A-Z of Pain
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You know it at once. It may be the fiery sensation of a burn
moments after your finger touches the stove. Or it's a dull ache
above your brow after a day of stress and tension. Or you may
recognize it as a sharp pierce in your back after you lift something
heavy.
It is pain. In its most benign form, it warns us that something
isn't quite right, that we should take medicine or see a doctor. At
its worst, however, pain robs us of our productivity, our
well-being, and, for many of us suffering from extended illness, our
very lives. Pain is a complex perception that differs enormously
among individual patients, even those who appear to have identical
injuries or illnesses.
In 1931, the French medical missionary Dr. Albert Schweitzer wrote, "Pain
is a more terrible lord of mankind than even death itself." Today, pain has
become the universal disorder, a serious and costly public health issue, and
a challenge for family, friends, and health care providers who must give support
to the individual suffering from the physical as well as the emotional consequences
of pain.
Ancient civilizations recorded on stone tablets accounts of pain
and the treatments used: pressure, heat, water, and sun. Early
humans related pain to evil, magic, and demons. Relief of pain was
the responsibility of sorcerers, shamans, priests, and priestesses,
who used herbs, rites, and ceremonies as their treatments.
The Greeks and Romans were the first to advance a theory of
sensation, the idea that the brain and nervous system have a role in
producing the perception of pain. But it was not until the Middle
Ages and well into the Renaissance-the 1400s and 1500s-that evidence
began to accumulate in support of these theories. Leonardo da Vinci
and his contemporaries came to believe that the brain was the
central organ responsible for sensation. Da Vinci also developed the
idea that the spinal cord transmits sensations to the brain.
In the 17th and 18th centuries, the study of the body-and the
senses-continued to be a source of wonder for the world's
philosophers. In 1664, the French philosopher René Descartes
described what to this day is still called a "pain pathway."
Descartes illustrated how particles of fire, in contact with the
foot, travel to the brain and he compared pain sensation to the
ringing of a bell.
In the 19th century, pain came to dwell under a new
domain-science-paving the way for advances in pain therapy.
Physician-scientists discovered that opium, morphine, codeine, and
cocaine could be used to treat pain. These drugs led to the
development of aspirin, to this day the most commonly used pain
reliever. Before long, anesthesia-both general and regional-was
refined and applied during surgery.
"It has no future but itself," wrote the 19th century American
poet Emily Dickinson, speaking about pain. As the 21st century
unfolds, however, advances in pain research are creating a less grim
future than that portrayed in Dickinson’s verse, a future that
includes a better understanding of pain, along with greatly improved
treatments to keep it in check.
What is pain? The International Association for the Study of Pain
defines it as: An unpleasant sensory and emotional experience
associated with actual or potential tissue damage or described in
terms of such damage.
It is useful to distinguish between two basic types of pain,
acute and chronic, and they differ greatly.
- Acute pain, for the most part, results from
disease, inflammation, or injury to tissues. This type of pain
generally comes on suddenly, for example, after trauma or surgery,
and may be accompanied by anxiety or emotional distress. The cause
of acute pain can usually be diagnosed and treated, and the pain
is self-limiting, that is, it is confined to a given period of
time and severity. In some rare instances, it can become chronic.
- Chronic pain is widely believed to represent
disease itself. It can be made much worse by environmental and
psychological factors. Chronic pain persists over a longer period
of time than acute pain and is resistant to most medical
treatments. It can—and often does—cause severe problems for
patients.
Hundreds of pain syndromes or disorders make up the spectrum of
pain. There are the most benign, fleeting sensations of pain, such
as a pin prick. There is the pain of childbirth, the pain of a heart
attack, and the pain that sometimes follows amputation of a limb.
There is also pain accompanying cancer and the pain that follows
severe trauma, such as that associated with head and spinal cord
injuries. A sampling of common pain syndromes follows, listed
alphabetically.
Arachnoiditis is a condition in which one of the three
membranes covering the brain and spinal cord, called the arachnoid
membrane, becomes inflamed. A number of causes, including infection
or trauma, can result in inflammation of this membrane.
Arachnoiditis can produce disabling, progressive, and even permanent
pain.
Arthritis. Millions of Americans suffer from arthritic
conditions such as osteoarthritis, rheumatoid arthritis, ankylosing
spondylitis, and gout. These disorders are characterized by joint
pain in the extremities. Many other inflammatory diseases affect the
body's soft tissues, including tendonitis and bursitis.
Back pain has become the high price paid by our modern lifestyle and
is a startlingly common cause of disability for many Americans, including
both active and inactive people. Back pain that spreads to the leg is called
sciatica and is a very common condition (see below). Another common type of
back pain is associated with the discs of the spine, the soft, spongy padding
between the vertebrae (bones) that form the spine. Discs protect the spine
by absorbing shock, but they tend to degenerate over time and may sometimes
rupture. Spondylolisthesis is a back condition that occurs when one
vertebra extends over another, causing pressure on nerves and therefore pain.
Also, damage to nerve roots is a serious condition, called radiculopathy,
that can be extremely painful. Treatment for a damaged disc includes drugs
such as painkillers, muscle relaxants, and steroids; exercise or rest, depending
on the patient's condition; adequate support, such as a brace or better mattress
and physical therapy. In some cases, surgery may be required to remove the
damaged portion of the disc and return it to its previous condition, especially
when it is pressing a nerve root. Surgical procedures include discectomy,
laminectomy, or spinal fusion.
Burn pain can be profound and poses an extreme challenge
to the medical community. First-degree burns are the least severe;
with third-degree burns, the skin is lost. Depending on the injury,
pain accompanying burns can be excruciating, and even after the
wound has healed patients may have chronic pain at the burn
site.
Central pain syndrome-see "Trauma" below.
Cancer pain can accompany the growth of a tumor, the
treatment of cancer, or chronic problems related to cancer's
permanent effects on the body. Fortunately, most cancer pain can be
treated to help minimize discomfort and stress to the patient.
Headaches affect millions of Americans. The three most
common types of chronic headache are migraines, cluster headaches,
and tension headaches. Each comes with its own telltale brand of
pain.
- Migraines are characterized by throbbing pain and sometimes by
other symptoms, such as nausea and visual disturbances. Migraines are more
frequent in women than men. Stress can trigger a migraine headache, and
migraines can also put the sufferer at risk for stroke.
- Cluster headaches are characterized by excruciating, piercing pain
on one side of the head; they occur more frequently in men than women.
- Tension headaches are often described as a tight band around the
head.
