When is SA/CRS diagnosed?
Because there is such a wide range of characteristics with SA/CRS (from missing only a small part of the sacrum to missing all of the sacrum, lumbar and part of the thoracic spine) diagnosis does not always happen prior to birth. Some children with SA/CRS are diagnosed during pregnancy, perhaps suspected in the first trimester of pregnancy and diagnosed in the second or third trimester. SA/CRS is a neural tube defect and this is one of the features of the fetus doctors begin to see in the second and third trimester ultrasounds, but that does not mean every type of neural tube defect can be seen at that time. Some parents may not receive a diagnosis during pregnancy at all, but are diagnosed at birth, when the condition is noticed at delivery and further testing confirms a diagnosis. For others, diagnosis may occur later, perhaps because of difficulties the child has in learning to use the toilet independently, or because of delays in learning to walk, or frequent urinary tract infections. For some, the diagnosis does not come until much later in childhood or in adulthood.
What factors make diagnosis challenging?
Usually, the more physical differences that are noticeably present, the earlier the diagnosis. So, a child who has complete absence of the sacrum and lumbar spine may be easier to notice in an early ultrasound than a child who has a very small portion of the sacrum absent. Keep in mind, however, that sacral agenesis is extremely rare. Many doctors have never seen a case. It would certainly not be one of the factors that they typically are on the alert for when viewing an ultrasound. Generally, evaluation of ultra sounds considers a large umbrella of skeletal features which might indicate one or more of a long list of possible conditions. There is not much research that would guide doctors in precise SA/CRS diagnosis and when there is research, it is often based on just a few case studies rather than a large population. Even if there is an early diagnosis, the extent to which the child will be impacted cannot be specifically determined until much later. The exact issues related to the spine are among the hardest to determine early in life. The spine isn’t fully hardened at birth. It still has a lot of cartilage and cartilage does not show up well in an ultrasound or xray. As the child becomes older and the spine fully hardens, it is easier to get a clearer picture about exact differences.
What other factors that contribute to early diagnosis?
There are other factors that contribute to the time of diagnosis. If the pregnancy is considered a high risk, because of a medical condition of the mother, then there is usually more testing and doctors are more inclined to know what to look for in an ultrasound. Because about half of the children with SA/CRS have diabetic mothers (while the other half do not), diabetes is considered a risk factor (not a direct cause) and a mother with diabetes may be monitored more closely. Increased monitoring of any pregnancy may result in an earlier diagnosis, even if there is no risk factor. If there is early indication of some other obvious condition in the fetus, such as a heart defect, a small jaw, or an extra thumb, then doctors may look for other issues and discover sacral agenesis is present as well.
References:
M. Boulas (2009) Recognition of caudal regression syndrome, in Advances in Neonatal Care, vol. 9, no. 2, pp. 61–69.
K. Singh, R. D. Singh, and A. Sharma (2005) Caudal regression syndrome—case report and review of literature. Pediatric Surgery International, vol. 21, no. 7, pp. 578–581.
T (Brachyury) Gene F. Fontanella, M. C. van Maarle, P. Robles de Medina, R. J. Oostra, R. R. van Rijn, E. Pajkrt, and C. M. Bilardo. (2016). Case Report Prenatal Evidence of Persistent Notochord and Absent Sacrum Caused by a Mutation. Case Reports in Obstetrics and Gynecology Volume 2016, Article ID 7625341, http://dx.doi.org/10.1155/2016/7625341