Canis ISSN: 2398-2942

Spinal cord: compressive hydrated nucleus pulposus extrusions (HNPE)

Synonym(s): Ventral intraspinal diskal cyst

Contributor(s): Laurent Garosi, Nicolas Granger

Introduction

  • Cause: acute herniation of non-degenerated nucleus pulposus material and subsequent acute spinal cord injury.
  • Signs: acute onset of often non-painful severe and symmetrical non-ambulatory tetraparesis/tetraplegia or less commonly paraparesis/paraplegia.
  • Diagnosis: MRI is the imaging modality of choice.
  • Treatment: conservative or surgical spinal cord decompression.
  • Prognosis: good to excellent in most dogs.

Pathogenesis

Etiology

  • Acute herniation of non-degenerated nucleus pulposus material.

Predisposing factors

General

  • None.

Specific

  • None.

Pathophysiology

  • Hydrated nucleus pulposus likely extrudes through a single fissure in the dorsal annulus fibrosus possibly as a result of sudden changes in the intervertebral disk pressure and its biomechanics.
  • Hydrated, gelatinous, extradural material can be identified in the vertebral canal which is causing varying degree of spinal cord compression Spinal cord diseases: overview.
  • Extruded material is often found ventral to an apparently intact dorsal longitudinal ligament.
  • Because of similarities between MRI findings in dogs and diskal cysts in humans, this condition was initially referred to as “canine intraspinal diskal cyst”. However cytological or histopathological examination of the extradural material has revealed the presence of partially degenerated nucleus pulposus and no capsule or cyst wall delineating the extradural material.

Timecourse

  • Acute onset.
  • Non-progressive. (However, this is a disease causing spinal cord contusion and so there is potential for secondary spinal cord injuries to progress.)

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • De Decker S, Fenn J (2018) Acute herniation of nondegenerate nucleus pulposus: acute noncompressive nucleus pulposus extrusion and compressive hydrated nucleus pulposus extrusion. Vet Clin North Am Small Anim Pract 48, 95-109 PubMed.
  • Borlace T, Gutierrez-Quintana R, Taylor-Brown F E et al (2017) Comparison of medical and surgical treatment of acute cervical compressive hydrated nucleus pulposus extrusion in dogs. Vet Rec 181, 625 PubMed.
  • Fazone C (2017) Canine acute cervical myelopathy: hydrated nucleus pulposus extrusion or intraspinal discal cysts? Vet Surg 46, 376-380 PubMed.
  • Royaux E, Martle V, Kromhout K et al (2016) Detection of compressive hydrated nucleus pulposus extrusion in dogs with multislice computed tomography. Vet J 216, 202-206 PubMed.
  • Kang B J, Jung Y, Park S et al (2015) Discal cysts of the cervical spine in two dogs. J Vet Sci 16, 543-545 PubMed.
  • Manunta M L, Evangelisti M A, Bergknut N et al (2015) Hydrated nucleus pulposus herniation in seven dogs. Vet J 203, 342-344 PubMed.
  • Hamilton T, Glass E, Drobatz K et al (2014) Severity of spinal cord dysfunction and pain associated with hydrated nucleus pulposus extrusion in dogs. Vet Comp Orthop Traumatol 27, 313-318 PubMed.
  • Beltran E, Dennis R, Doyle V et al (2012) Clinical and magnetic resonance imaging features of canine compressive cervical myelopathy with suspected hydrated nucleus pulposus extrusion. JSAP 53, 101-107 PubMed.
  • Konar M, Lang J, Fluhmann G et al (2008) Ventral intraspinal cysts associated with the intervertebral disc: magnetic resonance imaging observations in seven dogs. Vet Surg 37, 94-101 PubMed.


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