Why do children have “tails” on their backs? The spinal cord and spinal canal play a major role in the growth and development of an individual from embryonic formation through birth and into adulthood. However, some children are born with a “tail” or “bulge” in the back, which may be a result of problems with the development of the spinal cord or spinal canal, such as spina bifida or spondylolisthesis. But how do these developmental problems of the spinal cord and spinal canal develop? What are the differences? The human spine is made up of 33 vertebrae connected by ligaments, joints and intervertebral discs, holding the skull at the upper end and the hip at the lower end, supporting the trunk, protecting the organs and spinal cord, and maintaining motor function. The middle of the vertebrae is “hollow” and is called the vertebral foramen (see Figure 1), and when the vertebrae are connected, the middle foramen forms a canal – the spinal canal (see Figure 2). The spinal canal is connected to the occipital foramen, which is connected to the cranial cavity, and down to the sacral fissure. In the middle of the spinal canal, there are spinal cord, spinal cord peritoneum, spinal nerve roots, blood vessels and a small amount of connective tissue. Among them, the spinal tegument is the soft spinal membrane, arachnoid membrane and dura mater, which are wrapped around the spinal cord, referred to as the spinal membrane. Figure 1 Vertebral structure (picture from the Internet) Figure 2 Composition of the spinal canal (picture from the Internet) In layman’s terms, the spinal canal is like a “chimney” built of special bricks, and ligaments, disc joints and other tissues are like cement, repairing the spinal column to make it more stable so that the spinal cord and the spinal membranes wrapped around the spinal cord inside do not fold back and bulge. The spinal cord is not a part of the spinal cord. If the spinal column is cracked or broken, or if the “chimney” is not built securely during embryonic development, the contents of the “chimney” will spill out. This is often referred to as spina bifida. Spina bifida is a type of spina bifida. The “little tail” on the back of a child is often associated with spina bifida. In fact, there are two types of spina bifida: recessive spina bifida and dominant spina bifida (or open spina bifida). Occult spina bifida is usually not visible and requires imaging to assess the structure of the spinal cord and spinal canal to determine its presence. In some cases, symptoms do not appear until adulthood; in others, the child’s “tail” or “bulge” is visible. This can be divided into simple spina bifida, spinal cord spondylolisthesis, hemispheric spinal cord spondylolisthesis and simple spondylolisthesis.