Causes of a Numb Thumb or Hand

40 Common and Uncommon Conditions

Thumb numbness is often caused by extreme pressure placed on a nerve in the wrist or hand. It can also be caused by a pinched nerve in the spine that services the hand, or by medical conditions that damage the protective covering of nerves (called the myelin sheath).

Less commonly, thumb numbness may be a sign of an infection like Lyme disease, a vitamin deficiency, multiple sclerosis, or a stroke.

This article lists common and uncommon causes of a numb thumb. It also explains what is involved in the diagnosis and treatment and when it is time to see a healthcare provider.

causes of a numb thumb or hand
Illustration by Emily Roberts, Verywell

Symptoms of Thumb Numbness

Thumb numbness can mean different things to different people. The way that a person experiences "numbness" can give a clue as to what is causing it.

Thumb numbness may be described by some as:

  • The partial loss of sensation in the thumb
  • The total loss of sensation in the thumb
  • Burning, tingling, or pins-and-needle sensations (paresthesia)

Other differentiating factors that provide clues include whether the numbness is:

  • On the front, back, side, or all of the thumb
  • Constant or intermittent
  • Occurring with movement or independent of movement
  • Affecting the thumb or other fingers
  • Bilateral (affecting both hands) or unilateral (affecting one hand)
  • Accompanied by a loss of movement
  • Sudden or developed gradually

These distinctions can aid in the diagnosis of your thumb numbness.

Peripheral Nerve Entrapment

Peripheral nerves are those that extend from the spinal cord and relay information between your brain and the rest of your body. Two peripheral nerves, called the median nerve and radial nerve, service the thumb. Compression of these nerves (also known as a pinched nerve or nerve entrapment) can cause thumb numbness.

Median Nerve Compression

The median nerve, which runs from the forearm into the palm of your hand, provides sensations to the thumbprint side of the thumb (called the palmar aspect). The nerve also supplies the front of your index and middle fingers.

If the median nerve gets compressed, it can cause thumb numbness on the palmar side. It can also cause weakness in the muscles involved in bending your thumb toward the base of the little finger.

The main cause of median nerve compression is carpal tunnel syndrome, a painful condition caused by the entrapment of the median nerve in a bony passageway in the wrist called the carpal tunnel.

Many conditions can lead to carpal tunnel syndrome, including:

  • Diabetes (which can cause the inflammation of tendons in the wrist)
  • Obesity (which increases fatty tissues within the carpal tunnel)
  • Pregnancy (due to fluid retention that can narrow the carpal tunnel)
  • Repetitive use injury (such as caused by regular computer use or racket sports)
  • Rheumatoid arthritis (an autoimmune form of arthritis that often affects the wrist)
  • Wrist fracture (and other traumatic injuries of tendons or ligaments)

Radial Nerve Compression

The radial nerve, which starts at the armpit and branches off to the hand, provides sensation to the back of the thumb, hand, and first two fingers. If the radial nerve is compressed, it can cause numbness in the dorsal aspect (back) of these fingers.

Damage to the radial nerve is less common than damage to the median nerve. Possible causes include:

  • Forearm bone fracture (in which bone fragments entrap the radial nerve)
  • Ganglion cyst (a fluid-filled lump over a joint or tendon in the hand or wrist)
  • Improper use of crutches (which can compress the radial nerve where it originates)
  • Long-term wrist compression (such as wearing a tight wristwatch)

Some muscle weakness may be experienced. This is most noticeable when trying to bend your thumb down (as if you were cocking a trigger).

Cervical Radiculopathy

Referred pain is a nerve pain that originates from another part of the body than where it is felt. It is mostly caused by compression of spinal nerve roots that connect the spinal cord to the peripheral nerves. The pinching of the spinal nerve roots is called radiculopathy.

The nerve root servicing the thumb (as well as the wrist, bicep, and index finger) is situated at the neck portion of the spinal cord, called the cervical spine. The exact nerve is known as the C6 nerve which emerges between two bones in the spinal cord called the C6 and C7 vertebra.

If the C6 nerve gets compressed, it often causes shooting pains in the bicep, wrist, index finger, and thumb. In some people, however, it may only cause numbness or tingling. The numbness may be felt in the fingers as well as the webbing between the thumb and index finger.

Causes of C6 nerve compression include:

Demyelination and Peripheral Neuropathy

Most nerves of the body are covered with a protein membrane called the myelin sheath. It serves as an insulated coating, allowing electrical signals to transmit quickly and smoothly. If the myelin sheath is damaged, the electrical signals can "misfire," causing nerve pain in the peripheral nerves (known as peripheral neuropathy).

