Tufts OpenCourseware
Authors: John Morgan, Bonnie F. Zimble

Spina Bifida:

Definition, Incidence and Characteristics

Special Care in Dentistry
John Morgan, DDS
Tufts University School of Dental Medicine, 2008

 Study Questions:     

  1. What is spina bifida (definition)?

  2. How many forms of spina bifida are there?

  3. What percentage of all Americans are thought to have spina bifida occulta?

  4. What is the most serious of the three forms of SB? What are its main characteristics?

 What is Spina Bifida (SB)? 

According to the National Institute of Neurological Disorders and Stroke (NINDS), spina bifida (SB) is “a neural tube defect (a disorder involving incomplete development of the brain, spinal cord, and/or their protective coverings) caused by the failure of the fetus's spine to close properly during the first month of pregnancy. Infants born with SB sometimes have an open lesion on their spine where significant damage to the nerves and spinal cord has occurred. Although the spinal opening can be surgically repaired shortly after birth, the nerve damage is permanent, resulting in varying degrees of paralysis of the lower limbs. Even when there is no lesion present there may be improperly formed or missing vertebrae and accompanying nerve damage.”  

Click here to access the NINDS web site on SB. 

The term SB means “cleft spine.” In general, the higher the lesion (cyst) on the back, the more severe the paralysis. About 80 percent of SB cysts are in the lower back’s lumbar and sacral regions. The three most common forms of SB are: 

  • Spina Bifida Occulta

  • Meningocele

  • Myelomeningocele

What is the incidence of SB? 

Spina bifida is “the most common neural tube defect in the United States—affecting 1,500 to 2,000 of the more than 4 million babies born in the country each year” (NINDS).  It occurs more frequently among Hispanics and whites of European extraction. Approximately 40% of all Americans born with SB may have the occulta form. Of the infants born with the other two forms (SB “manifesta“ forms: meningocele and myelomeningocele), about 4% have the meningocele form, while about 96% have myelomeningocele form. 

Characteristics of Myelomengocele 

Myelomeningocele, the most serious form of SB, may include muscle weakness or paralysis below the area of the spine where the incomplete closure (or cleft) occurs, loss of sensation below the cleft, and loss of bowel and bladder control.  In addition, fluid may build up and  accumulate in the brain (a condition known as hydrocephalus).  A large percentage (70%-90%) of children born with myelomeningocele have hydrocephalus. Pressure buildup can cause brain damage, seizures or blindness. Now that surgery to drain spinal fluid and protect children against hydrocephalus can be performed in the first 48 hours of life, children with myelomeningocele are much more likely to live; however, they must have a series of operations throughout their childhood. Those who have a history of hydrocephalus may also experience learning problems.