windows. The tympanic membrane is flat and seals the ear canal. The anatomy of the paca ear is similar to the guinea pig and from the viewpoint of experimental model has major advantages compared with the mouse ear.

A paca (Cuniculus paca), um dos maiores roedores da fauna brasileira, possui características inerentes à sua espécie que podem contribuir como uma nova opção de animal experimental; assim, considerando-se que há crescente busca por modelos experimentais apropriados para pesquisas audiológicas e otológica cirúrgicas foram analisados e descritos em detalhes a anatomia macroscópica e ultraestrutural da orelha desse roedor. Para o estudo, utilizaram-se 15 animais adultos provenientes do plantel do Setor de Animais Silvestres da Faculdade de Ciências Agrárias e Veterinárias, Unesp-Jaboticabal, Jaboticabal/SP. Após anestesia e eutanásia, avaliou-se toda a composição da orelha externa, registrando-se e descrevendo-se os detalhes, também se dissecou a região temporal para melhor visibilização e detalhamento da bula timpânica e estas foram removidas e abertas a fim de expor as estruturas da orelha, as quais foram analisadas, macroscopicamente e ultraestruturalmente. O pavilhão auricular apresenta forma triangular e côncava com cristas irregulares e ápice pontiagudo; o conduto auditivo externo é sinuoso em seu trajeto até a membrana timpânica; a bula timpânica encontra-se na parte posterior-inferior do crânio; a orelha média é formada por uma região cavitária preenchida por estruturas ósseas e membranosas. É delimitada pela membrana timpânica e as janelas redonda e oval, sendo a membrana timpânica de forma plana e que veda todo o conduto auditivo. A anatomia da orelha da paca é semelhante à da cobaia e do ponto de vista de modelo experimental apresenta grandes vantagens em comparação com a orelha do rato.

¿Qué sabemos de otoesclerosis? aspectos anatomopatológicos / What do we know about otosclerosis? anatomo-pathological aspects

La otoesclerosis es una enfermedad que produce hipoacusia de conducción por un proceso de remodelación ósea denominado otoespongiosis. Se han estudiado aspectos anatomopatológicos para evaluar el foco de inicio, y las características de este proceso llamado otoespongiosis. Nos motivó a realizar este estudio el deseo de conocer qué pasaba en nuestra población, clasificar las observaciones anatomopatológicas, relacionar estos aspectos microscópicos con aspectos clínicos como: tiempo de evolución clínica y aspecto macroscópico de la platina. Para esto se realizó un estudio prospectivo tomando todos los pacientes operados de estapedostomía en el Hospital Clínico de la Universidad de Chile desde octubre 2003 a octubre 2004. Fueron un total de 22 pacientes que se agruparon en 4 subgrupos según su aspecto anatomopatológico. Este estudio mostró que la otoesclerosis es más frecuente en mujeres en la quinta década de vida, en el oído derecho y presenta un tiempo de evolución clínica promedio de 7 años, que no varía con el grado de otoespongiosis de la supraestructura del estribo. Se observó un 45 por ciento de otoespongiosis en los huesecillos estudiados, aspecto no descrito en la bibliografía. No se observó correlación entre el aspecto microscópico y macroscópico de la platina, lo que sugiere otros focos de otoespongiosis o un avance rápido desde la fissula antefenestra a las cruras del estribo. Se continuará este estudio aumentando la muestra y realizando un seguimiento a los pacientes para relacionar el resultado anatomopatológico y el resultado auditivo post-estapedostomía.

X-Ray energy dispersive analysis and scanning electron microscopic study of normal and otosclerotic stapes with associated middle ear mucosa

A thorough description of ultrastructure of the normal stapes was required to determine changes associated with disease processes. In this work, the morphological appearance and mineral composition of normal and otosclerotic stapes were studied. In addition to the x-ray diffraction and x-ray micro-analysis, these methods allowed us to compare not only the morphology but also the mineral distribution in normal bone with that of otosclerotic lesions in order to gain some new insights into the disease process.12 human specimens [including the stapes with its associated mucosa] were studied. Six of them were normal fresh frozen, while the remaining were otosclerotic ones. The specimens were examined and photographed with Philips Scanning Electron Microscopy XL 3 at 30 kv. Also X-ray energy dispersive micro-analysis was performed with EDAX New XL-30 Zaphire equipment. In examination of the normal stapes, the surface architectural appearance of the human stapes appeared to have four different types of distinct patterns in all the specimens namely; honeycomb, fibrillar, dense and pitted. In the scanning electron microscope of the otosclerotic one, the four types' architectural appearance was not evident. There were two clearly differentiated zones corresponding to apparently normal bone and otosclerotic foci, with clear line of demarcation separating them. The apparently normal bone showed only a fibrillar structure with an irregular trabecular diagram on which rounded expansions were seen. However, in the otosclerotic plate zone even the fibrillar aspect disappeared. Disorganized collagen fibers surrounding holes with incomplete walls were seen. Next to the holes, there were patches of neo-bone formation appeared as abnormal irregular deposited Ca compounds, which seemed to be formed of irregular hydroxyl apatite crystals and rounded Ca deposits. Moreover, the analytic data of the otosclerotic stapes reflected lesser mineral components also the Ca/P ratio of the otosclerotic bone was [1.7] less then that of the normal bone [1.87]. That, perhaps might be attributed not only to the poor mineralization, but also to a changed mineral composition most probably, transformation of apatite into another calcium phosphate crystals. As regards the mucosal changes, this study revealed apparently marked decrease in the ciliated cells and multiple ulcers with loss of epithelial cells in otosclerotic specimens, which might be secondary to the capillary obstruction that also might be proved also by decrease in oxygen content found in the microanalysis technique. The gross morphology and transmission electron microscope did not clearly differentiate between the normal and the otosclerotic stapes, yet the scanning electron microscope and X ray microanalysis described many changes between them that might help clarifying some of the pathogenesis of otosclerosis

Juvenile otosclerosis

Stapes surgery for correction of conductive hearing loss in children is a scarcely done procedure so we aimed to report on the outcome of this surgery and to determine the optimal timing for stapedectomy in juvenile otosclerosis, Twenty two children and three adults suffering from juvenile onset otoeclerosis were operated upon. The junction of the anterior crus and the footplate of the stapes were harvested and prepared for both ultathin histological and electron microscopic study. The hearing results pre, and postoperatively were compared. Closure of the air-bone gap to less than 10dB was achieved in 73%of the operated upon children while in 23% it was from 10-20 dB and in the remaining 4% the closure of the air-bone gap was from 20-30dB. The ultrastructure and the histological study of the foot plate of the stapes revealed that with more lapse of time there is more hardening of the Footplate of the stapes. Stapedectomy is a safe and effective option in juvenile otosclerosis and by deferring stapedectomy until adulthood, the degree of footplate pathology increases