Pain and the Brain – Science Thoughts

Last spring, after putting it off until getting dressed became a contortionist’s act, I finally agreed to shoulder surgery.  I expected the short-term pain – what the medical community calls “acute” pain.  I initially managed it with pharmaceuticals, and as one would hope, that pain dissipated with time.  What I never expected was long-term or “chronic” pain.  I decided to manage that by first finding out how pain works so I could make informed treatment decisions.  The most powerful thing I learned?   Knowing how pain works can make its treatment more effective.

As I get ready to launch into the nature of pain, you might be tempted to scan down to find the how-you-fix-it part.  Here’s my bias: most people do a better job of fixing things if they understand how they work.  I believe this to be particularly true in the case of pain.  When I first heard some of the recommendations for self-treating chronic pain, I thought they were almost laughable.  They certainly would not have worked for me at that point.  Because pain perception involves your mind, understanding how pain works can affect the outcome.

Nature of Pain

Most of us find it easier to tell the doctor where it hurts than to describe how it hurts, but the medical community needs to know “how” because it divides pain into two major categories: acute or chronic.  Acute pain initiates from the point of tissue injury, travelling via fast-conducting nerve fibers.  Characterized as sharp or stinging, it serves the very necessary function of letting us know when we damage ourselves and generally subsides once the injury heals. Chronic pain is more sinister.  Carried by slow conducting nerve fibers, chronic pain presents as dull, burning, tingling or aching.  Chronic pain lasts more than three months – some unfortunate individuals endure it for decades.  The sinister aspect: chronic pain serves little or no protective purpose.

programming-bugIf someone tells you chronic pain is all in your head, you can inform them that the spinal cord is also involved.  (My editor nixed what I would tell them.)  Chronic pain can be thought of as errant wiring or a programming bug in the brain and spinal cord. This bug allows false pain messages from long healed injuries.  In the case of phantom limb pain, an amputee may still feel pain from a lost limb.  Wiring, in the form of additional pain nerve cells, may also help transmit the old message.  Researchers have recently come to view chronic pain as a mal-adapted form of “neuroplasticity” – the central nervous system’s ability to change structure, function or chemistry.  This ability facilitates learning new tasks and, unfortunately for some of us, the efficient replay of useless pain messages.  Indeed pain is very mental.  So much so, that in some cases it can be forgotten, if temporarily, when something more interesting distracts us.

madmen_switchboard_opsTo explain why sensory input, thoughts and emotions influence pain perception, Ronald Melzack and Patrick Wall proposed a gate mechanism.  Picture an old-fashioned telephone switchboard: three operators connect messages into the switchboard. Each operator specializes in specific messages.  Operator 1: acute and chronic pain messages from the body; Operator 2 “regular” sensory (touch, vibration, temperature) messages from the body; Operator 3: messages, such as thoughts, from the brain.  An outgoing wire from the switchboard is a pain hotline to the brain.   Before reaching the brain, pain messages must pass through a switch or gate.  Specific combinations of incoming messages close the gate, preventing pain messages from reaching the brain.

No pain signals reach the brain (gate closed) with any one of the following conditions:

  • no incoming messages;
  • “regular” sensory nerves bring in more input than the pain nerves;
  • messages from the brain shut the gate.

Pain signals reach the brain (gate open) when both these conditions exist:

  • pain nerves (acute or chronic) bring in more input than regular nerves;
  • the brain does not send messages to shut the gate.

Some people vigorously rub their hand to relieve pain after pinching a finger.  Gate theory would say they increased regular sensory input to override the pain input.  The pain gate closes on the hotline – no pain messages pass to the brain.  Similarly, mental distractions can help us forget pain, as messages from the brain close the pain gate.

Non-Pharmaceutical Pain Relief

pillsPost-surgery, I took an opioid medication prescribed for moderate to severe pain.  At the time I remember thinking, “This recovery thing is a piece of cake!”  If something seems to be too good to be true, it probably is.  The longer I took the medication, the less relief it provided.  I began to understand the roots of misuse and slowly tapered off.  For unknown reasons, chronic pain from a previous, unrelated injury reactivated.

What a drag, it is, getting old.  After consulting two doctors who found nothing “wrong”, I decided to look for alternative treatments to close the pain gate.  Research shows that relief of pain can reverse neuroplastic changes to restore normal brain function.  I hoped to close the pain gate and then let reverse neuroplasticity produce long term relief.

As alternative therapies become more accepted, the number of studies increases until scientists can statistically combine results from multiple studies to reach conclusions on the benefit of these treatments. The therapies discussed below are widely used, but by no means comprehensive.  It goes without saying, appropriate treatment for a particular pain condition should be discussed with a doctor.