Head and facial pain can be agonizing, whether it results from dental
problems or from disorders such as cranial neuralgia, in which one of the
nerves in the face, head, or neck is inflamed. Another condition, trigeminal
neuralgia (also called tic douloureux), affects the largest of the cranial
nerves and is characterized by a stabbing, shooting pain.
Muscle pain can range from an aching muscle, spasm, or
strain, to the severe spasticity that accompanies paralysis. Another
disabling syndrome is fibromyalgia, a disorder characterized
by fatigue, stiffness, joint tenderness, and widespread muscle pain.
Polymyositis, dermatomyositis, and inclusion body
myositis are painful disorders characterized by muscle
inflammation. They may be caused by infection or autoimmune
dysfunction and are sometimes associated with connective tissue
disorders, such as lupus and rheumatoid arthritis.
Myofascial pain syndromes affect sensitive areas known as
trigger points, located within the body's muscles. Myofascial pain
syndromes are sometimes misdiagnosed and can be debilitating.
Fibromyalgia is a type of myofascial pain syndrome.
Neuropathic pain is a type of pain that can result from injury to
nerves, either in the peripheral or central nervous system. Neuropathic pain
can occur in any part of the body and is frequently described as a hot, burning
sensation, which can be devastating to the affected individual. It can result
from diseases that affect nerves (such as diabetes) or from trauma, or, because
chemotherapy drugs can affect nerves, it can be a consequence of cancer treatment.
Among the many neuropathic pain conditions are diabetic neuropathy
(which results from nerve damage secondary to vascular problems that occur
with diabetes); reflex sympathetic dystrophy syndrome, which can follow
injury; phantom limb and post-amputation pain, which can result
from the surgical removal of a limb; postherpetic neuralgia, which
can occur after an outbreak of shingles; and central pain syndrome,
which can result from trauma to the brain or spinal cord.
Reflex sympathetic dystrophy syndrome, or RSDS, is
accompanied by burning pain and hypersensitivity to temperature.
Often triggered by trauma or nerve damage, RSDS causes the skin of
the affected area to become characteristically shiny. In recent
years, RSDS has come to be called complex regional pain
syndrome (CRPS); in the past it was often called
causalgia.
Repetitive stress injuries are muscular conditions that result
from repeated motions performed in the course of normal work or
other daily activities. They include:
- writer's cramp, which affects musicians and writers and
others,
- compression or entrapment neuropathies, including carpal
tunnel syndrome, caused by chronic overextension of the wrist and
- tendonitis or tenosynovitis, affecting one or more tendons.
Sciatica is a painful condition caused by pressure on the sciatic
nerve, the main nerve that branches off the spinal cord and continues down
into the thighs, legs, ankles, and feet. Sciatica is characterized by pain
in the buttocks and can be caused by a number of factors. Exertion, obesity,
and poor posture can all cause pressure on the sciatic nerve. One common cause
of sciatica is a herniated disc.
Shingles and other painful disorders affect the skin. Pain
is a common symptom of many skin disorders, even the most common
rashes. One of the most vexing neurological disorders is shingles or
herpes zoster, an infection that often causes agonizing pain
resistant to treatment. Prompt treatment with antiviral agents is
important to arrest the infection, which if prolonged can result in
an associated condition known as postherpetic neuralgia.
Other painful disorders affecting the skin include:
- vasculitis, or inflammation of blood vessels;
- other infections, including herpes simplex;
- skin tumors and cysts, and
- tumors associated with neurofibromatosis, a
neurogenetic disorder.
Sports injuries are common. Sprains, strains, bruises,
dislocations, and fractures are all well-known words in the language
of sports. Pain is another. In extreme cases, sports injuries can
take the form of costly and painful spinal cord and head injuries,
which cause severe suffering and disability.
Spinal stenosis refers to a narrowing of the canal
surrounding the spinal cord. The condition occurs naturally with
aging. Spinal stenosis causes weakness in the legs and leg pain
usually felt while the person is standing up and often relieved by
sitting down.
Surgical pain may require regional or general anesthesia
during the procedure and medications to control discomfort following
the operation. Control of pain associated with surgery includes
presurgical preparation and careful monitoring of the patient during
and after the procedure.
Temporomandibular disorders are conditions in which the
temporomandibular joint (the jaw) is damaged and/or the muscles used
for chewing and talking become stressed, causing pain. The condition
may be the result of a number of factors, such as an injury to the
jaw or joint misalignment, and may give rise to a variety of
symptoms, most commonly pain in the jaw, face, and/or neck muscles.
Physicians reach a diagnosis by listening to the patient's
description of the symptoms and by performing a simple examination
of the facial muscles and the temporomandibular joint.
Trauma can occur after injuries in the home, at the
workplace, during sports activities, or on the road. Any of these
injuries can result in severe disability and pain. Some patients who
have had an injury to the spinal cord experience intense pain
ranging from tingling to burning and, commonly, both. Such patients
are sensitive to hot and cold temperatures and touch. For these
individuals, a touch can be perceived as intense burning, indicating
abnormal signals relayed to and from the brain. This condition is
called central pain syndrome or, if the damage is in the
thalamus (the brain's center for processing bodily sensations),
thalamic pain syndrome. It affects as many as 100,000
Americans with multiple sclerosis, Parkinson's disease, amputated
limbs, spinal cord injuries, and stroke. Their pain is severe and is
extremely difficult to treat effectively. A variety of medications,
including analgesics, antidepressants, anticonvulsants, and
electrical stimulation, are options available to central pain
patients.
Vascular disease or injury-such as vasculitis or
inflammation of blood vessels, coronary artery disease, and
circulatory problems-all have the potential to cause pain. Vascular
pain affects millions of Americans and occurs when communication
between blood vessels and nerves is interrupted. Ruptures, spasms,
constriction, or obstruction of blood vessels, as well as a
condition called ischemia in which blood supply to organs, tissues,
or limbs is cut off, can also result in pain.
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There is no way to tell how much pain a person has. No test can
measure the intensity of pain, no imaging device can show pain, and
no instrument can locate pain precisely. Sometimes, as in the case
of headaches, physicians find that the best aid to diagnosis is the
patient's own description of the type, duration, and location of
pain. Defining pain as sharp or dull, constant or intermittent,
burning or aching may give the best clues to the cause of pain.
These descriptions are part of what is called the pain history,
taken by the physician during the preliminary examination of a
patient with pain.
