Facts on File Encyclopedia of Health and Medicine

medications. Surgery to interrupt electrical activity
in the brain is sometimes an option for intractable
seizures (seizures that fail to respond to medica-
tion therapy).

Risk Factors and Preventive Measures

Neurologists do not know the cause of most
seizure disorders; thus there are no measures
known to prevent them from developing. People
who have recurrent seizures or do not experience
full suppression of seizures with treatment should
not drive or engage in other activities that can put
them or others at risk. Many states have laws that
regulate the conditions under which a person who
has a seizure disorder may obtain a driver’s
license; such laws vary among states.
See also MYOCLONUS.

spina bifida A form of neural tube defect in
which the distal (lower) portion of the neural tube
fails to close early in embryonic development. In
very mild spina bifida the defect may be unappar-
ent and cause no problems. Severe spina bifida
leaves the SPINAL CORD partially or completely
exposed, resulting in numerous complications that
often include deformity and PARALYSIS. Doctors
identify three forms of spina bifida:

• Spina bifida occulta is the most common and
  the mildest form. Only a small portion of a sin-
  gle vertebra fails to close properly. The spinal
  cord and the SPINAL NERVESdevelop correctly.
  The surface of the spine looks and feels normal,
  and the person has no symptoms.


• Meningocele is when the meninges (mem-
  branes that enclose the spinal cord) protrude
  under the surface of the SKIN through the
  incompletely closed vertebrae (usually two or
  more). The spinal cord and spinal nerves
  develop correctly, however.


• Myelomeningocele is the most severe form.
  The spinal canal is open and exposed along the
  lower spine. The spinal cord and meninges typ-
  ically appear as a saclike structure, which may
  be under or on top of the skin. The spinal cord
  and spinal nerves do not develop correctly, and
  often there are deformities of the pelvis,
  abdominal and pelvic organs, and lower limbs.

Meningocele and myelomeningocele are rare.

Myelomeningocele can be life threatening,

depending on its location and the extent of expo-

sure of the spinal cord, which presents a signifi-

cant risk for INFECTION(MENINGITISor ENCEPHALITIS).

Symptoms and Diagnostic Path

Diagnostic prenatal ULTRASOUNDdetects many neu-

ral tube defects before birth. At birth, symptoms of

meningocele and myelomeningocele are apparent

as deformities of the spine. COMPUTED TOMOGRAPHY

(CT) SCANor MAGNETIC RESONANCE IMAGING(MRI) help

the neurosurgeon assess the extent of the damage

and plan an appropriate course of treatment.

Treatment Options and Outlook

Spina bifida occulta requires no treatment.

Surgery is necessary to repair meningocele, though

nearly always recovery is complete. Meningocele

repair often heals with minimal or no residual con-

sequences, and the child grows up with normal

neurologic function. Complex surgery often is nec-

essary to repair myelomeningocele, and residual

complications are usually extensive. Ongoing com-

plications include paralysis, deformity, and HYDRO-

CEPHALY (excessive CEREBROSPINAL FLUID) that

requires a shunt. Children born with myelo-

meningocele require lifetime medical and support-

ive care. Many have permanent URINARY

INCONTINENCEand FECAL INCONTINENCEbecause the

lower spinal cord, which is nonfunctional, regu-

lates urination and defecation. Some may learn to

walk with crutches or braces. Developmental

delays and LEARNING DISORDERSare common.

Risk Factors and Preventive Measures

Folic acid supplementation greatly reduces the risk

for neural tube defects such as spina bifida, per-

haps by 70 percent. Health experts recommend

that all women of childbearing ability and age take

daily folic acid supplement regardless of their

pregnancy plans, as the most important period of

supplementation appears to be the four to six

weeks before CONCEPTION through the first

trimester of pregnancy. Some antiseizure medica-

tions (notably valproic acid), DIABETES, and OBESITY

increase the risk for neural tube defects. Though

most spina bifida seems to occur spontaneously,

282 The Nervous System