Disorders of the Spinal Column and Cord in Cats
Diseases of the spinal column and cord include congenital defects (discussed earlier in this chapter), degenerative diseases, inflammatory and infectious diseases, tumors, nutritional diseases, injury and trauma, toxic disorders, and vascular diseases.
Degenerative lumbosacral stenosis is a disorder of the vertebrae in the lower back that causes compression of the nerve roots. It is rare in cats. The cause is unknown. Signs typically begin at 3 to 7 years of age and may include weakness, incontinence, and difficulty using the hind legs. Cats 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). Cats in which mild pain is the only sign may improve with 4 to 6 weeks of rest and pain medications. 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, but rare in cats. A herniated or “slipped” disk causing severe signs can occur suddenly or emerge and progress slowly. 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, your veterinarian will determine whether pain sensation is present by pinching the toe or tail and watching whether the cat responds.
Diagnosis of herniated disks requires x-rays, myelography, computed tomography (CT), or magnetic resonance imaging (MRI). Cats 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 cat can be cage-rested. If the cat 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 animals 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 cat can still feel pain. If surgery is delayed for more than 24 hours after pain perception is lost, the chances of recovery decrease.
Degeneration of motor neurons is an inherited disease seen now and then in cats, dogs, cattle, pigs, and goats. Also called spinal muscular atrophy, this disease is characterized by progressive weakness, shaking, muscle loss, and weak reflexes. It usually appears by 2 years of age. Electronic muscle testing and biopsy help document the nerve changes, but definitive diagnosis can only be performed after death of the animal.
Spondylosis deformans is characterized by the production of bony growths along the underside of the spinal vertebrae. It develops as cats age. It does not typically cause signs, but in rare cases the cat may have back pain.
Infectious and inflammatory diseases of the spinal column and spinal cord include bacterial, rickettsial, viral, fungal, protozoal, and parasitic infections and inflammatory diseases of unknown causes. 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.
Diskospondylitis is inflammation of the disk between 2 vertebrae (bones in the spinal column). The vertebrae can also be inflamed without infection of the disk. It is rare in cats and is usually due to direct spread of infection from a nearby wound. (Also see diskospondylitis in dogs.) The most common sign is spinal pain, with some cats also having fever, depression, and weight loss. Neurologic signs can develop due to pressure on the spinal cord or, rarely, spread of infection to the spinal cord. X-rays are used to diagnose the condition, and cultures can identify the underlying infection. Signs usually disappear within 5 days of treatment with an appropriate antibiotic, but treatment should be continued for at least 8 weeks.
Feline infectious peritonitis is a disease of domestic cats caused by an abnormal immune response to a coronavirus. This condition commonly causes damage to the nervous system and the tissues surrounding it. Signs of spinal cord inflammation include spinal pain and partial paralysis in 2 or 4 legs. Signs affecting the blood and other organs, especially the eyes, are also common. Available blood tests are unreliable. Analysis of cerebrospinal fluid can be helpful in diagnosis. There is no effective treatment, and the prognosis for recovery is poor.
Myelopathy associated with feline leukemia virus is a spinal cord disease that affects some cats that have been infected with the feline leukemia virus for more than 2 years. The main signs are loss of motor control and weakness in the hind legs, which can progress to paraplegic paralysis within a year. Other signs include spinal pain and abnormal behavior. Diagnosis is based on the signs, blood tests, and eliminating other possible causes. There is no treatment.
Rabies is caused by a viral infection that spreads to the central nervous system from the peripheral nerves. It can affect all mammals, including cats and people. For several decades, there have been more reported cases of rabies in cats than in dogs in the United States. Rabies is common throughout the world except in Japan, and some other islands, including New Zealand, Iceland, and Hawaii. Initial signs are extremely variable, and rabies should be considered a possibility in any unvaccinated animal with severe neurologic dysfunction. Signs that the infection has reached the spinal cord include a loss of motor control and progressive paralysis, usually with a loss of reflexes. Affected animals typically, but not invariably, die within 2 to 7 days of when signs begin. There is no treatment. Vaccination is essential for prevention.