Physicians, however, do have a number of technologies they use to
find the cause of pain. Primarily these include:
- Electrodiagnostic procedures include
electromyography (EMG), nerve conduction studies,
and evoked potential (EP) studies. Information from
EMG can help physicians tell precisely which muscles or
nerves are affected by weakness or pain. Thin needles are inserted
in muscles and a physician can see or listen to electrical signals
displayed on an EMG machine. With nerve conduction studies
the doctor uses two sets of electrodes (similar to those used
during an electrocardiogram) that are placed on the skin over the
muscles. The first set gives the patient a mild shock that
stimulates the nerve that runs to that muscle. The second set of
electrodes is used to make a recording of the nerve's electrical
signals, and from this information the doctor can determine if
there is nerve damage. EP tests also involve two sets of
electrodes-one set for stimulating a nerve (these electrodes are
attached to a limb) and another set on the scalp for recording the
speed of nerve signal transmission to the brain.
- Imaging, especially magnetic resonance imaging or
MRI, provides physicians with pictures of the body's
structures and tissues. MRI uses magnetic fields and radio waves
to differentiate between healthy and diseased tissue.
- A neurological examination in which the physician tests
movement, reflexes, sensation, balance, and coordination.
- X-rays produce pictures of the body's structures, such
as bones and joints.
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The goal of pain management is to improve function, enabling
individuals to work, attend school, or participate in other
day-to-day activities. Patients and their physicians have a number
of options for the treatment of pain; some are more effective than
others. Sometimes, relaxation and the use of imagery as a
distraction provide relief. These methods can be powerful and
effective, according to those who advocate their use. Whatever the
treatment regime, it is important to remember that pain is
treatable. The following treatments are among the most
common.
Acetaminophen is the basic ingredient found in Tylenol®
and its many generic equivalents. It is sold over the counter, in a
prescription-strength preparation, and in combination with codeine
(also by prescription).
Acupuncture dates back 2,500 years and involves the
application of needles to precise points on the body. It is part of
a general category of healing called traditional Chinese or Oriental
medicine. Acupuncture remains controversial but is quite popular and
may one day prove to be useful for a variety of conditions as it
continues to be explored by practitioners, patients, and
investigators.
Analgesic refers to the class of drugs that includes most
painkillers, such as aspirin, acetaminophen, and ibuprofen. The word
analgesic is derived from ancient Greek and means to reduce or stop
pain. Nonprescription or over-the-counter pain relievers are
generally used for mild to moderate pain. Prescription pain
relievers, sold through a pharmacy under the direction of a
physician, are used for more moderate to severe pain.
Anticonvulsants are used for the treatment of seizure
disorders but are also sometimes prescribed for the treatment of
pain. Carbamazepine in particular is used to treat a number of
painful conditions, including trigeminal neuralgia. Another
antiepileptic drug, gabapentin, is being studied for its
pain-relieving properties, especially as a treatment for neuropathic
pain.
Antidepressants are sometimes used for the treatment of
pain and, along with neuroleptics and lithium, belong to a category
of drugs called psychotropic drugs. In addition, anti-anxiety drugs
called benzodiazepines also act as muscle relaxants and are
sometimes used as pain relievers. Physicians usually try to treat
the condition with analgesics before prescribing these drugs.
Antimigraine drugs include the triptans- sumatriptan
(Imitrex®), naratriptan (Amerge®), and zolmitriptan (Zomig®)-and are
used specifically for migraine headaches. They can have serious side
effects in some people and therefore, as with all prescription
medicines, should be used only under a doctor's care.
Aspirin may be the most widely used pain-relief agent and
has been sold over the counter since 1905 as a treatment for fever,
headache, and muscle soreness.
Biofeedback is used for
the treatment of many common pain problems, most notably headache
and back pain. Using a special electronic machine, the patient is
trained to become aware of, to follow, and to gain control over
certain bodily functions, including muscle tension, heart rate, and
skin temperature. The individual can then learn to effect a change
in his or her responses to pain, for example, by using relaxation
techniques. Biofeedback is often used in combination with other
treatment methods, generally without side effects. Similarly, the
use of relaxation techniques in the treatment of pain can increase
the patient's feeling of well-being.
Capsaicin is a chemical found in chili peppers that is also a primary
ingredient in pain-relieving creams.
Chemonucleolysis is a treatment in which an enzyme, chymopapain, is
injected directly into a herniated lumbar disc in an effort to dissolve material
around the disc, thus reducing pressure and pain. The procedure's use is extremely
limited, in part because some patients may have a life-threatening allergic
reaction to chymopapain.
Chiropractic refers to hand manipulation of the spine,
usually for relief of back pain, and is a treatment option that
continues to grow in popularity among many people who simply seek
relief from back disorders. It has never been without controversy,
however. Chiropractic's usefulness as a treatment for back pain is,
for the most part, restricted to a select group of individuals with
uncomplicated acute low back pain who may derive relief from the
massage component of the therapy.
Cognitive-behavioral therapy involves a wide variety of
coping skills and relaxation methods to help prepare for and cope
with pain. It is used for postoperative pain, cancer pain, and the
pain of childbirth.
Counseling can give a patient suffering from pain much
needed support, whether it is derived from family, group, or
individual counseling. Support groups can provide an important
adjunct to drug or surgical treatment. Psychological treatment can
also help patients learn about the physiological changes produced by
pain.
COX-2 inhibitors ("superaspirins") may be particularly
effective for individuals with arthritis. For many years scientists
have wanted to develop the ultimate drug-a drug that works as well
as morphine but without its negative side effects. Nonsteroidal
anti-inflammatory drugs (NSAIDs) work by blocking two enzymes,
cyclooxygenase-1 and cyclooxygenase-2, both of which promote
production of hormones called prostaglandins, which in turn
cause inflammation, fever, and pain. Newer drugs, called COX-2
inhibitors, primarily block cyclooxygenase-2 and are less likely to
have the gastrointestinal side effects sometimes produced by NSAIDs.
On 1999, the Food and Drug Administration approved two COX-2
inhibitors-rofecoxib (Vioxx®) and celecoxib (Celebrex®). Although
the long-term effects of COX-2 inhibitors are still being evaluated,
they appear to be safe. In addition, patients may be able to take
COX-2 inhibitors in larger doses than aspirin and other drugs that
have irritating side effects, earning them the nickname
"superaspirins."
Electrical stimulation, including transcutaneous
electrical stimulation (TENS), implanted electric nerve stimulation,
and deep brain or spinal cord stimulation, is the modern-day
extension of age-old practices in which the nerves of muscles are
subjected to a variety of stimuli, including heat or massage.
Electrical stimulation, no matter what form, involves a major
surgical procedure and is not for everyone, nor is it 100 percent
effective. The following techniques each require specialized
equipment and personnel trained in the specific procedure being
used:
- TENS uses tiny electrical pulses, delivered through the skin to
nerve fibers, to cause changes in muscles, such as numbness or contractions.
