Cubital Tunnel Syndrome

Cubital tunnel syndrome is compression or traction neuropathy of the ulnar nerve at the elbow. It is the second most common upper limb compression neuropathy after carpal tunnel syndrome, with an incidence of about 20 to 25 per 100,000 a year, and men are affected more often than women.

The nerve can be compressed at five sites: the arcade of Struthers (about 8 cm proximal to the epicondyle), the medial intermuscular septum, the groove behind the medial epicondyle, the cubital tunnel roof (the aponeurosis between the two heads of flexor carpi ulnaris), and the deep flexor pronator aponeurosis. Elbow flexion narrows the tunnel and stretches the nerve, and intraneural pressure rises several fold at full flexion.

Causes and risks:

• Prolonged elbow flexion (phone use, sleeping with bent elbows) and leaning on the elbow
• Ulnar nerve subluxation, anconeus epitrochlearis, osteophytes, ganglion, lipoma
• Cubitus valgus after a childhood lateral condyle fracture (tardy ulnar palsy)
• Diabetes, alcohol use, vitamin B12 deficiency, hypothyroidism

Staging by function: stage 1 intermittent paraesthesia, stage 2 constant sensory loss with weakness, stage 3 intrinsic muscle wasting and clawing. Mild disease often settles with conservative care, but motor loss recovers slowly and incompletely.

• Paraesthesia and numbness in the ring and little fingers, worse with elbow flexion, at night and when holding a phone
• Sensory loss over the dorsal ulnar hand, which separates this lesion from Guyon canal compression
• Clumsiness, weak grip and pinch, difficulty with fine tasks
• Wasting of the first dorsal interosseous and hypothenar muscles, Froment sign, Wartenberg sign (little finger abducted), and clawing of the ring and little fingers
• Tinel sign at the elbow, positive elbow flexion test (symptoms within 60 seconds of full flexion with the wrist extended), and subluxation of the nerve over the epicondyle on flexion
• Red flags: rapid weakness, a mass at the elbow, trauma, neck pain with C8 radicular signs, and bilateral disease with systemic neuropathy

• Clinical diagnosis from the symptom pattern and provocative tests.
• Nerve conduction studies: motor conduction velocity across the elbow under 50 m/s, a drop of over 10 m/s compared with the forearm segment, conduction block (amplitude drop over 20%), and reduced dorsal ulnar sensory potential. Needle EMG shows denervation in the first dorsal interosseous and abductor digiti minimi, with sparing of the flexor carpi radialis (which separates C8 root disease).
• Ultrasound: nerve cross sectional area over 10 mm2 at the epicondyle, hypoechoic swelling and dynamic subluxation.
• Radiographs of the elbow (including a cubital tunnel view) for osteophytes and deformity. MRI for a mass.
• Blood tests: HbA1c, vitamin B12, thyroid stimulating hormone.

Differentials: C8 and T1 radiculopathy, thoracic outlet syndrome, Guyon canal compression, medial epicondylitis, brachial plexopathy, motor neuron disease.

Mild to moderate, intermittent symptoms:

• Avoid prolonged elbow flexion and leaning on the elbow. Wear a soft elbow pad.
• Night splint or a towel wrapped around the elbow to hold it at about 45 degrees of flexion, for 3 months.
• Nerve gliding exercises twice daily.
• Ibuprofen 400 mg orally every 8 hours with food for up to 7 days. Avoid in peptic ulcer, renal impairment and heart failure.
• For neuropathic pain, gabapentin 300 mg orally at night, increased by 300 mg every 3 days to 900 to 1800 mg a day in 3 divided doses (reduce in renal impairment; it causes drowsiness and dizziness).
• Corticosteroid injection is not recommended.

Surgery (persistent symptoms beyond 3 to 6 months, constant numbness, weakness or wasting, conduction block):

• In situ decompression (open or endoscopic) when the nerve is stable in the groove.
• Anterior subcutaneous or submuscular transposition when the nerve subluxates, in revision surgery or with bony deformity.
• Medial epicondylectomy as an alternative.
• Cefazolin 2 g IV before incision (3 g if over 120 kg).
• Postoperative: splint for 1 to 2 weeks after in situ release and 2 to 3 weeks after transposition, then active motion.

Outcomes: good results in about 70 to 90% of mild to moderate cases. Severe disease improves less, and wasting rarely reverses fully.

Complications: medial antebrachial cutaneous neuroma (numbness and pain along the scar), recurrence (5 to 10%), nerve instability, haematoma, infection.

Follow up at 2 weeks, 6 weeks, 3 months and 12 months. Counsel on avoiding sustained elbow flexion and on a recovery that can take 6 to 12 months.