II. Epidemiology

  1. Ulnar Neuropathy is the second most common arm compression Neuropathy
    1. However, much less common than Median Nerve compression
    2. Ulnar Neuropathy at the Elbow (Cubital Tunnel) is most common Ulnar Nerve injury site
  2. Incidence
    1. Peaks in men over age 35 years

III. Anatomy: Ulnar Nerve Course

  1. Spine
    1. C8 and T1 nerve roots
    2. Injury: Cervical Disc Herniation
  2. Axilla
    1. Brachial Plexus (medial aspect)
    2. Injury: Thoracic Outlet Syndrome
  3. Elbow
    1. Ulnar Groove at medial epicondyle
    2. Injury: Ulnar Neuropathy at the Elbow (Cubital Tunnel)
  4. Wrist
    1. Guyon canal (medial wrist)
      1. Medial border: Pisiform Bone
      2. Lateral border: Hamate Bone
      3. Anterior border: Flexor carpi ulnaris tendon
      4. Posterior border: Transverse carpal ligament
    2. Injury: Ulnar Tunnel

IV. Causes: Ulnar Nerve compression

  1. Soft tissue tumors
  2. Ganglion Cyst
  3. Constricting bands or muscles
  4. Ulnar artery thrombosis
  5. Jackhammer use
  6. Compression against handlebar in bicyclists

V. Risk Factors

  1. Prolonged and repetitive wrist extension
  2. Bicycling
  3. Karate
  4. Baseball (e.g. catcher)

VI. Symptoms: Distal Ulnar NerveNeuropathy

  1. General
    1. Wrist discomfort
  2. Sensory deficit in the ulnar 1.5 fingers on palmar surface (4th and 5th fingers)
    1. Does not affect Forearm or finger dorsum
  3. Motor Neuropathy is uncommon since the motor aspect of the nerve is deeper at the wrist
    1. Grip strength weakness may be present in chronic cases

VII. Signs

  1. Tinel sign (tap) over Guyon Canal
    1. Paresthesias into the 4th and 5th fingers
  2. Phalen Sign (maximal passive wrist flexion for >1 minute)
    1. Paresthesias into the 4th and 5th fingers

VIII. Differential diagnosis

  1. See Wrist Pain
  2. Carpal Tunnel Syndrome
    1. Neuropathy is in Median Nerve distribution
  3. Ulnar Neuropathy at the Elbow (Cubital Tunnel)
    1. Affects ulnar innervation over Forearm
    2. Affects dorsal 1.5 fingers in ulnar distribution
  4. Thoracic Outlet Syndrome (or Brachial Plexopathy)
    1. Upper arm pain or weakness

IX. Imaging

  1. Wrist XRay (first line)
    1. See Wrist Pain
    2. Evaluate for Fracture or dislocation
  2. Electrodiagnostics (second line)
    1. Nerve conduction velocities
      1. Acute entrapment Neuropathy
    2. Electromyography (EMG)
      1. Chronic entrapment Neuropathy
  3. Advanced Imaging (third line)
    1. Peripheral nerve Ultrasound
      1. Evaluate for compression Neuropathy etiologies
    2. Wrist MRI
      1. Indicated in refractory and nondiagnostic cases
      2. Evaluates broad causes of Wrist Pain

X. Management

  1. See Carpal Tunnel Syndrome
  2. Avoid local Corticosteroid Injection
  3. Pad volar wrist
  4. Splint wrist in neutral position
  5. Avoid exacerbating factors
  6. Surgical intervention is rare

XI. Course

  1. Anticipate 6 month course

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