This in turn produces temporary pain relief. There is also evidence that
TENS can activate subsets of peripheral nerve fibers that can block pain
transmission at the spinal cord level, in much the same way that shaking
your hand can reduce pain.
- Peripheral nerve stimulation uses electrodes placed surgically
on a carefully selected area of the body. The patient is then able to deliver
an electrical current as needed to the affected area, using an antenna and
transmitter.
- Spinal cord stimulation uses electrodes surgically inserted within
the epidural space of the spinal cord. The patient is able to deliver a
pulse of electricity to the spinal cord using a small box-like receiver
and an antenna taped to the skin.
- Deep brain or intracerebral stimulation is considered an extreme
treatment and involves surgical stimulation of the brain, usually the thalamus.
It is used for a limited number of conditions, including severe pain, central
pain syndrome, cancer pain, phantom limb pain, and other neuropathic pains.
Exercise has come to be a prescribed part of some doctors'
treatment regimes for patients with pain. Because there is a known
link between many types of chronic pain and tense, weak muscles,
exercise-even light to moderate exercise such as walking or
swimming-can contribute to an overall sense of well-being by
improving blood and oxygen flow to muscles. Just as we know that
stress contributes to pain, we also know that exercise, sleep, and
relaxation can all help reduce stress, thereby helping to alleviate
pain. Exercise has been proven to help many people with low back
pain. It is important, however, that patients carefully follow the
routine laid out by their physicians.
Hypnosis, first approved for medical use by the American
Medical Association in 1958, continues to grow in popularity,
especially as an adjunct to pain medication. In general, hypnosis is
used to control physical function or response, that is, the amount
of pain an individual can withstand. How hypnosis works is not fully
understood. Some believe that hypnosis delivers the patient into a
trance-like state, while others feel that the individual is simply
better able to concentrate and relax or is more responsive to
suggestion. Hypnosis may result in relief of pain by acting on
chemicals in the nervous system, slowing impulses. Whether and how
hypnosis works involves greater insight-and research-into the
mechanisms underlying human consciousness.
Ibuprofen is a member of the aspirin family of analgesics,
the so-called nonsteroidal anti-inflammatory drugs (see below). It
is sold over the counter and also comes in prescription-strength
preparations.
Low-power lasers have been used occasionally by some
physical therapists as a treatment for pain, but like many other
treatments, this method is not without controversy.
Magnets are increasingly popular with athletes who swear
by their effectiveness for the control of sports-related pain and
other painful conditions. Usually worn as a collar or wristwatch,
the use of magnets as a treatment dates back to the ancient
Egyptians and Greeks. While it is often dismissed as quackery and
pseudoscience by skeptics, proponents offer the theory that magnets
may effect changes in cells or body chemistry, thus producing pain
relief.
Narcotics (see Opioids, below).
Nerve blocks employ the use of drugs, chemical agents, or surgical
techniques to interrupt the relay of pain messages between specific areas
of the body and the brain. There are many different names for the procedure,
depending on the technique or agent used. Types of surgical nerve blocks include
neurectomy; spinal dorsal, cranial, and trigeminal rhizotomy; and sympathectomy,
also called sympathetic blockade.
Nonsteroidal anti-inflammatory drugs (NSAIDs) (including
aspirin and ibuprofen) are widely prescribed and sometimes called
non-narcotic or non-opioid analgesics. They work by reducing
inflammatory responses in tissues. Many of these drugs irritate the
stomach and for that reason are usually taken with food. Although
acetaminophen may have some anti-inflammatory effects, it is
generally distinguished from the traditional NSAIDs.
Opioids are derived from the poppy plant and are among the
oldest drugs known to humankind. They include codeine and perhaps
the most well-known narcotic of all, morphine. Morphine can
be administered in a variety of forms, including a pump for patient
self-administration. Opioids have a narcotic effect, that is, they
induce sedation as well as pain relief, and some patients may become
physically dependent upon them. For these reasons, patients given
opioids should be monitored carefully; in some cases stimulants may
be prescribed to counteract the sedative side effects. In addition
to drowsiness, other common side effects include constipation,
nausea, and vomiting.
Physical therapy and rehabilitation date back to the
ancient practice of using physical techniques and methods, such as
heat, cold, exercise, massage, and manipulation, in the treatment of
certain conditions. These may be applied to increase function,
control pain, and speed the patient toward full recovery.
Placebos offer some individuals pain relief although
whether and how they have an effect is mysterious and somewhat
controversial. Placebos are inactive substances, such as sugar
pills, or harmless procedures, such as saline injections or sham
surgeries, generally used in clinical studies as control factors to
help determine the efficacy of active treatments. Although placebos
have no direct effect on the underlying causes of pain, evidence
from clinical studies suggests that many pain conditions such as
migraine headache, back pain, post-surgical pain, rheumatoid
arthritis, angina, and depression sometimes respond well to them.
This positive response is known as the placebo effect, which is
defined as the observable or measurable change that can occur in
patients after administration of a placebo. Some experts believe the
effect is psychological and that placebos work because the patients
believe or expect them to work. Others say placebos relieve pain by
stimulating the brain's own analgesics and setting the body's
self-healing forces in motion. A third theory suggests that the act
of taking placebos relieves stress and anxiety-which are known to
aggravate some painful conditions-and, thus, cause the patients to
feel better. Still, placebos are considered controversial because by
definition they are inactive and have no actual curative value.
R.I.C.E.-Rest, Ice, Compression, and
Elevation-are four components prescribed by many
orthopedists, coaches, trainers, nurses, and other professionals for
temporary muscle or joint conditions, such as sprains or strains.
While many common orthopedic problems can be controlled with these
four simple steps, especially when combined with over-the-counter
pain relievers, more serious conditions may require surgery or
physical therapy, including exercise, joint movement or
manipulation, and stimulation of muscles.
Surgery, although not always an option, may be required to relieve
pain, especially pain caused by back problems or serious musculoskeletal injuries.
