Ulnar Nerve Palsy – Causes, Symptoms & Treatment

What is Ulnar Nerve Palsy?

Ulnar nerve palsy refers to dysfunction or paralysis of the ulnar nerve, one of the three main nerves of the arm. The ulnar nerve runs from the neck down the inner side of the arm into the hand, where it supplies muscles and skin on the little finger side. Damage to this nerve results in characteristic motor and sensory deficits.

Causes

Ulnar nerve palsy can be caused by a variety of factors:

• Compression at the elbow: The most common cause is chronic pressure on the nerve at the cubital tunnel (the groove at the inner elbow), for example from prolonged leaning on the elbow. This is also known as cubital tunnel syndrome.
• Compression at the wrist: The nerve can also be compressed in the Guyon canal at the wrist, for example from cycling or use of vibrating tools.
• Traumatic injuries: Fractures of the elbow or wrist, lacerations, or penetrating injuries.
• Stretching or traction injuries: From sudden force or repetitive movements.
• Tumors or cysts: Space-occupying lesions along the course of the nerve.
• Systemic diseases: Diabetes mellitus or inflammatory conditions can impair nerve function.

Symptoms

Symptoms of ulnar nerve palsy depend on the location and severity of the nerve injury. Typical features include:

• Sensory disturbances: Numbness, tingling, or burning along the inner hand, little finger, and ring finger.
• Motor deficits: Weakness or paralysis of the small hand muscles (interossei, hypothenar muscles), affecting grip strength and the ability to spread the fingers.
• Claw hand (ulnar claw): A characteristic deformity of the ring and little fingers, with hyperextension at the knuckles and flexion of the middle and end joints.
• Froment sign: Compensatory bending of the thumb tip when attempting to hold a piece of paper between the thumb and index finger.
• Muscle atrophy: Wasting of the hand muscles in long-standing cases.

Diagnosis

Diagnosis of ulnar nerve palsy is based on a combination of:

• Clinical examination: Assessment of motor function, sensation, and characteristic clinical tests (Froment sign, finger abduction test).
• Nerve conduction studies (NCS): Measurement of nerve conduction velocity to localize and quantify the injury.
• Electromyography (EMG): Evaluation of the electrical activity in the affected muscles.
• Imaging: Ultrasound or MRI to visualize the nerve and identify potential causes such as tumors or bony abnormalities.
• X-ray: To rule out bony causes at the elbow or wrist.

Treatment

Conservative Treatment

For mild to moderate cases, non-surgical measures are the first line of management:

• Avoiding pressure-provoking activities and positions (e.g., elbow pads, ergonomic adjustments)
• Physical therapy and occupational therapy to strengthen muscles and improve function
• Splints or orthoses to relieve pressure on the nerve
• Anti-inflammatory medications if an inflammatory cause is identified

Surgical Treatment

When conservative measures fail or in severe cases, surgery may be required:

• Neurolysis: Release of the nerve from constricting tissue
• Anterior transposition of the ulnar nerve: Moving the nerve to a new position to reduce pressure
• Medial epicondylectomy: Removal of the bony prominence at the inner elbow

Prognosis

Recovery depends on the duration and severity of the injury. With early treatment, full recovery is possible in many cases. Long-standing or severe palsy may result in permanent functional limitations.

References

1. Assmus H., Antoniadis G. (eds.) - Nerve Compression Syndromes, 3rd edition, Springer Medizin Verlag, 2015
2. German Society of Neurology (DGN) - Guidelines for Diagnosis and Therapy in Neurology: Peripheral Nerve Lesions, 2022, available at: www.dgn.org
3. Mackinnon S.E., Novak C.B. - Compression Neuropathies, in: Green's Operative Hand Surgery, 7th edition, Elsevier, 2017