What is a ganglion cyst?

A ganglion cyst is a fluid-filled lump that lies under the surface of the skin. It is often painless, but--depending on its location--it may cause enough discomfort to need treatment.

Ganglion cysts occur most frequently on the joints and tendons of the wrist. Most are found on the top of the wrist. They also appear regularly, but less commonly, on the underside of the wrist, on the base of the finger, or at the end of the top joint of the finger.

Ganglion cysts are usually round and can feel soft or firm or rubbery to the touch. Ganglion cysts are connected to the joint atop a stalk-like structure known as a pedicle, but they often feel like they can be moved on that stalk. The skin over a ganglion cyst remains the same color as the rest of the person’s skin.

Ganglion cysts are usually small, most often less than an inch. They can appear almost suddenly, or can grow slowly over a period of months or years. Ganglion cysts are not cancerous.

Ganglion cysts are very common, but occur more frequently in women than in men. They can occur at any age, but are rare in children and most often affect people in their 20s, 30s and 40s.

What causes a ganglion cyst?

The exact cause of ganglion cysts is unknown, although there appears to be a link between them and joint or tendon irritation.

What are the symptoms of ganglion cysts?

Many ganglion cysts cause no symptoms at all. Some can grow large enough to be unattractive, but otherwise cause no other symptoms. Still others do not cause any symptoms for months and sometimes years, and then suddenly cause discomfort or affect a person’s range of motion.

If a ganglion cyst presses up against nerves in the wrist, it can cause symptoms that include numbness, tingling, a weakened grip and a reduced range of motion. When there is pain, it is usually an annoying ache rather than unbearable, sharp pain.

Two major nerves in the arm and wrist, the ulnar and median nerves, can be affected by pressure from a ganglion cyst:

  • The ulnar nerve runs along the arm, close to the inner elbow, and helps provide sensation and movement to the forearm and hand. When a ganglion cyst applies pressure to this nerve, a person may feel numbness or tingling on both the topside and underside of his or her small finger, and parts of the ring finger.
  • The median nerve runs down the middle of the arm into the palm. When a ganglion cyst applies pressure to this nerve, it can cause similar symptoms in the thumb, index and middle fingers.

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