"Nerve" Pain (Neuropathic)

Today I'll talk about a specific kind of pain — neuropathic pain, or what's popularly called "nerve" pain.

Unlike nociplastic pain (which I expanded on in previous articles), tied to a change in the functioning of the nervous system, "nerve" pain is tied to physical damage to the nerves themselves, which are responsible for carrying sensory information through our body.

You can think of a computer malfunction, which can stem from problems in its operating software (nociplastic pain), or from damage to the hardware ("nerve" pain).

Sometimes nerves are damaged temporarily and recover, and then the "nerve" pain is expected to pass. For example, when we bang our elbow and feel pain radiating to the pinky, that's a passing "nerve" pain caused by a knock to the ulnar nerve running through that area.

By contrast, in cases of irreversible damage, "nerve" pain can persist over time and cause significant suffering and a reduced quality of life.

Common causes of "nerve" pain include damage to peripheral nerves or the spinal cord, amputation of a limb, shingles, diabetes (which damages nerve fibers, mainly in the feet), brain injury (stroke / head injury / multiple sclerosis…), and more.

Another cause is mechanical and sustained pressure on a nerve. For instance, in the condition called "sciatica," pain radiates down the leg following pressure on a nerve root in the lower back. In this context it's important to note that in the vast majority of lower back pain (including cases with pain radiating to the leg) there's no real pressure on a nerve [1], and in many cases it's mistakenly diagnosed as "sciatica."

"Nerve" pain is usually felt as burning / tingling / itching / electric… It's different in character from the "ordinary" pain of an injury, and can therefore be very alarming — especially since it's often referred to an area far from the injury itself (as in sciatica).

It's important to note — these features of pain aren't specific to "nerve" pain, and on their own they aren't enough to diagnose it. For that, a number of additional signs need to be identified [2]:

1. The area of pain matches, anatomically, the input area of a known nerve. For example, in carpal tunnel syndrome (where the median nerve is compressed at the wrist) the pain will radiate from the thumb to the middle of the ring finger, but not to the pinky. A different distribution of pain may indicate that this isn't the correct diagnosis.
2. Sensory impairment — that is, a reduced ability to feel sensations other than pain (such as touch, heat, and cold).
3. Motor deficits — such as muscle weakness or impaired reflexes (these won't always be present in "nerve" pain).
4. Lab tests — tests such as EMG, US or CT imaging may help clarify whether there's nerve damage or not.

Following on from this, people who suffer from "tingling" or "electric" pain but without matching findings often receive a mistaken diagnosis of neuropathic pain — such as carpal tunnel syndrome for wrist pain, and trigeminal neuralgia for facial pain.

Why Would Nerve Damage Cause Pain?

It's assumed that after the injury, a number of physiological processes take place inside and outside the nerve cells that cause abnormal nerve information to be sent to the brain, including a signal of tissue damage (even in the absence of damage to the painful organ). As in the computer analogy, after damage to the electrical cables the electrical signal in them becomes chaotic, which causes the screen to distort the image it displays.

But — this explanation has a number of problems. One is the fact that a considerable percentage of people, after nerve injuries, suffer no "nerve" pain at all [3–7]. They may have impaired sensation or movement, but no pain.

Moreover, it appears that those changes in injured nerves that are assumed to cause "nerve" pain don't predict well who will suffer pain and who won't [7–8].

In other words — the fact that there's nerve damage doesn't necessarily mean there will be pain!

So Why Is There Pain After Nerve Damage Anyway?

The honest answer is that it's hard to know, but here's a possible explanation:

As I explained before (articles 1–2 in the series) — the brain is the only organ that determines whether there will be pain or not, and this is true 100% of the time. Both in an acute injury (where it's a survival mechanism, and a welcome one) and after an injury heals (as in chronic nociplastic pain). This pain is of course entirely real, 100% of the time!

The assumption is that the brain does this by constantly analyzing the threat level of the sensory information from the body (what's called the "danger mechanism"), a process done automatically and unconsciously. When there's an injury, a nerve signal of damage rises to the brain, is identified as dangerous, and is experienced as pain.

But what happens when the injury is in the conducting cable (that is, in the nerves)? As in the analogy of the computer screen, the cable will send a chaotic signal to the brain, but (!) — the brain will produce pain in response only if that signal activates the "danger mechanism."

Therefore, despite irreversible damage to a nerve, the brain can, over time and gradually, ignore the chaotic signal and not produce pain in response to it — which explains why a considerable percentage of nerve injuries don't cause chronic "nerve" pain.

The treatment accepted today for "nerve" pain includes a combination of medication, physical, behavioral, and psychological treatment.

Generally, the methods for recovering from pain by rewiring the brain (see article 6 in the series) aren't intended for "nerve" pain, since in many cases nerve damage is irreversible. And because they haven't been studied on people with "nerve" pain, it's hard to know how effective they are in this situation.

On the other hand, there are many reasons to think these methods might help in the case of "nerve" pain too — with a nerve injury, once the initial wound has healed, there's no real danger to the body's tissues that one needs to guard against. So if we reduce the activity of the brain's "danger mechanism" in response to the nerve pain, we may be able to reduce its intensity over time.

In my clinical work I've worked with many patients who suffer from "nerve" pain, and I've seen patients whose pain was significantly reduced and even disappeared after treatment that combined mental training to reduce the sense of danger from pain. Since the damaged nerves didn't heal (unfortunately I'm not a magician…), those patients continued to have sensory and motor disturbances in the affected area, but no pain.

Further evidence of this is the extraordinary story of a guy named Dan, who recovered from neuropathic pain after a spinal-cord injury through mental practice, and tells his story on a podcast (see the links below).

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Recommended links:

• Podcast — a recovery story from neuropathic pain after a spinal-cord injury
• Talk — Dr. Howard Schubiner on the misdiagnosis of trigeminal neuralgia

Sources:

Disclaimer: The information in this article is for general knowledge only. It is not personal medical or psychological advice and is not a substitute for it. If you have any health or mental-health concern, please consult a qualified professional to evaluate it.