What is the appropriate diagnosis and treatment for a patient with symptoms such as numbness, tingling, or weakness in the ring and little fingers, as well as pain or discomfort in the elbow or wrist, who may have been misdiagnosed?

Ulnar Tunnel Syndrome: Diagnosis and Management

For a patient with numbness, tingling, or weakness in the ring and little fingers with pain at the elbow or wrist, the diagnosis depends on the anatomic location: cubital tunnel syndrome (elbow-level compression) versus ulnar tunnel syndrome (wrist-level compression), which require different diagnostic and treatment approaches.

Distinguishing Between Cubital Tunnel and Ulnar Tunnel Syndrome

Cubital Tunnel Syndrome (Elbow)

• Most common site of ulnar nerve entrapment, occurring at the elbow level in the cubital tunnel 1, 2
• Presents with numbness in ring and little fingers, hand weakness, and intrinsic muscle atrophy 1, 3
• Pain or symptoms typically localized to the elbow region 2
• Ulnar nerve subluxation with elbow flexion/extension may be present on examination 4

Ulnar Tunnel Syndrome (Wrist)

• Compression of the ulnar nerve at the wrist level in Guyon's canal 5
• Presentation varies by anatomic zone:
  • Zone I: Both motor and sensory deficits 5
  • Zone II: Isolated motor deficits only 5
  • Zone III: Purely sensory deficits 5
• Symptoms localized to the wrist, not the elbow 5

Diagnostic Workup

Initial Evaluation

• Plain radiographs are the most appropriate initial imaging study to rule out osseous pathology, intra-articular bodies, heterotopic ossification, osteochondral lesions, or occult fractures 4, 6
• Clinical diagnosis confirmed by nerve conduction studies and EMG to localize the site of compression 4, 2

Advanced Imaging (When Indicated)

• MRI without contrast is indicated when radiographs are normal and there is suspicion of nerve entrapment or soft tissue pathology 4
• T2-weighted MR neurography is the reference standard for imaging ulnar nerve entrapment, showing high signal intensity and nerve enlargement 4
• Ultrasound has become a useful diagnostic tool by showing morphological changes in the nerve 2

Key Diagnostic Pitfall

• Do not rely solely on location of paresthesias to distinguish between cubital and ulnar tunnel syndrome—both cause ring and little finger numbness 1, 5
• The critical distinguishing feature is whether pain/tenderness is at the elbow versus wrist 5, 2

Treatment Algorithm

Conservative Management (First-Line)

• Activity modification to avoid repetitive wrist flexion, forearm pronation, or elbow flexion depending on compression site 6, 5
• Night splinting to prevent prolonged elbow flexion in cubital tunnel syndrome 2
• NSAIDs for short-term pain relief 6
• Physical therapy with stretching and strengthening exercises 6

When Conservative Treatment Fails

• Consider conservative treatment in early stages only 2
• Surgical decompression is indicated when:
  • Nonoperative treatment fails 2, 7
  • Motor weakness is present 2, 7
  • Muscle atrophy develops 2, 3
  • Fixed sensory changes occur 2
  • Sensory or motor impairment progresses 1

Surgical Options

For Cubital Tunnel Syndrome

• Simple in situ decompression is the treatment of choice for primary cubital tunnel syndrome, extended at least 5-6 cm distal to the medial epicondyle 2, 7
• Can be performed via open or endoscopic technique under local anesthesia 2
• Anterior transposition (subcutaneous, intramuscular, or submuscular) may be indicated when:
  • Ulnar nerve luxation is painful or "snaps" over the medial epicondyle 2
  • Severe bone or tissue changes of the elbow are present (especially cubitus valgus) 2
  • Scarring is present (submuscular preferred for healthy vascular bed) 2

For Ulnar Tunnel Syndrome

• Surgical exploration with ulnar nerve decompression is often indicated, as conservative treatment is less successful than in cubital tunnel syndrome 5

Critical Clinical Pearls

Red Flags Requiring Urgent Evaluation

• Night pain or pain at rest suggests inflammatory or neoplastic process 4
• Progressive motor weakness or muscle atrophy indicates need for surgical intervention 1, 2
• Consider differential diagnosis including C8 radiculopathy, Pancoast tumor, or pressure palsy in atypical cases 2

Common Pitfalls to Avoid

• Failing to obtain initial radiographs to rule out osseous pathology before assuming nerve entrapment 4, 6
• Overreliance on corticosteroid injections without addressing underlying biomechanical issues 4, 6
• Delaying surgery in patients with motor weakness or atrophy—advanced disease leads to irreversible muscle atrophy and hand contractures 3
• Insufficient nerve mobilization during transposition can cause kinking and compromise blood flow, requiring revision surgery 2