September 12, 2018

What is Pain?

By dryeongs

Pain. An ancient instinct meant to protect us from harm, pain has developed into its own type of disease.

Chronic pain syndromes, such as arthritis, neuropathic pain, the chronic pain of old injuries- these have long lasting repercussions on not just physical health, but emotional and mental as well. Over these next series of blog posts, I’m going to explore some facts about pain, and what can be done about it.

What is pain?
Pain is defined as an “unpleasant sensory and emotional experience associated with actual or potential tissue damage.” This makes sense, it’s something we can all understand. Pain is our body’s way of warning us that either something is damaged, or it’s about to be damaged. Anybody who has ever stubbed their toe or cut their finger knows the truth of that statement. The sensory part is easy to understand- we feel it because there are receptors in our body that sense the damage and send the signal through nerves to our brain to make us feel the pain. But what about the emotional part?

Pain is emotional. It makes us emotional, and it is intricately tied in with our emotions. How many people get headaches when they feel stressed?

So pain isn’t just a biological phenomenon, it’s more than that. It’s subjective, which means no two people experience pain in the same way. I have no idea if whether the pain I feel when I stub my toe against the door is the same kind of pain you feel when it happens to you. Maybe it’s less, maybe it’s more. That depends on all sorts of individual factors- how sensitive your receptors are, how severe the pressure was, your memory of previous incidents, how you are feeling at the time. Us doctors try to use things like pain scales to figure out how severe your pain, but that doesn’t get anywhere close to properly quantifying or capturing what you, as an individual, feel.

Pain is difficult, because you can’t see it. It isn’t like a broken bone, or a rash. It isn’t something that you can take pictures of. All doctors know is what you tell us- and when it comes to chronic pain, that really is it.

What is chronic pain?
Pain Australia breaks pain into three different categories- Acute pain, chronic pain, and cancer pain. Cancer pain is fairly self explanatory- it is the pain felt by patients with cancer. Acute pain is short-lived pain as a response to injury that, in general, resolves as the injury heals. But occasionally it can progress on to chronic pain, which is pain that lasts longer than what would normally be expected after injury or surgery. It is pain that continues after an injury has healed. It is considered a type of chronic disease.

What happens to the body in chronic pain?
There are several different types of chronic pain, as outlined on the Chronic Pain Australia website. The most difficult type of chronic pain to explain is the type where there is no physiological evidence or understanding for the pain experienced by the patient. An example of this is chronic migraines or headaches. Brain scans including MRIs and CT scans don’t show any abnormalities, yet migraines are a distinct disease category.

Another type of chronic pain is neuropathic pain, where there are physiological changes to the nerves and the brain that make them work inappropriately. Normally, your nerves send a signal to your brain when there is some sort of tissue damage. In neuropathic pain, these nerves themselves become damaged, and become triggered even when there isn’t any tissue damage. For example, even light touch, which should normally not cause pain, sets off these ultra sensitive nerves, and patients experience pain. Types of neuropathic pain include post-herpetic neuralgia (pain that continues after a shingles attack) and diabetic polyneuropathy (tingling hands and feet due to damage to the nerves from excessive blood sugars).

Another type of chronic pain is Complex Regional Pain Syndrome. It is thought in this syndrome that there is damage to both the autonomic and somatosensory nervous systems. This gives rise to characteristic signs and symptoms- pain, swelling, skin colour change, changes in the hair and nails, sweating. Physical signs that can be seen, although not always.

With all of these types of chronic pain, there is no investigation that can give the diagnosis. There is no scan, no X-ray, no special test that tell us exactly what is going on with the nerves. However, chronic pain syndromes are common. Common enough, that when patients come to us with their story of pain, with their normal test results, with their limits in function- we recognize the patterns. And there are some things we can do about it.

Next time: What can we do about chronic pain?