What is chronic pain?
When there is an obvious cause for pain we hope that a physician will remove the cause. If you have pain in your low back that came on when helping to lift a piano, shoots down one leg, is aggravated by any activity and associated with weakness of the foot and numbness on the side of the foot you are likely to have a disk herniation. An MRI scan might show a disk herniation between the fifth lumbar and first sacral vertebra. If physical therapy and anti-inflammatory medication fail to help and you are getting worse, then surgery can make you better.
The surgery is designed to remove the source of injury or pressure on a nerve root. It relieves the acute pain, improves the weakness and the numbness.
When the pain is still there, and perhaps the pain is changed in its quality and the surgery was long ago done and the MRI no longer shows that a herniated disk is present then you may have chronic pain syndrome.
One form of chronic pain is neuropathic pain. This is pain that derives from an injured nerve and persists despite the cause of the pain having been removed. Whereas the pain of disk herniation is often dull and aching like a tooth ache, neuropathic pain is often burning or hard to put words to describe or just "odd" feeling. Often the area is extremely sensitive to things that normally should not be painful, like a cool breeze or just your clothes touching the skin. The usual "pain" medications do not help anymore. Instead of anti inflammatory medications or even narcotics, the pain may only be helped by quite different types of medicaiton- medications also used as antidepressants, used to improve mood, or with anticonvulsants, medications also used to stop seizures.
The treatment of chronic pain is conceptually different then the treatment of acute pain. The cause can not be identified and the treatment is directed towards relief from the pain rather than removal of the cause.
What does a neurosurgeon do?
Neurosurgeons treat disorders of the brain, spinal cord and peripheral nerves. They also treat problems with the supporting elements of these structures--the skull and the spine and the blood vessels feed and lead to and from these important structures. Because of this training, neurosurgeons are also spine surgeons and may be pain specialists.
What can a neurosurgical pain specialist do to treat chronic pain?
Probably the most common form of chronic pain is low back pain, especially pain that persists after surgery on the spine. Persistent pain after traumatic injury is another common cause. Sometimes the origin of the pain is never identified.
The evaluation of a patient with chronic pain begins with a summary of the history of its onset and development. A physical examination defines the extent of physical disability. Imaging studies will aide in determining the anatomy of any source of irritation to neurological function. Electrophysiologic studies (electromyography and nerve conduction velocity evaluation) will show the changes that occur in the electrical activity of the associated nerves and muscles.
It is helpful to fill out a detailed pain evaluation questionnaire. This will document the level of pain and list the words that describe the quality of the pain. The kinds and quantities of medications taken to alleviate the pain should be delineated. As much as possible neurosurgeons strive to limit the extent and risks of surgery on patients with chronic pain. Several forms of surgery designed to alleviate pain are available depending on the nature of the pain.
When the pain is neuropathic in origin and often burning in quality and present more in one leg or one arm it may be possible to treat it with implantation of neurostimulation device. An electrode is carefully positioned over the covering of the spinal cord and connecting to a pacemaker-like device that is buried underneath the skin of the abdomen. Patients sense a comforting electrical tingling that overlays and overcomes the discomfort from which they have suffered.
In some instances when the pain is in both legs it is possible to insert a catheter in the fluid space surrounding the spinal cord. The catheter is connected to a pump implanted beneath the skin of the belly and capable of being repeatedly refilled through the skin. The pump delivers microdoses of morphine directly to the spinal cord at doses ten times lower than that which is required should medication be taken by mouth, doses low enough to reduce the drowsiness commonly experienced with oral narcotic usage. A test injection of morphine is first done to evaluate the likelihood that one will benefit from such surgery before deciding to proceed.
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