Neurologic conditions causing lameness in companion animals

Animals presented with non-weight-bearing lameness are a diagnostic challenge for the veterinarian. It is extremely important to distinguish between orthopedic and neurologic causes of lameness, because the diagnostic and therapeutic plans can be quite different. Myopathies can be confused with orthopedic disease because of gait abnormalities and associated muscle pain. Common myopathies seen in companion animal medicine include polymyositis, muscular dystrophy, endocrine and infectious myopathies, and myasthenia gravis. Lameness caused by disease of the nerve root or nerve is confused with orthopedic disease because of the disturbances of a nerve's sensory distribution (nerve-root signature) or disruption of the motor innervation. The diseases of the nerve root or nerve discussed are lateralized intervertebral disk disease, spinal cord neoplasia, malignant peripheral nerve sheath tumors, and traumatic neuropathies. The diagnosis of these diseases requires careful attention to the signalment, a complete history, and a thorough physical examination focusing on the neurologic and orthopedic components. Ancillary testing should be selected based on these results and a minimum database. Electrodiagnostic testing, radiography, and advanced imaging may help to localize the lesion more precisely and sometimes to confirm the diagnosis. Surgical exploration and histopathology often provide the definitive diagnosis. These cases of non-weight-bearing lameness are a diagnostic challenge, but when successful resolution can be reached, it is gratifying to the clinician, client, and patient.