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Ulnar nerve entrapment

Last updated: April 19, 2021

Summarytoggle arrow icon

Ulnar nerve entrapment occurs when the ulnar nerve is compressed, typically at the elbow or the wrist. Compression at the elbow is called cubital tunnel syndrome; compression at the wrist it is referred to as Guyon's canal syndrome or ulnar tunnel syndrome. The compression causes paresthesias, numbness, and/or pain in the ulnar nerve distribution. Depending on the site of compression, the patient may experience weakness in certain hand muscles. Ulnar entrapment neuropathy may be suspected based on clinical symptoms and signs, but it must be confirmed by electromyography (EMG). Conservative treatment involves NSAIDs, behavior modification, and bracing. Severe, persistent, or worsening symptoms require surgical decompression.

Overview

Sensory innervation

Motor innervation

The ulnar nerve is most commonly compressed at or near the cubital tunnel of the elbow and Guyon canal of the wrist.

Cubital tunnel syndrome

  • Leaning on the elbow or prolonged elbow flexion during occupational activities (e.g., leaning on a desk), athletic activities, or surgical procedures (e.g., during general anesthesia)
  • Blunt trauma
  • Masses (e.g., tumors, hematomas)
  • Metabolic abnormalities (e.g., diabetes)

Guyon canal syndrome

Muscle weakness and atrophy

Sensory loss and pain

  • Lesions at the elbow
  • Lesions at the ulnar canal (located in the wrist)
    • The ulnar canal is divided into three zones
      • Zone I: proximal to the bifurcation of the ulnar nerve
        • Motor and sensory symptoms (i.e., sensory loss in the palmar surface of the small finger and medial aspect of the ring finger) possible
        • Sensory features similar to those caused by proximal lesions at the elbow
      • Zone II: lesions at the deep motor branch cause motor symptoms only
      • Zone III: lesions at the distal sensory branch cause sensory symptoms only

Proximal and distal lesions of the ulnar nerve lead to claw hand deformity.

  • EMG
    • Main confirmatory diagnostic test
    • Identifies the level of nerve compression
  • Ultrasound and MRI: used to support the EMG findings and to detect possible causes of compression (e.g., space-occupying lesions)
  • X-ray: Consider cervical spine, chest, elbow, and wrist films to rule out other possible causes of symptoms.
  • Conservative therapy
  • Surgical decompression: if clinical features are severe, persistent (i.e., lasting more than 6 to 12 weeks), or progressively worsen despite conservative therapy.
  1. Wilder-Smith EP, Van Brakel WH. Nerve damage in leprosy and its management. Nature Clinical Practice Neurology. 2008; 4 (12): p.656-663. doi: 10.1038/ncpneuro0941 . | Open in Read by QxMD