Reflecting on the concept of pain as applied to concussions

By Abigail Mclellan 
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As someone dealing with Post Concussion Syndrome, and a student of Cognitive Science, I was very impressed by a recent  lecture on pain given by Dr. Jeffrey Mogil. It appears that the paradigms used by pain researchers have not been applied or adapted to Post Concussion care, nor have pain researchers considered Post Concussion Syndrome as a case of chronic pain.

What makes post concussion pain so unusual under the pain paradigms is that it is a case of chronic pain that appears to be evoked pain, since it correlates with certain activities. Typically, chronic pain is thought to be spontaneous, that is, not correlated with a particular activity. This contrasts acute pain, which warns of a danger to quickly avoid, or tonic pain (days, weeks or a few months) which suggests rest and immobility of the pained area, to optimize healing. In contrast, chronic pain is considered spontaneous because the pain seems to persist after its cause is no longer there (like phantom limbs continuing to hurt). In the cases where the cause does persist (like in cancer pain) researchers wonder if the pain might promote general caution, which might keep the individual away from dangerous situations considering their compromised health. It certainly directs them to a healthcare professional, which hopefully increases their chance of recovery.

In all cases, pain acts as a clue that something is wrong. What makes chronic pain so strange is that often, the only thing that is wrong seems to be that the person is experiencing pain. This has been a breakthrough in thinking because it allows both the patient and the doctor to only worry about the problem of pain itself. But when something more is going on, it is important to use the bodies clue to explore underlying issues. Pain from inflammation might be caused by the food someone eats, which means that any other method of mitigating that pain would leave the underlying inflammation a serious health problem.

When evoked pain is correlated to an activity, the message is clear to avoid the activity. This works so well in the case of the broken arm. Any movement causing pain is avoided. However, with inflammatory pain evoked by food, it might feel spontaneous. This is because the pain does not occur immediately after eating the food, and it becomes a challenge to sift between many possible causes. Pain may feel spontaneous on the surface before we understand what is evoking it. How many types of evoked pain might we be missing?

I would argue that Post Concussion Syndrome is a case of chronic pain that is evoked. This means that the pain occurs when the individual does certain activities, and stops when they stop doing the activity. Like in the tonic case, this can be useful to prevent the individual from overdoing themselves. The problem is that the pain might be correlated with doing most of the things that provide meaning in life: music, socialization, exercise, reading, playing games, and thinking deeply. New research agrees that doing nothing all day in a dark room does not promote recovery. The problem is that when the sensation of pain is so strongly correlated to the level of activity, even low levels of pain stop activity. In my case, it's not necessarily the intensity of post concussion pain that makes it debilitating, it is the fact that it pops up whenever I start to do something. That, and its direct association to the times when I can't think and feel myself slowing down.

Like with a food sensitivity, the evoked pain of Post Concussion Syndrome does not always arrive immediately after a provoking event. Instead, it might take a few hours to kick in. This makes it hard to directly pinpoint which activities are more problematic. In addition, it seems to be cumulative, so that something that is usually not a problem or even energizing can provoke pain on a low day. This cumulative effect can often cause unpredictable crashes when looking at the last day. It is only in looking at the last few weeks that levels of pain and fatigue make more sense. For these reasons, the evoked pain can be even more frustrating, because it is not easy to get a grasp on. It is much more complicated than keeping an arm still. 

At its most extreme level, a concussion effects almost every voluntary behaviour. When teaching children, I explain that the first step to recovery is No Activity. When asked what they can still do, we list sleep and eating as the two safe bets, though sleep disturbances and nausea may make even these activities difficult. We tell the kids to stay in this stage until they have no symptoms, and then slowly to progress up to Some Activity, More Activity until Back To Normal. We stress that at the sign of any symptom, they should return to No Activity. The underlying message to this procedure is clear: activity provokes symptoms. Evoked pain. 

This procedure for an injury to the brain is along the same lines as one you would advice for an injury to the arm, with one key difference. Behaviour involving the arm is localized, behaviour involving the brain is pretty much all behaviour. Most people are pretty bad at doing nothing, which makes it essential that this advice is given in a way that increases its chance of being listened to. Doing nothing might look different for different people. Anxiety can be a huge energy drain, and crying all day can cause a headache worse than the concussion. This makes concussion protocol a difficult balancing act. The key message is to rest, the hard question is what does that look like?

