CAUDAL REGRESSION SYNDROME

· Caudal regression syndrome is a term used to describe a spectrum of congenital malformations that range from and include:

• Simple anal atresia.
• Sacral agenesis and occasionally absence of the lumbar and lower thoracic vertebrae (caudal aplasia/dysplasia).
• Fusion of the lower extremities and visceral malformations (sirenomelia).
• Pathogenesis – thought to be due to disruption of the caudal portion of the spinal cord complex prior to 4 weeks gestation. Vascular hypoperfusion has been suggested as a possible cause.
• Incidence: Approximately 1:60,000 births.
• Male: Female = 2.7:1
• 200-250 times higher frequency in diabetic pregnancies.
• Associated with maternal diabetes in 16% - 22%of affected cases.
• Recurrent risk is low as it is not hereditary. Recurrent risk in diabetic patients is higher.

ULTRASOUND

• Lower spine abnormality with varying degrees of involvement of the thoracic, lumbar and sacral spine.
• Sacrum may be completely absent, with variable absence of the lumbar vertebrae. Typically the absent sacrum results in approximation or fusion of the iliac blades resulting in a “shield-like” appearance.

• Abrupt ending of the lumbar/sacral spine without the normal distal terminal elevation. This finding is pathognomonic.

• There may be a terminal myelocystocele.

Video clip of Caudal Regression Syndrome

• Two umbilical arteries.
• Hypoplastic lower extremities and clubbed feet and contractures of the knees. Webbing of the popliteal joint is typical but may be difficult to appreciate antenatally. There may be decreased movement of the legs. Absent of significant fusion differentiates the findings from sirenomelia.

• Normal or imperforate anus; Colonic / cecal atresia; tracheo-esophageal fistulae.
• Non-lethal renal disorders – bladder or Cloacal extrophy; absent bladder; renal dysplasia or agenesis; hydronephrosis; urethral anomalies.
• Anomalies of the upper limb are rare but may include hypoplastic or absent radii.
• Amniotic fluid is normal or increased.
• CNS anomalies – holoprosencephaly / arhinencephaly; hydrocephaly.

Comparison of Caudal Regression Syndrome and Sirenomelia

ASSOCIATED ANOMALIES

Link to Associated Anomalies

ASSOCIATED SYNDROMES

• 16-22% of cases will have a history of maternal diabetes mellitus (2,3).

PROGNOSIS

The prognosis depends on the severity of the spinal defect and the presence of associated anomalies. The vast majority of infants require orthopedic and urological intervention. Early neonatal death is usually due to co-existent cardiac, renal and respiratory complications.

REFERENCES

1. Adra A, Cordero D, Mejides A et.al. Caudal regression syndrome: Etiopathogenesis, prenatal diagnosis, and perinatal management. Obstet Gynecol Surv 1994;49(7):508-516.
2. Twickler D, Budorick N, Pretorius D et.al. Caudal regression syndrome versus sirenomelia. Sonographic clues. J Ultrasound Med 1993;12:323-330.
3. Renshaw TS. Sacral agenesis: A classification and review of twenty-three cases. J Bone Joint Surg 1978;60:373.
4. Jaffee R, Zeituni M, Fejgin M. Caudal regression syndrome. Fetus 1991;7561:1-3.