Why Is My Hand Numb? Understanding Carpal Tunnel Syndrome vs. Cubital Tunnel Syndrome

Why is my hand numb?

Unfortunately, this is an all-too-common question, particularly for numbness in the dead of night or first thing in the morning.

While many different causes can lead to numbness in the fingers and hand, today we will outline two of the most common offenders: carpal tunnel syndrome and cubital tunnel syndrome.

Nerve Anatomy

To understand hand numbness, it is helpful to first have a basic understanding of the anatomy.

For the sake of simplicity, a nerve begins in the brain, travels down the spinal cord in the neck, and exits at some point from the neck into the body. There are five major nerves that exit the spinal cord from the neck and then travel into the arm.

Of these five nerves, three will make it all the way through the arm to end in the fingers.

Figure 1 - In this model’s right arm, notice the yellow fibers. These represent the five ‘major nerves’ that exit from the neck and travel down the arm. See Figure 2 below for a closer view of the nerves as they exit the neck.

But why is my hand numb? Do I have a pinched nerve?

Numbness is the end result of a nerve that is not functioning. Nerve dysfunction of any kind, anywhere along this path can result in a feeling of numbness in your fingers.

And that’s the diagnostic ‘battle.’ As a hand and upper extremity surgeon, my job is to uncover where along the nerve (from the brain to the fingertip) the dysfunction is occurring.

The most common cause of nerve dysfunction is a compression or ‘pinching’ of the nerve. You’ve probably encountered peripheral nerve compression before at Thanksgiving when Uncle Jim complains about the ‘pinched nerve’ in his neck. And if this compression occurs at any point in the arm after the nerve has left the neck, it is known as peripheral nerve compression.

Figure 2 - The nerves are the yellow structures in this model. Notice the five nerves that exit each side of the neck. They exit through small openings between the bones of the spine known as foramina. It is at this site where a nerve can become ‘pinched’ at the neck, resulting in symptoms known as cervical radiculopathy.

What is carpal tunnel syndrome? What is cubital tunnel syndrome?

With regards to numbness in the hand, the two most common peripheral nerve compression conditions are known as ‘carpal tunnel syndrome’ and ‘cubital tunnel syndrome.’

Put simply, carpal tunnel syndrome is a pinching of one of the three nerves we mentioned earlier, known as the median nerve. The median nerve gets compressed at the point where it crosses from the wrist into the hand.

Alternatively, cubital tunnel syndrome is the compression of a different nerve called the ulnar nerve. The ulnar nerve usually gets pinched at the point where it travels around the inside of your elbow.

Many people know this as the ‘funny bone’ nerve. You may recall the lightning bolt of pain and tingling that travels down to your hand if you accidentally strike the inside of your elbow. An upset ulnar nerve is not comfortable, nor is it funny!

“... carpal tunnel syndrome is a pinching of one of those three nerves we mentioned earlier, known as the median nerve ... Alternatively, cubital tunnel syndrome is the compression of a different nerve called the ulnar nerve.”

What are carpal tunnel symptoms?

Let’s zoom in on the specifics. If you have carpal tunnel syndrome, you may experience sharp pain, burning, numbness, and/or tingling that is often at its worst during the night. These sensations are usually felt on the palm side of your thumb, index finger, middle finger, and sometimes part of the ring finger.

Carpal tunnel symptoms are typically not felt on the back side of your hand or in the small finger. The symptoms may wake you up at night and you may find relief by aggressively shaking out your hands.

Morning can also be a time of worsening symptoms. My patients commonly note that certain activities aggravate their symptoms, such as washing their hair, typing for extended periods of time, or driving.

Finally, many patients with carpal tunnel symptoms may notice their hands becoming more clumsy or sense new feelings of weakness as time goes on. Fine motor tasks such as buttoning your shirt or sorting coins become more difficult.

What are cubital tunnel symptoms?

Cubital tunnel symptoms are similar in character but different in location compared to carpal tunnel. These symptoms are typically felt in the small finger and occasionally in part of the ring finger.

Cubital tunnel symptoms may be worse at night as well, but compared to carpal tunnel, they are often more common during the day.

If you learn one thing about cubital tunnel, make it this. Time you spend with your elbow bent at 90 degrees, or greater, will naturally compress the ulnar nerve and worsen the symptoms of cubital tunnel syndrome.

Unfortunately, this elbow position is how many of us spend our days, whether typing, texting, eating, or other common activities. To make matters worse, in our deepest stages of sleep, most of us curl up into the fetal position, yet again bending the elbow and putting unrelenting pressure on the ulnar nerve…all night long.

Is peripheral nerve compression serious?

While occasional numbness and tingling in the hand are fairly common, symptoms that are more consistent can progress to irreversible nerve damage. The most severe end outcome is loss of muscle strength in the muscles critical to hand function. This often results in permanent hand weakness and loss of coordination.

“If you learn one thing about cubital tunnel, make it this. Time you spend with your elbow bent at 90 degrees, or greater, will naturally compress the ulnar nerve and worsen the symptoms of cubital tunnel syndrome.”

To prevent this avoidable outcome, if you develop consistent carpal tunnel or cubital tunnel symptoms, it is best to see a hand and upper extremity surgeon right away. Early intervention can often reverse the nerve damage, and there are a few practical ways to treat and prevent these syndromes. If these options fail, a small surgery is very effective at releasing the pinched nerve. In future articles, we will examine the various treatments for carpal tunnel and cubital tunnel in closer detail.

When should I see a doctor for carpal tunnel or cubital tunnel?

So there you have it. Hopefully, this is a helpful answer to the question “why are my fingers numb?” If you are experiencing these symptoms, remember not to delay evaluation by a physician. Your doctor will be able to determine whether your symptoms are a result of carpal tunnel syndrome, cubital tunnel syndrome, or an entirely separate condition in your shoulder, neck, or even brain.