Strategies that close the pain gates can be divided into sensory (physical), cognitive (thoughts), or emotional (feelings), with substantial overlap between these areas.

Sensory

Regular sensory inputs provide competing input to close the pain gate (rubbing the hand to relieve pain from a pinched finger).  Acupuncture, massage and exercise are examples of sensory-based therapies.   Statistically combined studies found they can provide pain relief for chronic pain, depending on the specific condition.  The takeaway for those who prefer some science in their decision-making: there is science behind these particular alternative therapies – both a theoretical model (gate theory) and experimental data for specific conditions.

yoga-1Therapies that have not yet gained scientific acceptance for specific pain conditions also have their adherents.  Yoga helps illustrate the difference between individuals finding relief and a statistical conclusion.  Researchers in the U.K. conducted a literature search on the effects of yoga in relieving chronic pain.  They found ten comparable clinical trials, involving hundreds of patients.  Though nine out of the ten trials found yoga could help provide pain relief, they concluded, “yoga has the potential for alleviating pain. However, definitive judgments are not possible.”   Though many people in these studies found pain relief with yoga, many did not.  Statistically conclusions depend in how much noise or variation exists in the data – too much variation yields no definitive conclusion.

For those who find a human connection powerful in their decision-making:  My friend Jan, an avid hiker, has experienced intermittent leg pain for three years.  She writes, “I think I’ve tried about everything: physical therapy, chiropractic therapy, massage, acupuncture, and rolfing (structural integration). Of these, I’d say acupuncture was the most effective, but none of them have had lasting results. Even though I’m very new to it, yoga seems to be helping more than anything else I’ve done.”  Personally, I also find yoga effective.  As with any unproven treatment, cautious participation may be the only way to draw your own conclusions.

Cognitive

Substantial research has shown that we can diminish pain perception through our thoughts – messages from the brain closing the pain gate.  Over time, repeatedly closing the pain gate may reverse the misguided neuroplasticity that causes chronic pain.

brainFor those skeptical about our ability to “think” our way out of pain, Stanford’s Neuroimaging and Pain Lab provides one of the most dramatic demonstrations of our cognitive ability to dial down pain.  In this program, trained volunteers tried various thought strategies (e.g., relaxation, imagery and distraction) to increase or decrease their pain. They received real-time feedback by watching a pain-perception portion of their brains through functional Magnetic Resonance Imaging (fMRI).  The Stanford studies show that individuals can gain enough control to impact even severe chronic pain through their thoughts.

Biofeedback and meditation have both been evaluated using statistically combined studies.  Both were found to provide moderate to effective relief for specific pain conditions.  It should be noted that effective meditation programs involve eight to ten weeks training, with continued and consistent practice showing best results.

With the mind-body connection introduced in a scientific context, this is a good time to discuss the placebo effect.  People need not feel embarrassed if they learn their perceived pain relief came from a “sugar pill” or other non-active therapy.  fMRI research demonstrates that the placebo effect has a scientific basis.  The placebo response reduces pain by closing the pain gate and/or by activating natural opiates in the brain.   Surprisingly, the placebo effect does not necessarily require deception.   A  2010 Harvard study told patients they would be taking inert drugs; patients were also told that placebos often have healing effects.  Even the Harvard researchers were taken aback when patients who knew they were taking placebos reported twice as much symptom relief as the no-treatment group – an improvement better than many pharmaceutical drugs.

placeboStudies evaluating alternative treatments generally include test groups to rule out the placebo effect.  However, given the potential for significant pain relief and the lack of side-effects, the question arises: If you are self-evaluating a particular treatment, does it really matter if pain relief comes from the actual treatment or from the brain’s placebo response?

Emotional

It does not take a medical degree to know emotions affect your perception of pain.  You feel better when you take control of your well-being, keep a positive attitude, reduce stress, and work to overcome depression.  Certainly, chronic pain can lead to depression, but the reverse also applies.  Chronic pain and depression share some of the same nerve pathways and neurotransmitters – the chemicals traveling between nerves.  As with chronic pain, depression reduces signals that close the pain gate (mal-adapted neuroplasticity); the gate stays open, increasing pain perception.  When dealing with depression and chronic pain combined, the need to work with a physician is even greater.  Fortunately, many treatments found effective for chronic pain also help alleviate depression.

