spina bifida
Concise Oxford English Dictionary © 2008 Oxford University Press:
spina bifida /ˌspʌɪnə ˈbɪfɪdə/
▶noun a congenital defect in which part of the spinal cord is exposed through a gap in the backbone, and which can cause paralysis and mental handicap.
'spina bifida' also found in these Oxford entries:

