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Viewer Viewpoint - Degenerative Myelopathy - Is It Stalking Your Dog?

Viewer Viewpoint - Degenerative Myelopathy - Is It Stalking Your Dog?

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Q: What signs and symptoms are seen in DM?

A: DM is very subtle. It comes on slowly and gradually, making the disease horribly insidious. It may attack one or both sides of the body and presents with waxing and waning of the following symptoms, or combinations:

Hindquarter weakness, rear limb ataxia (unsteadiness), loss of balance, stumbling, difficulty rising up or laying down, knuckling (toes bent under while walking), rear legs crossing under body, rear leg drag, spinal ataxia, hoarseness of bark, limp tail, muscle wasting, and/or the loss of rear musculature.

This debilitating illness leads to paralysis and incontinence in its final stages.

Q: How is diagnosis confirmed?
A: DM used to be a “rule out” disease. That is no longer the case. There are now specific tests to “rule in” DM. While there remains no one specific test for DM, there is a combination of tests which help confirm the diagnosis, while also looking for other diseases that may mimic its clinical signs or even co-exist with DM.

Tests for DM:

1. Physical examination: including history (susceptible breed included). Physical exam should include routine blood tests (CBC, Chemistry Profile and UA), radiographs of the chest and abdomen and abdominal ultrasound. Other test may be indicated based upon physical findings. Splenic masses are not uncommon in DM patients, so abdominal palpation, radiographs or (preferably) ultrasound can be important, initially and for monitoring patients.

2. Neurological examination: looking for a non-localizing posterior paresis. Most cases of DM present as a non-localizing (no pain) upper motor neuronal dysfunction (rear leg reflexes are present to hyperactive) to the rear legs, suggesting the problem is in the white matter of the TL spinal column.

3. Electromyogram: including a Spinal Evoked Potential test. In uncomplicated DM cases, the needle EMG, motor nerve conduction velocity and repetitive nerve stimulation responses are normal, but the spinal evoked potential is abnormal. In inter-vertebral disc disease and myelitis, the EMG is abnormal (focally), but the spinal evoked potential is normal. In polyradiculoneuropathy, the EMG is abnormal, diffusely, and the spinal evoked potential is normal.

4. Lumbar CSF: (cerebral spinal fluid) analysis with appropriate titers and cholisnesterase level. In uncomplicated DM, the lumbar CSF protein is elevated, the CSF cell count is normal, the titers are negative and the cholinesterase is elevated. In infectious or inflammatory diseases, the protein and cholinesterase levels are also elevated, but the cell counts and titers are also abnormal. In inter-vertebral disc disease, the protein and cell counts are minimally elevated and the titers and cholinesterase levels are normal.

5. Spinal Radiographs: (regular and appropriate imaging {myelogram** or MRI}) Spinal column imaging only shows signs of age, unless there are complications of DM.

It is the additional tests, above, which actually rule-in DM.

**A myelogram is to rule out surgical disease, not to rule in DM.

Some DM patients do not handle myelography very well and their neurological symptoms can worsen, or they may become paralyzed. On the other hand, myelography can be a very important test when looking for surgical disease. It is not wrong to rule out the presence of surgical disease. DM is one of the non-surgical diseases; but it can be better to start testing for DM with the least invasive tests, leaving the more serious tests for last.

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