What is the impression of a patient with neuropathic pain, described as paresthesia (pins and needles) and a cold feeling, pain, and heaviness in both arms and legs, with a normal Electromyography (EMG) - Nerve Conduction Velocity (NCV) test?

Clinical Impression: Small Fiber Neuropathy

This patient most likely has small fiber neuropathy, which characteristically presents with neuropathic pain symptoms (pins and needles, cold sensations, burning pain) in a symmetric distribution affecting both arms and legs, despite having normal EMG-NCV studies. 1, 2

Why EMG-NCV is Normal

• Standard nerve conduction studies only evaluate large myelinated nerve fibers (A-beta fibers) and will be completely normal in small fiber neuropathy, which affects unmyelinated C-fibers and thinly myelinated A-delta fibers responsible for pain and temperature sensation 1, 3
• The normal EMG-NCV does not exclude neuropathy—it simply indicates that large fiber function is preserved 3, 4

Clinical Features Supporting Small Fiber Neuropathy

• The "pins and needles" sensation (paresthesias) represents abnormal firing of damaged sensory nerves, a hallmark of small fiber dysfunction 1
• The cold feeling and altered temperature perception indicate dysfunction of small C-fibers (heat sensation) and A-delta fibers (cold sensation) 1
• The symmetric distribution affecting both upper and lower extremities is characteristic of peripheral neuropathic pain, which is invariably symmetrical 1, 2
• Pain and heaviness in all four limbs suggests a length-dependent polyneuropathy pattern, though typically symptoms begin distally in the feet 2

Essential Diagnostic Workup

You must exclude secondary causes of neuropathy before confirming the diagnosis: 5, 2

• Screen for diabetes mellitus (fasting glucose, HbA1c) as diabetic neuropathy is the most common cause of small fiber neuropathy 5, 6
• Check vitamin B12 levels, thyroid function (TSH), and renal function (creatinine) 2
• Review medications for neurotoxic agents 2
• Consider testing for heavy metal exposure, alcohol abuse history, and inherited neuropathies if initial workup is negative 2

Confirmatory Testing for Small Fiber Neuropathy

• Skin biopsy to measure intraepidermal nerve fiber density is the gold standard for diagnosing small fiber neuropathy when clinical signs suggest small fiber dysfunction 4
• Quantitative sensory testing can provide more accurate sensory profiling for small fiber function 4
• Clinical examination should specifically assess pinprick sensation, temperature sensation (cold and warm), and light touch 6, 2

Treatment Approach

Initiate first-line pharmacological therapy with pregabalin, duloxetine, or gabapentin for neuropathic pain management 6, 1:

• Pregabalin, duloxetine, and gabapentin achieve ≥50% pain reduction in approximately 38% of patients at optimal dosing 1
• Gabapentin dosing: 300-1,200 mg three times daily 6
• Duloxetine improves neuropathy-related quality of life 6

Alternative pharmacological options if first-line agents fail: 6, 1

• Tricyclic antidepressants (amitriptyline) are effective but require monitoring for anticholinergic side effects, especially in patients ≥65 years 6
• Topical capsaicin (8% patch or 0.075% cream) has FDA approval for neuropathic pain 6

Address underlying etiology aggressively if identified (e.g., optimize glycemic control if diabetic) 1

Non-Pharmacological Management

• Physical activity and exercise are recommended as adjunctive approaches, with early evidence suggesting protective effects on neuropathy progression 1
• Screen for depression and anxiety, as over two-thirds of patients with painful neuropathy develop these comorbidities, and addressing them improves overall pain outcomes 1

Critical Pitfalls to Avoid

• Do not dismiss the diagnosis simply because EMG-NCV is normal—this is the classic presentation of small fiber neuropathy 1, 3
• Avoid prolonged cold water immersion or ice application for symptom relief, as this can lead to immersion foot, skin ulceration, and infection risk 1
• Avoid opioids for chronic neuropathic pain due to addiction risk and limited efficacy 6
• Start medications at lower doses with slower titration in older patients to minimize adverse events 6