Progressive Myelomalacia After IVDD

Progressive myelomalacia (PMM) is a rare but devastating complication of severe spinal cord injury. It is most often discussed in dogs with acute thoracolumbar intervertebral disc extrusion (IVDE), particularly dogs that are paraplegic and have lost deep pain perception.

PMM is an emergency. If your dog is deteriorating neurologically after an IVDD/IVDE episode, contact the veterinary team responsible for their care immediately.

What is progressive myelomalacia?

PMM is a clinical syndrome in which severe damage to the spinal cord progresses beyond the original injury site. Veterinary consensus literature describes progressive necrosis, ischaemia and haemorrhage spreading cranially and caudally through the spinal cord.

IVDE and PMM are not the same thing. IVDE is extrusion of intervertebral disc material. PMM is a potential complication of severe spinal cord injury associated with an extrusion.

When can it happen?

Progressive myelomalacia usually develops during the days following an acute thoracolumbar IVDE-associated spinal cord injury. Published veterinary consensus guidance describes a reported window from approximately 24 hours up to 14 days, and it may not be apparent when a dog first presents to hospital.

Which dogs are at greatest risk?

Risk is most strongly associated with severe neurological injury. Studies focusing on paraplegic dogs without deep pain perception have reported PMM in approximately 10–33% of dogs, although estimates vary between populations and studies.

French Bulldogs have been reported to have a higher incidence in some research, but veterinary consensus guidance cautions that breed-specific risk is not yet fully established because other factors may contribute.

What signs do veterinary teams monitor?

Veterinary teams assess progression through repeated neurological examinations. Findings associated with concern for PMM can include loss of pelvic-limb reflexes and muscle tone, reduced abdominal and trunk tone, progression of neurological deficits towards the front of the body, changes in the cutaneous trunci reflex and, in advanced cases, involvement of the front limbs or breathing muscles.

These are specialist neurological findings. Owners should not attempt to diagnose PMM or repeatedly test deep pain at home.

Why repeated monitoring matters

A dog’s neurological examination can change after the initial injury. That is why vets may repeat examinations over time, especially in severely affected dogs. A single examination at presentation cannot always rule out later progression.

Deep pain and PMM are not the same thing

Loss of deep pain perception is an important marker of severe spinal cord injury and is associated with increased PMM risk, but a deep-pain-negative dog does not automatically have progressive myelomalacia. Some deep-pain-negative dogs survive the acute injury and can go on to have meaningful quality of life, including some that develop spinal walking or use mobility aids.

When should I seek urgent help?

Contact your veterinary hospital urgently if a dog recovering from severe IVDD/IVDE shows new or rapidly worsening neurological signs, marked changes in muscle tone or reflexes, weakness progressing forwards through the body, changes in breathing, or any deterioration your veterinary team has told you to monitor.

Do not wait for an online symptom checklist to match perfectly. If you are worried that neurological function is worsening, contact a veterinary professional.

Questions to ask your neurologist

• Is my dog considered at risk of progressive myelomalacia?
• What changes should I watch for at home?
• For how long is close monitoring particularly important?
• Which changes mean I should return to hospital immediately?
• How will you distinguish expected recovery changes from neurological progression?

This page provides general educational information and is not veterinary advice. Progressive myelomalacia is a serious neurological condition requiring veterinary assessment and monitoring.