Bone, Joint Ills; Nervous System, Fits, Disks

By Mark J. Dallman and Irving Cashell.

Musculoskeletal problems in dogs and cats are most often evident as lameness or an abnormal gait. This usually is due to pain or discomfort that interferes with normal use or normal movement of the affected bones, joints or muscles. Common causes of musculoskeletal disease are inflammation, fractures, tearing, sprains, strains, congenital malformations, and breakdown of normal bone, joint or muscle tissue due to age or trauma (injury).

Bone Diseases. Panosteitis is a painful inflammation of the long bones of the legs in medium and large breeds of dogs 5 to 18 months of age. The lameness that results shifts from one leg to another and gradually disappears as the dog matures.

Secondary nutritional hyperparathyroidism is seen in both dogs and cats as the result of a calcium and phosphorus imbalance in the diet. The bones will weaken and may fracture spontaneously due to a lack of calcium in the bones withdrawn by the parathyroid gland to balance an excess of phosphorus in the diet. High phosphorus diets are often made up entirely of red meat.

Bone tumors are not uncommon in dogs. Osteosarcomas, fibrosarcomas and chondrosarcomas are seen in older dogs. These tumors cause pain and may interfere with normal musculoskeletal function. They are malignant and often spread (metastasize) to the lungs or other organs from the affected bone.

Hypertrophic osteodystrophy is a disease of young, rapidly growing dogs of the larger breeds that affects the distal ends of the radius and ulna bones in the front legs. There is inflammation of the bones, pain, swelling and fever which gradually disappears as the dog matures.

Joint Diseases. Hip dysplasia is a very common disease of the larger breeds of dogs, affecting the hip joint. It is transmitted genetically and the severity may vary widely from dog to dog and litter to litter.

This widespread disease causes a hind leg lameness as the result of pain originating in the malformed ball and socket type joint. Flattening of the socket (acetabulum) and a rubbing movement of the ball (femoral head) produces inflammation and eventually arthritis of the hip joint. The diagnosis is confirmed by x rays of the hips (pelvis).

Affected dogs exhibit pain on attempting to arise and when moving, particularly in damp, cold weather. Treatment is aimed at relief of the joint pain.

Osteochondroses are a group of joint diseases involving a disturbance in bone formation of the growth centers at the ends of certain leg bones.

The shoulder joint is most commonly affected and the result is a painful joint condition called osteochondritis dissecans. Lameness involving one or both front legs is caused by a loose flap of joint cartilage in the shoulder joint. It is seen most often in young, rapidly growing male dogs, usually weighing 50 pounds or more. Diagnosis is confirmed by x rays, and treatment involves surgery of the joint.

Similar problems may affect the elbow and hock joints in dogs.

Legg-Calve-Perthes disease involves the hip joint of young dogs of the miniature breeds. Damage to the head of the femur occurs as the result of either congenital or traumatic damage to the blood supply of that area. Lameness and pain result.

Luxation of the patella is a congenital problem in miniature and toy breeds of dogs affecting the knee (stifle) joint of the hind legs. The patella (knee cap) moves out of its normal position as the joint is flexed and extended. Joint looseness, abnormal gait, and pain usually result. This condition can be successfully treated using surgery.

Degenerative joint disease and arthritis are characterized by joint pain and lameness.

Degenerative joint disease involves breakdown of the articular (joint surface) cartilage and thickening of the joint capsule accompanied by excess bone formation (calcification) around and in the joint.

Nervous System

Paralysis loss of control of muscle activity usually is due to an interruption to the conduction of signals from the brain or spinal cord to the affected muscles.

Interruption can occur anywhere from the involved brain center to the muscle itself. A brain damaged by the presence of a tumor, infection, or injury cannot begin the signal that orders muscle activity. A nerve damaged temporarily by a blow, or permanently by being crushed or cut, cannot transport the signal to the muscle.

Infections capable of causing central nervous system damage in dogs and cats include rabies, distemper, toxoplasmosis and systemic fungus diseases.

Tumors of the brain and spinal cord are not common. Symptoms are varied and depend on location and size of the tumor.

Changes from accustomed patterns of behavior, persistent spasm or weakness of muscles, loss of vision or hearing can be signs of central nervous system damage. Diagnostic procedures must be guided by the veterinarian.

Epilepsy (Fits)

Epilepsy is a disturbance of brain function. It occurs more often in certain breeds and certain families of dogs and cats, which suggests a hereditary basis.

The characteristic fit or seizure begins with a dazed appearance or other odd behavior, quickly followed by toppling over and more or less violent muscular contractions over most of the body. Profuse salivation and passage of urine and feces may occur.

Seizures may last for several seconds up to several hours. Some are so slight as to pass unnoticed. Others are of great severity. Seizures rarely result in death but they are very alarming. After the seizure the dog or cat may hide quietly for a time.

Frequency of the seizures varies from several times a day to perhaps once a year. At the time, protecting the convulsing animal from injury is the only home treatment. In hot weather soaking the dog or cat with cold water will prevent heat buildup and heat stroke due to the violently exercising muscles.

Diagnosis is based on the character of the seizures and the repetition of the episodes. Electroencephalograms are useful for diagnosis but not often available for animals.

Treatment with anticonvulsant drugs can be very effective in suppressing epileptic seizures. Since no cure is expected, treatment is often needed for a lifetime.

Cooperation between the owner and the veterinarian is needed in working out the most effective medication and the proper dose. Drugs commonly used are phenobarbital, diphenylhydantoin, and primidone.

Infrequent mild seizures may not justify treatment once the benign nature of the particular case is understood.

Disk Syndrome

Interruption of nerve conduction in the spinal cord may be brought about by a bulging or displaced disk. Disks are the tough, flexible cushions that occupy the flat round spaces between the vertebrae.

Degeneration of disk material leaves them a soft pasty consistency which may become hardened with calcium. The cushioning effect is lost and the disk material bulges or bursts out of its position, usually in the direction of the spinal cord. Severe pain is followed by loss of muscle control from the site of the disk downward, away from the brain.

Disks most often affected are in the neck and again in the back just to the rear of the last ribs. Displaced neck disks are by far the most painful, but may correct themselves in time. Symptoms may be transient as the disk shifts by itself. Surgery to relieve the pressure is less drastic than in the lower back.

Paralysis resulting from cord damage in the neck may be fatal because of the possible loss of nerve supply to the muscles of breathing. This would be unpredictable and possibly instantaneous.

The course of disk problems in the lower back can also be erratic but is less likely to be. Often there is a period of varying length of back pain stiffness and reluctance to go up steps. This could disappear with no further consequence. More often it will proceed to a stumbling, scuffling gait in the hind legs, then to paralysis of hind quarters, but with an end to the pain.

Treatment of disk pain is difficult because of the deep-seated nature of the cause. Continuous use of narcotics has side effects which are hard to deal with.

Surgery is aimed at removing displaced disk material and relieving pressure on the spinal cord. Good results have been obtained when it is done early. There is, however, a temptation to wait because in more than half the cases the problem will go away in two to six weeks. Complete or at least adequate recovery can occur without treatment even in animals unable to walk. If no recovery occurs, surgery may be too late.

The decision to operate can be evaluated by the veterinarian at the time based on the individual case.

Mark J. Dallman is Assistant Professor, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg. Irving Cashell is a former veterinary practitioner who resides in Fairfax County, Va.