Surgery may take the form of a nerve block or it may involve an operation
to relieve pain from a ruptured disc. Surgical procedures for back problems
include discectomy or, when microsurgical techniques are used, microdiscectomy,
in which the entire disc is removed; laminectomy, a procedure in which
a surgeon removes only a disc fragment, gaining access by entering through
the arched portion of a vertebra; and spinal fusion, a procedure where the
entire disc is removed and replaced with a bone graft. In a spinal fusion,
the two vertebrae are then fused together. Although the operation can cause
the spine to stiffen, resulting in lost flexibility, the procedure serves
one critical purpose: protection of the spinal cord. Other operations for
pain include rhizotomy, in which a nerve close to the spinal cord is
cut, and cordotomy, where bundles of nerves within the spinal cord
are severed. Cordotomy is generally used only for the pain of terminal cancer
that does not respond to other therapies. Another operation for pain is the
dorsal root entry zone operation, or DREZ, in which spinal neurons
corresponding to the patient's pain are destroyed surgically. Because surgery
can result in scar tissue formation that may cause additional problems, patients
are well advised to seek a second opinion before proceeding. Occasionally,
surgery is carried out with electrodes that selectively damage neurons in
a targeted area of the brain. These procedures rarely result in long-term
pain relief, but both physician and patient may decide that the surgical procedure
will be effective enough that it justifies the expense and risk. In some cases,
the results of an operation are remarkable. For example, many individuals
suffering from trigeminal neuralgia who are not responsive to drug treatment
have had great success with a procedure called microvascular decompression,
in which tiny blood vessels are surgically separated from surrounding nerves.
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It is now widely believed that pain affects men and women
differently. While the sex hormones estrogen and testosterone
certainly play a role in this phenomenon, psychology and culture,
too, may account at least in part for differences in how men and
women receive pain signals. For example, young children may learn to
respond to pain based on how they are treated when they experience
pain. Some children may be cuddled and comforted, while others may
be encouraged to tough it out and to dismiss their pain.
Many investigators are turning their attention to the study of
gender differences and pain. Women, many experts now agree, recover
more quickly from pain, seek help more quickly for their pain, and
are less likely to allow pain to control their lives. They also are
more likely to marshal a variety of resources-coping skills,
support, and distraction-with which to deal with their pain.
Research in this area is yielding fascinating results. For
example, male experimental animals injected with estrogen, a female
sex hormone, appear to have a lower tolerance for pain-that is, the
addition of estrogen appears to lower the pain threshold. Similarly,
the presence of testosterone, a male hormone, appears to elevate
tolerance for pain in female mice: the animals are simply able to
withstand pain better. Female mice deprived of estrogen during
experiments react to stress similarly to male animals. Estrogen,
therefore, may act as a sort of pain switch, turning on the ability
to recognize pain.
Investigators know that males and females both have strong
natural pain-killing systems, but these systems operate differently.
For example, a class of painkillers called kappa-opioids is named
after one of several opioid receptors to which they bind, the
kappa-opioid receptor, and they include the compounds
nalbuphine (Nubain®) and butorphanol (Stadol®).
Research suggests that kappa-opioids provide better pain relief in
women.
Though not prescribed widely, kappa-opioids are currently used
for relief of labor pain and in general work best for short-term
pain. Investigators are not certain why kappa-opioids work better in
women than men. Is it because a woman's estrogen makes them work, or
because a man's testosterone prevents them from working? Or is there
another explanation, such as differences between men and women in
their perception of pain? Continued research may result in a better
understanding of how pain affects women differently from men,
enabling new and better pain medications to be designed with gender
in mind.
Pain is the number one complaint of older Americans, and one in
five older Americans takes a painkiller regularly. In 1998, the
American Geriatrics Society (AGS) issued guidelines* for the
management of pain in older people. The AGS panel addressed the
incorporation of several non-drug approaches in patients' treatment
plans, including exercise. AGS panel members recommend that,
whenever possible, patients use alternatives to aspirin, ibuprofen,
and other NSAIDs because of the drugs' side effects, including
stomach irritation and gastrointestinal bleeding. For older adults,
acetaminophen is the first-line treatment for mild-to-moderate pain,
according to the guidelines. More serious chronic pain conditions
may require opioid drugs (narcotics), including codeine or morphine,
for relief of pain.
Pain in younger patients also requires special attention,
particularly because young children are not always able to describe
the degree of pain they are experiencing. Although treating pain in
pediatric patients poses a special challenge to physicians and
parents alike, pediatric patients should never be undertreated.
Recently, special tools for measuring pain in children have been
developed that, when combined with cues used by parents, help
physicians select the most effective treatments.
Nonsteroidal agents, and especially acetaminophen, are most often
prescribed for control of pain in children. In the case of severe
pain or pain following surgery, acetaminophen may be combined with
codeine.
* Journal of the American Geriatrics Society (1998; 46:635-651).
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We may experience pain as a prick, tingle, sting, burn, or ache. Receptors
on the skin trigger a series of events, beginning with an electrical impulse
that travels from the skin to the spinal cord. The spinal cord acts as a sort
of relay center where the pain signal can be blocked, enhanced, or otherwise
modified before it is relayed to the brain. One area of the spinal cord in
particular, called the dorsal horn, is important in the reception of
pain signals.
The most common destination in the brain for pain signals is the thalamus
and from there to the cortex, the headquarters for complex thoughts. The thalamus
also serves as the brain's storage area for images of the body and plays a
key role in relaying messages between the brain and various parts of the body.
In people who undergo an amputation, the representation of the amputated limb
is stored in the thalamus.
Pain is a complicated process that involves an intricate
interplay between a number of important chemicals found naturally in
the brain and spinal cord. In general, these chemicals, called
neurotransmitters, transmit nerve impulses from one cell to
another.
There are many different neurotransmitters in the human body;
some play a role in human disease and, in the case of pain, act in
various combinations to produce painful sensations in the body. Some
chemicals govern mild pain sensations; others control intense or
severe pain.
The body's chemicals act in the transmission of pain messages by
stimulating neurotransmitter receptors found on the surface
of cells; each receptor has a corresponding neurotransmitter.
Receptors function much like gates or ports and enable pain messages
to pass through and on to neighboring cells. One brain chemical of
special interest to neuroscientists is glutamate. During
experiments, mice with blocked glutamate receptors show a reduction
in their responses to pain. Other important receptors in pain
transmission are opiate-like receptors. Morphine and other opioid
drugs work by locking on to these opioid receptors, switching on
pain-inhibiting pathways or circuits, and thereby blocking pain.
Another type of receptor that responds to painful stimuli is
called a nociceptor. Nociceptors are thin nerve fibers in the
skin, muscle, and other body tissues, that, when stimulated, carry
pain signals to the spinal cord and brain. Normally, nociceptors
only respond to strong stimuli such as a pinch. However, when
tissues become injured or inflamed, as with a sunburn or infection,
they release chemicals that make nociceptors much more sensitive and
cause them to transmit pain signals in response to even gentle
stimuli such as breeze or a caress. This condition is called
allodynia -a state in which pain is produced by innocuous
stimuli.
The body's natural painkillers may yet prove to be the most
promising pain relievers, pointing to one of the most important new
avenues in drug development. The brain may signal the release of
painkillers found in the spinal cord, including serotonin,
norepinephrine, and opioid-like chemicals. Many pharmaceutical
companies are working to synthesize these substances in laboratories
as future medications.
