Caudal regression syndrome
Sacral agenesis, congenital (agenesis of the lumbar spine, sacrum, and coccyx, and hypoplasia of the lower extremities)
Hypoplasia of the sacrum
Currarino syndrome
Caudal dysplasia
Caudal dysplasia sequence
Congenital sacral agenesis
Sacral regression
Lumbo sacral agenesis
Introduction
Caudal regression syndrome or sacral agenesis (or hypoplasia of the sacrum) is a congenital disorder in which there is abnormal fetal development of the lower spine—the caudal partition of the spine.
Incidence
It occurs at a rate of approximately one per 25,000 live births.
Signs
This condition exists in a variety of forms, ranging from partial absence of the tail bone regions of the spine to absence of the lower vertebrae, pelvis and parts of the thoracic and/or lumbar areas of the spine.
In some cases where only a small part of the spine is absent, there may be no outward sign of the condition.
In cases where more substantial areas of the spine are absent, there may be fused, webbed, or smaller lower extremities and paralysis (resembling the spread legs of a frog).
Bowel and bladder control is usually affected (affected children have to wear pampers even at school-going age).
Prognosis
There are four levels (or "types") of malformation.
1. The least severe indicates partial deformation (unilateral) of the sacrum.
2. The second level indicates a bilateral (uniform) deformation.
3. The most severe types involve a total absence of the sacrum.
1. Genitourinary system
Depending on the type of sacral agenesis, bowel or urinary bladder deficiencies may be present. A permanent colostomy may be necessary in the case of imperforate anus. Incontinence may also require some type of continence control system (e.g. self-catheterization) be utilized.
2. Musculoskeletal system
Occasionally if deformities of the knees, legs or feet would prove unresponsive to corrective action, amputation at the knee may be proposed.
Before more comprehensive medical treatment was available, full amputation of the legs at the hip was often performed.
More recently, the 'amputation' (actually a disarticulation because no cutting of the bone is involved) is done at the knee for those who have bent knee positions and webbing between thigh and calf to enable more ease of mobility and better seating.
Some children with knee disarticulation use prosthetic legs to walk.
Prosthetics for children without substantial hip and trunk control is usually abandoned in favor of faster and easier wheelchair mobility as the child's weight and age increases.
Children may 'walk' on their hands and generally are able to climb and move about to accomplish whatever they need and want to accomplish. (Walking on hands and dragging the bent legs is an adaptive feature in affected children. With strong hands, they can easily jump up onto a sturdy low table and sit on the table to do many things. When they are propped up on the table, they are the height of a seated child.)
Children more mildly affected may have normal gait and no need for assistive devices for walking.
Others may walk with bracing or crutches.
3. Brain development
There is typically no cognitive impairment associated with this disability. (The affected child has normal intelligence.)
Adults with this disability live independently, attend college, and have careers in various fields.
Etiology
There are many causes of this syndrome and the exact etiology is unknown.
1. Fetal development
The condition arises from some factor or set of factors present during approximately the 3rd week to 7th week of fetal development (first to second trimester).
Formation of the sacrum/lower back and corresponding nervous system is usually nearing completion by the 4th week of development (end of 1 month).
Due to abnormal gastrulation, the mesoderm migration is disturbed. This disturbance results in symptoms varying from minor lesions of the lower vertebrae to more severe symptoms such as complete fusion of the lower limbs.
2. Dietary deficiency
It has been speculated that the condition may be associated with certain dietary deficiencies including a lack or insufficient amounts of folic acid. Folic acid is required for nervous tissue development and that of the spinal cord.
3. Maternal diabetes
Sacral agenesis syndrome is a well-established congenital anomaly associated with maternal diabetes mellitus (not gestational diabetes). (Complications of maternal diabetes (retinopathy, nephropathy) is associated with caudal regression syndrome, and is detectable at 25 weeks gestation by x-ray of the foetus.)
The sacral agenesis syndrome is a severe congenital abnormality consisting of agenesis of the lumbar spine, sacrum, and coccyx, as well as hypoplasia of the lower extremities. It is considered the most characteristic of all congenital anomalies associated with maternal diabetes mellitus. We describe the sonographic and radiologic findings of agenesis of the lumbosacrococcygeal spine with lower limb and genital hypoplasia in the offspring of a woman with both diabetic retinopathy and nephropathy. The diagnosis was established at 25 weeks' gestation and was confirmed by radiologic evaluation of the neonate. Am J Obstet Gynecol. 1990 Mar;162(3):806-8.
However, other etiologic factors are presumably involved, as demonstrated by the rare incidence of caudal regression syndrome (1:60,000) compared to diabetes.
Certainly not all children born with Caudal Regression Syndrome have diabetic mothers.
4. Genetics and inheritance
The dominant inherited sacral agenesis is very often correlated with a mutation in the Hb9 (also called HlxB9) gene (shown by Sally Ann Lynch, 1995, Nature Genetics).
It may be the cause of sirenomelia ("Mermaid Syndrome") - the most severe form of caudal regression syndrome.
External links
Am J Obstet Gynecol. 1990 Mar;162(3):806-8.
Antenatal diagnosis of sacral agenesis syndrome in a pregnancy complicated by diabetes mellitus.
Sonek JD1, Gabbe SG, Landon MB, Stempel LE, Foley MR, Shubert-Moell K.
American Association of Neurological Surgeons (AANS)
Birth Defects Research for Children, Inc.
https://www.facebook.com/BDRCFL
YouTube: Because every birth defect has a cause
Tell Me a Story: Birth Defects Teaches Parents to Look at Life Differently
YouTube: Caudal Regression Syndrome