Cryptococcus neoformans is the most common fungus to cause a central nervous system infection in cats. Other fungal organisms may also invade the central nervous system (including Blastomyces dermatitidis, Histoplasma capsulatum, Coccidioides immitis, Aspergillus spp, and phaeohyphomycosis). Infections often affect other organs, such as the lungs, eyes, skin, or bones. Signs of spinal cord infection include partial or total paralysis and spinal pain. Blood or cerebrospinal fluid tests are necessary to diagnose an infection and identify the organism.
Treatment and the outlook for recovery depend on the specific fungus involved. The drug fluconazole is often effective for Cryptococcus and Coccidioides infections. Infections with Blastomyces or Histoplasma fungi are difficult to treat, and the outlook for recovery in cats infected with these fungi is uncertain to poor.
Toxoplasmosis is caused by a protozoan called Toxoplasma gondii, which can occasionally cause inflammation of the brain and spinal cord in kittens. Infected kittens usually have signs of disease in other organs. A blood test or tissue sample can diagnose the infection. Various drugs are recommended for treatment.
Verminous myelitis is inflammation of the spinal cord caused by a parasite. The most common cause in cats is larvae of Cuterebra flies. Signs of spinal cord inflammation strike suddenly and severely, often affecting one side of the body more than the other, and may progressively worsen over time. This condition is difficult to diagnose except by examination of tissue after death. Drug treatment can be beneficial, but a full recovery is uncertain.
Feline nonsuppurative meningoencephalomyelitis, also called feline polioencephalomyelitis or staggering disease, is a slowly progressive, inflammatory disease of the central nervous system in domestic cats. It has been reported in North America, Europe, and Australia. The cause is unknown, but a virus or some other infectious agent is probably involved. The disease causes the neurons to degenerate and is most severe in the thoracic segments of the spinal cord. The disease is difficult to diagnosis in a living animal, and there is no treatment, so the outlook is poor. Signs include weakness in the legs that worsens over 1 to 2 months, in addition to sensitivity to touch, head tremors, and changes in behavior.
In cats, lymphoma is the most common tumor to affect the spinal cord. Adult cats of any age can be affected. There is a sudden and severe or slowly progressive onset of signs that center around a specific, often painful, tumor on the spinal cord. About 85% of affected cats have positive tests for feline leukemia virus. Treatment consists of combination chemotherapy. Remission is possible, but the longterm outlook is poor.
Hypervitaminosis A can develop in cats that are fed diets that contain excess vitamin A, such as diets that contain a large amount of liver. Growths form on the surface of the bones in the spine in affected cats. Signs include neck pain and rigidity with foreleg lameness. Reducing the amount of vitamin A will prevent further damage but does not reverse the damage that has already occurred.
Cats that do not get enough vitamin B1 (thiamine deficiency) can exhibit brain dysfunction. Causes include improperly formulated cat food, vegetarian diets, food preserved with sulfur dioxide, and raw fish diets. Affected cats typically exhibit abnormal balance, head tremors, difficulty controlling movement, depression, weakness of the rear legs, seizures, and death. The condition is diagnosed based on signs, diet, and response to vitamin B1 supplementation.
Spinal cord injuries usually occur as a result of a spinal fracture or dislocation. Common causes in cats 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 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 may be seen on x-rays, but computed tomography (a CT scan) may be necessary to see some fractures. 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 cats that have lost the ability to feel pain at locations below the spinal injury, the outlook for recovery is poor.
Organophosphates are a common type of pesticide used to protect both animals and plants from destructive insects. Poisoning due to organophosphates occurs in three forms: acute, intermediate, and delayed. 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 cat’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. Cats 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 cat may recover completely with early treatment. In severe cases, death may occur due to respiratory paralysis.
Pieces of cartilage (likely from the disks found between vertebrae) can block blood flow to the spinal cord in a condition called fibrocartilaginous embolism. It is rare in cats. It typically begins after jumping or running and causes a sudden, nonpainful change in the cat's gait. The signs do not typically worsen after 12 hours past when it occurred. Magnetic resonance imaging (MRI) is used to make the diagnosis. Mildly affected cats usually improve within 1 to 2 weeks, but the outlook is poor for severely affected cats or those that do not show signs of improvement.
Also see professional content regarding diseases of the spinal column and cord.