• 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.

Presenting signs

• Ascending or descending, progressive myelomalacia may become apparent hours to several days after the onset of paraplegia. Clinical signs include: loss of all nociception caudal to the site of spinal cord injury.
• Complete pelvic limb paralysis (no voluntary movement).
• Anal flaccidity and areflexia; loss of cutaneous trunci reflex at a level more cranial to a previous evaluation over a period of hours to days; the development of lower motor neuron signs in the hind limbs.
• Respiratory difficulty due to intercostal and diaphragmatic paresis/paralysis.
• Occasional development of tetraparesis; focal myelomalacia is not accompanied by progressive clinical signs.

Acute presentation

• Diffuse myelomalacia occurs in approximately 9-11% in dogs with acute paraplegia and loss of deep pain perception due to intervertebral disk extrusion Intervertebral disk: type 1 herniation Intervertebral disk: type 2 herniation.

Age predisposition

• Severe and permanent clinical signs leading to death or euthanasia Euthanasia in many cases. Improvement of neurologic function is possible in focal disease.
• There is no specific age associations for this condition. There are age associations noted for dogs with thoracolumbar intervertebral disk disease, with which diffuse myelomalacia may be associated.
• Thoracolumbar disk disease is a common disorder in dogs that affects mainly chondrodystrophoid breeds. Peak incidence in these breeds is between 3 and 6 years of age.

Breed/Species predisposition

• As diffuse myelomalacia is associated with thoracolumbar disk disease it is most commonly seen in chondrodystrophoid breeds of dog.
• Dachshunds Dachshund represent approximately 40% of all dogs with thoracolumbar disk disease.

Cost considerations

• Expensive to investigate as it requires advanced imaging and potentially surgical explorations.
• Moderately expensive to care for these patients due to intensive nature of supporting dogs with respiratory weakness in the extreme, as well as managing recumbency and urinary retention.

Special risks

• Respiratory paralysis and death as the spinal cord malacia ascends to lower-cervical or mid-cervical levels.