There are four different types of spina bifida: occulta, closed neural tube defects, meningocele, and myelomeningocele.
Occulta is the mildest and most common form in which one or more vertebrae are malformed. The name "occulta," which means "hidden," indicates that the malformation, or opening in the spine, is covered by a layer of skin. This form of spina bifida rarely causes disability or symptoms.
Closed neural tube defects consist of a diverse group of spinal defects in which the spinal cord is marked by a malformation of fat, bone, or membranes. In some patients, there are few or no symptoms; while in others, the malformation causes incomplete paralysis with urinary and bowel dysfunction.
In meningocele, the meninges protrude from the spinal opening, and the malformation may or not be covered by a layer of skin. Some patients with meningocele may have few or no symptoms, while others may experience symptoms similar to closed neural tube defects.
Myelomeningocele, the fourth type of defect, is the most severe and occurs when the spinal cord is exposed through the opening in the spine, resulting in a partial or complete paralysis of the body below the spinal opening. The paralysis may be so severe that the affected individual is unable to walk and may have urinary and bowel dysfunction.
This answer is based on source information from the National Institute of Neurological Disorders and Stroke.