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, pisohamate ligament
      4. Posterior border: Transverse carpal ligament
    2. Injury: Ulnar Tunnel

IV. Causes: Ulnar Nerve Compression over Volar Wrist

  1. Soft tissue tumors (Ganglion Cysts, Lipomas)
  2. Wrist Fracture
  3. Constricting bands or Muscles
  4. Ulnar artery thrombosis
  5. Jackhammer or sledgehammer use
  6. Compression against handlebar in bicyclists
  7. Local Edema (e.g. Rheumatoid Arthritis, Hypothyroidism)

V. Risk Factors

  1. Prolonged and repetitive wrist extension
  2. Road Bicycling (Cyclist's Palsy, Handlebar Neuropathy)
  3. Weight lifting
  4. Karate
  5. 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
  3. Altered Sensation
    1. Numbness, pain or Paresthesias at hypothenar eminence, fourth (half of digit) and fifth finger
  4. Weakness (less common since motor branches are deeper and less susceptible to injury)
    1. Atrophy of hypothenar Muscles, lumbrical Muscles and interosseous Muscles
    2. Weak finger abduction and adduction

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
  5. Cervical Radiculopathy (C7, C8, T1)
    1. Double crush injury may also occur (cervical root and Ulnar Nerve injury)
    2. Especially consider when bilateral symptoms are present

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 NerveUltrasound
      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
  3. Avoid local Corticosteroid Injection
    1. Not helpful as compression is due to structural abnormalities
  4. Drain Ganglion Cysts
  5. Pad volar wrist
  6. Pad handlebars of Bicycle
  7. Splint wrist in neutral position
  8. Avoid exacerbating factors
  9. Surgery indications (surgery is typically followed by Splinting, rehabilitation, return to work at 4-6 weeks)
    1. Anatomic or structural causes (Ganglion Cyst, Lipoma, hook of hamate Fracture)
    2. No improvement after 2-4 months of conservative therapy

XI. Course

  1. Anticipate 6 month course

Images: Related links to external sites (from Bing)

Related Studies