Introduction: The Universal Disorder
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.
A Brief History 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.
The Two Faces of Pain: Acute and Chronic
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.
The A to Z of Pain
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 (see Spine
Basics in the Appendix) 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 (see section on surgery in How
is Pain Treated? for more information on these treatments).
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 (see The
Nervous Systems in the Appendix) 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 (see The
Nervous Systems in the Appendix). 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 (see below), which can follow injury; phantom limb and
post-amputation pain (see Phantom
Pain in the Appendix), 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 (see Spine
Basics in the Appendix).
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.
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.
How is Pain Treated?
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 (see Chili
Peppers, Capsaicin, and Pain in the Appendix).
Chemonucleolysis is a treatment in which an enzyme, chymopapain,
is injected directly into a herniated lumbar disc (see Spine
Basics in the Appendix) 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
(see Nerve
Blocks in the Appendix).
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 (see
Nerve
Blocks in the Appendix) 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.
What is the Role of Age and Gender in Pain?
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).
A Pain Primer: What Do We Know About Pain?
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 (see section on Spine
Basics in the Appendix), 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. (For a
discussion of the thalamus and its role in this phenomenon, called phantom
pain, see section on Phantom
Pain in the Appendix.)
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.
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.
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.
Spine Basics: The Vertebrae, Discs, and Spinal
Cord
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 Nervous Systems
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.
Phantom Pain: How Does the Brain Feel?
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.
Chili Peppers, Capsaicin, and Pain
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
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 (see The Nervous
Systems). 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 (see The
Nervous Systems) and may involve, for example, cutting a nerve that
controls contraction of one or more arteries.
Keeping on Top of Your Condition
Keeping in tune with your disease or condition not only makes treatment less intimidating but also increases its chance of success, and has been shown to lower a patients risk of complications. As well, as an informed patient, you are better able to discuss your condition and treatment options with your physician.
A new service available to patients provides a convenient means of staying informed, and ensures that the information is both reliable and accurate. If you wish to find out more about HealthNewsflash's innovative service, take the tour.
Information Resources
BRAIN
P.O. Box 5801
Bethesda, MD 20824
301-496-5751
800-352-9424
http://www.ninds.nih.gov/
Public Information and Liaison Branch
National Institute of Dental
and Craniofacial Research
National Institutes of Health
Building
45, Room 4AS19
Bethesda, MD 20892-6400
301-496-4261
http://www.nidcr.nih.gov/
American Chronic Pain Association
P.O. Box 850
Rocklin, CA
95677-0850
916-632-0922
http://www.theacpa.org/
American Pain Foundation
201 North Charles Street, Suite 710
Baltimore, MD 21201
410-783-7292
888-615-PAIN (7246)
http://www.painfoundation.org/
Arthritis Foundation
1330 West Peachtree Street
P.O. Box 7669
Atlanta, GA 30309
404-965-7100
800-283-7800
http://www.arthritis.org/
National Chronic Pain Outreach Association
P.O. Box 274
Millboro, VA 24460
540-862-9437
ncpoa@cfw.com
National Foundation for the Treatment of Pain
1330 Skyline Drive,
Suite #21
Monterey, CA 93940
831-655-8812
http://www.paincare.org/
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