Cubital Tunnel Syndrome – When the Ulnar Nerve Gets Compressed

What is Cubital Tunnel Syndrome?

The ulnar nerve runs from the neck down to the hand, supplying sensation and motor function to the little finger and part of the ring finger. At the inner side of the elbow, it passes through a narrow groove in the bone called the cubital tunnel (also: sulcus ulnaris). This is the spot commonly known as the “funny bone” – when bumped, it causes a tingling sensation down the arm.

In cubital tunnel syndrome (also known as ulnar groove syndrome), this nerve becomes compressed or irritated at the elbow. The condition is usually caused by prolonged pressure, anatomical narrowing, or repetitive bending of the arm. It is the second most common nerve entrapment syndrome of the upper limb, after carpal tunnel syndrome.

What symptoms can occur?

Symptoms typically develop gradually and can vary in severity:

• Tingling, numbness, or “falling asleep” of the little finger and half of the ring finger
• Pain in the inner elbow, especially after prolonged bending (e.g. while using the phone or sleeping with bent arms)
• Weakness or unsteadiness when gripping objects or performing fine motor tasks such as writing or buttoning
• In advanced cases: muscle wasting (atrophy) in the hand and noticeable loss of strength

Symptoms often worsen with certain positions or movements, such as leaning on the elbow or sleeping with the arm flexed.

Having trouble turning a key in a lock may indicate damage to the ulnar nerve.

Limitations in hand dexterity can indicate damage to the ulnar nerve.

If you can no longer finely control your index finger, this may be a sign of ulnar nerve entrapment (Sulcus ulnaris syndrome).

If the ulnar nerve slips out of its groove when bending the arm, sharp pain may occur.

What causes cubital tunnel syndrome?

Various factors can lead to pressure on or irritation of the ulnar nerve, often in combination:

• Frequent leaning on the elbow (e.g. at a desk)
• Anatomical narrowing due to bone structure, scar tissue, or arthritis
• Repeated or prolonged elbow bending, for example while sleeping
• Nerve instability, where the nerve slips out of its groove when the elbow is bent (ulnar nerve subluxation)
• In rare cases: cysts, tissue swelling, or bone spurs pressing on the nerve from outside

Identifying the cause early improves the chances of relieving pressure and preserving nerve function.

How is the diagnosis made?

Clinical examination

Diagnosis begins with a thorough medical history and physical examination. The doctor will typically:

• Check sensation and muscle strength in the little finger and hand
• Perform provocation tests, such as holding the elbow in a bent position
• Gently tap the nerve at the elbow (Tinel’s sign) to check for reproduction of symptoms

If nerve compression is suspected, further diagnostic tests may be recommended.

Nerve conduction study (neurography)

Nerve conduction studies measure how quickly the nerve transmits electrical signals. If compression is present, conduction speed is often reduced — a sign of functional impairment.

While this test provides important data, it mostly shows that the nerve is affected — not necessarily why or exactly where. Especially in cases involving short or motion-dependent narrowing, it may miss critical structural changes.

Ultrasound – a precise look at the nerve

High-resolution nerve ultrasound allows direct, real-time visualization of the ulnar nerve at the elbow — without radiation or needles. This modern imaging method provides valuable insight that may not be detectable by functional testing alone.

Ultrasound is particularly useful in the following situations:

• Very short segments of compression — such as by fine scar tissue — may not be detected by standard nerve conduction studies. The nerve may conduct normally over longer distances, despite localized pressure.
• In cases of nerve instability — where the nerve slips out of the groove when bending the elbow (ulnar nerve subluxation) — dynamic ultrasound can show the movement in real time, while static tests may appear normal.
• When electrical testing shows no clear findings, ultrasound can reveal structural causes for symptoms, such as anatomical narrowing or changes in nerve cross-section.

In summary:
Ultrasound not only detects whether a nerve is affected — it also helps determine why, and exactly where. This precise anatomical information is key to choosing the most appropriate further evaluation or treatment.

How is cubital tunnel syndrome treated?

If you experience numbness, tingling, or weakness in the hand, it is important to seek medical evaluation.

Following a detailed clinical assessment, the severity of nerve dysfunction can be evaluated and possible causes identified. Based on this, the most appropriate treatment can be determined.

Management options may include:

• Conservative measures such as reducing pressure on the elbow, adapting sleeping positions, or wearing a night splint
• In more advanced cases or when structural abnormalities are present, surgical decompression of the nerve may be necessary

The selection of treatment should always be based on medical evaluation and tailored to the individual findings. The main goal is to relieve pressure on the nerve in time and preserve its function as fully as possible.

Disclaimer: The information provided on this page is for general informational purposes only and does not constitute medical advice. It is not a substitute for personal consultation, examination, or treatment by a physician or other qualified healthcare professional. No guarantees of healing or cure are made. While we strive for accuracy and completeness, we cannot guarantee that all content is up to date or free from errors, and we accept no liability for any inaccuracies.