Ischemic myelopathy and Acute Non-compressive Nucleus Pulposus Extrusion (ANNPE) are neurologic problems that share similar clinical symptoms in dogs. The diagnosis is made presumptively, based on the presence of typical clinical findings as well as established MRI criteria (see MRI picture).
A retrospective study* was undertaken to compare the clinical signs and outcomes of dogs diagnosed with presumptive ischemic myelopathy (aka Fibro-Cartilagenous Embolus or FCE) or presumptive acute non- compressive nucleus pulposus extrusion (ie a non-compressive disc hernia or “traumatic disc”).
The study involved 127 dogs who exhibited an acute onset of symptoms of spinal cord dysfunction that became non-progressive after 24 hours. These dogs were examined at the University of London vet school. A board-certified neurologist and radiologist were tasked to review the MRI sequences.
Of the 93 dogs selected, 51 dogs were diagnosed with ischemic myelopathy and 42 dogs with a non-compressive disc.
Results of the study revealed the possibility of certain breed predispositions. A high number of English Staffordshire Bull Terriers and Whippets were represented in the ischemic myelopathy group. Border Collies and sighthounds (Greyhounds and Whippets) were over-represented in the traumatic disc group.
Dogs diagnosed with non-compressive discs were significantly older, likely to vocalize at the initial manifestation of clinical symptoms, exhibited spinal hyperesthesia during the initial exam, have a lesion at C1-C5 and tended to be ambulatory upon discharge from the hospital compared to dogs with ischemic myelopathy. Age-related changes that occur in the microstructure and biomechanics of the annulus fibrosus and the decrease of the intervertebral disk strength with age suggest that the risk of non-compressive discs tends to increase with age.
Although the mean age for dogs with non-compressive discs was significantly greater than dogs with ischemic myelopathy, it is not a reliable factor that can be used to differentiate the two conditions.
Dogs diagnosed with ischemic myelopathy tend to have a lesion at L4-S3 and sometimes suffer from long-term fecal incontinence.
Long-term follow-up results showed favorable outcome for 74% of dogs, 59% of which had regained normal neurologic functions. The rest of the dogs showed minor neurologic deficits but did not have urinary and fecal incontinence.
* J. Fenn et al. “Comparison of Clinical Signs and Outcomes Between Dogs with Presumptive Ischemic Myelopathy and Dogs with Acute Non-Compressive Nucleus Pulposus Extrusion”. JAVMA 2016, Vol 249, N 7, p. 767–775.