Is it neuro or ortho? Sorting out lameness, paresis and dogs that won't get up (Proceedings)

Lameness, difficulty walking, and reluctance or inability to rise are common presentations for patients presented to small animal practitioners. Disorders of the central and peripheral nervous systems, spine, long bones, joints, tendons, or musculature can all result in these potential signs. Identifying the organ system and anatomic structures responsible are critical to recommending subsequent diagnostic testing, therapy, and possibly referral to the appropriate specialist. The most critical steps in this evaluation are careful observation of the animal's gait, and a thorough neurologic and orthopedic examination.

Gait examination

Gait examination is arguably the most important part of the evaluation of patients with difficulty ambulating, but is often not performed by veterinary practitioners. The patient should be evaluated while walking towards and away from the examiner, and should also be observed from the side. If the animal is unable to stand or bear weight, adequate support of the limbs in question should be provided while assessing the ability of the animal to voluntarily advance its limbs, bear weight, and move in a coordinated manner.

Several abnormalities may be detected with the gait examination. These include:

     • Ataxia: incoordination characterized by a failure to walk or move the limbs in a straight line, crossing of the limbs over the body midline, and possibly stumbling and falling. Ataxia indicates neurologic dysfunction, and may be caused by involvement of several areas of the nervous system.
          o Sensory ataxia: Lesions of the sensory nerve, spinal cord or brainstem commonly cause incoordination. Spinal cord and brainstem lesions are typically accompanied by paresis (see below).
          o Cerebellar ataxia: Cerebellar lesions can cause a profound ataxia characterized by dysmetria (hypermetria and hypometria), and intention tremors. Animals with pure cerebellar lesions maintain good strength without obvious paresis.
          o Vestibular ataxia: Characteristic incoordination typified by leaning, drifting, stumbling, and falling to one side. Usually accompanied by a head tilt, nystagmus, and possibly positional strabismus. Bilateral involvement of the vestibular system can lead to ataxia and bizarre, wide head excursions but without an obvious head tilt or ataxia, although loss of a normal physiologic nystagmus can often be appreciated.
     • Paresis: muscular weakness. On the gait exam, this is characterized by scuffing of the nails, dragging of one or more limbs, a short-strided gait, or rapid tiring with activity/exercise. Paresis denotes dysfunction of the nervous or muscular systems.
     • Lameness: Inability or reluctance to bear weight on one or more limbs. Lameness often indicates a lesion in the long bones, joints, tendons, or musculature (i.e., orthopedic), although entrapment or compression of a nerve or nerve root can also lead to lameness ("root signature").