*3.1.3. Spina bifida*

Spina bifida is the most common congenital anomaly of the CNS, resulting from the incomplete fusion of the vertebrae and hence exposure of the spinal cord. It can be classified into spina bifida occulta (**Figure 2D** and **E**), and spina bifida cystica (or aperta), which can be further classified into meningocele, meningomyelocele, and myelocele [12]. Spina bifida occulta is the mildest form, caused by the malformation of the bony arch that extends caudally, failing to fuse dorsal midline to the spinal cord. The spinal cord itself, however, is unaffected, extended caudally, or duplicated at the end, with no neurological damage. The bone defect is covered by skin, although sometimes patches of hair or pigment may be observed in the area covering the defect. **Figures 4** and **5** exhibit an embryo with spina bifida occulta, presenting a malformation of the bony arch, with neither neurological defect nor swelling.

On the other hand, spina bifida cystica refers to the malformation of the bony arch as well as the neural tube that has failed to close. Meningocele has a fluid-containing cystic swelling, emerging from a defect in the vertebral arch; the spinal cord is completely confined to the spinal canal, but may exhibit myelodysplasia.

Meningomyelocele and myelocele also refer to cystic swellings emerging dorsally through a vertebral arch, although the spinal cord (located inside the sac) bears its fundus. Myelocele is different from meningomyelocele in the following aspects: spinal cord is exposed to the external surface, often in the lumbosacral area; neutral folds stay flat, and will not elevate; not only the spinal cord, the brain is also often malformed, which may result in hydrocephalus, Chiari 2 malformation, and other defects [13].

Although spina bifida can be recognized as early as CS 12, it becomes observable earliest by CS 13, when the closure of the neural tube is supposed to be completed.

A significant amount of folic acid is known to prevent spina bifida; early postnatal treatments, including the closure of the spinal lesion within 48 h after birth, and medical management are essential for life henceforth [14].
