Progressive myelomalacia after disc herniation: signs and prognosis
5-year-old Dachshund operated on for a T12-T13 extrusion without deep pain. At 48 hours the pelvic patellar and withdrawal reflexes, previously increased, have disappeared; the cutaneous trunci cut-off has moved several vertebrae cranially and the dog has abdominal pain, fever and is starting to weaken in the thoracic limbs.
What is happening and what should you tell the owners?
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A. Transient spinal shock: reflexes will return within hours and the prognosis is unchanged
Spinal shock is a transient loss of reflexes immediately after injury, not a progressive ascent days later with thoracic limb weakness and fever.
B. Ascending and descending progressive myelomalacia: there is no treatment and it usually ends in respiratory paralysis, so euthanasia is indicated
Correct. Haemorrhagic necrosis spreads caudally (loss of reflexes through involvement of the lumbosacral intumescence) and cranially (cranial movement of the trunci cut-off, thoracic involvement). It is fatal within days; euthanasia prevents suffering.
C. A new extrusion at another disc: imaging should be repeated and surgery redone
A second extrusion does not explain progressive, ascending loss of function across many segments with fever and diffuse pain; this is the pattern of myelomalacia.
D. Surgical wound infection with meningitis: broad-spectrum antibiotics and a favourable prognosis
Fever in myelomalacia is caused by the cord necrosis itself. Attributing it to infection would delay a decision that cannot wait.
lightbulb Key takeaway
Progressive myelomalacia mainly affects dogs without deep pain (around 10%), almost always within the first few days. Warn owners before surgery and check pelvic reflexes, the cutaneous trunci cut-off and breathing daily. Some centres propose durotomy, but the prognosis remains very poor.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.