Sacral Agenesis

What is sacral agenesis? Sacral agenesis is a congenital abnormality, which affects the sacrum, the part of the spine just above the coccyx or tailbone. The sacrum is formed by the fusing of five vertebrae. Children with sacral agenesis are born with part or all of their sacrum missing. The sacrum gives the buttock its rounded shape, is important for the placement of the pelvis and acts as a passageway for some of the nerves from the spinal cord.

Sometimes some parts of the vertebrae higher up in the spine can be missing too. When it extends to the lumbar region it is called lumbo-sacral agenesis. It can extend further again into the thoracic spine, but this is very rare.

The terms caudal regression syndrome and caudal dysplasia are often used interchangeably with sacral agenesis.

How common is sacral agenesis? The reported incidence of sacral agenesis varies from 1 in 10,000 to 1 in 100,000 live births. Some of the differences in reporting may arise from the use of different definitions of sacral agenesis and the increased likelihood of its diagnosis with recent progress in diagnostic tools.

Causes The cause or causes of sacral agenesis are not well understood. There is no cure for the condition and no known way to prevent it. It is believed that sacral agenesis forms during the third to eighth week of foetal development possibly due to some form of toxic or infective damage when this part of the spine is starting to develop.

There have been a number of reports of sacral agenesis occurring in families, but there has been no clear cut pattern of inheritance.

An increased incidence of sacral agenesis has been associated with maternal diabetes and with parents who have spina bifida or scoliosis.

Symptoms These nerves leading from the sacral spine deliver messages to and from the bowel, bladder and muscles of the lower limbs and provide and receive sensory feedback to the brain. Having some or all of these bones missing may lead to disruptions of the nerve supply to the lower half of the body. These can lead to bowel, bladder and walking problems. Bowel problems can include constipation and faecal incontinence. • Urinary problems may involve incontinence, urinary tract infections and kidney damage due to bladder dysfunction. • Lower limb paralysis and decreased muscle strength can also occur, affecting the person’s mobility. • Lower limb complications can range from very minor walking difficulties or abnormalities, to complete paralysis of the lower limbs requiring the use of a wheelchair. • Some children with sacral agenesis may also have lower leg deformities which may require orthoses or corrective surgery.

SBH Queensland 2017

These effects are similar to those experienced by children with spina bifida and are usually treated similarly by both medical and allied health professionals.

Appearance A child who has sacral agenesis may appear with a flattened buttock, scoliosis or kyphoscoliosis (abnormal curves in the spine). They may also appear to have a short trunk in comparison with other children. Some children may also have missing or deformed lower limbs.

Diagnosis Sometimes sacral agenesis may be detected by ultrasound during the second trimester of pregnancy. At birth it can usually be detected by a physical examination of the lower spine. If the condition is comparatively mild, it may not be detected until the child presents for a medical examination for urinary incontinence – usually between four and five years of age.

Is it progressive? The abnormality does not get any worse, but there may be some deterioration in nerve functioning due to pressure on abnormally positioned nerve roots or associated with a tethered spinal cord. This deterioration may mean an increase in problems with continence, particularly bladder continence and movement and feeling in the lower limbs.

Each child with sacral agenesis is an individual and each has a different experience of sacral agenesis.

Early detection is a key factor as it will assist with intervention in the early stages of life, when it is of most benefit.

Early intervention can prevent harmful kidney damage and recurrent urinary tract infections. It can also enable the child to grow up to be more independent; achieve continence from an early age; and maximise their mobility. Nevertheless children with sacral agenesis require medical monitoring throughout the course of their lives.

SBH Queensland 2017