Ulnar Nerve Compression at the Wrist: Clinical Presentation
Ulnar nerve compression at the wrist (Guyon's canal syndrome) presents with motor and/or sensory deficits in the hand that vary based on the specific site of compression within the canal, requiring careful anatomical localization to guide management. 1
Clinical Presentation Patterns
The presentation depends on which portion of the ulnar nerve is compressed within Guyon's canal:
Type 1: Combined Motor and Sensory Deficits
- Numbness and paresthesias in the 4th and 5th fingers (ulnar distribution) 1, 2
- Weakness of intrinsic hand muscles innervated by the ulnar nerve 1
- Intermittent or constant pain in the palm and ulnar side of the wrist 2
- This represents compression of the main ulnar nerve trunk before it divides 1
Type 2: Pure Motor Deficits
- Weakness without sensory loss when only the deep motor branch is compressed 1
- Affects intrinsic hand muscles while sparing sensation 1
Type 3: Pure Sensory Deficits
- Sensory impairment in the 5th finger and ulnar half of the 4th finger without motor weakness 1, 2
- Results from isolated superficial sensory branch compression 1
Key Physical Examination Findings
- Palpable mass on the ulnar side of the wrist (when caused by ganglion, lipoma, or other space-occupying lesion) 2, 3
- Sensory testing reveals decreased sensation in ulnar nerve distribution 2
- Motor examination may show weakness of ulnar-innervated intrinsic hand muscles 1
- Vascular assessment is essential as ulnar artery pathology can coexist 1, 3
Common Etiologies to Consider
- Ganglion cysts (most common cause) 3
- Lipomas compressing the nerve 2
- Repetitive or acute trauma (occupational traumatic neuritis) 1, 3
- Fractures of the hamate bone 4, 3
- Ulnar artery disease (thrombosis, aneurysm) 1, 3
- Anomalous muscles or fibrous bands 1, 3
- Iatrogenic injury (including complications from prior carpal tunnel surgery) 4
Diagnostic Workup
Clinical Assessment
- Complete motor testing of ulnar-innervated intrinsic muscles 1
- Sensory mapping to determine distribution of deficits 1
- Vascular examination including Allen test 1
Imaging Studies
- Ultrasound is the preferred initial diagnostic modality to directly visualize the ulnar nerve and identify space-occupying lesions 5
- MRI with T2-weighted neurography serves as the reference standard if ultrasound is inconclusive, showing nerve signal intensity and enlargement 5
Electrodiagnostic Testing
- Electromyography and nerve conduction studies confirm the diagnosis and localize the lesion to the wrist level 5, 2
- Helps differentiate between demyelinating versus axonal injury 5
Critical Diagnostic Pitfall
Concurrent median nerve compression at the wrist (carpal tunnel syndrome) may coexist, particularly in metabolic conditions, and should be evaluated simultaneously 5. This is especially important in patients with recurrent carpal tunnel syndrome who develop new ulnar symptoms 4.
Management Approach
Conservative Management
- Indicated for compression caused by repetitive activity without significant motor weakness or muscle atrophy 1
- Trial period of 2-4 months before considering surgical intervention 1
- Avoid elbow flexion beyond 90° and maintain neutral forearm position to minimize nerve tension 5
- Proper padding at pressure points without creating tourniquet effect 5