Resumen

This article presents the results of a case study of a 12-year old student who is currently in the 6th grade of Elementary School at a private school in the city of São Leopoldo, state of Rio Grande do Sul, Brazil. He has Spina Bifida and Arnold Chiari Syndrome. The purpose of this investigation was to identify this subject’s cognitive difficulties in Mathematics and how the school has dealt with these difficulties. To answer these questions, it was decided to take a case study type qualitative descriptive and exploratory approach and to use structured interviews, filming and transcripts of the study sessions for data collection. The article presents the results of the experiment performed from March to August 2010, lasting 20 hours, with weekly study sessions between the student investigated and the researcher, which indicate a lag between the mathematics concepts worked on at school and the concepts the student has, especially regarding the concept of numbers and the decimal numbering system.