• Clinical science

Ulnar nerve entrapment (Ulnar nerve palsy…)

Abstract

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.

Basic anatomy

References:[1]

Etiology

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

References:[1]

Clinical features

  • Muscle weakness and atrophy
  • Sensory loss
    • Loss of sensation over the hypothenar eminence, medial 1 ½ fingers.
    • Lesion at the elbow: positive Tinel test → Marked paresthesias can be reproduced in the ulnar portion of the hand by tapping on the medial epicondyle of the humerus.
    • Lesion at the wrist: Sensory symptoms may or may not be present.
      • Guyon’s canal is divided into three zones
        • Zone I - proximal to bifurcation of the ulnar nerve: motor and sensory symptoms
        • Zone II - at the deep motor branch: motor symptoms only
        • Zone III - at the distal sensory branch: sensory symptoms only
  • Pain: Elbow lesions typically present with referred pain in the forearm.
  • Paresthesias are usually absent in distal nerve lesions (at the palm).

Proximal as well as distal lesions lead to claw hand deformity!

References:[2][1]

Diagnostics

  • EMG: main confirmatory diagnostic test; it 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.

References:[1]

Treatment

  • Conservative therapy
    • Analgesia (e.g., NSAIDs)
    • Modify behavior (i.e., avoid prolonged resting on or repeated flexion of elbow)
    • Bracing at night
  • Surgical decompression if clinical features are severe, persistent (lasting more than 6–12 weeks), or progressively worsen despite conservative therapy.

References:[1]

last updated 08/24/2018
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