Most people associate carpal tunnel symptoms with hand or finger pain, tingling or numbness. These sensations are well known. In fact, they're the hallmark symptoms of this common neurological condition.

But why aren’t they consistent across the board? For example, some people start off with occasional pain while others have constant numbness or intermittent tingling.

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Still others feel finger tingling from time to time but never have pain. Yet others with carpal tunnel syndrome feel shooting electric shocks and nothing else.

What’s going on? It’s all how your particular nerve is designed.

Carpal tunnel syndrome is a disease centering around the major nerve in your wrist joint. Named the median nerve, it’s the source of all those unpleasant to debilitating sensations.

Normally, the median nerve sends signals to the brain about how the environment "feels" on the fingers and hand. Those signals are interpreted as are "feelings" like touch, temperature, pressure, etc.

But when the nerve is damaged, the signals are abnormal. They get jumbled and amplified, causing abnormal sensations. These abnormal sensation are called paresthesia.

For instance, let’s say a nerve fiber normally carries vibration feelings. But when crushed, the paresthesia might feel like burning or prickling instead.



The median nerve also serves to move muscles. But more on that in a moment.

Like all nerves, the median nerve is a ropy bundle of fine microscopic fibers. If you magnify them thousands of times, they’re actually like a bundle of drinking straws.

There are tens of thousands of such fibers in each nerve. And each individual fiber carries only one sensation from one specific point on the fingers or hand.

As an example, look at the image above. There are 4 color straws, and each color represents a symptom:

• Red = Pain
• Pink = Numbness
• Blue = Tingling
• Yellow = Burning

Therefore, each color straw (representing a nerve fiber) carries a certain sensation from only one location, like a fingertip or knuckle. Thus, a particular red straw representing pain might arise from a sharp pinprick only in the fingertip.

Essentially, each bundle of fibers in the nerve specializes in carrying one particular sensation like pain. In reality, there are many more sensations, like vibration, tickling, burning, etc.

All of these feelings travel within the fiber bundle that makes up the median nerve. The sensations travel from the skin of the fingers and hand, through the wrist joint, and finally to the brain.

On its way to the brain from the fingers and hand, the fibers of the median nerve pass through the wrist joint. At its narrowest, the nerve travels through a very cramped space called the “carpal tunnel”. That space is actually a passageway whose walls are the wrist bones. 

Not only does the median nerve pass through here, but so do the tendons which flex the fingers. This jam-packed space is no wider than a finger, and is one of the most overcrowded spaces in the body.

In carpal tunnel syndrome, the tendons inside that tight passageway gradually swell up. Scientists still don’t understand exactly why tendons swell up to begin with. But the result is that the slow, steady tendon swelling pushes against the adjacent median nerve inside that tight space.

Eventually, as swelling continues, the pushing on the nerve results in a crushing action. Basically, nerves don’t like being crushed. When they are, they produce paresthesia. an abnormal sensation doctors call paresthesia. For instance, let’s say a nerve fiber normally carries vibration sensation. But when crushed, the paresthesia might feel like burning or prickling instead.

The median nerve is also responsible for moving muscles. Muscles are activated by signals from the brain and travel down the nerve to the hand. Specifically, the nerve bundles are called motor fibers.

Good muscle strength involves two important components. First, the muscle itself has to be healthy. Second, the signals that travel from the brain and into the muscle must be intact. (That means the median nerve going to the muscle must be normal.) 

However, in carpal tunnel syndrome, the median nerve is not normal or healthy. It's crushed by tendon pressure on the nerve. This ultimately damages the motor fibers responsible for activating hand muscles.

Usually, the motor fibers carrying movement commands to the muscles are thicker in diameter than sensory fibers. That makes them heartier or heftier than sensory fibers. Thus, motor fibers are more resistant to damage. 

That’s why motor problems like loss of hand strength and dexterity generally occur later than sensory problems when you have carpal tunnel syndrome. Therefore, if a patient experiences any hand strength loss, their carpal tunnel syndrome is more advanced.

Along the same lines, a patient’s motor fibers might be more densely located on the edges of the median nerve. In that case, the fibers would be more exposed to the crushing pressure of swelling tendons. 

In such instances, even though the patient’s carpal tunnel syndrome is not truly “advanced,” severe motor disturbances can nonetheless occur.

Fibers arranged on the outer edges of the nerve are more susceptible to crushing injury. And the arrangement of fibers within a nerve bundle is different in everybody. Therefore, if your outer fibers are more densely packed with a certain type of fiber (e.g., pain, touch, temperature), then those fibers will be more susceptible to damage.

Let’s get back to the drinking straw analogy and the illustration. When you grab a bundle of straws, you might end up with more red straws on the outside of the bundle, as in the picture. That might translate into more pain fibers on the outer edges of the bundle. Such would be illustrated as more red straws on the outside than inside the bundle.

But somebody else might end up grabbing the bundle so more blue straws are on the inside of the bundle. That might translate into more tingling fibers on the bundle’s outer edge.

Essentially, everybody’s arrangement of fibers within the a nerve is as different as randomly grabbing colored straws. In other words, some people may have more pain fibers on the outside than inside their nerve bundle. In contrast, other people may have more vibration fibers on the outside than inside their nerve bundle.

This “individualized” arrangement is why some people feel one kind of abnormal (paresthesia) sensation with carpal tunnel syndrome that’s different than somebody else. If tendons start to crush a nerve bundle that has more pain fibers on the outside, then pain will be the primary unpleasant sensation. 

In time, as tendons crush more of the fiber bundle, additional sensations arise. This is why it’s common for other symptoms to appear in a short period of time. They include pain, numbness, tingling, burning, pins-and-needles, soreness, electric shocks, itching, and weakness.

No two patients feel the signs of carpal tunnel syndrome exactly the same way. That’s because of how an individual’s nerve fibers within their median nerve is arranged. The median nerve is organized in bundles of tiny nerve fibers. Inside the wrist joint, where compression of the nerve occurs, that arrangement makes you more or less susceptible to certain sensations.