Paralysis of a leg often results from damage to the peripheral spinal nerves. Paralysis of a front leg is usually associated with injury to the nerve roots in the neck or shoulder, or injury to the radial, median, or ulnar nerve in the leg. Paralysis of a hind leg is usually associated with injury to the nerve roots in the lower back or tailbone, or the femoral, sciatic, peroneal, or tibial nerve in the leg. Trauma is the most common cause of sudden limb paralysis, but equine protozoal myeloencephalitis can also cause single limb paralysis and muscle atrophy.
The horse’s posture and gait, spinal reflexes, pain sensation, and the condition of the muscles in the affected limb are evaluated to identify the location of the injury. The closer a nerve injury is to the muscle, the better the outlook for recovery, so it is important to determine the exact location of the injury, if possible. The ability or inability of the animal to flex the joint and bear weight on the leg, and the presence or absence of pain sensation and reflexes at various places in the leg, depend on the site of the nerve damage. Within a few days, muscles wither and lose mass when nerve connection is lost. Electrical stimulation of the nerve can be used to determine whether the nerve is partially intact. Nerves regenerate slowly (at a rate of about 1 inch per month), and full functional recovery depends on the condition of the nerve sheath and on the distance between the injury and the muscle where the nerve ends. Some nerve injuries can resolve after several weeks or months, but if the nerve has been completely ruptured, surgical reattachment is required for regeneration.
Applying heat, performing massage, and stretching tendons should be done as directed by the veterinarian to keep muscles, tendons, and joints of a paralyzed leg healthy while the nerve is regenerating. Acupuncture may help recovery. A light, but not tight, bandage may prevent damage to the foot from dragging. No specific treatment is available to help nerve regeneration, but nonsteroidal anti-inflammatory drugs can help control swelling. If voluntary movement, pain sensation, and spinal reflexes improve over 1 to 2 months, the outlook for recovery is good.
Also see professional content regarding limb paralysis.