Veterinary neurologists often evaluate, diagnose, and treat patients that are referred to us for back pain and/or weakness. Polyarthritis is often considered the Great Imitator as patients suffering from this problem can appear very similar to patients with intervertebral disc disease, myopathies, meningitis, and even myasthenia gravis.
The most critical step required to diagnose polyarthritis is to consider it on your differential diagnosis list. As neurologists, we harp on localizing the lesion (i.e. C1-C5, T3-L3, left prosencephalon, etc.) and if you can’t localize the lesion because you’re only finding poorly localized back pain, think, “What about the joints?” In patients with polyarthritis, the facet joints of the vertebral column may be affected and/or the pressure placed on the back may cause discomfort in the hock or stifle joints. In patients without an obvious neuroanatomic localization, remember to pay special attention to the joints.
Initial clinical signs may include lethargy, inappetance, pyrexia, reluctance to walk, shifting-leg lameness, and poorly localized pain and discomfort. Many of these patients are small breed dogs and it’s very easy to mistakenly suspect intervertebral disc disease and start an anti-inflammatory medication, which makes diagnosis more challenging. Joint palpation and joint manipulation usually leads to findings that will lead to a diagnosis. The carpal joints can be very reliable in palpating effusion and eliciting discomfort with gentle flexion.