Myelomalacia in the Dog

Understanding Progressive Myelomalacia

This guide aims to offer clarity and understanding about the devastating condition of myelomalacia in dogs. It explains what myelomalacia is, why it occurs, and why, despite our very best efforts, it remains untreatable and fatal.

What is myelomalacia

Myelomalacia is a progressive, often fatal softening and necrosis of the spinal cord that follows severe spinal cord injury, most commonly after an acute intervertebral disc extrusion. The condition involves ascending and/or descending hemorrhagic necrosis that extends beyond the initial site of injury.

Myelomalacia is a less common, but catastrophic side effect, that most frequently develops after an acute thoracolumbar intervertebral disc extrusion (IVDE). The pressure of the prolapsed disc causes severe spinal cord contusion and ischemia (stop of the blood flow and oxygen depletion). These injuries set the stage for the progressive destruction of spinal cord tissue.

Clinical Signs

The clinical signs of myelomalacia are progressive and typically emerge within 24-72 hours to days after the onset of acute paralysis. These signs worsen over time, reflecting the ongoing damage to the spinal cord.  It is not possible to know in the initial stages of IVDE that myelomalacia will develop.

Pain

Myelomalacia is extremely painful for affected dogs. The severe nature of the spinal cord injury and the ongoing tissue destruction contribute to intense discomfort.

Outcomes / Prognosis

The prognosis for dogs diagnosed with myelomalacia is grave. The disease is uniformly fatal, and there are currently no effective treatments.

Common Breeds / Predispositions

Breeds predisposed to acute intervertebral disc extrusion and severe spinal cord injury are most commonly affected by myelomalacia – in particular French Bulldogs and Dachshunds.

The Progression of Myelomalacia

Loss of Spinal Reflexes

As myelomalacia advances, spinal reflexes in the pelvic limbs, including the patellar (knee-jerk) reflex and the withdrawal reflex (foot pulling back from a pinch), disappear—even in limbs that were previously only paralysed. Anal tone also becomes lax, and the limbs become completely flaccid.

Progressive March of Sensory Loss

A key diagnostic feature is the forward progression of the loss of the panniculus reflex (skin twitching response). We can track the spread of the damage by gently pinching the skin along the back and observing where the twitch response stops. This line moves up the back toward the head over time, mapping the spinal cord’s deterioration.

Involvement of the Thoracic Limbs

As the destruction reaches the part of the spinal cord that controls the thoracic limbs (front limbs), these limbs also become paralysed and flaccid.

Respiratory Failure

The final and inevitable stage occurs when myelomalacia reaches the nerves in the cervical spine that control the diaphragm and respiratory muscles. At this point, the dog loses the ability to breathe, leading to respiratory arrest and death. The entire process from the first sign of progression to respiratory failure may take only a few hours to a couple of days.

Can Myelomalacia Be Predicted or Prevented?

Currently, myelomalacia cannot be reliably predicted or prevented.

Why Is There No Cure?

There is no cure for myelomalacia at this time, as the damage to the spinal cord is irreversible and progressive.