Definition

Spina Bifida refers to a group of disorders that share the common problem characterized by the failure of the closure or fusion of the posterior arch (back part) of the vertebrae during the first month of development. The bony deficit can occur with or without neurological injury to the spinal cord and associated spinal nerves.

There are three main types of spina bifida that are defined by the degree of bony closure and spinal cord involvement. These include:

1. Spina bifida occulta: in this condition the posterior (back) part of the vertebrae is incompletely fused, but the spinal cord and spinal nerves are usually unaffected. Spina bifida occulta is often undiagnosed until later in life when it may be discovered during an x-ray for a back pain evaluation.

2. Meningocele: in this condition the tissue surrounding the spinal cord (meninges) can herniate or protrude through the bony deficit as a fluid filled cyst, though the spinal cord is usually within the spinal canal and may function normally.

3. Myelomeningocele (MMC): this condition was previously called spina bifida aperta or spina bifida cystica. This is the condition most people associate with the term “spina bifida” (with neurological deficits in movement, sensation, bowel, and bladder). During development, the bony arch fails to form and the meninges (spinal cord covering), spinal cord, and related nerves herniate through the opening which leads to neurological injury. These tissues may be partially or completely covered by skin. There may even be an open defect with leakage of spinal fluid and the spinal structures exposed to air.