Paresthesia is a central feature of peripheral neuropathy, causing numbness, burning, and tingling. Pain, weakness, and a loss of joint reflexes are also common.

Peripheral neuropathy commonly affects the hands, fingers, feet, and toes. The sensations are typically bilateral and can sometimes be severe. It is rare for peripheral neuropathy to be isolated to the thumb or any individual finger; typically all fingers are affected.

The loss of myelin, called demyelination, can be caused by numerous conditions that strip away the protective sheath, including:

Other Causes of a Numb Thumb or Hand

There are numerous other causes of numbness of that thumb and hand. Some cause inflammation in specific parts central nervous system (involving the brain and spinal cord), affecting peripheral nerves.

Others involve ischemia, or the obstruction of blood flow to tissues. The lack of oxygen causes rapid necrosis (tissue death), directly damaging peripheral nerves. Tingling or numbness of the hand are common consequences of this.

Other possible explanations for hand or thumb numbness include:

  • Amyloidosis (a rare disease that causes the excess deposit of proteins on peripheral nerves)
  • Brachial plexus injury (damage caused to a network of nerves in the shoulder area, often due to a sports injury)
  • Ischemic stroke (a type of stroke caused by blockage of a blood vessel in the brain)
  • Lyme disease (a tick-borne infection that damages peripheral nerves directly and indirectly with inflammation)
  • Myocardial infarction (also known as a heart attack, caused by the blockage of blood flow to the heart)
  • Spinal cord injury (such as might occur with a car accident or severe fall)
  • Neurosyphilis (a manifestation of advanced syphilis that damages the central nervous system)
  • Vasculitis (blood vessel inflammation caused by infections, medications, and autoimmune diseases)

Diagnostic Tests for a Numb Thumb

The causes of thumb or hand numbness are many, and it can take time to run tests to determine if the cause is the result of an injury, infection, disease, autoimmunity, or ischemia.

Blood Tests

There are several tests a healthcare provider may order at baseline to narrow the possible causes of your symptoms. These include:

Nerve Tests

Several minimally invasive, in-office tests can be used to detect whether nerve signals aren't being delivered as they should. These include:

  • Electromyography (EMG); A test that uses needles to detect and record electrical signals in your muscles and nerve cells while they are active and at rest
  • Nerve conduction study (NCS): A similar test that applies electrodes on the skin to measure the velocity (speed) of nerve signals to an electrical impulse

Imaging Tests

Imaging tests can be used to detect injuries in the brain, spine, neck, shoulder, wrist, hand, or thumb. Certain imaging studies can detect ischemia or changes to the central nervous system consistent with multiple sclerosis and lead poisoning, Imaging tests are also commonly used to diagnose carpal tunnel syndrome, tumors, and different types of arthritis.

Options include:

Spinal Tap

A lumbar puncture, also known as a spinal tap, involves the use of a long needle to extract a sample of cerebrospinal fluid (CSF) for evaluation in the lab. A spinal can help diagnose serious infections or disorders of the central nervous system, such as Guillain-Barré syndrome, neurosyphilis, or multiple sclerosis.

How a Numb Thumb Is Treated

The treatment for a numb thumb depends on the underlying cause. They can be broadly characterized as physical therapy, medications, and surgery.

Physical Therapy

If you have an injury that causes a numb thumb, you may just need to rest and give your body time to heal. You may also need to avoid certain activities (like sports) or movements (like typing on your computer) that make it worse.

Your provider might also recommend that you work with a physical therapist during your recovery. The therapist can give you exercises that can help with recovery and prevent future injuries.

An occupational therapist can also help you make changes in your life or provide tools to help manage conditions like carpal tunnel syndrome, cervical radiculopathy, or chronic nerve impingement. For example, an ergonomic assessment can help you find ways to support your body while at your desk.

Medications

The list of medications used to treat nerve-related conditions like peripheral neuropathy is pretty expansive. The choice depends largely on the cause and severity of your condition.

Options include:

Surgery

Surgery may be an option for chronic nerve impingement, cervical radiculopathy, and carpal tunnel syndrome when conservative options fail to provide relief. Options may include:

Summary

A numb thumb is most often caused by a problem with the nerves that service the hand. It may be due to the compression of nerves in the hand or wrist, the entrapment of a nerve in the cervical spine, or conditions that cause nerve demyelination of nerves.

Other causes like stroke, diabetes, vitamin deficiency, autoimmune diseases, and infections can cause also numbness in the thumb. 

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Peter Pressman, MD
Peter Pressman, MD, is a board-certified neurologist developing new ways to diagnose and care for people with neurocognitive disorders.