Carpal tunnel syndrome (CTS) can affect the thumb. It occurs due to pressure on the median nerve and can cause numbness and tingling in the fingers and thumb.

The median nerve runs through a narrow tunnel of surrounding bone and ligament on the palm side of the hand, alongside the tendons responsible for bending the fingers. The nerve supports small muscles at the base of the thumb and controls feeling in the thumb, index finger, and middle finger.

If swelling, mechanical problems, or nerve issues cause the surrounding ligaments to squeeze the median nerve, CTS may develop.

Read on to learn more about how CTS can affect the thumb. This article looks at symptoms, causes, treatment options, and more.

Closeup of a person's hands with paint on the palm and thumb.Share on Pinterest
Westend61/Getty Images

CTS can affect the thumb. Symptoms may include:

  • numbness
  • tingling
  • weakness
  • pain

Symptoms may also develop in the index finger and forefinger. Any of these digits might also feel swollen and cold.

CTS may also affect one or both hands.

Numbness and tingling commonly worsen at night but resolve or improve during waking hours. However, as the condition progresses, symptoms might become more noticeable during daytime activities involving the wrist or hand, such as:

  • driving
  • using a phone
  • turning the pages of a book or newspaper

The muscles in the base of the thumb may become much weaker over time, making holding or gripping small objects difficult or impossible. In severe cases, the muscles may also be visibly smaller.

Learn about the early signs of CTS.

CTS occurs due to pressure on the median nerve, which contributes to sensation in several fingers, the thumb, and the muscles in the base of the thumb. The flexor tendons that bend the thumb also run through the carpal tunnel.

Issues with the median nerve can lead to weakness. It can affect the sensation in the thumb and how someone uses it for gripping, holding, and movement.

Risk factors

The direct cause of CTS is unclear, but several factors can cause pressure on the median nerve, including:

  • swelling or fluid buildup in the area
  • reduced circulation to the tiny blood vessels that feed the median nerve
  • conditions that reduce how much blood can leave the median nerve
  • lesions on the protective cover of the median nerve, known as the myelin sheath

Factors that can contribute to these include:

CTS affects around 1% to 5% of people. It can affect anybody, though it is more common in females.

Treatments for CTS address symptoms and the progression of the condition for the whole hand, including the thumb.

Early treatments may include:

  • wearing a splint or brace at night time to keep the wrist in a neutral position
  • taking nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen, to relieve pain and swelling
  • adjusting wrist positioning during daytime activities, such as during work or recreational tasks
  • undergoing physical therapy to provide exercises that help the nerve move with more freedom
  • taking steroid injections, which help relieve any pain that develops and reduce swelling

People with advanced CTS may benefit from carpal tunnel release surgery. The doctor divides a ligament running along the top of the carpal tunnel, increasing the tunnel’s size and relieving pressure on the median nerve. This approach can help restore grip strength and pinch strength within 2 to 3 months after surgery.

Below are answers to common questions about CTS in the thumb.

How do you tell if you have carpal tunnel in your thumb?

People may feel tingling, numbness, burning, and weakness in their thumbs if they have CTS. They may find holding small items or performing fine movements difficult. The pain and tingling might move toward the shoulder up the forearm.

How can a person tell the difference between thumb arthritis and carpal tunnel?

Both thumb arthritis and CTS can reduce grip strength and range of motion in the thumb. Thumb arthritis affects the joint, not the nerve, and may trigger pain during particular activities, such as turning a key.

Arthritis might also cause bony bumps at the base of the thumb, leading to swelling, tenderness, and an enlarged appearance. CTS in the thumb may cause muscle wasting over time, which can make the muscles at the base of the thumb smaller.

Learn more about the difference between CTS and arthritis.

What is the difference between thumb tendonitis and carpal tunnel?

Thumb tendonitis, also known as De Quervain’s tenosynovitis, causes swelling in the tendons that control thumb movement. Even though it occurs in roughly the same area as CTS, it affects the tendons, not the median nerve.

Thumb tendonitis can lead to a catching feeling when moving the thumb and might cause swelling on the side of the wrist closest to the thumb. Certain movements can cause or worsen pain.

Learn more about De Quervain’s tenosynovitis.

Thumb symptoms commonly occur in people with carpal tunnel syndrome (CTS). These might include numbness, burning, tingling, and pain.

Muscle weakness and wasting may eventually develop at the base of the thumb, making it difficult to grip or hold objects.

The condition occurs due to pressure on the median nerve, which runs alongside the tendons, controlling movement in the thumbs and other digits. This can occur due to trauma, underlying health problems, or mechanical issues.

General treatments for CTS include splinting, anti-inflammatory medications, and mechanical adjustments during daily use of the wrist. These treatments can also relieve thumb symptoms. Surgery may be necessary to restore grip strength or prevent further muscle wasting in the thumb muscles.