Leg nerve problems in dogs can be quite difficult to diagnose due to the nature of the disease. If trauma to the limb is not apparent, it may take a number of veterinary procedures to provide the cause of illness, treatment protocol and prognosis for the injured animal.
The leg of a dog contains what are called peripheral nerves--nerves that reside outside of the central nervous system (the brain and spinal cord). Peripheral nerves carry both sensory and motor (movement) information from the involved area to the brain. Injury or disease of the nerves in the body is called neuropathy. Any neuropathy of the front limbs of the dog usually involves the brachial plexus - the musculocutaneous, radial, ulnar or median nerves. Neuropathy of the back legs will affect either the femoral, fibular, sciatic or tibial nerve.
Most peripheral nerve injury in dogs is caused by trauma--such as being hit by a car. The force of the trauma commonly causes the roots of the nerve to be stretched or torn away from their origin, causing the limb to be paralysed and have no sensation at its lower end. The dog may be unable to flex the attendant limb and proprioception deficit of the foot on that limb is common; the animal will act as though it doesn't know how or where its foot should be placed and will often keep the foot turned under.
Neuropathy has also been seen in dogs with diabetes mellitus, hypothyroidism and Addison's disease. Nerve sheath tumours and lymphosarcoma in the chest or pelvic area of the dog can also be responsible for neuropathies. Symptoms are usually chronic and progressive, varying from a growing weakness of the limbs to muscle atrophy and eventual partial or complete paralysis.
Treatment of neuropathy depends on the cause of the disease. If traumatic injury is the cause, the nerve ends may be able to be surgically reattached but there is no guarantee the nerve sheath that allows for electrical impulses and movement will regenerate. Veterinarians will often recommend electrical stimulation of the injured nerves, but prognosis for full recovery is guarded unless the nerves respond to treatment within three to five days after reattachment. Limiting the neurological damage caused by disease will mean gaining control of the underlying illness. Depending on the illness, this may mean surgically excising any tumours that can be removed, plus chemotherapy; and/or complying with lifelong medications prescribed by the vet.
Dogs that experience nerve injuries need medical intervention, time, physical therapy and protection from further injury to heal. If the leg tissue is still intact or is healing well, the vet will not usually recommend amputation until six months after the initial injury and/or paralysis. However, if the leg tissue is too traumatised or becomes infected, amputation may be necessary for the comfort of the animal.