What is pain?

Pain is a signal triggered in the nervous system to alert us to possible injury.

Acute pain, the result of sudden trauma, has a purpose. This kind of pain can usually be diagnosed and treated so the discomfort is managed and confined to a given period of time.

Chronic pain, though, is much more confounding. It is the kind of alarm that doesn't go away and is resistant to most medical treatments.

It may be as a result of an ongoing cause – arthritis, cancer, infection – but some people have chronic pain for weeks, months and years in the absence of any obvious pathology or evidence of damage.

A type of chronic pain called neurogenic or neuropathic pain often accompanies paralysis – it is a cruel irony for people who lack sensation to experience the agony of pain.

Why does pain occur?

Pain is a complicated process that involves an intricate interplay between a number of chemicals found naturally in the brain and spinal cord. These chemicals, called neurotransmitters, transmit nerve impulses from one cell to another.

There is a critical lack of GABA (gamma-aminobutyric acid), an inhibitory neurotransmitter, in the injured spinal cord. This may "disinhibit" spinal neurons that are responsible for pain sensations, causing them to fire more than normal. This disinhibition is believed to be the root of spasticity, too.

Recent data also suggest that there maybe a shortage of the neurotransmitter norepinephrine, as well as an over abundance of the neurotransmitter 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 receptors, switching on pain-inhibiting pathways or circuits, and thereby blocking pain.

Following injury, the nervous system undergoes a tremendous reorganization. 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. Therefore, new drugs must be developed.

Unfortunately, current medications for most chronic pain conditions are relatively ineffective and are used mostly in a trial by error manner.

The problem with chronic nerve pain is not just the distraction of hurting. Pain can lead to inactivity, which may lead to anger and frustration, isolation, depression, sleeplessness, sadness, and potentially more pain.

It's a cycle of misery with no easy exit, and modern medicine doesn't offer a wide range of help. Pain control becomes a matter of pain management to improve function and allow people to participate in day-to-day activities.

Types of pain

Musculoskeletal or mechanical pain: occurs at or above the level of a spinal cord lesion and may stem from the overuse of remaining functional muscles or those used for unaccustomed activity. Wheelchair propulsion and transfers are responsible for most mechanical pain.

Central pain or deafferentation pain is experienced below the level of injury and generally characterized by burning, aching and/or tingling. Central pain doesn't always show up right away. It may take weeks or months to appear and is often associated with recovery of some spinal cord function. This type of pain is less common in complete injuries. Other irritations, such as pressure sores or fractures, may increase the burning of central pain.

Psychological pain: increased age, depression, stress and anxiety are associated with greater post-spinal cord injury pain. This doesn't mean the sensation of pain is in your head – it's real, but pain appears to have an emotional component, too.

Treatment options for neuropathic pain

Heat and massage therapy: sometimes are effective for musculoskeletal pain related to spinal cord injury.

Acupuncture: this practice dates back 2,500 years to China and involves the application of needles to precise points on the body. While some research suggests this technique boosts levels of the body's natural painkillers (endorphins), acupuncture is not fully accepted in the medical community. Still, it is noninvasive and inexpensive compared to many other pain treatments. In some limited studies, this method helps relieve SCI pain.

Exercise: individuals living with SCI who underwent a regular exercise program showed significant improvement in pain scores, as well as improved depression scores. Even light to moderate walking or swimming can contribute to an overall sense of well-being by improving blood and oxygen flow to tense, weak muscles. Less stress equals less pain.

Hypnosis: visual imagery therapy, which uses guided images to modify behavior, helps some people alleviate pain by changing perceptions of discomfort.

Biofeedback: trains people to become aware of and to gain control over certain bodily functions, including muscle tension, heart rate and skin temperature. One can also learn to effect a change in his or her responses to pain, for example, by using relaxation techniques. By consciously modifying out-of-balance brain rhythms, individuals can improve body processes and brain physiology. There are many claims made for treating chronic pain with biofeedback, especially using brain wave information (EEG).

Transcranial electrical stimulation (TCES): electrodes are applied to an individual's scalp, allowing electrical current to stimulate the underlying cerebrum. Studies indicate this newer treatment may be useful in reducing SCI-related chronic pain.

Transcutaneous electrical nerve stimulation (TENS): has been shown to help with chronic musculoskeletal pain. In general, TENS has not been as effective for pain below injury level.

Transcranial magnetic stimulation (TMS): electromagnetic pulses are applied to the brain. TMS has helped with post-stroke pain and in limited studies has reduced post-SCI pain over long-term use.

Spinal cord stimulation: electrodes are surgically inserted within the epidural space of the spinal cord. The patient triggers a pulse of electricity to the spinal cord using a small box-like receiver. This is most commonly used for lower back pain but some people with MS or paralysis can benefit.

Deep brain stimulation: considered an extreme treatment and involves surgical stimulation of the brain, usually at the thalamus. It is used for a limited number of conditions, including central pain syndrome, cancer pain, phantom limb pain and other types of neuropathic pain.

