How to diagnose brachial pruritus?

Diagnosis of Brachioradial Pruritus

Brachioradial pruritus is a specific neuropathic form of itching that requires targeted diagnostic evaluation focusing on cervical spine imaging and careful clinical assessment to identify its neurological origin.

Clinical Presentation and Key Diagnostic Features

• Location: Primarily affects the dorsolateral aspect of the forearm at the insertion of the brachioradialis muscle, may extend to shoulders and arms 1, 2
• Characteristics: Intense, often burning pruritus without primary rash (excoriations may develop from scratching)
• Demographics: More common in fair-skinned females 2
• Exacerbating factors:
  • Sun exposure/UV radiation 2
  • Cervical spine pathology 1, 3, 4

Diagnostic Algorithm

Step 1: Focused History

• Document precise location and character of pruritus
• Inquire about:
  • Duration of symptoms (often delayed diagnosis 2-3 years) 2
  • Relationship to sun exposure
  • Associated neurological symptoms (paresis, pain, numbness)
  • Previous cervical spine issues
  • Failed treatments (especially antihistamines and corticosteroids)
  • "Ice-pack sign" - relief with application of cold packs is pathognomonic

Step 2: Physical Examination

• Examine affected areas for:
  • Excoriations (secondary to scratching)
  • Absence of primary rash
  • Neurological deficits in the affected limb
  • Cervical spine range of motion and tenderness

Step 3: Initial Laboratory Workup

Based on guidelines for generalized pruritus 5, 6:

• Complete blood count with differential
• Liver function tests
• Renal function tests (urea and electrolytes)
• Ferritin levels

Step 4: Targeted Diagnostic Imaging

• Cervical spine MRI - crucial for diagnosis to identify:
  • Cervical disc herniation
  • Cervical spinal stenosis
  • Nerve root compression 3, 4

Step 5: Additional Testing Based on Clinical Suspicion

If other causes are suspected:

• Consider skin biopsy if cutaneous lymphoma is suspected 5
• If hematological disorders are suspected: blood film, LDH, ESR 6
• In cases with systemic symptoms: targeted investigations for specific malignancies 5

Common Diagnostic Pitfalls

1. Misdiagnosis: Often misdiagnosed as dermatological condition rather than neuropathic disorder 2
2. Unnecessary testing: Avoid routine screening for malignancy without specific symptoms 6
3. Medication review: Always review medications as potential causes of pruritus 6
4. Delayed diagnosis: Consider brachioradial pruritus early to avoid years of unnecessary suffering and invasive testing 2

Diagnostic Confirmation

• Positive response to neuropathic pain medications (gabapentin, pregabalin) can be both therapeutic and diagnostic 1, 3, 7
• Relief with cervical epidural steroid injections supports cervical spine etiology 4

Key Differentials to Consider

• Generalized pruritus due to systemic causes (renal, hepatic, hematologic disorders)
• Other neuropathic pruritus syndromes
• Dermatological conditions with pruritus
• Drug-induced pruritus

Remember that brachioradial pruritus is a specific neuropathic syndrome, and all patients with this condition should be evaluated for cervical spine injuries 1. Failure to recognize the neuropathic origin leads to ineffective treatments and prolonged patient suffering.