Arnold-Chiari in a Fetal Rat Model of Dysraphism

Abstract

Dysraphism is a defect in neural tube development, leading to dysplastic growth of the spinal cord and meninges. Myelomeningocele (MM) is just one of its forms. Hydrocephalus is among the most important alterations in MM and occurs as a consequence of Arnold-Chiari malformation (AC). Experimental models have been developed in sheep, rabbits and rats to study MM physiopathology, allowing a more detailed evaluation of clinical parameters involved in this anomaly. Objective: Using the experimental model of dysraphism in fetal rats, the aim of this study was to evaluate the relevance of AC malformations, clinical parameters and grade of histological lesions. Materials and Methods: Three groups with 16 fetuses in each were compared, MM, Control and Sham, after intrauterine surgical creation of MM on day 18.5 of gestation (term = 22 days). AC was evaluated by photographic comparison of sagittal cuts of fetal heads. Clinical and histological evaluations were also made. Results: 88% of AC (14/16) in MM fetuses were obtained, besides 100% of clinical alterations. Necrosis and erosion of the spinal cord exposed to amniotic fluid were verified in histology. Conclusion: The presence of AC in the dysraphism rat model was high. These results allowed the use of this model to study alterations and intrauterine evolution of MM in a fashion similar to those observed in humans.

Chiari Malformation with Surgically Induced Open Neural Tube Defect in Late Chick Embryos : Characterization by Magnetic Resonance Imaging and Histopathological Analysis

“…In 1996, we reported Chiari-like malformation associated with surgically induced ONTD in chick embryos at midgestation (total age, 14 days) [ 12 ]. Other surgical experimental models of CM II associated with spinal ONTD were demonstrated in mice by Inagaki et al [ 7 ], in rats by Weber Guimarães Barreto et al [ 14 ] and in lambs by Fontecha et al [ 3 ]. In 2000, Paek et al [ 9 ] reported the first large animal model using sheep to demonstrate hindbrain herniation associated with myelomeningocele.…”

Avaliação da evolução neurocirurgica de crianças com diagnostico intrauterino de mielomeningocele e elaboração de protocolo de cirurgia fetal para prevenção de hidrocefalia

“…Após análise dos modelos experimentais que foram desenvolvidos em ovelhas, coelhos e ratos para estudar a fisiopatologia da mielomeningocele, permitindo uma avaliação mais detalhada de parâmetros clínicos envolvendo esta anomalia. Weber GuimarãesBarreto et al (2005) do Grupo de Medicina Fetal -UNICAMP, decidiram usar o modelo experimental de disrafismo em ratos fetais, com o objetivo de avaliar a relevância de malformações de Arnold-Chiari, em relação aos parâmetros clínicos e grau de lesões histológicas. Três grupos com 16 fetos em cada foram comparados, ratos com mielomeningocele, ratos controle e ratos fraude, depois da criação cirúrgica da mielomeningocele intra-útero no dia 18,5 de gestação (termo = 22 dias).…”