Cubital Tunnel Syndrome

What is cubital tunnel syndrome?

It is entrapment of the ulnar nerve at the elbow—specifically where the nerve passes behind the medial epicondyle.

The ulnar nerve provides sensation to the little finger and the ulnar half of the ring finger, and innervates key intrinsic hand muscles responsible for fine motor control. When the nerve is compressed at the elbow, sensory symptoms appear first and, if compression persists, motor dysfunction may develop.

Entrapment may be caused by a tight fascial roof, bony anatomical variants, or subluxation/snapping of the nerve over the medial epicondyle during elbow flexion.

How common is it & who is at higher risk?

It is the second most common nerve entrapment after carpal tunnel syndrome and occurs more frequently in men.

Ulnar nerve entrapment at the elbow has an estimated incidence of approximately 24.7 per 100,000 persons per year and is more common in men. Risk factors include age, male sex, smoking, and occupational or athletic activities involving repetitive elbow flexion or sustained pressure on the medial elbow.

Importantly, there is no single cause for all patients. The goal is to determine whether symptoms reflect a positional/functional stress or a fixed mechanical entrapment requiring more definitive intervention.

Where is the nerve “compressed” – basic anatomy in simple terms

The ulnar nerve passes behind the medial epicondyle through a narrow tunnel that becomes tighter during elbow flexion.

The ulnar nerve originates from the brachial plexus (primarily C8–T1, with contribution from C7). At the elbow it courses posterior to the medial epicondyle and enters the cubital tunnel, where maximal compression most often occurs.

• Roof of the cubital tunnel: Osborne’s ligament/fascia.
• Floor: the medial collateral ligament of the elbow.
• Distally, the nerve passes between the heads of the flexor carpi ulnaris and continues into the forearm.

A second important site of ulnar nerve entrapment is at the wrist, within Guyon’s canal. This distinction matters because symptoms may be similar, but management differs.

What are the symptoms and how is it distinguished from carpal tunnel syndrome?

The hallmark symptom is numbness in the 4th–5th fingers, often nocturnal and exacerbated by elbow flexion.

Common symptoms:

• Tingling/numbness in the little finger and ulnar half of the ring finger.
• Pain at the elbow or along the medial forearm.
• Nocturnal worsening that may awaken the patient.
• Exacerbation with prolonged elbow flexion (e.g., phone use, driving, desk work, sports).

When entrapment occurs at the wrist (Guyon’s canal), dorsal hand sensation is often preserved (due to sparing of the dorsal cutaneous branch), which helps differentiate it from elbow-level entrapment.

In contrast to carpal tunnel syndrome (median nerve), cubital tunnel syndrome is characterized by 4th–5th finger numbness, rather than symptoms in the thumb/index/middle fingers.

What are the Wartenberg & Froment signs and what do they indicate?

These are clinical signs that indicate dysfunction of intrinsic hand muscles innervated by the ulnar nerve.

• Wartenberg sign: the little finger rests in slight abduction even when the patient attempts to adduct it toward the ring finger, due to weakness of the palmar interosseous muscle innervated by the ulnar nerve.
• Froment sign (paper pinch test between thumb and index finger): in ulnar neuropathy, the adductor pollicis is weak, and the patient compensates by flexing the distal phalanx of the thumb (median nerve innervation) to hold the object.

The presence of these signs—especially together with atrophy (hypothenar/interossei) or “clawing” of the hand— indicates progression to motor neuropathy.

Which clinical tests are performed in the office?

Diagnosis begins with a detailed history and targeted neurological examination, along with specific provocative tests.

During examination we assess:

• Sensation in the 4th–5th fingers and ulnar aspect of the palm.
• Intrinsic muscle strength (interossei, hypothenar) and fine motor function.
• Signs of muscle atrophy (prominent metacarpals) or hand “clawing.”

Common tests:

• Tinel’s sign at the elbow (reproduction of paresthesias along the nerve).
• Pressure test over the cubital tunnel for ~30 seconds.
• Elbow flexion test (up to 1–3 minutes): symptom reproduction with sustained flexion.
• Assessment of nerve subluxation over the medial epicondyle during active elbow flexion/extension.

When weakness or signs of advanced injury are present, surgical decompression should not be delayed: timing is critical for the likelihood of recovery.

When is EMG/NCV needed and what does it show?

Electrodiagnostic studies confirm the diagnosis, assess severity, and help exclude alternative causes.

EMG/NCV (electromyography/nerve conduction studies) can:

• identify conduction slowing at the elbow and localize the site of entrapment,
• determine whether there is axonal injury (important for prognosis),
• exclude C8–T1 radiculopathy, brachial plexopathy, or polyneuropathy,
• help differentiate from wrist-level entrapment (Guyon’s canal).

EMG does not replace clinical assessment. It must always be interpreted in conjunction with symptoms and physical examination findings.

When is imaging required (X-ray, ultrasound, MRI)?

Imaging is used to identify anatomical causes (bony prominence, cyst, mass) or when studies do not clearly localize the entrapment.

• Elbow X-rays: useful in the setting of trauma, arthritis, or suspected bony abnormalities.
• Ultrasound: can demonstrate nerve enlargement/edema and dynamically reveal subluxation.
• MRI: helpful when a mass or anatomical abnormality is suspected or when soft tissue assessment is needed.

How is it treated conservatively – what can you do yourself?

In mild to moderate cases, conservative management is often effective, particularly when there is no significant weakness.

Key measures:

• Avoid prolonged elbow flexion (e.g., phone use, driving with a bent arm, sleeping with the elbow flexed).
• Night splinting to keep the elbow in extension.
• Ergonomic adjustments at work: avoid pressure on the medial elbow, use padded supports, optimize chair/desk height.
• Physiotherapy and guided nerve-gliding exercises when indicated.

Studies suggest conservative treatment is particularly beneficial in mild cases. If there is persistent symptomatology or progressive weakness, surgical decompression should be considered.

When is surgery indicated and what are the goals?

Surgical decompression is indicated when compression causes persistent neurological symptoms or when conservative measures fail.

Common surgical indications:

• Progressive or persistent weakness (especially of intrinsic hand muscles).
• Atrophy of hypothenar/interossei or loss of fine motor function.
• Persistent sensory symptoms despite adequate conservative care.
• Significant subluxation of the ulnar nerve or an anatomical cause maintaining entrapment.

Goals of surgical treatment:

1. Achieve decompression of the nerve along the entire course of entrapment.
2. Reduce mechanical irritation (especially during flexion) and prevent further injury.
3. Maximize the potential for neural recovery (particularly before atrophy becomes fixed).

Which operations are available (decompression, transposition, etc.)?

Several techniques exist. Today, simple in situ decompression is often preferred as an initial approach.

Main options:

• In situ decompression: release of the structures compressing the nerve within the cubital tunnel (e.g., Osborne’s fascia/FCU aponeurosis), without relocating the nerve.
• Anterior transposition of the ulnar nerve: the nerve is mobilized and moved anterior to the medial epicondyle (subcutaneous/intramuscular/submuscular), typically when subluxation or specific anatomical variants are present.
• Medial epicondylectomy: less commonly used due to potential morbidity (reserved for selected cases).
• Endoscopic decompression: a minimally invasive approach with a smaller incision, but with specific technical demands and a distinct complication profile.

Technique selection is individualized and based on clinical severity, electrodiagnostic findings (EMG/NCS), anatomy/subluxation, symptom duration, and patient-specific needs.