Genetics Northern California

Glossary

TermDescription
Alpha-fetoproteinAlpha-fetoprotein (AFP) is a protein produced mainly in the developing baby's liver and released into the amniotic fluid. A small amount crosses the placenta and can be measured in a pregnant woman's blood towards the end of the first trimester. Levels rise at a steady rate throughout the second trimester. In most babies affected with open spina bifida, anencephaly, or an abdominal wall defect, more AFP is in the amniotic fluid and that leads to a higher amount of AFP in the maternal blood. In Down syndrome, trisomy 18, and SLOS, AFP levels may be lower than average.  
Folic acid

A vitamin that helps to prevent birth defects such as spina bifida and other neural tube defects in the newborn. Found in leafy green vegetables, liver, legumes, yeast, and some fruits. Important component of multivitamins and prenatal vitamins.

Lipomyelomeningocele, lipomeningocele

A spinal cord lipoma associated with an underlying spina bifida lesion. Often, the fatty tissue of the lipoma extends into the spinal canal, and may press on the spinal cord, resulting in progressive neurological deterioration.

Myelomeningocele

Most serious and most common form of spina bifida. The skin, muscle, and bone over the opening in the spinal column fail to close properly. The spinal cord and meninges (fibrous protective sheath/covering) protrude through an opening on the back into a sac. Most infants born with myelomeningocele will have significant spinal cord dysfunction.

Neural tube

The organ which becomes the baby's brain and spinal cord. Completely formed by 5 weeks after conception. If the neural tube does not develop properly, birth defects such as spina bifida, anencephaly, and encephalocele can occur.

Neural tube defect

Birth defects which involve incomplete development of the brain, spinal cord and/or the protective coverings for these organs. Types of NTDs include spina bifida, anencephaly, and encephalocele.

Spina bifidaA condition that results from altered fetal development of the spinal cord causing the individual to usually have hydrocephalus, bowel and bladder dysfunction and spotty sensation to no sensation in the lower extremities. Folic acid felt to help lower incidence of this birth defect if taken by mothers during the first trimester and a month prior to conception.
Spina bifida occultaLiterally “hidden” spina bifida. Most often involves a bony defect of the spinal column only and is discovered incidentally during a routine x-ray. Sometimes accompanied by external signs, such as a tuft of hair or discolored area on the back. Some forms of spina bifida occulta may involve the spinal cord, and require surgery (such as release of tethered spinal cord). Such as lipomyelomeningocele, lipomeningocele, split cord malformations, thickened or fatty filum terminale, and some dermal sinus tracts.
Spinal cord lipomaA collection of fatty tissue attached to the spinal cord that may or may not be associated with spina bifida. There are three types of lipomas: dorsal, transitional, and terminal. Dorsal and transitional lipomas are defects of primary neurulation, and may be associated with spina bifida. Terminal lipomas are considered secondary neurulation defects.