Although a suitable approach will depend upon the particular neurodiversity and stage of the student I would recommend educational robotics, such as the Roamer robot. The Roamer developers have reported some success with neurodiversity students. Look for the names Catlin and Blamires.
It's important to delineate exactly what mathematics you will be teaching (early numeracy, algebra, geometry, etc.) then tailor it to the specific needs of the student. Browder et al., 2008, conducted a meta-analysis of mathematics and identified systematic prompting with immediate feedback, the use of a task analysis, and generalization to real-life contexts to be EBPs for mathematics. The specific instructional strategies utilized those that can be found in the MAST Modules I've attached as a link. If you need further clarification on how to access the modules, please do not hesitate to ask.
Students with special needs are simply students who do not meet, in the processes of institutional and formal learning the standard norm of schooling, not meaning that they cannot have normal development and to higher average in other areas. Therefore, the Charter of Salamanca should be reviewed. Its causes are bio-neuro-physiological, motivational, emotional or affective.
Their forms of education in mathematics, as in education, should be based in affective stimuli, motivating, engaging, sensory and sensitive, with colorful and emotional images and with tools and technologies centralized in specific and sensitive operations and his psycho-corporal self as a essential and engaging support base. My book: "“A Criança dos 6 aos 11 anos de Idade: suas aprendizagens e desenvolvimentos” studies this theme
as a educational psychologist (http://www.injs-paris.fr/page/recherche) I am deeply concerned about this topic,
so I described an experiment which took place at the INJS of Paris (the paper is available in English) : http://acim.ouvaton.org/IMG/pdf/acim_at_injs.pdf