Cauda Equina Syndrome

INTRODUCTION
Between each of the vertebrae (bones of the spine) is an intervertebral disk. This disk is composed of a soft tissue, called fibrocartilage that allows movement and acts as a shock absorber.

Normal wear and tear with aging results in deterioration of these disks (disk degeneration). Although some older patients can show clinical signs, more often the deterioration progresses without any problems or symptoms. In some pets, this deterioration is accelerated and middle-aged patients can show clinical signs. Occasionally, a specific traumatic event may have precipitated the disk herniation.

The patients most commonly affected with disk degeneration are large breed dogs, usually 4 to 9 years of age. In these patients the disk degeneration results in a slowly protruding or bulging disk.

If the disk between the lowest lumbar vertebra and the sacrum is bulging (the lumbosacral disk), the nerves of the spinal cord adjacent (called the cauda equina) may become compressed (as seen in the diagram on the right). Compression of the cauda equina can result in back pain, pain of the sciatic nerve (sciatica) and neurologic weakness.

This compression may occur over the course of many months and thus symptoms may be gradual and often mistaken for arthritis. Treatment should be started before irreversible damage to the cauda equina nerves has occurred. The decision for medical treatment or surgery will depend on the severity of the symptoms.

DIAGNOSIS
Although we can be suspicious that disk degeneration is the cause of the clinical signs, Magnetic Resonance Imaging (MRI) is required to be certain of the diagnosis. MRI is a special diagnostic study wherein the anesthetized patient is placed into a large and powerful electromagnet. MRI uses the physics of the behavior of atoms in the body, when the body is placed in a electromagnetic field.

When these electromagnetically excited atoms are subjected to a transmitted radiowave, the atoms resonate, and send back a radiowave signal (echo). The signal is detected and translated by a computer into a 3 dimensional image. These images can be printed on x-ray film directly from the computer. By varying the frequency of the transmitted radiowave and the time between the transmitted radiowave and the echo, different characteristics of the tissues can be seen.

TREATMENT
If surgery is indicated, decompression of the nerves is accomplished with a laminectomy and diskectomy. Enough bone is removed to visualize the nerves of the cauda equina and the degenerate disk is carefully removed and the compression relieved. If vertebral instability is present or develops in the future, a stabilization/fusion procedure may also be required.

AFTER-CARE
Patients may be in the hospital up to a week or more depending on the severity of their problem. If permanent, irreversible damage has not already occurred, patients may begin to show improvement within a few days to a few weeks after surgery. Strict crate or pen confinement and leash controlled walks to urinate and defecate is required for 8 weeks. Physical therapy consisting of slings, carts, exercises and swimming may be important for recovery of strength and coordination. Patients may continue to show improvement for up to 6 months after treatment.

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