What is the best way for practitioners to distinguish neurodegenerative disorders from other CNS disorders such as inflammatory,
neoplastic, or toxic conditions?
Antemortem diagnosis of neurodegenerative disorders is often presumptive after ruling out other disease processes with a full
neurologic workup. A full neurologic workup includes a physical and neurologic examination, fundic examination, blood pressure
measurement, thoracic radiographs, a minimum data base (complete blood count, serum chemistry profile, and urinalysis), and
appropriate advanced imaging of the part of the nervous system to which the signs are localized followed by cerebrospinal
fluid (CSF) analysis. Further diagnostic tests may be indicated depending on the findings. For example, if CSF analysis indicates
inflammation, titers for infectious diseases endemic to that geographic area should be measured. The definitive diagnosis
of a neurodegenerative disorder is typically made postmortem.
It is tempting to diagnose degenerative myelopathy or canine cognitive dysfunction in an older animal with progressive neurologic
signs in order to avoid subjecting the patient to general anesthesia for a thorough workup. However, many different classes
of disorders produce similar clinical pictures, and a failure to perform the appropriate workup could lead to diagnostic errors
and inappropriate treatment.
What are the latest treatment recommendations for degenerative myelopathy?
Degenerative myelopathy has long posed a therapeutic challenge, with many different approaches advocated, depending on the
prescribing veterinarian's belief about the cause. Many different theories on the etiology of degenerative myelopathy in German
Shepherds have been proposed, most of which have been disproved. This failure to understand the disease has led to the failure
to identify a successful therapy.
Perhaps the first and most important step in treating a dog suspected to have degenerative myelopathy is to perform an appropriate
workup to rule out disorders with similar signs (e.g. type II thoracolumbar intervertebral disk disease or degenerative lumbosacral disease). This kind of workup includes advanced
imaging; radiographs alone cannot identify disorders of the soft tissues of the vertebral column and spinal cord. This approach
also allows you to identify concurrent disorders that may exacerbate clinical signs. For example, degenerative joint disease
of the stifles or hips tends to exacerbate the severity of pelvic limb weakness due to neurologic disease.
Several groups have proposed metabolic disturbances as the cause of degenerative myelopathy because of similarities to syndromes
in different species. These include disorders of vitamin E and vitamin B12 metabolism, both of which seem unlikely based on the results of recent studies.38-40 However, ensuring that the diet is adequately supplemented with antioxidants and B vitamins is recommended by most neurologists,
with the hope that this will mitigate the effects of oxidative damage that occur with age. Others go further and suggest adding
a wide variety of mitochondrial cofactors and antioxidants to the diet.41 To date, there is no objective evidence that these supplements are beneficial, and, indeed, one study suggested that supplementation
with α-tocopherol and cyanocobalamin did not slow progression of clinical signs.39
There is some evidence that degenerative myelopathy is immune-mediated, and it has been compared to multiple sclerosis.42 This theory is arguable, however, since immunosuppressive therapy does not influence the disease course.41 The drugs N-acetylcysteine (an antiprotease) and aminocaproic acid (a drug that prevents fibrinolysis and may block inflammation) have
been recommended as a treatment,42 but no objective data demonstrating efficacy have been published.
Is physical therapy or exercise beneficial in patients with degenerative myelopathy? Are corticosteroids recommended? Are
Physical therapy is recommended for dogs with degenerative myelopathy to maintain muscle strength and joint integrity. Depending
on the severity of the clinical signs, the exercises can be done at home or at a dedicated center. The dog should be exercised
regularly, three or four times a day if possible, starting with five minutes and building up daily or every other day to a
level the dog can maintain and tolerate. Because of scuffing of the feet, it is often better to exercise affected dogs on
a soft surface. Protective boots may be necessary. A sling may be needed to help steady and support the hindquarters. Regular
swimming and work on a treadmill may also help. Dogs with concurrent degenerative joint disease will benefit from this exercise
routine and from the addition of NSAIDs. Neither corticosteroids nor NSAIDs will improve signs due to degenerative myelopathy.