Radial Nerve Paralysis in Dogs

The radial nerve is the largest nerve in the front leg, and is responsible for extending the elbow, wrist and toes. When this nerve is damaged, dogs appear lame, often dragging the front paw on the ground. Trauma above the elbow is the most common cause of radial nerve paralysis in dogs. There may be a complete loss of sensation in the upper foreleg and upper side of the paw. While visually shocking, radial nerve paralysis is a more common nerve injury in both dogs and cats. The severity of symptoms varies per the amount of damage to the radial nerve, and particularly where along the nerve pathway the injury occurred.

The radial nerve originates under the upper front leg from a group of nerves called the brachial plexus. The brachial plexus comprises nerves that extend from the spinal cord in the neck region.  Since the radial nerve is behind all movements of the elbow, carpus (the wrist), and toes, it is the primary nerve of support for the limb. Hence, the dog’s mobility and stability will be tremendously impacted if this nerve is injured. Dogs with radial nerve paralysis will lose the ability to control their triceps and the muscles that extend down the front leg, and accordingly, they are unable to extend the elbow. The result is a limb that can't be placed in a fixed standing position and is unable to bear body weight. The leg will remain flexed or bent, and may dangle in front of the dog.

The radial nerve is the largest nerve in the front leg, and is responsible for extending the elbow, wrist, and toes.  When the radial nerve is injured, paralysis of the front leg can occur.

• Leg remains flexed or bent
• Will be unable to stand or bear weight on the leg
• Dragging of the paw
• Loss of cutaneous sensation on the forelimb

Types

Radial nerve paralysis is characterized by the degree of injury to the nerve.

• Neuropraxia  - This is a temporary loss of nerve function without anatomical injury; the dog will regain full use of the leg 
• Axonotmesis – This injury causes rupture of some of the nerve fibers within an intact sheath; the prognosis for this degree of nerve injury is unclear, though there is a chance that the nerve will regrow and the limb will regain a degree of function  
• Neurotmesis – In this case, the nerve is completely severed, including the fibers and the protective sheath; if the dog can sense pain with pressure, there is a chance that the limb may regain limited function but without the response, prognosis is poor.

• Trauma to leg (such as hit by automobile)
• Tumor
• Nerve damage
• Nerve lesion
• Neoplasia
• Nerve rupture

Three levels of injury are associated with nerves and the outcome will depend on how much of the nerve is damaged. Neuropraxia is the most desirable option as it represents only a temporary loss of nerve function and bears no long-term physical damage. In the case of Axonotmesis, nerve fibers rupture inside of the sheath (protective covering) due to pinching, crushing or sustained pressure to the nerve. If the injury is quickly addressed, there is a chance that the nerve will re-grow, returning the limb to guarded function. In the worst scenario, Neurotmesis, the nerve, nerve fibers and protective covering are completely severed. Prognosis is poor as there is no chance that function will be recovered. 

Careful diagnosis plays a considerable role in treating foreleg paralysis. While trauma to the radial nerve is the most common cause of such an injury, other neuromuscular diseases and neuropathies may be at play. Additional causes of radial nerve paralysis include a tumor occurring on or around the brachial plexus.

A thorough history and physical examination by a veterinarian is essential. Electrodiagnostic tests will be helpful, and referral to a specialist might be recommended. Neurologic examination should follow or accompany physical examination.

During examination, the major nerve groups should be routinely tested. Cutaneous sensation testing is valuable when attempting to localize forelimb paralysis.

Nerve injuries bear some mystery, and are difficult to treat. . 

• Recommendations may include:
• Daily manipulation (as instructed by the veterinarian) of the muscle, joints, and tendons
• NSAID’s
• Cortisone or prednisone as the nerve heals
• Laser therapy
• Massage
• If after 3 to 6 months, no reparation is apparent, it may be necessary to amputate as many dogs may self mutilate due to strange sensations from the leg

The limb must be protected during recovery. Re-injury is quite possible as the dog attempts to use the healing leg and paw. During recovery, the dog may lose muscle function. Physical therapy may be helpful to maintain blood flow in the muscles. If any injured nerves begin to re-grow, the animal may experience strange sensations from the affected limb, and self-mutilation may occur. In this case, amputation of the limb may be considered.