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Rear Weakness in Dogs and Cats

If your pet suddenly has trouble using its hind legs, a back injury may be the cause. Dogs can have intervertebral disk problems. These are the little gel-filled cushions between the vertebrae. Sometimes one will slip out of place and cause pressure to the spinal cord. An injured disk will be painful, and often the nerves to the hind end are affected, causing weakness or even paralysis. Another condition that can cause rear end weakness or paralysis is fibrocartilaginous thromboembolism. Cats most commonly experience these symptoms secondary to trauma or clots lodged in the aorta or other rear end blood vessels because of heart disease.

Fibrocartilaginous Embolic Myelopathy

What is fibrocartilaginous embolic myelopathy?
Fibrocartilaginous embolic myelopathy is the blockage of blood flow to part of the spinal cord by pieces of cartilage-like material (fibrocartilage) that accidentally get displaced from their normal location in the body and move into blood vessels supplying the spinal cord. This blockage of spinal cord blood flow damages the spinal cord in the same way that a stroke would damage the brain.

What causes fibrocartilaginous embolic myelopathy?
How the cartilage gets into the spinal blood supply is not known, but it is suspected that it arises from an abnormal, degenerating disc along the back or neck. The disc's normal function is to serve as a shock absorber between the bones of the spine. If the shock absorber material inside of the disc turns into fibrocartilage, it can get forced into the blood stream and cause this problem.

What are the signs of fibrocartilaginous embolic myelopathy?
There are no warning signs that a sudden blockage of blood flow is about to happen. As soon as it does, a sudden loss of the ability to walk occurs owing to a shortage of blood supply to the spinal cord and subsequent nervous tissue damage. Occasionally, the animal is exercising when the disorder occurs and may cry out, causing the guardian and veterinarian to believe that a vertebral fracture or luxation (displacement) has happened.

How is fibrocartilaginous embolic myelopathy diagnosed?
Your veterinarian may suspect fibrocartilaginous embolic myelopathy after examining your pet, but he or she may need to run several tests to confirm the diagnosis and eliminate other possible causes of such sudden spinal cord damage. Blood clotting function tests may be needed to rule out internal bleeding. Spinal radiographs (X-rays) are often necessary and, in some animals, a myelogram (injection of dye into the area around the cord) may be needed to obtain a diagnosis.

How is fibrocartilaginous embolic myelopathy treated?
High doses of corticosteriod (cortisone) drugs can sometimes limit the extent of the damage if given within a few hours of the onset of signs. Once this initial treatment is completed, no other medication is available that will speed recovery. Good nursing care at home to prevent pressure sores and encouraging attempts to walk will help to maintain the ideal environment for the spinal cord to slowly heal itself.

What is the prognosis for animals with fibrocartilaginous embolic myelopathy?
The prognosis varies with the severity of the spinal cord injury. If the animal has some voluntary movement remaining in all limbs, the changes are good for recovery of walking to take place in 6 to 8 weeks. If all voluntary movement in a limb is lost but feeling remains, recovery is less likely to be complete, but it is still possible. Unfortunately, if all feeling in a limb is lost, the chance of recovery of any limb function is poor.

Lumbosacral Stenosis

What is lumbosacral stenosis?
Lumbosacral stenosis is a syndrome caused by abnormal narrowing (stenosis) of the lumbosacral (lower back) vertebral canal (the tube within the spine where the spinal cord lies).

What causes lumbosacral stenosis?
There are two primary causes of lumbosacral stenosis that may occur separately, or together:
  • Congenital narrowing of the canal caused by a defect of the vertebrae in this region that occurs during fetal development
  • Degenerative changes such as disk herniation, thickening of ligaments, and new bone production secondary to biomechanical stress in this area of the spine

    What are the signs of lumbosacral stenosis?
    Narrowing of the spinal canal causes gradual but progressive pressure on nerve roots in this area. Clinical signs occur with increasing severity and include:
  • Low back pain most noticeable when your pet jumps or goes up stairs.
  • Lameness of one or both hind legs.
  • Abnormal tail carriage (tail usually held down) or tail paralysis.
  • Weakness in the back legs.
  • Inability to control bowel and urinary function.
  • Biting at the tail or hind legs (in some dogs).

