Caudal Regression Syndrome¶

Definition¶

Caudal regression syndrome (sacral agenesis) is a spectrum of congenital anomalies characterized by varying degrees of agenesis of the sacrum and lumbar spine, with associated anomalies of the spinal cord, lower extremities, genitourinary system, and gastrointestinal tract. It is strongly associated with maternal diabetes (present in 15–25% of cases).

Imaging Findings¶

Radiography/CT¶

Partial or complete absence of the sacrum, with variable absence of lumbar vertebrae
The iliac bones may articulate directly with the remaining lowest vertebra
Hip and lower extremity anomalies may be present

MRI¶

Abrupt termination of the conus — The conus ends bluntly at a high level, with a characteristic "wedge-shaped" or "blunted" appearance. The actual level of cord termination can range widely; and in severe cases it may terminate as high as T6 with agenesis of the vertebral bodies below T9.
Absence of sacral and/or lumbar segments
The thecal sac terminates prematurely
Associated anomalies of the genitourinary system (renal agenesis, horseshoe kidney) and anorectal malformations

Clinical Pearl

The MRI hallmark of caudal regression is an abruptly terminating, blunted conus at a high level — the cord simply ends without tapering to a normal conus tip. This is in contrast to a tethered cord, where the conus is low but tapered. The degree of sacral agenesis correlates with the severity of neurological deficit and associated anomalies.

Key Points¶

Spectrum of sacral and lumbar agenesis, strongly associated with maternal diabetes
Abruptly terminating, blunted conus on MRI is the hallmark
Associated with genitourinary and anorectal anomalies
Severity ranges from partial sacral agenesis to complete lumbosacral absence
Radiography/CT evaluates bony anomalies; MRI evaluates the cord and associated soft tissue anomalies

References¶

Krishnan V, Jaganathan S, Jayappa S, Glasier C, Choudhary A, Ramakrishnaiah R, Murphy J. Clinical and radiological evaluation of caudal regression syndrome. Pediatr Radiol. 2024;54(9):1451-1461. doi:10.1007/s00247-024-05945-1. PMID: 38750326.
Boruah DK, Dhingani DD, Achar S, Prakash A, Augustine A, Sanyal S, Gogoi M, Mahanta K. Magnetic resonance imaging analysis of caudal regression syndrome and concomitant anomalies in pediatric patients. J Clin Imaging Sci. 2016;6:36. doi:10.4103/2156-7514.190892. PMID: 27833778.
Purbasari U, Nazar H, Miraj F, Aprilia D, Widiani W, Suprihatin M, Eureka AN. Caudal regression syndrome from radiology and clinical perspective: a case series and a proposed new integrated diagnostic algorithm. Radiol Case Rep. 2023;18(7):2478-2486. doi:10.1016/j.radcr.2023.04.015. PMID: 37235076.
Abrahams E, Robinson M, Pak A. Caudal regression syndrome and interventional pain techniques. Interv Pain Med. 2022;2(1):100173. doi:10.1016/j.inpm.2022.100173. PMID: 39239600.
Caudal regression syndrome. Radiopaedia.org. Available at: https://radiopaedia.org/articles/caudal-regression-syndrome. Accessed May 2026.