Ulnar Nerve Compression Diagnosis and Management

Clinical Features and Diagnosis

The American Academy of Neurology suggests that numbness and tingling isolated to the 4th and 5th digits is most commonly caused by ulnar nerve compression, typically at the cubital tunnel or less commonly at Guyon's canal 1
The ulnar nerve innervates the 4th and 5th digits, and compression along its course produces the characteristic distribution of symptoms, with pure 4th and 5th digit involvement strongly suggesting ulnar nerve pathology 1, 2
Sensory examination should document the exact distribution, distinguishing from "stocking-glove" distribution which would affect all digits and suggest systemic neuropathy like diabetic peripheral neuropathy 1, 2
Provocative testing, such as the elbow flexion test and Tinel's sign at the cubital tunnel or Guyon's canal, can help diagnose ulnar nerve compression 1

Cervical radiculopathy (C8-T1) can produce similar 4th and 5th digit symptoms, but typically includes neck pain, radiating arm pain, and may affect intrinsic hand muscles more diffusely, with a positive Spurling's test 1
Diabetic peripheral neuropathy presents with symmetric "stocking-glove" distribution affecting all digits, not isolated to ulnar distribution, and can be screened with 10-g monofilament testing, vibration with 128-Hz tuning fork, and ankle reflexes 2, 3
Metformin-induced B12 deficiency neuropathy also causes stocking-glove distribution, not isolated ulnar pattern, and B12 levels should be checked if the patient takes metformin, especially at doses ≥2g daily 1, 4

The diagnostic workup should include a focused neurologic examination, identification of the compression site, and ruling out systemic causes if atypical features are present, with electrodiagnostic studies confirming ulnar nerve pathology and localizing the compression site 1, 2
Conservative management is first-line for mild-moderate cases, with activity modification, nighttime elbow splinting, and ergonomic modifications, while surgical intervention is indicated for severe cases with muscle atrophy or complete paralysis of little finger abduction/adduction, or progressive motor weakness despite 3-6 months of conservative therapy 1