Any damage to the spinal nerves of the peripheral nervous system that enervate the limbs can result in leg paralysis in dogs. Forelimb paralysis in most cases results from damage caused to nerve roots due to neck or shoulder injuries. In some instances, injury to the radial, ulnar and median nerves in the forelimb can also paralyze the affected limb. Hind limbs often get paralyzed when femoral, tibial, sciatic or peroneal nerves get damaged due to an injury to the hind limb. Their nerve roots are in the lower back area or the tailbone; hence any injury to that area also has the potential to cause leg paralysis.
To determine the cause of leg paralysis in dogs, the veterinarian may conduct a thorough physical examination of the dog, besides observing its gait, posture, and reaction to pain inflicted and other reflexes. Checking the changes in the muscle mass and tone of the affected limb may also help in the diagnosis. Since the location of nerve damage directly influences the chances of recovery, the veterinarian tries to locate it. For example, nerve injuries close to a muscle are comparatively easier to resolve. The ability to bear weight or move a joint may change according to the location of nerve damage. Sensation of pain and other reflex responses are also dependant on it.
The muscles connected to a nerve start deteriorating when the connection is severed. Loss of muscle mass in a particular area is an indication of damage to a specific nerve. The nerve can be stimulated with electric current to find out whether the damage is partial or complete. Since the rate of regeneration of nerve tissue is quite slow, at approximately an inch per month, the higher the distance between the muscle and the site of nerve damage, the lower the chances recovery before the muscle completely deteriorates. Whether the nerve sheath is damaged or not is also important. Partially severed nerves may mend themselves in a few weeks to a few months, but if a nerve is completely severed, the ends have to be reattached surgically for it to heal and become functional again.
Sometimes, forelimb paralysis may be associated with Horner’s syndrome, in which the pupils of the eye are small and the eyelids are closed partially except the third eyelid which remains elevated. The eye on the same side of the paralyzed leg is affected. Horner’s syndrome indicates torn nerve roots, and the dog has very little chance of recovering from the paralysis. When paralysis of a forelimb is not accompanied by Horner’s syndrome, the prognosis is better.
The paralyzed limb should be maintained in healthy condition during the period of recovery. All the instructions of the veterinarian such as regular massage of the muscles, application of heat, physiotherapy to stretch the joints and tendons etc., should be followed diligently. The foot should be kept covered with a loose and light bandage to keep it from getting injured by dragging on the ground. It can be put in a sling too.
There is no medical treatment to accelerate the regeneration of nerves. Acupuncture has been shown to be useful to some extent. Periodic assessment of the affected limb may be done for about 2-3 months to check for any improvement in the sensation of pain and other reflexes, as well as motor functions. While considerable progress indicates the possibility of complete recovery, the absence of any improvement during this period makes the prognosis poor. The dog should be prevented from chewing up its paralyzed limb during this period by using a special prosthesis called Elizabethan collar. In case of permanent paralysis, it may be best to amputate the limb to prevent further complications. The quality of life of dogs with only three legs is quite good.
Paralysis Caused by Tumors
Dogs may develop many types of tumors, but those affecting the nerves often result in lameness. This chronic type of lameness can occur in any of the limbs. They are usually painful and progressive, resulting in partial to total paralysis of the affected limb.
CT scans or MRI scans are done to locate the tumors and determine their size and spread. A biopsy is taken to diagnose the type of tumor and to determine the type of treatment that would be required. The tumor is surgically removed in most cases, but surgical intervention may not always be possible, as in the case of nerve sheath tumors which affect several nerves. Since it is not feasible to remove all the tumors, prognosis is poor for dogs having this type of tumors.