meningocele: a congenital anomaly of the central nervous system in which a sac protruding from the brain or the spinal meninges contains cerebrospinal fluid (but no nerve tissue)
birth defect: a defect that is present at birth
recombination: (physics) a combining of charges or transfer of electrons in a gas that results in the neutralization of ions; important for ions arising from the passage of high-energy particles