spi·na bif·i·da 
(spī′nə bĭfĭ-də)
(spī′nə bĭfĭ-də)n.
A congenital defect in which the spinal column is imperfectly closed so that part of the meninges or spinal cord protrudes, often resulting in hydrocephalus and other neurological disorders.
[New Latin spīna bifida : Latin spīna, spine + Latin bifida, feminine of bifidus, split in two.]
spina bifidatop: normal spine
bottom: spina bifida