What is the diagnosis for suspected ulnar nerve (nerve that runs from the neck to the hand) compression at the wrist?

Ulnar Tunnel Syndrome (Guyon's Canal Syndrome)

The diagnosis for suspected ulnar nerve compression at the wrist is called ulnar tunnel syndrome or Guyon's canal syndrome. 1, 2

Anatomic Definition

• Ulnar tunnel syndrome is defined as a compressive neuropathy of the ulnar nerve at the level of the wrist, specifically within Guyon's canal 1, 3
• This is the second most common compression syndrome in the wrist after carpal tunnel syndrome 4
• The ulnar tunnel (Guyon's canal) has complex and variable anatomy, making the clinical presentation dependent on the specific zone of compression 1

Clinical Presentation by Anatomic Zone

The presentation varies dramatically based on where compression occurs within the canal:

• Zone I compression: Both motor and sensory signs and symptoms 1
• Zone II compression: Isolated motor deficits only 1
• Zone III compression: Purely sensory deficits 1

This zonal classification is critical because it helps localize the exact site of compression and guides surgical planning 1, 2

Common Etiologies

• Ganglion cyst: Most common cause 2
• Fractures, inflammatory conditions, neoplasms, vascular anomalies, or aberrant musculature 2
• Occupational traumatic neuritis or musculotendinous arch compression 5
• Disease of the ulnar artery 5

Diagnostic Approach

Clinical examination is paramount to localize the compressed nerve segment by assessing specific motor and sensory changes in the hand 3

Imaging and Electrodiagnostic Studies:

• Ultrasound: Diagnoses ganglion cysts and vascular anomalies, and can localize the level of compression 2
• X-rays or CT: Exclude fractures 2
• Nerve conduction studies: Support the diagnosis and exclude proximal compression sites (such as cubital tunnel syndrome) 2
• MRI: Can provide detailed soft-tissue characterization when ultrasound is inconclusive 2

Management Strategy

• Mild symptoms: Activity modification and conservative management may be helpful 1, 2
• Definitive treatment: Surgical exploration of the ulnar tunnel with ulnar nerve decompression is the gold standard for neurocompressive causes, with largely good outcomes 1, 2

Critical Clinical Pitfall

Do not confuse ulnar tunnel syndrome with cubital tunnel syndrome—the former occurs at the wrist (Guyon's canal), while the latter occurs at the elbow. 3 Nerve conduction studies help differentiate between these two distinct compression sites and ensure appropriate surgical planning. 2