Webster's New World Medical Dictionary

nervous system, autonomic
See 
autonomic
nervous system.
nervous system, central
See 
central nervous
system.
nervous system, parasympathetic
See
parasympathetic nervous system.
nervous system, peripheral
See 
peripheral
nervous system.
nervous system, sympathetic
See 
sympathetic
nervous system.
neural
Having to do with nerve cells (neurons).
neural tube defect
A major birth defect caused
by abnormal development of the neural tube, the
structure that is present during embryonic life that
gives rise to the central nervous system. Abbreviated
NTD. NTDs are among the most common birth
defects resulting in infant death and serious disabil-
ity. There are a number of different types of NTDs,
including anencephaly, spina bifida, and encephalo-
cele. In anencephaly there is absence of the cranial
vault (the skull) and absence of most or all of the
cerebral hemispheres of the brain. Encephalocele is
a hernia of part of the brain, and the membranes
covering it (meninges), through a skull defect.
Spina bifida is an opening in the vertebral column
encasing the spinal cord. Through this opening, the
spinal cord and the meninges may herniate to cre-
ate a meningomyelocele. All pregnancies are at risk
for NTDs. Factors that increase the risk include a
prior NTD in the family and type 1 diabetes in the
mother. More than half of NTDs can be prevented if
women consume supplements that contain folic
acid before and during the early weeks of pregnancy
in addition to getting folate in their diets. Because
the risk for NTDs is not totally eliminated by folic
acid use, routine prenatal screening for NTDs is still
advisable.
neuralgia
Pain along the course of a nerve; for
example, with and after shingles. See also 
neuralgia,
postherpetic.