What Is Ulnar Nerve Entrapment?

Ulnar nerve entrapment occurs when structures, such as muscles, bones, or ligaments, put too much pressure on a nerve, leading to numbness, tingling, pain, and in severe cases, muscle weakness or atrophy (wasting away). The ulnar nerve can be entrapped in the elbow or wrist.

This article discusses the symptoms, diagnosis, and treatment of ulnar nerve entrapment.

Types of Ulnar Nerve Entrapment

The ulnar nerve is one of the terminal branches (main nerves) of the brachial plexus—a network of nerves that runs through your arms. The ulnar nerve provides sensation to the inside of your forearm, the pinky side of your hand, your pinky finger, and half of the ring finger. This nerve also supplies muscles that help bend your wrists and fingers, spread your fingers apart, and bring them back together.

The ulnar nerve can be entrapped or compressed inside the elbow or the pinky side of the hand.

Compression at the elbow causes a condition called cubital tunnel syndrome. When the ulnar nerve is compressed in the wrist or hand, it is called Guyon's canal syndrome.

Cubital tunnel syndrome is the second most common type of nerve compression (after carpal tunnel syndrome). However, Guyon's canal syndrome is rare.

What Does Ulnar Nerve Entrapment Feel Like?

If you've ever hit your "funny bone"—the point where your ulnar nerve travels close to the skin near the bone on the inside of your elbow—you have an idea what ulnar nerve entrapment symptoms feel like.

Ulnar nerve entrapment causes tingling, pain, and numbness along the path of the ulnar nerve in the forearm and hand, specifically the inside border of your forearm and hand and your fourth and fifth fingers.

When the ulnar nerve is compressed in the cubital tunnel of the elbow, you can experience these symptoms in both your forearm and hand. However, if your nerve is compressed in Guyon's canal, you will only have symptoms in your hand.

If the ulnar nerve is compressed for extended periods, the muscles it supplies can become weak. In severe cases, these muscles atrophy (waste away). If severe ulnar nerve entrapment is left untreated, a condition that causes the fingers to bend toward the wrist can develop.

Causes of Ulnar Nerve Entrapment

There are various causes for cubital tunnel syndrome and Guyon's canal syndrome. However, in some cases, it can develop without an apparent reason.

Cubital tunnel syndrome can be caused by the following:

• Leaning on the elbow for an extended period
• Stretching the nerve by repeatedly bending the elbow (such as in activities that require repetitive pulling or lifting)
• Direct trauma to the inside of the elbow
• Arthritis
• Bone spurs
• Swelling in the elbow

Guyon's canal syndrome can occur from:

• Manual labor
• Prolonged pressure on the hand (such as during bicycling)
• Abnormal tendons, muscles, or blood vessels
• A fractured (broken) bone in the hand
• A cyst or tumor

Diagnosis of Ulnar Nerve Entrapment

A healthcare provider will review your symptoms and perform a physical exam to diagnose ulnar nerve entrapment. They might use a Tinel's test by gently tapping over the nerve to see if it reproduces your symptoms.

A provider may recommend additional testing to confirm a diagnosis of ulnar nerve entrapment, such as:

• Nerve conduction studies are the primary tests used to confirm a diagnosis of ulnar nerve entrapment and assess the condition's severity. These tests determine how quickly electrical impulses travel along the nerve and how muscles supplied by the nerve respond to stimulation.
• X-ray images can rule out other causes of pain, as well as arthritis or bone spurs that might compress the nerve.
• Ultrasound is used to look for physical damage to the nerve.
• Magnetic resonance imaging (MRI) scans provide pictures of soft tissue structures (such as muscles and tendons) and the nerve.

Treatment for Ulnar Nerve Entrapment

Treatment for ulnar nerve entrapment depends on the severity of the condition. Conservative treatment consists of:

• Nonsteroidal anti-inflammatory drugs (NSAIDs) or other anti-inflammatory medications
• Avoiding positions and activities that increase pressure on the nerve
• Splinting at night to prevent full bending of the elbow (to decrease pressure on the nerve)
• Nerve gliding exercises

Occupational and physical therapists who treat upper extremity injuries often treat ulnar nerve entrapment conditions. Some of these therapists are specialists called certified hand therapists (CHTs).

Interventions used by these therapists can include:

• Custom splinting
• Strengthening exercises
• Modalities (such as ultrasound and electrical stimulation)
• Manual therapy
• Dry needling

In some cases, nerve decompression surgery is required to relieve pressure on the ulnar nerve.

Summary

Ulnar nerve entrapment occurs when the nerve is compressed in the elbow or the hand and wrist. It can cause pain, tingling, and numbness along the inside of the forearm, pinky side of the hand, pinky finger, and half of the ring finger. Nerve entrapment is typically diagnosed with a physical exam and nerve conduction studies.

Treatment includes anti-inflammatory medications, splinting, nerve gliding exercises, and avoiding activities that increase nerve pressure. Occupational or physical therapy can also be beneficial. In severe cases, surgery might be required.