Chronic Pain

Glial Cells and Pain

What is a Glial Cell?

Glial cells are non neuronal cells of the central nervous system. That is, they are cells that don’t transmit and receive electrical signals as do the neuronal cells in the brain and spinal cord. They have historically been considered support cells, or a type of scaffolding that holds up the neuronal “thinking” structures of the brain. They were thought to play the role of housekeepers. Cleaning up debris, and insulating the neuronal cells of the central nervous system. There are a variety of different glial cells, but for our interests in Pain Medicine, there are two that are very important; the microglial cells and the astrocytes. There are other non neuronal cells in the central nervous system that participate in the pain response, but these are the two that are the easiest to study, and hence two that are the most studied. There are far more glial cells than there are neurons in the central nervous system.

Under baseline conditions, glial cells have no influence on pain, but once activated, they have the ability to enhance the pain experience and response. As I have discussed before, glial cells can be activated by illness or injury not related to the brain. A simple case of the flu can result in the activation of glial cells and lead to the sickness response-the feeling of wanting to curl up in a ball and die. It is also known that pain can also activate this glial cell response and the subsequent production of pro inflammatory cytokines.

 

Microglia

Microglia comprise around 10% of all glia in the central nervous system and make up about the same percentage of all the cells in the central nervous system. Most of the time, microglia function as immune cells in the central nervous system, but they can be activated by stimuli including infection, trauma and other stressors which causes them to change function. (Raivich G. Like cops on the beat: the active role of resting microglia. Trends Neurosci 2005;28:571–3) Microglia can then begin to migrate towards the cite of damage and release inflammatory mediators including cytokines. After the injury or insult resolves, they can revert back to normal, or they may enter a state where they are “primed” to respond again (Watkins LR, et al. Glia as the “bad guys”: Implications for improving clinical pain control and the clinical utility of opioids. Brain Behav Immun. 2007 February; 21(2): 131–146). Once they are primed, they may over respond to the next episode of pain. This is thought to be an explanation for why some people seem to be more sensitive to painful stimulation than others

 

Astrocytes

There are more astrocytes than neurons in the central nervous system. They are found tightly wrapped around most synapses in the central nervous system and are felt to influence nerve to nerve communication at the synapse. They are believed to enhance function at the synapse and with repeated activation they contribute to memory at the level of the synapse. They also act to provide energy to the nerve cells and aid in the production of chemicals found in the synapse between nerve cells. Astrocytes can become activated by the same conditions that activate microglia. When activated, microglia and astrocytes serve to enhance each others function.

Standard
Chronic Pain

Reading Minds

http://www.scientificamerican.com/article.cfm?id=brain-researchers-can-detect-who-we-are-thinking-about

http://www.nature.com/nature/journal/v452/n7185/abs/nature06713.html

http://pinktentacle.com/2008/12/scientists-extract-images-directly-from-brain/

If the study posted previously about fMRI being able to peer into your mind and determine not only if you are experiencing pain, but how much pain you are experiencing didn’t give you pause, these reports should.

Researchers are developing techniques using fMRI to see what you are thinking, or who you are thinking about. Soon it will be possible to read your mind, see your dreams and see what you are feeling. MRI technology is increasing in speed every day. Soon it may be possible to acquire one when you walk through a doorway. No longer will you have to lie still in a magnet for an hour.

Standard
Chronic Pain

Stems Cells and Low Back Pain

http://www.painmed.org/2013posters/poster203.pdf

http://www.painmed.org/2013posters/poster203.pdf

Two recent studies have been published evaluating treatment options for degenerative disc disease.  Discogenic low back pain is one of the most common conditions I treat. Almost half the patients who come to see me have symptoms including aching back, occasional radiating pain into the legs which often waxes and wanes or moves back and forth from leg to leg and pain in the back with prolonged sitting or standing, It is one of the hardest conditions to treat.  Surgery doesn’t work well, conventional injections don’t work well and medications generally don’t work well. The pain can be very debilitating.

Stem cells are showing promise in relieving this pain.  One study demonstrated that stem cells from human umbilical cord blood will start building collagen within the disc of a rabbit. Collagen is the primary material that makes up the disc and it is thought that the breakdown of collagen within the disc is responsible for the development of pain. By demonstrating that it is possible to heal collagen, there is hope that we may be able to some day restore the native disc to normal function and take away the pain. The other study demonstrates that injecting bone marrow, which is a rich source of stem cells, into the disc will ease pain in some patients. This pain relief can last longer than a year, at least in this pilot group. While neither of these two studies is conclusive, it is the best hope I have seen for treating discogenic pain in a long time.

