Piemonte and Valle d'Aosta Interregional Network for Rare Diseases (RD) is a model of "diffuse" network; it involves all the health system specialists devoted to the diagnosis, the therapy and the follow-up of a RD. The Consortium is a multidisciplinary team operating throughout the Region composed of volunteer Physicians and Biologists that promotes periodical meetings to develop shared protocols. In 2008 the Specialist-Technical Committee for the Interregional RD Network approved the set up of the "Chiari and Syringomyelia Consortium" (CSC) with two specific objectives: to identify the shared diagnostic criteria and to develop the interdisciplinary diagnostic-therapeutic-assistance path (DTAP) to be used interregionally. Other objectives are: to define the prevalence of the pathologies (both symptomatic and asymptomatic, both in adults and children) and to improve collaboration between the patient Associations and the Physicians.