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AJNR Awards, New Junior Editors, and more. Read the latest AJNR updates

Case of the Week

Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada

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February 9, 2015
  • Description
  • Legends
  • Diagnosis
  • Brain Teaser
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Sacral Agenesis

  • Sacral agenesis considered a part of caudal regression syndrome. It is a rare sacral developmental abnormality consisting of absence of part or all of the sacrum.
  • It is clinically associated with malformation of the hindgut, caudal spinal cord, lower limbs, and the urogenital system.
  • Sacral agenesis has an incidence of 1 in 25,000 live births and is associated with maternal diabetes in approximately 25% cases.
  • Renshaw classified sacral agenesis into four types, based on the amount of sacrum remaining and articulation between pelvis and spine.
  • Key Diagnostic Features
    • Developmental malformations of the caudal spinal cord include sacral meningomyelocele, tethered cord, transistional lipoma, and cauda equina syndrome due to stenosis of the dural sac.
    • As seen on MRI, the position of the conus defines 2 distinct groups of patients with sacral agenesis:
      • In group 1 the conus is absent and the spinal cord ends with a blunted appearance, cranial to the lower border of the L1 vertebra. In this group the sacrum is completely absent.
      • In group 2 there is a tethered cord and the conus is present below L1. In these patients variable parts of the sacrum are present.
    • Multiple vertebral anomalies such as fused vertebra, hemivertebra, butterfly vertebra, and diastematomyelia may also be seen.
  • Rx Treatment and progression depend on the extent of regression. Management options are often centered around genitourinary and neuromuscular complication with orthopedic input.

Suggested Reading

Diel J, Ortiz O, Losada RA, et al. The sacrum: pathologic spectrum, multimodality imaging, and subspecialty approach. Radiographics 2001;21:83–104, 10.1148/radiographics.21.1.g01ja0883

Nievelstein RAJ, Valk J, Smit LME, et al. MR of the caudal regression syndrome: embryologic implications. AJNR Am J Neuroradiol 1994;15:1021–29

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American Journal of Neuroradiology: 46 (6)
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