What investigations are recommended for a patient presenting with tingling in both feet?

Investigations for Tingling in Both Feet

For a patient presenting with tingling in both feet, a comprehensive neurological assessment should be performed, including a 10-g monofilament test, vibration testing with a 128-Hz tuning fork, pinprick sensation testing, and ankle reflex assessment to identify loss of protective sensation (LOPS). 1, 2

Initial Evaluation

• Obtain a detailed history of the tingling symptoms, including onset, progression, exacerbating factors, and associated symptoms 2
• Assess for pain using a simple pain scale and document the characteristics of the symptoms (numbness, burning, etc.) 1, 2
• Evaluate for risk factors and potential causes:
  • Diabetes mellitus (most common cause) 1, 2
  • Vitamin B12 deficiency 2
  • Thyroid dysfunction 1, 2
  • History of chemotherapy 2
  • Alcohol use 2
  • HIV, hepatitis B and C 2

Physical Examination

• Perform a comprehensive neurological examination focusing on:
  • 10-g (5.07 Semmes-Weinstein) monofilament testing at three sites on each foot 1, 3
  • Vibration testing using a 128-Hz tuning fork on the dorsal side of the distal phalanx of the first toe 1, 4
  • Pinprick sensation testing 1, 2
  • Ankle reflex assessment 1, 2
  • Cotton wisp test for light touch sensation 1
• Conduct a vascular examination including:
  • Palpation of lower extremity pulses (femoral, popliteal, dorsalis pedis, posterior tibial) 1, 5
  • Auscultation for femoral bruits 1
  • Assessment of capillary refill time 5
• Inspect the feet for:
  • Skin integrity, ulcers, or wounds 1, 5
  • Deformities (hammertoes, prominent metatarsal heads, bunions) 1, 5
  • Calluses or areas of increased pressure 1, 5

Laboratory Testing

• Fasting blood glucose and hemoglobin A1c to assess for diabetes 2
• Complete blood count to evaluate for anemia 1
• Thyroid function tests (TSH, free T4) 1, 2
• Vitamin B12 level 2
• Hepatitis B, C, and HIV testing if clinically indicated 2
• Consider testing for anti-ganglioside antibodies if Guillain-Barré syndrome is suspected 2

Additional Diagnostic Testing

• Ankle-Brachial Index (ABI) if peripheral arterial disease is suspected 1
• Electromyography (EMG) and nerve conduction studies to differentiate between axonal and demyelinating neuropathies 6, 7
• Exercise treadmill ABI testing if resting ABIs are normal or borderline but symptoms suggest peripheral arterial disease 1
• Toe-Brachial Index (TBI) if ABI >1.40 (non-compressible arteries) 1
• Consider skin biopsy for intraepidermal nerve fiber density assessment in suspected small fiber neuropathy 6

Imaging Studies (When Indicated)

• MRI of the lumbar spine if radiculopathy is suspected 7
• MRI of the brain if central nervous system pathology is suspected 8
• Vascular imaging studies if peripheral arterial disease is identified 1

Referrals to Consider

• Neurology for complex or rapidly progressing neuropathy 2
• Vascular surgery for significant peripheral arterial disease 1
• Endocrinology for diabetes management 1, 2
• Podiatry for foot care and management of foot deformities 1

Common Pitfalls to Avoid

• Failing to perform a complete foot examination in patients with diabetes (should be done at least annually) 1, 5
• Relying on a single test for diagnosing peripheral neuropathy (at least two tests should be performed) 1, 2
• Not considering non-diabetic causes of peripheral neuropathy in patients with diabetes 2
• Overlooking the need for vascular assessment in patients with neuropathic symptoms 1
• Failing to educate patients with LOPS about proper foot care and daily foot inspection 1