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  Degenerative Myelopathy Tests

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Degenerative Myelopathy 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, the combination of tests which helps confirm the diagnosis of DM while also looking for other diseases that can mimic its clinical signs or exist together with DM as additional complications are as follows:
  • 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.

  • 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.

  • Electromyogram including a Spinal Evoked Potential test
    In uncomplicated DM cases, then needle EMG, motor nerve conduction velocity and repetitive nerve stimulation responses are normal, but the spinal evoked potential is abnormal. In intervertebral 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.

  • Lumbar CSF (cerebral spinal fluid) analysis with appropriate titers and cholinesterase level
    In uncomplicated DM, the lumbar CSF protein is elevated, the CSF cell count is normal, the titers are negative and the cholinesterase levels in CSF are elevated. In infectious or inflammatory diseases, the protein and cholinesterase levels are also elevated; but the cell counts and titers are also abnormal. In intervertebral disc disease, the protein and cell counts are minimally elevated, yet the titers and cholinesterase levels are normal.

  • Spinal Radiographs (regular and appropriate imaging {myelogram** or MRI})
    Spinal column imaging only shows signs of age unless there are complications to 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 neurologic symptoms can worsen or they can 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 best to start testing for DM with the least invasive tests, leaving the more serious tests as the last tests to be conducted.

    Dr. Clemmons
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Physical Exam should include:

Suggested Tests: (always start with the least expensive and least invasive!)

CBC (bloodwork) to make sure everything is as it should be, and look for problems which may give a direct lead as to the source of the problem.

Inflammatory Disease Panel - (eg: Tick borne illnesses can often present with the same symptoms of DM)

Thyroid Function - Hindquarter weakness can be a result of a Thyroid problem. Check T3 and Free T4 levels

Radiographs - If this is an older dog, one would wish to do plain non- sedated radiographs of the abdomen and chest, as a start. Often, one can see some of the spinal cord on these radiographs. This type of radiograph may also show potential problems such as certain types of heart problems, or tumors of the spleen. This is also a good way to avoid trouble, in the event that more involved testing, requiring sedation, becomes necessary.


Neuro Exam Should Assess:

Knowledge of leg position - the dog should right its foot immediately, if the foot is placed toes down, rather than pad down. If the dog does not right its foot immediately, and stands or walks on its toes, this is known as "knuckling".

Gait Analysis - unsteadiness of gait, stumbling, weakness, disproportionate movement of legs ( ie: moving legs too far or too little- also known as dysmetria). The forementioned enables one to view what is also called "proprioceptive functions".

Ataxia - an inability to coordinate voluntary muscular movements


Reflex Analysis:

Knee Jerk Reflex should be examined and evaluated to be either present, non-existent, or exaggerated . This is known as the patellar tendon reflex.

Crossed Extensor Response - If one toe is pinched, does the opposite leg extend? If so, this is not normally observed in healthy dogs. It could indicate a possible chronic neurologic problem.

Pain - absence or presence of pain/lack of painful reaction, look for areas of discomfort, and try to locate area of spinal cord which may be involved.


What is an EMG?
An EMG is an Electromyogram.

An EMG tests for spinal evoked potential. This is to determine if :
1) there is any problem in the lower motor units
2) a neuropathy ( any disorder of the peripheral nervous system)
3) a problem in nerve conduction

How is spinal evoked potential measured?
SEP is determined by stimulating the sciatic nerve by placing needles which stimulate, near it, and measuring the transmission up the spinal cord.


Myelogram or MRI (Use One or the Other)

The Myelogram:

a) A myelogram is done when the CSF shows no sign of any active infection. The outline of the spine can be seen radiographically via an injection of a contrast agent.
b) A myelogram is used to rule out surgical disease, not to rule in DM.
c) The contrast agents given via injection are irritative. The agents are inflammmatory, on their own, and when administered to a dog with an autoimmune problem, which is inflammatory in and of itself, the dog can become worse.

MRI:

a) Less invasive than a Myelogram
b) More expensive
c) Yields similar information
d) Considered to be a reasonable alternative to a myelogram.

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Hope this helps.  Our group is a close knit, caring group. If you have to deal with this disease, its easier with support.....  May all our dogs live a thousand years..

Marjorie + Jack Flash
...two hearts, two hearts that beat as one....
....you know it's true, everything I do, I do it for you..
 
 


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