Magnets: usually dismissed as pseudoscience, but proponents offer the theory that magnetic fields may effect changes in cells or body chemistry, thus producing pain relief.

Botulinum toxin injections (Botox): commonly used to treat focal spasticity, can also have an effect on pain.

Nerve blocks: drugs, chemical agents or surgical techniques interrupt the transmission of pain messages between specific areas of the body and the brain. Types of surgical nerve blocks include neurectomy, spinal dorsal, cranial, and trigeminal rhizotomy, and sympathetic blockade.

Physical therapy and rehabilitation: often utilized to increase function, control pain and speed a person toward recovery.

Surgeries: includes 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: used to treat pain associated with terminal cancer. The dorsal root entry zone operation, or DREZ, destroys spinal neurons corresponding to the patient's pain. This surgery can be done with electrodes that selectively damage neurons in a targeted area of the brain.

Marijuana: while illegal in many states, its proponents place pot alongside other pain remedies. In fact, for many years, it was sold in cigarette form by the U.S. government for just that purpose. Marijuana appears to bind to receptors found in many brain regions that process pain information.

Research in neuroscience will lead to a better understanding of the basic mechanisms of pain, and to superior treatments in the years to come. Blocking or interrupting pain signals, especially when there is no apparent injury or trauma to tissue, is a key goal in the development of new medications.

Other treatments

Options for chronic pain include a ladder of drugs, starting with over the counter nonsteroidal anti-inflammatories such as aspirin, all the way to tightly controlled opiates such as morphine.

Aspirin and ibuprofen may help with muscle and joint pain but are of minimal use for neuropathic pain. This includes COX-2 inhibitors (superaspirins) such as celecoxib (Celebrex).

At the top of the ladder are opioids. These are drugs derived from the poppy plant that are among the oldest drugs known to humankind. They include codeine and morphine.

While morphine is still the go-to therapy at the top of the treatment ladder, it is not usually a good long-term solution. It depresses breathing, causes constipation and fogs the brain. People also develop tolerance and addiction for it. Moreover, it isn't effective against many types of neuropathic pain. Scientists hope to develop a morphine-like drug that will have the pain-deadening qualities of morphine but without its debilitating side effects.

There is a middle ground of medications that work for some types of chronic pain:

  • Anticonvulsants were developed to treat seizure disorders, but are also sometimes prescribed for pain.
  • Carbamazepine (Tegretol) is used to treat a number of painful conditions, including trigeminal neuralgia.
  • Gabapentin (sold as Neurontin) is commonly prescribed "off label" (unapproved by the FDA) for neuropathic pain.

Pfizer received FDA approval in 2012 of an anticonvulsant to target pain, this time specific to SCI. Pregabalin (marketed as Lyrica) reduced neuropathic pain associated with SCI from baseline compared to placebo. Patients receiving Lyrica showed a 30 percent to 50 percent reduction in pain compared to those getting placebo. Lyrica won't work for everyone. And it comes with a wide range of possible side-effects, including anxiety, restlessness, trouble sleeping, panic attacks, anger, irritability, agitation, aggression, and a risk for suicidal behavior.

For some, tri-cyclic antidepressant drugs can be helpful for the treatment of pain. Amitriptyline (sold as Elavil and other brands) is effective in the treatment of post-SCI pain and there is some evidence it works in individuals living with depression.

In addition, the class of anti-anxiety drugs called benzodiazepines (Xanax, Valium) act as muscle relaxants and are sometimes used to deal with pain. Another muscle relaxant, baclofen, applied by an implanted pump (intrathecally), improves chronic post-SCI pain, but may only work when it is related to muscle spasms.

Research in neuroscience will lead to a better understanding of the basic mechanisms of pain, and to superior treatments in the years to come. Blocking or interrupting pain signals, especially when there is no apparent injury or trauma to tissue, is a key goal in the development of new medications.

Webcast: Dr. Dan on pain

In this recording on an online discussion, Dr. Dan discusses the various types of pain associated with living with paralysis - and how you can cope with them.

Resources

If you are looking for more information on how to manage pain or have a specific question, our information specialists are available business weekdays, Monday through Friday, toll-free at 800-539-7309 from 9am to 5pm ET.

Additionally, the Reeve Foundation maintains fact sheets on pain, alternative medicine, and complex regional pain syndrome with additional resources from trusted Reeve Foundation sources. Check out our repository of fact sheets on hundreds of topics ranging from state resources to secondary complications of paralysis.

We also encourage you to reach out to support groups and organizations, including:

Sources: National Institute of Neurological Disorders and Stroke (NINDS),National Multiple Sclerosis Society, Dana Foundation

This project was supported, in part by grant number 90PR3002, from the U.S. Administration for Community Living, Department of Health and Human Services, Washington, D.C. 20201. Grantees undertaking projects under government sponsorship are encouraged to express freely their findings and conclusions. Points of view or opinions do not, therefore, necessarily represent official Administration for Community Living policy.