Cubital Tunnel Syndrome

Cubital tunnel syndrome is compression or traction neuropathy of the ulnar nerve at the elbow, the second most common upper limb entrapment neuropathy after carpal tunnel syndrome.

In an Italian population study the mean age at diagnosis was 56, incidence rose with age, and it was almost twice as common in men. Prolonged elbow flexion, direct pressure on the medial elbow and repetitive flexion and extension are the usual drivers, and it commonly coexists with medial epicondylalgia.

Most mild cases improve with information and activity modification. Established intrinsic wasting (McGowan grade III) reflects axonal loss that does not reliably reverse, so motor signs need prompt referral.

The ulnar nerve (C8, T1) passes behind the medial epicondyle through the cubital tunnel, a fibro-osseous channel formed by the medial epicondyle, the olecranon and the arcuate (Osborne) ligament. It is superficial here, with little soft-tissue protection. Elbow flexion narrows the tunnel and stretches the nerve, which is why symptoms are worst with the elbow bent. In some people the nerve subluxes over the epicondyle in flexion.

Sites of compression, proximal to distal:

• •Arcade of Struthers
• •Medial intermuscular septum
• •Retroepicondylar groove
• •Cubital tunnel beneath Osborne ligament (the most common site)
• •Between the 2 heads of flexor carpi ulnaris (the second most common)
• •Deep flexor-pronator aponeurosis

Mechanisms are compression (leaning on the elbow, a space-occupying lesion), traction (sustained or repeated flexion), friction (subluxation) and post-traumatic change, such as tardy ulnar nerve palsy after a childhood elbow fracture with cubitus valgus.

Modified McGowan grading guides management:

• •Grade I: intermittent paraesthesia, no weakness or wasting
• •Grade II: paraesthesia with measurable weakness, no wasting
• •Grade III: persistent paraesthesia with intrinsic wasting

Risk factors include occupational elbow flexion or pressure, previous elbow fracture or surgery, elbow osteoarthritis, diabetes, rheumatoid arthritis, obesity and smoking.