    How is lumbosacral stenosis diagnosed?
    Clinical signs are highly suggestive of the disease but the diagnosis may be difficult to confirm. Radiographs (X-rays) of the lumbosacral area may show degenerative changes, but often (particularly in the acquired form) the survey radiographs may be unremarkable. Even with special dye radiographic studies (myelogram), the diagnosis may not be reached. Recently, computed tomography (CT) and magnetic resonance imaging (MRI) have been found more helpful for visualizing the degree of narrowing of the spinal canal and for characterizing the type of tissue causing the stenosis.

    How is lumbosacral stenosis treated?
    Exercise restriction and anti-inflammatory medications (aspirin, or corticosteroids such as prednisone) help relieve the pain in milder cases. Medical management is only palliative, not curative. For permanent improvement, and in cases with partial or full paralysis, surgical removal of the tissue compressing the nerve roots is required.

    What is the prognosis for animals with lumbosacral stenosis?
    The prognosis varies with the severity of the clinical signs. In cases with pain or mild weakness as the major clinical sign, the prognosis for recovery is excellent. If the tail or rear legs are paralyzed or the animal has lost control of its bowel or bladder, the prognosis is guarded. Surgical decompression relieves the signs of pain and halts the progression of the disease in these cases, but the damage to the nerves that already occurred may not recover.

    Thoracolumbar (Mid-Back) Intervertebral Disk Disease

    What is thoracolumbar intervertebral disk disease?
    An intervertebral disk is a cushioning "spacer" found between two adjoining vertebrae (back bones). In dogs and cats, there are 12 thoracic disks (in the spine above the chest) and 8 lumbar disks (in the spine above the abdomen). Thoracolumbar intervertebral disk disease is the result of age-related degeneration within the thoracolumbar intervertebral disks. This can result in disk protrusion or extrusion into the spinal canal, with consequent trauma to or compression of the spinal cord.

    What causes thoracolumbar intervertebral disk disease?
    With age, intervertebral disks undergo degeneration resulting in the loss of flexibility. This loss predisposes the disk to eventual protrusion and rupture. Pressure on the spinal cord can result in the development of pain and loss of spinal cord function. Certain breeds of dogs are prone to early degeneration of their intervertebral disks and thus the clinical symptoms related to intervertebral disk disease. Chondrodystrophic dogs (e.g., Dachshund, Basset hound) are predisposed to this condition. Obesity will increase the risk of intervertebral disk disease.

    How is thoracolumbar intervertebral disk diagnosed?
    Your veterinarian may suspect thoracolumbar intervertebral disk disease after examining your pet. Radiographs (X-rays) and a special radiographic procedure called a myelogram are required to confirm the presence, location, number of affected disks, and severity of disease. A myelogram is a special study performed with your pet under generally anesthesia. A contrast material is injected next to the spinal cord to highlight and outline the spinal cord. Doing so allows your veterinarian to accurately diagnose the condition. In some cases the results of the myelography tests do not provide adequate diagnostic information. In these cases, additional special tests such as computed tomography (CAT) or magnetic resonance imaging (MRI) scans may be indicated.

    How is thoracolumbar intervertebral disk disease treated?
    Dogs with thoracolumbar disk disease can be broken down into four categories:
  • those with a first-time episode of back pain,
  • those with repeated episodes of back pain,
  • those with varying degrees of weakness or paralysis, but maintaining the ability to perceive pain in their hind limb toes,
  • those with complete paralysis and the complete loss of pain perception in their hind limb toes.
    Dogs in the first category may be treated with medical therapy only, while those in the other three categories may need surgery as well.

    What is the prognosis for pets with thoracolumbar intervertebral disk disease?
    The prognosis for dogs with thoracolumbar disk disease is generally good as long as they maintain the ability to feel pain in their hind limb toes. The prognosis for dogs that have lost all pain perception in their hind limbs is guarded to poor, although recoveries do occur occasionally. Dogs with sudden loss of deep pain perception may benefit from emergency decompressive surgery. Following surgical treatment, recurrence of symptoms is very uncommon.

    Paralysis and Paresis

    What are paralysis and paresis?
    Paralysis is the loss of the ability to move one or more body parts. It is the loss of voluntary movement "Quadriplegia" is the loss of voluntary movement of all four limbs. "Paraplegia" is loss of voluntary movement in the pelvic (rear) limbs only. "Paresis" is a similar condition; however, paresis is a weakness of voluntary movement or partial paralysis as opposed to a complete lack of voluntary movement. "Quadriparesis" or "tetraparesis" is a weakness in all four limbs, and "paraparesis" is a weakness of the pelvic (rear) limbs only.

