What is the diagnosis and treatment for foot nerve pain?

Diagnosis and Treatment of Foot Nerve Pain

Start with plain radiographs of the foot, then proceed to MRI without contrast if radiographs are negative or equivocal, while simultaneously initiating first-line pharmacological treatment with pregabalin or duloxetine if neuropathic pain is suspected. 1, 2

Diagnostic Approach

Initial Clinical Assessment

Determine the pain pattern and location to guide your differential diagnosis:

• Distal symmetric burning, tingling, or numbness starting in the toes suggests diabetic peripheral neuropathy (DPN), which affects up to 50% of diabetic patients and may be asymptomatic 2
• Burning pain in the ball of the foot radiating to the third and fourth toes indicates Morton's neuroma 3
• Dorsal foot pain worsening with flexion or toe extension points to extensor tendon inflammation or nerve entrapment 4
• Plantar heel pain suggests plantar fasciitis or Baxter's neuropathy (inferior calcaneal nerve compression) 1

Physical Examination Findings

Perform these specific tests to identify the nerve pathology:

• Small fiber function: Test pinprick and temperature sensation 2
• Large fiber function: Use a 128-Hz tuning fork for vibration perception 2
• Protective sensation: Perform 10-g monofilament testing to identify feet at risk for ulceration 2
• Point tenderness: Palpate along extensor tendons, metatarsal shafts, navicular bone, and the deep peroneal nerve course on the dorsal foot 4
• Provocative maneuvers: Assess pain with resisted dorsiflexion to evaluate for tendonitis 4

Imaging Algorithm

Follow this stepwise imaging approach:

1. Initial imaging: Obtain weight-bearing radiographs of the foot for all patients with foot nerve pain 1, 4

   • Note: Initial radiographs have only 12-56% sensitivity for stress fractures, so negative X-rays do not exclude the diagnosis 4

2. If radiographs are negative or equivocal and pain persists beyond 1 week:

   • For suspected nerve entrapment (Baxter's neuropathy, Morton's neuroma): MRI foot without IV contrast is the preferred next study 1
   • For suspected stress fracture: MRI without contrast or CT without contrast are equivalent alternatives 4
   • For plantar fasciitis or plantar fascia tear: MRI without IV contrast or ultrasound are both appropriate 1

3. Reexamine patients 3-5 days post-injury if initial examination is limited by swelling 4

Rule Out Secondary Causes

DPN is a diagnosis of exclusion—screen for these alternative etiologies:

• Vitamin B12 deficiency 2
• Hypothyroidism 2
• Renal disease 2
• Neurotoxic medications 2
• Chronic inflammatory demyelinating neuropathy 2
• Peripheral arterial disease (PAD) with claudication 1

Treatment Approach

First-Line Pharmacological Treatment for Neuropathic Pain

Initiate pregabalin or duloxetine as first-line therapy for neuropathic foot pain:

• Pregabalin: Start at 75 mg twice daily and titrate to 150-300 mg twice daily based on response and tolerability 2, 5

  • FDA-approved for diabetic peripheral neuropathy 5
  • Demonstrated efficacy with 50% or greater pain reduction in controlled trials 5
  • Pain reduction may occur as early as Week 1 5

• Duloxetine: 60 mg once daily 2

  • Improves neuropathy-related quality of life 2
  • May cause a small increase in HbA1c in longer-term studies 2

Alternative Pharmacological Options

If first-line treatments fail or are poorly tolerated:

• Gabapentin: 300-1,200 mg three times daily 2, 6

  • Supported by one high-quality study and multiple smaller studies 2
  • FDA-approved for postherpetic neuralgia with demonstrated efficacy in neuropathic pain 6

• Tricyclic antidepressants (amitriptyline, nortriptyline): Effective for neuropathic pain but require monitoring for anticholinergic side effects, especially in patients ≥65 years 2

• Sodium channel blockers (carbamazepine, lamotrigine, lacosamide): Supported by five medium-quality studies 2

• Topical capsaicin: 8% patch or 0.075% cream, FDA-approved for DPN pain 2

Condition-Specific Non-Pharmacological Treatments

For Morton's neuroma:

• Activity restriction, orthotics, and interdigital corticosteroid injection as first-line therapy 3
• Note: Approximately 30% of patients may not respond to conservative treatment 3

For plantar fasciitis:

• Stretching of the plantar fascia and foot orthotics as first-line therapy 3
• If ineffective, consider extracorporeal shockwave therapy, corticosteroid injection, or platelet-rich plasma injection 3
• Approximately 44% of patients continue to have pain 15 years after diagnosis 3

For diabetic peripheral neuropathy:

• Optimize glucose control with target HbA1c of 6-7% to prevent or delay neuropathy development in type 1 diabetes and slow progression in type 2 diabetes 2
• Annual 10-g monofilament testing to identify feet at risk for ulceration 2

Critical Pitfalls to Avoid

Do not rely solely on initial radiographs to exclude stress fractures due to their low sensitivity (12-56%) 4

Avoid corticosteroid injections near extensor tendons due to risk of tendon rupture 4

Generally avoid opioids (tapentadol, tramadol) for chronic neuropathic pain due to risk of addiction 2

Start with lower doses and titrate slowly in older patients to attenuate adverse events 2

Consider neurologic causes when patients describe burning, tingling, or numbness rather than purely mechanical pain 4

Screen for autonomic neuropathy in patients with evidence of DPN by asking about orthostatic dizziness, syncope, and dry/cracked skin 2