Spinal Pain

Written by Sue Fitzmaurice BVSc, DipACVIM(Neurology), DipECVN, MRCVS  

Pain is a subjective sensation. Its presence is inferred by a change in:

  • Gait e.g. a shorter weight-bearing phase
  • Posture e.g. arched lumbar spine, lower head carriage,
  • Behaviour e.g. withdraws from human contact, less active, decreased appetite, decreased interest in the surroundings, aggressive

 

When historical and physical clues suggest spinal pain, the clinician should take a moment to consider the anatomy of the painful area(s) and types of pathology that can occur at that site:

  • vertebrae: infection, neoplasia, trauma all cause pain
  • articular facets: polyarthropathies can affect the synovial joints of the spine as well as the limbs
  • intervertebral discs: tearing/rupture of the annulus fibrosis; discospondylitis
  • muscle: abscesses from migrating foreign bodies or bite wounds, spasm from hypocalcaemia
  • nerve roots: compression, inflammation, neoplasia. Pain may be referred to the associated limb.
  • meninges: inflammation (including that caused by haemorrhage), neoplasia, impingement by IVD, articular facets
  • spinal cord: syringomyelia

After the lesion has been localised to an area of spine, it is important to make a list of possible causes for the clinical signs. This is achieved by knowing the age, breed, onset and progression of clinical signs.  Textbooks provide lists of breed-related conditions. Reading and clinical experience together enable the clinician to list the diseases in the “most likely” order.

Consider the progression and prognosis with and without treatment of these possible diseases.

  • Is the condition self-limiting?
  • Is there any other problem with the animal that will negatively affect further diagnostic or therapeutic steps?
  • Are the benefits of a treatment regime worth the risks taken in diagnosis and treatment?
  • What are the owners’ expectations for the pet?

The timing and degree and order of investigation are dictated by these factors. There are financial implications too. Always ask: will this test change or improve the treatment of the animal? If it won’t, then don’t do the test. If it might, then discuss the limitations and benefits of the test with the owner. The presence of insurance funds is no excuse for performing poorly thought-out testing.

 

CSF analysis is useful in cases with spinal pain, fever of unknown origin, and animals with CNS signs. The changes seen are rarely pathognomic but are useful when combined with historical and physical findings. Non-contrast radiographs are useful when trauma or neoplasia are differentials. Discospondylitis may not appear on non-contrast radiographs in the acute stages of disease: MRI, in contrast, can detect inflammation of the disc space and surrounding soft tissues. Contrast agent within the subarachnoid space during myelography does not outline the nerve roots and lateralised disc extrusion can be missed; this is a real concern in cases of neck pain.

MRI has the added advantage of imaging the centre of the spinal cord, which is invaluable if syringomyelia, spinal cord neoplasia or inflammation are possible differentials. Spinal neoplasia is rare but can be detected on radiographs or MRI. Haematology and biochemistry should not be forgotten. Hyperviscosity syndromes, hypocalcaemia, myopathies, can cause pain. Changes may indicate more organ system involvement than previously thought. Joint fluid analysis is useful as a polyarthropathy may present as spinal pain.

Abdominal pain and neuromuscular causes of weakness can both result in an "arched back" and physical examination will aid diagnosis.