    What causes paralysis or paresis?
    Paralysis or paresis is caused by diseases or malformations involving the nervous system (the brain, the spinal cord, or individual nerves). Whether the animal becomes paralyzed or is weak (paresis) is determined by the amount of damage to the nervous system. The extent of the paralysis or paresis will depend on the areas of the nervous system that are affected. The causes of paralysis or paresis include:

    "Slipped" disk, also known as disk herniation or intervertebral disk disease (protrusion of material from the intervertebral disks into the spinal column resulting in pressure or injury to the spinal cord)
  • Trauma, especially in animals that are allowed to roam
  • Tick paralysis
  • Botulism (food poisoning)
  • Coonhound paralysis (polyradiculoneuritis, acute polyneuritis)
  • Myasthenia gravis (a specific syndrome involving weakness of the muscles due to lack of normal nerve transmissions)
  • Cancer
  • Myelitis (inflammation of the spinal cord)
  • Congenital disorders present at birth such as spina bifida (defective closure of the spinal bones)
  • Seizures
  • Encephalitis (inflammation of the brain)
  • Stroke
  • Inherited disorders
  • Discospondylitis (inflammation of the vertebrae)

    What are the signs of paralysis or paresis?
    The signs of paralysis or paresis will depend on the area of the nervous system that is affected and the severity of injury to the nervous system. The pet may be unable to move, walk, or get up. Many spinal cord diseases begin with poor coordination, progress to weakness (paresis), and finally to paralysis. Most pets with paralysis or paresis are alert. The pet may be in pain and may be uncomfortable during the physical examination. The nails on the affected leg(s) may be worn. If the pelvic limbs are paralyzed, it is likely that the bladder also is paralyzed and the pet may have no control of urination or may not be able to urinate. If you suspect paralysis in your pet, be careful when moving the animal as movement could cause further damage. If the paralysis is due to a blockage to circulation rather than a nervous system disorder, the limbs will be cool and the nailbeds may be blue in color.

    How is paralysis or paresis diagnosed?
    Paralysis or paresis will be diagnosed by obtaining a good medical history and performing a thorough physical examination. The veterinarian also will do an evaluation of the nervous system. The spinal reflexes provide information to localize the nervous system problem to the upper, middle, or lower spinal cord. The femoral pulses will be evaluated to rule out circulatory blockages (such as an embolus). The veterinarian will need to determine the cause of the paralysis or paresis; therefore, many of the diagnostic tests are performed to identify the cause. Diagnostic tests (complete blood counts [CBCs], blood chemistry panels, and urinalysis) may be performed to assess the pet's health status. Blood and urine cultures may be done. Radiographs (X-rays) of the spinal cord can diagnose many abnormalities such as trauma (example, broken back), disk herniations, tumors, congenital malformations, and discospondylitis. Myelograms (special contrast X-rays) may be needed to evaluate problems of the spinal cord. Specialized nerve and muscle tests and biopsies often are needed to obtain a diagnosis of the cause of the paralysis or paresis.

    How is paralysis or paresis treated?
    The treatment will vary, depending on the cause of the paralysis or paresis, the severity of the signs, and the location of the affected nerves and muscles. Paralysis of some muscles, such as the respiratory muscles, is life threatening and will require emergency veterinary medical attention. Pets with paralysis or severe weakness (paresis) should be treated in the hospital until bladder function can be ascertained. Hand feeding or feeding through special tubes may be done if the muscles of swallowing are affected. Paralyzed animals must be placed on padded bedding and turned from side-to-side frequently to help prevent skin breakdown ("bed sores") and lung congestion. They must be checked and cleaned frequently because they are not able to move away from soiled bedding. The pet may have all activity restricted until spinal trauma and disk herniation can be ruled out. Physical therapy is important to keep muscles and joints from deteriorating in those animals allowed activity. Surgery often is the most effective method of treatment, depending on the condition. The veterinarian may prescribe medication. Animals with ticks should be treated with appropriate insecticides.

    What is the prognosis for animals with paralysis or paresis?
    The prognosis (outcome) for animals with paralysis or paresis is variable. The outcome for these animals depends on the underlying cause. Many complications including minor problems (such as constipation) or major problems (such as pneumonia, lack of ability to urinate, or permanent paralysis) can occur. Once bladder function has returned, the pet can be cared for at home. If bladder function does not return, bladder evacuation via manual expression or catheterization (insertion of a flexible tube into the bladder) is necessary.

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