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Research comment
Acute hydrated non-compressive nucleus pulposus extrusion: what do we know so far?
  1. Elsa Beltran, Ldo Vet, DipECVN, PGCertVetEd, FHEA, MRCVS
  1. Department of Clinical Science & Services, Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Hertfordshire AL9 7TA, UK
  1. E-mail: ebeltran{at}

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An acute extrusion of non-degenerated nucleus pulposus material through a tear in the annulus fibrosus can occur after sudden changes of intradiscal pressure and biomechanics; for example, during vigorous exercise, running, jumping. This type of intervertebral disc extrusion can be characterised as compressive or non-compressive and is more commonly recognised and studied as the cause of acute myelopathy in dogs and less frequently in cats.16

The term acute non-compressive nucleus pulposus extrusion was proposed to indicate when the extruded hydrated (as a description of non-degenerated) nucleus pulposus contuses the spinal cord and dissipates within the epidural space without significant spinal cord compression.2 Other terms have been used to describe this type of intervertebral disc extrusion including: high-velocity low-volume disc extrusion, traumatic disc extrusion, dorsolateral intervertebral disc explosion, traumatic disc prolapse and, erroneously, Hansen type III intervertebral disc disease.1,2,4,7 From all the terms used, the one that ideally should be avoided is Hansen type III as Hansen described intervertebral disc degenerations (type I and type II) and this particular type of disc disease is non-degenerated and, moreover, it was never described by Hansen.8

A new study by Ros and colleagues9 on this type of intervertebral disc extrusion, summarised on page 594 of this week’s issue of Vet Record, uses the term acute hydrated non-compressive nucleus pulposus …

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