Analgesia, Pain, and the Shape of The Brain

I was returning from Saturday brunch with my friend a month or so ago. We took the metro back from the restaurant, and it was quite crowded. While disembarking from the metro, my leg slipped (or maybe I was pushed, I don’t know), and got lodged in the gap between the train and the platform. In my vigorous attempts to free myself, I twisted one knee and scraped the other.

Thankfully, I reached home safely, but as I lay in bed that night, writhing in pain, I found my mind wandering back to 2020. The summer of the lockdown, I had found myself quite enamoured with a certain book, PiHKAL: A Chemical Love Story. The main title, PiHKAL, is an acronym that stands for “Phenethylamines I Have Known and Loved.”

PiHKAL, and its sequel, TiHKAL are strange, yet fascinating books. Each is divided into two parts: “The Love Story”, and “The Chemistry”. Most books about science and scientists often focus either on the science itself, or on the scientist and their thoughts or moral flaws of character. But PiHKAL is different. It tells the story of not only the science, but also that of the scientist, and how his research shapes his personality, his personal life, and how they shape the research back. It’s a long (2500+ pages with the sequel) read, but it is worth it.

The Thumb and the Knee

In the first chapter of the book, the narrator recounts his experience as a Navy man during the Second World War. On a destroyer in the middle of the Atlantic in the winter, he contracts an infection on his thumb that causes him immense pain. He required surgery, which wasn’t possible at sea, so all that could be done by the Navy medics was to manage his pain:

The man with the needle would interrupt a good rolling poker game to ask me how I was feeling. I would look at my thumb and say, “It’s a little worse,” or “It’s a little better,” and put my arm out for another morphine shot, then immerse myself again in the poker game. I knew the pain was there, and I could report on the intensity of it with accuracy, but it didn’t bother me. I could play poker, I could deal, I could judge the opposition, and I could bet shrewdly, and I came out ahead more than behind. My left thumb was viciously painful, but the pain just didn’t get in my way. It was fascinating to me that one could be hurting, in agony, and that the administering of a little bit of a chemical that came from some poppy flowers somewhere, could make it all quite unimportant.

This is what is meant by central analgesia. The pain is not deadened; it is still there. The site of action is not the thumb but, rather, the brain. The problem is simply no longer of concern.

Morphine is a pretty remarkable drug.

-PiHKAL

I got to thinking about how I had chosen to manage my own pain:

I put Moov (Diclofenac spray) on the knee which had been twisted.

When diclofenac spray is applied to the skin, it is absorbed through the skin and penetrates into the underlying tissues. Once absorbed, diclofenac works by preventing the body from making chemicals called prostaglandins. Prostaglandins are produced at the place of injury, and are responsible for causing pain, swelling, and inflammation. By not letting the body make prostaglandins, diclofenac helps to reduce these symptoms in the affected area.

In other words, the spray stopped my knee from telling my brain it was “hurt”. It also had a host of “counter-irritants” which overloaded the pain receptors with other sensations (a notable burning one) which simply didn’t let the brain feel the full magnitude of the pain. Scientists call this “working on the periphery.”

“Clever”, I thought to myself.

The spray wasn’t magical by any means, but it did provide enough relief for me to be able to fall asleep.

On Pain

Pain is essentially a way for our body to communicate with us, alerting us that something isn’t quite right. Think of it as a warning system, like a fire alarm. When we experience pain, it’s our body’s way of saying, “Hey, pay attention! Something needs your immediate attention here.”

So, how does pain work? Well, it all starts with specialized nerve endings. These are found throughout our body, including our skin, muscles, organs, and even bones. When we touch a hot stove or getting a paper cut, these spring into action. It sends an electrical signal to the brain.

Now, the brain plays a crucial role in processing and interpreting this signal. It evaluates the intensity, location, and quality of the pain. It also takes into account your previous experiences, emotions, and context to give the pain a subjective meaning.

You see, pain is not just a physical sensation. It’s influenced by various factors, including our emotions, thoughts, and memories. That’s why the same injury can be perceived differently by different people. For example, a minor bruise might be extremely painful to one person but relatively tolerable to another.

Interestingly, pain can also serve as a protective mechanism. Keeping with the stove analogy, the pain you feel immediately forces your hand to avoid further hurt.

Growth and the nature of suffering

“Pain is inevitable, but suffering is optional,” is a Buddhist saying that points to a fundamental truth of existence, which is that pain and affliction are an inherent part of life: we contract illnesses, get wounded, lose our loved ones, our possessions, our social status. But despite the hardships we encounter, the degree of suffering we generate still varies per person. The greatest misfortune hardly affects some people, while the slightest inconvenience leads other people into states of deep agony. Thus, could it be that suffering is something we can manage and doesn’t always have to result from pain?

- Why Pain is Inevitable, but Suffering is Optional, Einzelganger

All growth brings with it naturally, some degree of pain. This is because growth requires us to get out of our comfort zone, which causes us psychological pain. But that pain is justifiable, as long as it helps us to achieve the growth that we are aiming for. This pain should not be confused with suffering.

Suffering is pain that exists without purpose. It has no higher goals.

The Doctor will see you now

“Go to the doctor”, my mother said after observing me hobbling around with my bandaged leg, “He will make it better”

The doctor was sympathetic, emphasizing how lucky I had been to avoid further harm. He then prescribed an X-Ray, and paracetamol.

Paracetamol, also known as acetaminophen, is a commonly used medication to relieve pain and reduce fever. Its exact mechanism of action is not fully understood, but it is believed to work through multiple mechanisms, but primarily in the central nervous system (CNS). It is believed to inhibit the synthesis of prostaglandins in the brain, which can help reduce the perception of pain and lower fever.

Additionally, paracetamol may act on other neurotransmitter systems in the brain, such as the endocannabinoid system, which could contribute to its pain relieving and fever relieving effects too.

It might be useful to take a moment to note the purpose of a fever: The body raises the temperature to make it hard for the infector to survive.

So the doctor isn’t actually making anything better in this case. When we take paracetamol for a fever, or to relieve pain, it doesn’t actually deal with the root cause. It only addresses the symptoms, and fakes our brain into believing that all is okay while the body takes its own sweet time to heal itself.

Closing thoughts

What prompted me to write this was the analogous behaviour to the doctors that I have observed in different software teams that I have worked with. Often, when we are presented with a problem: a bug that is being faced, or some latent issue found in the system, we attempt to treat the symptom, rather than find the root cause:

  • Too many errors? Just silence it. PHP even comes with a handy @ operator
  • Program keeps crashing? Just make systemd restart it.
  • Program OOM’s? Just run it on a bigger machine
  • Database query takes time? Just cache it

Yes, this is bad practice, but bad practice can’t always be avoided due to organizational issues. Yes, doctors have their perfectly valid reasons for treating the symptoms (because the human body is difficult and it takes a lot of time to fully understand root causes)

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