Finally, some people turn to their own spiritual beliefs to deal with pain.  I have another particularly courageous friend, Lynne, who lives a full life while dealing with multiple sclerosis and its multiple points of chronic pain.  She explains, “The primary way I deal with pain, besides due diligence in pursuing medical treatment/therapy, is spiritual.  It depends on an informed faith as revealed in Scripture and as demonstrated by how the Lord has sustained me in the past.”  We each have our own profile in courage to draw from.

Stick To It

The commonality for most of these non-pharmaceutical therapies: they are time-consuming and require long-term commitment.  Most people will likely have to try more than one.  The payoff is in taking charge of your own well-being and potentially helping to reverse the neuroplasticity causing chronic pain.  While evaluating a particular therapy in conjunction with a doctor, pain management experts recommend monitoring quality of life, as well as reduction in pain.  This includes improvements in daily functions, mood, sleep, relationships and pleasure in living.  Many find this particularly powerful because it reinforces the idea that quality of life is not solely or rigidly connected to chronic pain.persevere

References:

[deCharms, 2005] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1311906/.  Viewed 02/09/2014.

[Freudenrich, 2007] http://science.howstuffworks.com/life/inside-the-mind/human-brain/pain4.htm.  Viewed 01/29/2104.

[Goyal, 2014]  http://archinte.jamanetwork.com/article.aspx?articleid=1809754.  Viewed 02/08/2014.

[Mayo, 2013] http://www.mayoclinic.org/massage/art-20045743. Viewed 01/29/2014.

[Melzack and Wall, 1965] http://www.sciencemag.org/content/150/3699/971.citation. Viewed 01/29/2014.

[Millar, 2013]  Pharmacology of Pain Management 2013 by Sue B. Millar Pharm.D. Clinical Pharmacist Specialist-Geriatrics, Portland VA Medical Center, Power Point presentation.  Email correspondence 01/29/2014.

[Morley, 1998] http://www.researchgate.net/publication/13092976_Systematic_review_and_meta-analysis_of_randomized_controlled_trials_of_cognitive_behaviour_therapy_and_behaviour_therapy_for_chronic_pain_in_adults_excluding_headache/file/d912f50af5a79d2bfe.pdf. Viewed 02/08/2014.

[Naugle et. al., 2012] Naugle KM, Fillingim RB, Riley JL. A Meta-Analytic Review of the Hypoalgesic Effects of Exercise. J Pain. 2012(Dec);13(12):1139-1150.  http://updates.pain-topics.org/2012/12/exercise-chronic-pain-relief-meta.html. Viewed 01/30/2014.

[Posadzki et. al., 2011]  http://www.ncbi.nlm.nih.gov/pubmed/21944658. Viewed 01/30/2014.

[Thernstrom, 2006]  http://www.nytimes.com/2006/05/14/magazine/14pain.html?_r=0. Viewed 01/29/2014.

[Tsao, 2007] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1876616/. Viewed 01/31/2014.

[Vickers, 2012] http://archinte.jamanetwork.com/article.aspx?articleid=1357513.  Viewed 02/07/2014.

[Wagner, 2013]  http://wagerlab.colorado.edu/files/papers/Wager_Fields_Textbookofpain_toshare.pdf. Viewed 02/20/14

[WebMD] http://www.webmd.com/depression/managing-pain.  Viewed 02/10/14.

Other sources:

[Abaci,2012] http://www.huffingtonpost.com/peter-abaci-md/chronic-pain_b_2185616.html.  Viewed 02/07/2014

[Jacques, 2009] http://pain.about.com/od/painandmentalhealth/a/depression_cp.htm.  Viewed 01/31/2104.

[Kerr, 2013] http://www.frontiersin.org/journal/10.3389/fnhum.2013.00012/abstract. Viewed 01/31/2014.

[Levy, 2008] http://www.health.com/health/condition-article/0,,20189539,00.html. Viewed 01/29/2014.

[Pickert, 2014] http://healthland.time.com/2014/01/22/learning-to-pay-attention-5-steps-to-mindfulness-meditation/. Viewed 01/31/2014.

[Pain and Wellness] http://www.painandwellness.com/how-pain-works. Viewed 01/29/2014.

[Rosenzweig, 2007] https://www.google.com/search?q=comorbid+definition&ie=UTF-8&oe=UTF-8&hl=en&client=safari.  Viewed 01/31/2014

[Rubinstein, 2011] http://www.healthtourismmagazine.com/article/treatment-of-chronic-pain-a-neuroplastic-approach.html.  Viewed 02/08/2014.

[Sherman] http://www.aapb.org/files/public/ReviewOfBFBForPain.pdf. Viewed 01/30/2104.

Advertisements