Disorders of the Spinal Column and Cord in Dogs

Degenerative lumbosacral stenosis is a disorder of the vertebrae in the lower back that causes compression of the nerve roots. It is most common in large breeds of dogs, especially German Shepherds. The cause is unknown. Signs typically begin at 3 to 7 years of age and may include difficulty using the hind legs, tail weakness, and incontinence. Dogs often experience pain when the lower back is touched or moved. Other signs include a loss of paw position sense, muscle wasting, or weakened reflexes in the hind legs. X-rays may show signs of degeneration, but diagnosis requires magnetic resonance imaging (MRI) or computed tomography (CT). Dogs in which mild pain is the only sign may improve with 4 to 6 weeks of rest. Specific treatment requires surgery. The outlook for recovery after surgery is good, although urinary incontinence may continue.

Intervertebral disk disease is a degenerative disease of the spinal column that results in compression of the spinal cord and spinal nerves. It is a common cause of spinal cord disorders in dogs, especially of small breeds, particularly the Dachshund, Beagle, Shih Tzu, Lhasa Apso, and Pekingese. In these breeds, spinal disks can begin degenerating in the first few months of life. A herniated or “slipped” disk causing severe signs can occur suddenly, as early as 1 to 2 years of age. In contrast, disk degeneration in large breeds of dogs typically occurs after the age of 5 years, and signs continue to worsen. Herniated disks are most common in the neck and the middle of the back. A herniated disk in the neck leads to neck pain, stiffness, and muscle spasms. There may be muscle weakness or other signs, ranging from mild partial paralysis in the legs to total paralysis of all legs. A herniated disk in the middle of the back leads to back pain, and possibly curvature in the spine and a reluctance to move. Neurologic signs range from a loss of motor control in the hind legs to paralysis and incontinence. In paralyzed animals, it is important to determine whether pain sensation is present by pinching the toe or tail and watching whether the dog makes a behavioral response, such as a bark or turn of the head.

Diagnosis of herniated disks requires x‑rays, myelography, computed tomography (CT), or magnetic resonance imaging (MRI). Dogs with minimal to moderate signs that can still feel pain often recover with a few weeks of rest. Anti-inflammatory or pain medication can be used, but generally only if the dog can be cage-rested. If the dog increases its activity, the disk(s) may extrude further and worsen the spinal cord compression. Unfortunately, signs recur in 30 to 40% of cases. In dogs with severe neurologic signs, surgery must be performed promptly to relieve the pressure on the spinal cord. Surgery is also needed if drug therapy is unsuccessful and signs return. The outlook for recovery after surgery is good if the dog can still feel pain. If surgery is delayed for more than 48 hours after pain perception is lost, the chances of recovery decrease.

Infectious and inflammatory diseases of the spinal column and spinal cord include bacterial, rickettsial, viral, fungal, protozoal, and parasitic infections. Many of these diseases, such as meningitis and encephalitis, can also affect the brain. Some of the more common infectious and inflammatory diseases that affect the spinal column or cord are discussed below.

Tumors that affect the spinal column and cord in dogs include cancers of the bone, connective tissue, meninges, and nerve sheath, in addition to metastatic cancers, which are cancers that have spread from other parts of the body. A specific tumor called a nephroblastoma can affect young dogs (from 5 to 36 months of age), with German Shepherds affected most commonly. This tumor is frequently in the middle or lower back, causing progressively worsening partial paralysis in the hind legs. Imaging (including x-rays, myelography, computed tomography, magnetic resonance imaging) and surgical biopsy are used to identify and confirm a diagnosis of spinal cancer. Surgery is possible in some cases.

Spinal cord injuries usually occur as a result of a spinal fracture or dislocation. Common causes in dogs include automobile accidents, bite wounds, and gunshot wounds. The injury not only causes initial damage to the spinal cord, but also causes secondary damage from swelling, bleeding, destruction of the nerve sheath, and tissue decay. Signs of spinal trauma typically have a sudden and severe onset, and may progressively worsen. Severe spinal cord injury to the middle or lower back may cause a rigid paralysis, or a limp paralysis that spreads to the entire body over several days and leads to death from respiratory paralysis. Fractured or dislocated vertebrae can often be seen on x‑rays. Drug treatment can be helpful if started within the first few hours of injury. Animals with mild neurologic signs from injury often recover after 4 to 6 weeks of cage rest. Surgery is necessary for some types of injuries that cause severe neurologic signs. In dogs that have lost the ability to feel pain at locations below the spinal injury, the outlook for recovery is poor.

Delayed organophosphate intoxication can be seen after ingestion or skin contact with insecticides or pesticides that contain organophosphates. In addition to the signs of severe exposure, delayed paralysis can develop 1 to 4 weeks after exposure. Partial paralysis of the hind legs worsens progressively, and occasionally all 4 legs become paralyzed. A veterinarian will need a history of the dog’s possible chemical exposure to make the correct diagnosis. The outlook for recovery is poor for animals with severe signs.

Tetanus is caused by toxins produced by Clostridium tetani bacteria that usually enter the body at the site of a wound. Dogs are fairly resistant to tetanus, but cases do sometimes occur. Signs usually develop within 5 to 10 days of infection and include muscle stiffness and rigid leg extension, inability to swallow, protruding eyelids, and locking of the jowl and facial muscles. In severe cases, the animal may be unable to stand as a result of muscle spasms. Treatment consists of wound care, antibiotics to kill any remaining organisms, and tetanus antitoxin. In mild cases, a dog may recover completely with early treatment. In severe cases, death may occur due to respiratory paralysis.

Also see professional content regarding diseases of the spinal column and cord.