Progressive myelomalacia

6 March 2018 – News

Progressive myelomalacia (PMM) is characterized by progressive necrosis of the spinal cord after acute spinal injury. A spinal injury is often caused by type I disk herniation and, as such, breeds like the Dachshund are more at risk of developing progressive myelomalacia. Histopathology of samples collected at necropsy is the definite diagnosis for PMM.

While limited by its retrospective nature, this paper tries to provide answers on clinical signs, time of onset and disease progression. Severe thrombosis and the accompanying hemorrhage after acute trauma (seen the most in T12-T13 and L3-L6) will cause progressive destruction of the spinal cord and suggestive clinical signs including lower motor neuron signs in pelvic limbs and cranial progression of the cutaneous trunci muscle reflex. Disease progression will lead to loss of anal and abdominal tone, paralysis of thoracic limbs and eventually death due to paralysis of the respiratory muscles.

Time of onset ranged from immediately at first evaluation to 5 days, being that the majority of them started showing PMM within 2 days. Disease progression is fast with most dogs being euthanized 3 days after onset, though the authors state that onset can be delayed up to 5 days and progression to euthanasia can take as long as 2 weeks.

In Castel, A., Olby, N.J., Mariani, C.L., Muñana, K.R. and Early, P.J. (2017), Clinical Characteristics of Dogs with Progressive Myelomalacia Following Acute Intervertebral Disc Extrusion. J Vet Intern Med, 31