Endorphins and enkephalins are other natural
painkillers. Endorphins may be responsible for the "feel good"
effects experienced by many people after rigorous exercise; they are
also implicated in the pleasurable effects of smoking.
Similarly, peptides, compounds that make up proteins in
the body, play a role in pain responses. Mice bred experimentally to
lack a gene for two peptides called tachykinins-neurokinin A
and substance P-have a reduced response to severe pain. When exposed
to mild pain, these mice react in the same way as mice that carry
the missing gene. But when exposed to more severe pain, the mice
exhibit a reduced pain response. This suggests that the two peptides
are involved in the production of pain sensations, especially
moderate-to-severe pain. Continued research on tachykinins,
conducted with support from the NINDS, may pave the way for drugs
tailored to treat different severities of pain.
Scientists are working to develop potent pain-killing drugs that
act on receptors for the chemical acetylcholine. For example,
a type of frog native to Ecuador has been found to have a chemical
in its skin called epibatidine, derived from the frog's scientific
name, Epipedobates tricolor. Although highly toxic,
epibatidine is a potent analgesic and, surprisingly, resembles the
chemical nicotine found in cigarettes. Also under development are
other less toxic compounds that act on acetylcholine receptors and
may prove to be more potent than morphine but without its addictive
properties.
The idea of using receptors as gateways for pain drugs is a novel
idea, supported by experiments involving substance P. Investigators
have been able to isolate a tiny population of neurons, located in
the spinal cord, that together form a major portion of the pathway
responsible for carrying persistent pain signals to the brain. When
animals were given injections of a lethal cocktail containing
substance P linked to the chemical saporin, this group of cells,
whose sole function is to communicate pain, were killed. Receptors
for substance P served as a portal or point of entry for the
compound. Within days of the injections, the targeted neurons,
located in the outer layer of the spinal cord along its entire
length, absorbed the compound and were neutralized. The animals'
behavior was completely normal; they no longer exhibited signs of
pain following injury or had an exaggerated pain response.
Importantly, the animals still responded to acute, that is, normal,
pain. This is a critical finding as it is important to retain the
body's ability to detect potentially injurious stimuli. The
protective, early warning signal that pain provides is essential for
normal functioning. If this work can be translated clinically,
humans might be able to benefit from similar compounds introduced,
for example, through lumbar (spinal) puncture.
Another promising area of research using the body's natural
pain-killing abilities is the transplantation of chromaffin cells
into the spinal cords of animals bred experimentally to develop
arthritis. Chromaffin cells produce several of the body's
pain-killing substances and are part of the adrenal medulla, which
sits on top of the kidney. Within a week or so, rats receiving these
transplants cease to exhibit telltale signs of pain. Scientists,
working with support from the NINDS, believe the transplants help
the animals recover from pain-related cellular damage. Extensive
animal studies will be required to learn if this technique might be
of value to humans with severe pain.
One way to control pain outside of the brain, that is,
peripherally, is by inhibiting hormones called
prostaglandins. Prostaglandins stimulate nerves at the site
of injury and cause inflammation and fever. Certain drugs, including
NSAIDs, act against such hormones by blocking the enzyme that is
required for their synthesis.
Blood vessel walls stretch or dilate during a migraine attack and
it is thought that serotonin plays a complicated role in this
process. For example, before a migraine headache, serotonin levels
fall. Drugs for migraine include the triptans: sumatriptan
(Imitrix®), naratriptan (Amerge®), and zolmitriptan (Zomig®). They
are called serotonin agonists because they mimic the action
of endogenous (natural) serotonin and bind to specific subtypes of
serotonin receptors.
Ongoing pain research, much of it supported by the NINDS,
continues to reveal at an unprecedented pace fascinating insights
into how genetics, the immune system, and the skin contribute to
pain responses.
The explosion of knowledge about human genetics is helping
scientists who work in the field of drug development. We know, for
example, that the pain-killing properties of codeine rely heavily on
a liver enzyme, CYP2D6, which helps convert codeine into morphine. A
small number of people genetically lack the enzyme CYP2D6; when
given codeine, these individuals do not get pain relief. CYP2D6 also
helps break down certain other drugs. People who genetically lack
CYP2D6 may not be able to cleanse their systems of these drugs and
may be vulnerable to drug toxicity. CYP2D6 is currently under
investigation for its role in pain.
In his research, the late John C. Liebeskind, a renowned pain
expert and a professor of psychology at UCLA, found that pain can
kill by delaying healing and causing cancer to spread. In his
pioneering research on the immune system and pain, Dr. Liebeskind
studied the effects of stress-such as surgery-on the immune system
and in particular on cells called natural killer or NK
cells. These cells are thought to help protect the body against
tumors. In one study conducted with rats, Dr. Liebeskind found that,
following experimental surgery, NK cell activity was suppressed,
causing the cancer to spread more rapidly. When the animals were
treated with morphine, however, they were able to avoid this
reaction to stress.
The link between the nervous and immune systems is an important
one. Cytokines, a type of protein found in the nervous system, are
also part of the body's immune system, the body's shield for
fighting off disease. Cytokines can trigger pain by promoting
inflammation, even in the absence of injury or damage. Certain types
of cytokines have been linked to nervous system injury. After
trauma, cytokine levels rise in the brain and spinal cord and at the
site in the peripheral nervous system where the injury occurred.
Improvements in our understanding of the precise role of cytokines
in producing pain, especially pain resulting from injury, may lead
to new classes of drugs that can block the action of these
substances.
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In the forefront of pain research are scientists supported by the
National Institutes of Health (NIH), including the NINDS. Other
institutes at NIH that support pain research include the National
Institute of Dental and Craniofacial Research, the National Cancer
Institute, the National Institute of Nursing Research, the National
Institute on Drug Abuse, and the National Institute of Mental
Health. Developing better pain treatments is the primary goal of all
pain research being conducted by these institutes.
Some pain medications dull the patient's perception of pain.
Morphine is one such drug. It works through the body's natural
pain-killing machinery, preventing pain messages from reaching the
brain. Scientists are working toward the development of a
morphine-like drug that will have the pain-deadening qualities of
morphine but without the drug's negative side effects, such as
sedation and the potential for addiction. Patients receiving
morphine also face the problem of morphine tolerance, meaning that
over time they require higher doses of the drug to achieve the same
pain relief. Studies have identified factors that contribute to the
development of tolerance; continued progress in this line of
research should eventually allow patients to take lower doses of
morphine.
