Canis ISSN: 2398-2942

Diffuse progressive myelomalacia

Synonym(s): Ascending/descending myelomalacia, hemorrhagic myelomalacia

Contributor(s): Kyle Braund, Prof. Alexander de Lahunta, Simon Platt, Harry Scott

Introduction

  • Cause: myelomalacia is ischemic or hemorrhagic necrosis of the spinal cord that can occur following acute spinal cord injury, and represents extensive damage of the intramedullary spinal vasculature. Diffuse progressive myelomalacia is a unique form that progresses cranially and caudally from an initial locus.
  • The exact pathophysiology is poorly understood but it seems to be the result of the concussive effects of trauma, ischemia, and the release of vasoactive substances, oxygen free radicals and cellular enzymes.
  • Signs: progressive spinal cord neurological signs.
  • Diagnosis: MRI, myelography.
  • Treatment: none.
  • Prognosis: hopeless - animals will die within 2-3 days of diagnosis.

Pathogenesis

Etiology

  • A peracute endogenous or exogenous trauma to the spinal cord is most often responsible.

Predisposing factors

General
  • Associated most commonly with an acute thoracolumbar intervertebral disk extrusion in chondrodystrophoid dogs.

Specific

  • Breeds predisposed to disk disease.

Pathophysiology

  • Myelomalacia is ischemic or hemorrhagic necrosis of the spinal cord that can occur following acute spinal cord injury, and represents extensive damage of the intramedullary spinal vasculature.
  • The destruction is often so severe that anatomic divisions of white and gray matter are lost.
  • The exact pathophysiology is poorly understood but it seems to be the result of the concussive effects of trauma, ischemia, and the release of vasoactive substances, oxygen free radicals and cellular enzymes. When the spinal cord is acutely damaged, white blood cells respond to chemotactic signals and enter the damaged area within 3-6 hours. Cell death in the gray matter may occur within 4 hours, with this area of necrosis expanding for a few days. Initially the white blood cells are neutrophils but macrophages become more prominent by the third day. From the level of spinal cord injury, a core of necrosis may extend cranially and caudally, typically in the base of the dorsal funiculi. Focal areas of necrotic tissue, distant from the immediate point of impact, may reflect regions of ischemia following post-traumatic secondary injury to blood vessels. Such areas of spinal cord necrosis can be seen secondary to intervertebral disk extrusion, in the segments neighboring the site of injury, but do not seem to have a prognostic inference.
  • Diffuse vasospasm of arterioles within the spinal cord parenchyma accounts for a large component of this spinal cord necrosis.

Timecourse

  • Most affected dogs develop paralysis over less than 12 hours. The condition usually develops within 5 days of initial paralysis, with a range of 1-10 days; signs may therefore only become evident in the post-operative period. The condition then progresses over 3-7 days.

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.
  • Platt S R, McConnell J F & Bestbier M (2006) Magnetic resonance imaging characteristics of ascending hemorrhagic myelomalacia in a dog. Vet Radiol Ultrasound 47 (1), 78-82 PubMed.
  • Olby N, Levine J, Harris T, Munana K, Skeen T, Sharp N (2003) Long-term functional outcome of dogs with severe injuries of the thoracolumbar spinal cord: 87 cases (1996-2001). JAVMA 222 (6), 762-769 PubMed.
  • Lu D, Lamb C R, Targett M P (2002) Results of myelography in seven dogs with myelomalacia. Vet Radiol Ultrasound 43 (4), 326-330 PubMed.
  • Coates J R (2000) Intervertebral disk disease. Vet Clin North Am Small Anim Pract 30 (1), 77-110 PubMed.
  • Scott H W, McKee W M (1999) Laminectomy for 34 dogs with thoracolumbar intervertebral disc disease and loss of deep pain perception. J Small Anim Pract 40 (9), 417-422 PubMed.
  • Duval J, Dewey C, Roberts R, Aron D (1996) Spinal cord swelling as a myelographic indicator of prognosis: a retrospective study in dogs with intervertebral disc disease and loss of deep pain perceptionVet Surg 25 (1), 6-12 PubMed.
  • Mesher C I et al (1996) Intracellular myelin in cerebrospinal fluid from a dog with myelomalacia. Vet Clin Pathol 25 (4), 124-126 PubMed.
  • Griffiths I R (1978) Spinal cord injuries: a pathological study of naturally occurring lesions in the dog and catJ Comp Pathol 88 (2), 303-315 PubMed.
  • Griffiths I R (1978) Early vascular changes in the spinal grey matter following impact injuryActa Neuropathol (Berl) 41 (1), 33-39 PubMed.
  • Griffiths I R (1978) Ultrastructural appearances of the spinal microvasculature between 12 hours and 5 days after impact injuryActa Neuropathol (Berl) 43 (3), 205-211 PubMed.

Other sources of information

  • Summers B A, Cummings J F, De Lahunta A (1995)Veterinary neuropathology.St. Louis: Mosby, pp 202-204.


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