Standard
Chronic Pain

Tylenol, the New Mood Elevator?

http://pss.sagepub.com/content/early/2013/04/23/0956797612464786.full.pdf+html

It has long been known that Acetaminophen (Tylenol) treats pain. I give it to my daughter when she has a fever, or pain that is too much to bear. It is mixed into pills containing opioids in order to improve the pain relieving qualities of those drugs and it is known to have opiate sparing properties. That is, it relieves pain even when a stronger pain reliever is also being used.

Not all pain comes from the body. When you injure yourself, your brain and spinal cord go through changes that amplify your pain. This has some advantages for survival.  If you break your arm, the brain will make your pain feel more intense to encourage you to rest and let the broken bones knit. Acetaminophen will also relieve this type of pain and help prevent this amplification from occurring. It is a well established pain reliever.

In the study above, researchers found that acetaminophen doesn’t just ease physical pain. It eases psychic pain.  People who were given the drug before being exposed to emotional stress handled it more easily than those who weren’t given acetaminophen.  Pain doesn’t just come from the body; it also comes from the brain. The suffering that we feel is directly linked to the pain we feel. Things that ease suffering will ease pain and vice versa. It doesn’t have to just be a pill.

Standard
Chronic Pain

Mood is Contagious

http://cpx.sagepub.com/content/early/2013/04/15/2167702613485075

I have discussed this topic in my book. It was noted by Paul Eckman that simply frowning all day left him feeling poorly. Dr. Eckman is well known for learning how to read faces. He spent his entire career describing what muscles were responsible for displaying a specific mood and conducted experiments in how to read mood by observing the expressions on someone’s face.  He and his colleagues noted that after spending a day displaying sadness on their faces, they actually felt sad. Simply expressing sadness on your face will change the way your brain is functioning.

Similarly, it has been noted in the literature, and also in my book, that botulinum toxin type A (Botox) injected into facial muscles has the potential to blunt feelings.  Being unable to frown or smile, because of the botulinum toxin that was injected to reduce the appearance of wrinkles on the face, left subjects feeling blunted as well. Again a link between how we look and how we feel.

Now the authors of the study above find that living with someone who is depressed can make you feel depressed, especially if you are prone to moodiness yourself. So the old saying “smile and the world smiles with you, frown and you frown alone” isn’t completely true. It should read “smile and the world smiles with you, frown and you can make the world frown too.”

Just as it has been shown that frowning and looking sad can worsen your mood and being depressed can be contagious, the opposite is also true. If you smile, you will feel better and smiling is also contagious.

Standard
Chronic Pain

Seeing Pain

http://www.nejm.org/doi/pdf/10.1056/NEJMoa1204471

fMRI is a technique that allow us to see inside your mind. Other studies such as CT and MRI let us visualize anatomy.  They take a snapshot of what the brain looks like. fMRI, on the other hand, superimposes an image of which parts of the brain are metabolically active on the anatomy of the brain.  This technique allows us to see which parts of the brain are thinking.  Keep in mind that the brain is active in a lot of ways that we don’t realize. When you feel the joy of victory or the agony of defeat, many parts of the brain are active to create those feelings.

With fMRI, we are able to see the brain in action. We can see what parts of the brain are active and by controlling what the subject experiences, we are able to see what parts of the brain are responsible for what experience.

Up until very recently, when someone told me they were experiencing pain, I had no way to confirm or disprove it.  I had to take someone at their word. Unlike a symptom with a sign I can see-like a rash, there is nothing to look at when someone is having pain.  Sometimes there is a broken bone that accompanies the pain that I can point to as the cause, but very often, figuring out what is causing the pain is not so clear cut and often I am unable to find anything at all to explain the symptom. Things are becoming much clearer now. In the case of pain, I can pinch you to induce it, or shock you to cause pain and then look and see which parts of your brain are involved in the experience of pain you feel from my pinch, or electric shock. This study demonstrates that it is becoming very possible to see experimental pain as it is being experienced. Soon we will be able to see any pain, not just experimental pain. Finally we will have a test to determine not just where the pain is coming from, but how much pain you are actually experiencing.

Standard