Spina Bifida

Definition of Spina Bifida

Spina bifida is a congenital disorder characterized by defective embryonic development of one or more vertebrae. Vertebrae are the bones in the back and neck that support the body and provide a protective corridor through which the spinal cord passes. Collectively, the vertebrae are referred to as the spine or the spinal column.

Some basic anatomy may be helpful to understand what spina bifida is and why it affects dogs the way that it does. Each individual vertebra is made up of several distinct bony parts. The vertebral body is the bottom-most (ventral) part of an individual vertebral bone. It is cylindrical in shape and separated from the vertebral bodies in front and behind by disks made of cartilage and fibrous tissue. The vertebral bodies and associated intervertebral disks function as shock-absorbers. A semicircular vertebral arch rises from the top (dorsal) side of each vertebral body, surrounding, enclosing and protecting the spinal cord. Several paired bony projections (the dorsal spinous processes) grow upward from the vertebral arch and normally form connections with the ribs and with the dorsal spinous processes of vertebrae in front and behind. It is this anatomical system that allows the spine to bend and flex.

Spina bifida occurs when the two halves of one or more vertebral arches do not fuse normally during prenatal development. When this happens, the spinal cord may or may not squeeze out through the resulting gap in the bone. The defect can occur anywhere along the spine. However, the vertebrae at the base of the spine – in what are known as the caudal lumbar and lumbosacral areas - are most commonly affected in domestic dogs.

Causes of Spina Bifida

The causes of spina bifida in domestic dogs are unknown. Because the condition occurs with more frequency in certain breeds (e.g., Bulldogs and Manx cats), a genetic component is highly likely. Ingestion by a pregnant bitch of substances that are known to cause birth defects (teratogenic compounds), malnutrition during pregnancy and possible environmental conditions are also reported to be contributing factors. It is clear that spina bifida develops in utero and is an abnormality of embryonic development that is present in affected puppies at birth. Most authorities believe that the causes of spina bifida are multifactorial.

Prevention of Spina Bifida

Because the causes of spina bifida are not well-understood, there is no meaningful way to describe an appropriate prevention protocol. Of course, pregnant bitches should be fed a high-quality diet and kept away from potential toxic substances.

Special Notes

Spina bifida is the most common ailment in a medical complex referred to as spinal dysraphism. Dysraphism is the defective fusion of parts that normally unite. Dogs with spina bifida have defective or nonexistent fusion of the top (dorsal) parts of one or more of the bones in their spine.