90% of concussions resolve in 6-8 weeks. The numbers might change but the message we tell children is clear. Concussion recovery happens. Good rest promotes quicker recoveries. And most importantly, we stress that the rest in the beginning is the most effective: three weeks of rest right away saves the months or years needed when initial rest isn’t taken. This is where concussions become chronic: the initial healing didn’t fully happen and now conventional advice to rest becomes problematic. 

But doing no activity for months and years cannot be healthy, and is in fact depressing and isolating. Something else is needed.

What is going on in this post concussion situation? Symptoms have persisted into the chronic stage, and seem to be evoked by a variety of behaviours. Some people get headaches and fatigue when they read, others get dizzy and nauseous from exercise. Individuals suffering from post concussion syndrome tend to adapt their lifestyle to avoid overly provoking symptoms. We demonstrate avoidance behaviour, the common response to pain. But when the thing we are trying to avoid is our entire life, full of its various pleasures, it becomes a delicate balancing act.

If the goal is to prevent pain from restricting one’s lifestyle, this goal must look to the future. A painkiller does not work if it allows me to push myself for one day to the point of fatigue which requires a week to recover. Likewise, developing high pain tolerance in the face of symptoms contradicts this goal if it provokes an increase in neurodegeneration and associated symptoms in the long run. What makes this question so urgent is that the opposite could very well be true. Avoiding pain could very well be the cause of neurodegneration, if the situation is comparable to the pain required to re-strengthen hurt muscles. If injured cognitive functions require targeted activity to recover, pain associated with this activity is part of recovering. Leaving the vestibular, visual, processing, and language systems unhealed does not seem good for long term brain health. If pain goes along with the recovery of these types of systems, it is not a bad thing. 

This is the paradigm I have been living under for five years. To recover a deficit, I must work on this deficit. Sub-symptom threshold training would be ideal. This is when the activity is below the level that provokes symptoms. However, this is a challenge in practice when many things provoke symptoms, and fatigue is not compartmentalized. Once one thing tires me, my tolerance for other activity drops. Playing music usually helps me regain my energy, but if I am tired enough, the situation flips and it to provokes symptoms. So I can’t measure a standard sub-threshold activity's length and intensity and simply keep in that range. I have to use the symptoms themselves as a clue that I need to rest. Masking the pain that is a common symptom tends to lead to a bigger more debilitating crash later. For example, working out is healthy, but not if muscles need 3 weeks of recovery time after each session. The muscles would lose all the strength they had just gained, during that resulting inactivity. This idea is supported by concepts like the Parkwood Pacing Program. They advise avoiding cycles of high activity and subsequent low periods, and instead slowly building up strength in small increments. Extreme symptoms do not mean that further harm is occurring, but they may slow down recovery.

This concept helped my healing because it allowed a balance between still pushing, but not feeling guilt in the cases when I push to hard. Guilt insidiously turns healthy activities unhealthy, so a framework to understand pain in a positive light is important. Attitude can make the same activity stressful and energy draining, or exciting, tiring but motivating. 

This is the reality when it comes to thinking about recovery. This framework has allowed me to balance the desire to avoid pain with the joy I get from certain activities that cause this pain. It means accepting pain as part of the road to recovery. No research can change this. What can change is the upper and lower limits. How much pain is too much? How much rest is too much? With many lifestyle aspects we don’t have a choice, we must learn to cope. But for other activities we do have a choice. We don’t have to take long drives, or go to loud concerts, or study at university. Certainly contact sports or military service push the limits of Post Concussion Syndrome. Activities with a high risk of re-injury should be avoided. But beyond that, the line is not clear. In the short term I might have less symptoms when I am not in school, but in the long term, school work might be the very activity that stimulates healing. More generally, what activities stimulate healing and which increase the likelihood of neurodegeneration? And by how much? The problem is, we don’t have an answer to this, so lifestyle decisions are difficult to make. 

How has pain limited my lifestyle the past 5 years? Big crashes limit my lifestyle, as does chronic fatigue. But the constant presence of pain can actually enhance my lifestyle if it is used as a clue to predict fatigue. It might be the very thing that lets me maximize the limited energy that I do have. 

In my lecture last week, I learnt that pain is an unpleasant sensory or emotional experience associated with actual or potential tissue damage, or described in terms of such damage. In all cases, pain feels like cell damage, but is not always. Knowing the difference is huge. It makes me wonder, if one day research will show that the pain evoked by my lifestyles does indeed cause tissue damage. Somehow, I think not. Despite living in a materialistic age, I know that I can’t grasp at immortality, and must live this life now, in these moments. I try to live a healthy life so that I can do the things I love, not to prevent me from doing these things. It would be for nothing if I spent my entire life not living, just to die with a healthy body.