Referral to Neurology for Quantitative Sensory Testing and Skin Biopsy
Refer patients requiring quantitative sensory testing (QST) or skin biopsy to a neurologist, preferably one with expertise in neuromuscular disorders or peripheral neuropathy. These specialized diagnostic procedures for evaluating small fiber neuropathy are typically performed and interpreted within neurology practices that have the necessary equipment, technical expertise, and established protocols for these tests 1.
Why Neurology is the Appropriate Specialty
The American Academy of Neurology practice parameter explicitly addresses these diagnostic modalities as part of the neurological evaluation of polyneuropathy 1. Neurologists specializing in neuromuscular medicine have:
- Access to autonomic testing equipment including quantitative sudomotor axon reflex testing (QSART), which complements QST and skin biopsy findings 1
- Established protocols for skin biopsy processing with PGP 9.5 immunohistochemistry and intraepidermal nerve fiber (IENF) density quantification 1
- Expertise in correlating QST results with nerve conduction studies and clinical findings to establish comprehensive diagnoses 2, 3
Specific Clinical Scenarios for Referral
Small Fiber Sensory Neuropathy (SFSN)
Refer when patients present with:
- Burning pain in feet with minimal objective signs on examination
- Normal nerve conduction studies but persistent neuropathic symptoms (tingling, numbness, neuropathic pain)
- Clinical suspicion of autonomic dysfunction (sweating abnormalities, circulatory instability) 1
Skin biopsy is particularly valuable here because it provides direct objective measurement of small fiber loss when electrodiagnostic studies are normal 1. The sensitivity ranges from 45-90% with specificity of 95-97% 1.
Distal Symmetric Polyneuropathy (DSP)
Consider referral for:
- Suspected autonomic neuropathy (amyloidosis, autoimmune autonomic neuropathy) where autonomic testing is essential 1
- Diabetic or pre-diabetic patients with pain symptoms but equivocal electrodiagnostic findings 4
- Patients requiring documentation of small fiber involvement for diagnosis or treatment decisions 1
Important Caveats
Verify laboratory capabilities before referral. Not all neurology practices have:
- The specialized immunohistochemistry processing required for skin biopsy specimens 1
- Normative databases for IENF density adjusted for age and anatomical site 4
- Autonomic testing equipment (QSART, heart rate variability testing) 1
QST and skin biopsy cannot establish causality between nerve damage and pain 5. These tests demonstrate structural or functional abnormalities but clinical assessment remains paramount for diagnosing neuropathic pain.
Practical Referral Approach
When making the referral, specify:
- Clinical question: Confirm small fiber neuropathy vs. rule out peripheral cause of pain
- Prior testing completed: Nerve conduction studies results, relevant laboratory work
- Specific symptoms: Duration, distribution, character of pain; presence of allodynia, thermal sensitivity, or autonomic symptoms
- Associated conditions: Diabetes, impaired glucose tolerance, autoimmune diseases 4, 2
The diagnostic efficiency of skin biopsy (88.4%) exceeds that of QST (46.9%) or clinical examination alone (54.6%) for small fiber neuropathy 2, making it the preferred objective test when available through neurology referral.