One objective of investigators working to develop the future
generation of pain medications is to take full advantage of the
body's pain "switching center" by formulating compounds that will
prevent pain signals from being amplified or stop them altogether.
Blocking or interrupting pain signals, especially when there is no
injury or trauma to tissue, is an important goal in the development
of pain medications. An increased understanding of the basic
mechanisms of pain will have profound implications for the
development of future medicines. The following areas of research are
bringing us closer to an ideal pain drug.
Systems and Imaging: The idea of mapping cognitive
functions to precise areas of the brain dates back to phrenology,
the now archaic practice of studying bumps on the head. Positron
emission tomography (PET), functional magnetic resonance imaging
(fMRI), and other imaging technologies offer a vivid picture of what
is happening in the brain as it processes pain. Using imaging,
investigators can now see that pain activates at least three or four
key areas of the brain's cortex-the layer of tissue that covers the
brain. Interestingly, when patients undergo hypnosis so that the
unpleasantness of a painful stimulus is not experienced, activity in
some, but not all, brain areas is reduced. This emphasizes that the
experience of pain involves a strong emotional component as well as
the sensory experience, namely the intensity of the stimulus.
Channels: The frontier in the search for new drug targets
is represented by channels. Channels are gate-like passages found
along the membranes of cells that allow electrically charged
chemical particles called ions to pass into the cells. Ion channels
are important for transmitting signals through the nerve's membrane.
The possibility now exists for developing new classes of drugs,
including pain cocktails that would act at the site of channel
activity.
Trophic Factors: A class of "rescuer" or "restorer" drugs
may emerge from our growing knowledge of trophic factors, natural
chemical substances found in the human body that affect the survival
and function of cells. Trophic factors also promote cell death, but
little is known about how something beneficial can become harmful.
Investigators have observed that an over-accumulation of certain
trophic factors in the nerve cells of animals results in heightened
pain sensitivity, and that some receptors found on cells respond to
trophic factors and interact with each other. These receptors may
provide targets for new pain therapies.
Molecular Genetics: Certain genetic mutations can change
pain sensitivity and behavioral responses to pain. People born
genetically insensate to pain-that is, individuals who cannot feel
pain-have a mutation in part of a gene that plays a role in cell
survival. Using "knockout" animal models-animals genetically
engineered to lack a certain gene-scientists are able to visualize
how mutations in genes cause animals to become anxious, make noise,
rear, freeze, or become hypervigilant. These genetic mutations cause
a disruption or alteration in the processing of pain information as
it leaves the spinal cord and travels to the brain. Knockout animals
can be used to complement efforts aimed at developing new drugs.
Plasticity: Following injury, the nervous system undergoes
a tremendous reorganization. This phenomenon is known as plasticity.
For example, the spinal cord is "rewired" following trauma as nerve
cell axons make new contacts, a phenomenon known as "sprouting."
This in turn disrupts the cells' supply of trophic factors.
Scientists can now identify and study the changes that occur during
the processing of pain. For example, using a technique called
polymerase chain reaction, abbreviated PCR, scientists can study the
genes that are induced by injury and persistent pain. There is
evidence that the proteins that are ultimately synthesized by these
genes may be targets for new therapies. The dramatic changes that
occur with injury and persistent pain underscore that chronic pain
should be considered a disease of the nervous system, not just
prolonged acute pain or a symptom of an injury. Thus, scientists
hope that therapies directed at preventing the long-term changes
that occur in the nervous system will prevent the development of
chronic pain conditions.
Neurotransmitters: Just as mutations in genes may affect
behavior, they may also affect a number of neurotransmitters
involved in the control of pain. Using sophisticated imaging
technologies, investigators can now visualize what is happening
chemically in the spinal cord. From this work, new therapies may
emerge, therapies that can help reduce or obliterate severe or
chronic pain.
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Thousands of years ago, ancient peoples attributed pain to
spirits and treated it with mysticism and incantations. Over the
centuries, science has provided us with a remarkable ability to
understand and control pain with medications, surgery, and other
treatments. Today, scientists understand a great deal about the
causes and mechanisms of pain, and research has produced dramatic
improvements in the diagnosis and treatment of a number of painful
disorders. For people who fight every day against the limitations
imposed by pain, the work of NINDS-supported scientists holds the
promise of an even greater understanding of pain in the coming
years. Their research offers a powerful weapon in the battle to
prolong and improve the lives of people with pain: hope.
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Stacked on top of one another in the spine are more than 30
bones, the vertebrae, which together form the spine. They are
divided into four regions:
- the seven cervical or neck vertebrae (labeled C1-C7),
- the 12 thoracic or upper back vertebrae (labeled T1-T12),
- the five lumbar vertebrae (labeled L1-L5), which we know as
the lower back, and
- the sacrum and coccyx, a group of bones fused together at the
base of the spine.
The vertebrae are linked by ligaments, tendons, and muscles. Back
pain can occur when, for example, someone lifts something too heavy,
causing a sprain, pull, strain, or spasm in one of these muscles or
ligaments in the back.
Between the vertebrae are round, spongy pads of cartilage called
discs that act much like shock absorbers. In many cases,
degeneration or pressure from overexertion can cause a disc to shift
or protrude and bulge, causing pressure on a nerve and resultant
pain. When this happens, the condition is called a slipped, bulging,
herniated, or ruptured disc, and it sometimes results in permanent
nerve damage.
The column-like spinal cord is divided into segments similar to
the corresponding vertebrae: cervical, thoracic, lumbar, sacral, and
coccygeal. The cord also has nerve roots and rootlets which form
branch-like appendages leading from its ventral side (that is, the
front of the body) and from its dorsal side (that is, the back of
the body). Along the dorsal root are the cells of the dorsal root
ganglia, which are critical in the transmission of "pain" messages
from the cord to the brain. It is here where injury, damage, and
trauma become pain.
The central nervous system (CNS) refers to the brain and spinal
cord together. The peripheral nervous system refers to the cervical,
thoracic, lumbar, and sacral nerve trunks leading away from the
spine to the limbs. Messages related to function (such as movement)
or dysfunction (such as pain) travel from the brain to the spinal
cord and from there to other regions in the body and back to the
brain again. The autonomic nervous system controls involuntary
functions in the body, like perspiration, blood pressure, heart
rate, or heart beat. It is divided into the sympathetic and
parasympathetic nervous systems. The sympathetic and parasympathetic
nervous systems have links to important organs and systems in the
body; for example, the sympathetic nervous system controls the
heart, blood vessels, and respiratory system, while the
parasympathetic nervous system controls our ability to sleep, eat,
and digest food.
The peripheral nervous system also includes 12 pairs of cranial
nerves located on the underside of the brain. Most relay messages of
a sensory nature. They include the olfactory (I), optic (II),
oculomotor (III), trochlear (IV), trigeminal (V), abducens (VI),
facial (VII), vestibulocochlear (VIII), glossopharyngeal (IX), vagus
(X), accessory (XI), and hypoglossal (XII) nerves. Neuralgia, as in
trigeminal neuralgia, is a term that refers to pain that arises from
abnormal activity of a nerve trunk or its branches. The type and
severity of pain associated with neuralgia vary widely.
Sometimes, when a limb is removed during an amputation, an
individual will continue to have an internal sense of the lost limb.
This phenomenon is known as phantom limb and accounts describing it
date back to the 1800s. Similarly, many amputees are frequently
aware of severe pain in the absent limb. Their pain is real and is
often accompanied by other health problems, such as depression.
What causes this phenomenon? Scientists believe that following
amputation, nerve cells "rewire" themselves and continue to receive
messages, resulting in a remapping of the brain's circuitry. The
brain's ability to restructure itself, to change and adapt following
injury, is called plasticity (see section on Plasticity).
Our understanding of phantom pain has improved tremendously in
recent years. Investigators previously believed that brain cells
affected by amputation simply died off. They attributed sensations
of pain at the site of the amputation to irritation of nerves
located near the limb stump. Now, using imaging techniques such as
positron emission tomography (PET) and magnetic resonance imaging
(MRI), scientists can actually visualize increased activity in the
brain's cortex when an individual feels phantom pain. When study
participants move the stump of an amputated limb, neurons in the
brain remain dynamic and excitable. Surprisingly, the brain's cells
can be stimulated by other body parts, often those located closest
to the missing limb.
Treatments for phantom pain may include analgesics,
anticonvulsants, and other types of drugs; nerve blocks; electrical
stimulation; psychological counseling, biofeedback, hypnosis, and
acupuncture; and, in rare instances, surgery.
The hot feeling, red face, and watery eyes you experience when
you bite into a red chili pepper may make you reach for a cold
drink, but that reaction has also given scientists important
information about pain. The chemical found in chili peppers that
causes those feelings is capsaicin (pronounced cap-SAY-sin),
and it works its unique magic by grabbing onto receptors scattered
along the surface of sensitive nerve cells in the mouth.
In 1997, scientists at the University of California at San
Francisco discovered a gene for a capsaicin receptor, called the
vanilloid receptor. Once in contact with capsaicin, vanilloid
receptors open and pain signals are sent from the peripheral
nociceptor and through central nervous system circuits to the brain.
Investigators have also learned that this receptor plays a role in
the burning type of pain commonly associated with heat, such as the
kind you experience when you touch your finger to a hot stove. The
vanilloid receptor functions as a sort of "ouch gateway," enabling
us to detect burning hot pain, whether it originates from a 3-alarm
habanera chili or from a stove burner.
Capsaicin is currently available as a prescription or
over-the-counter cream for the treatment of a number of pain
conditions, such as shingles. It works by reducing the amount of
substance P found in nerve endings and interferes with the
transmission of pain signals to the brain. Individuals can become
desensitized to the compound, however, perhaps because of long-term
damage to nerve tissue. Some individuals find the burning sensation
they experience when using capsaicin cream to be intolerable,
especially when they are already suffering from a painful condition,
such as postherpetic neuralgia. Soon, however, better treatments
that relieve pain by blocking vanilloid receptors may arrive in
drugstores.
As a painkiller, marijuana or, by its Latin name,
cannabis, continues to remain highly controversial. In the
eyes of many individuals campaigning on its behalf, marijuana
rightfully belongs with other pain remedies. In fact, for many
years, it was sold under highly controlled conditions in cigarette
form by the Federal government for just that purpose.
In 1997, the National Institutes of Health held a workshop to
discuss research on the possible therapeutic uses for smoked
marijuana. Panel members from a number of fields reviewed published
research and heard presentations from pain experts. The panel
members concluded that, because there are too few scientific studies
to prove marijuana's therapeutic utility for certain conditions,
additional research is needed. There is evidence, however, that
receptors to which marijuana binds are found in many brain regions
that process information that can produce pain.
Nerve blocks may involve local anesthesia, regional anesthesia or
analgesia, or surgery; dentists routinely use them for traditional
dental procedures. Nerve blocks can also be used to prevent or even
diagnose pain.
In the case of a local nerve block, any one of a number of local
anesthetics may be used; the names of these compounds, such as
lidocaine or novocaine, usually have an aine ending. Regional
blocks affect a larger area of the body. Nerve blocks may also take
the form of what is commonly called an epidural, in which a drug is
administered into the space between the spine's protective covering
(the dura) and the spinal column. This procedure is most well known
for its use during childbirth. Morphine and methadone are opioid
narcotics (such drugs end in ine or one) that are sometimes used for
regional analgesia and are administered as an injection.
Neurolytic blocks employ injection of chemical agents such as alcohol, phenol,
or glycerol to block pain messages and are most often used to treat cancer
pain or to block pain in the cranial nerves. In some cases, a drug called
guanethidine is administered intravenously in order to accomplish the block.
Surgical blocks are performed on cranial, peripheral, or
sympathetic nerves. They are most often done to relieve the pain of
cancer and extreme facial pain, such as that experienced with
trigeminal neuralgia. There are several different types of surgical
nerve blocks and they are not without problems and complications.
Nerve blocks can cause muscle paralysis and, in many cases, result
in at least partial numbness. For that reason, the procedure should
be reserved for a select group of patients and should only be
performed by skilled surgeons. Types of surgical nerve blocks
include:
- Neurectomy (including peripheral neurectomy) in which a
damaged peripheral nerve is destroyed.
- Spinal dorsal rhizotomy in which the surgeon cuts the
root or rootlets of one or more of the nerves radiating from the
spine. Other rhizotomy procedures include cranial rhizotomy
and trigeminal rhizotomy, performed as a treatment for
extreme facial pain or for the pain of cancer.
- Sympathectomy, also called sympathetic blockade, in which
a drug or an agent such as guanethidine is used to eliminate pain in a specific
area (a limb, for example). The procedure is also done for cardiac pain,
vascular disease pain, the pain of reflex sympathetic dystrophy syndrome,
and other conditions. The term takes its name from the sympathetic nervous
system and may involve, for example, cutting a nerve that controls contraction
of one or more arteries.
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BRAIN
Public Information and
Liaison Branch National Institute of Dental and Craniofacial Research National
Institutes of Health
American Chronic Pain Association
(ACPA)
American Pain Foundation
Arthritis Foundation
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