What is the initial workup for a patient presenting with numbness and tingling in fingertips and toes?

Initial Workup for Numbness and Tingling in Fingertips and Toes

Begin with a comprehensive neurological examination including 10-g monofilament testing, vibration assessment with a 128-Hz tuning fork, pinprick sensation testing, and ankle reflex evaluation to identify loss of protective sensation and determine the pattern of neuropathy. 1, 2

History and Symptom Characterization

• Obtain detailed characteristics of the numbness and tingling, including onset, progression, distribution (symmetric vs. asymmetric), and whether symptoms are worse distally (length-dependent pattern) 2, 3
• Document associated symptoms including burning pain, weakness, or autonomic symptoms such as orthostatic hypotension 1, 4
• Assess pain severity using a simple pain scale 1
• Identify risk factors: diabetes mellitus, alcohol use, chemotherapy exposure (taxanes, platinum agents, vincristine), vitamin deficiencies, thyroid disease, HIV, hepatitis B/C, and occupational exposures 2, 3

Physical Examination Components

Neurological Assessment:

• Perform 10-g monofilament testing at multiple sites on each foot to detect loss of protective sensation 1, 2
• Test vibration perception using a 128-Hz tuning fork on the great toes and bony prominences 1, 2
• Assess pinprick sensation (small-fiber function) and temperature sensation 1, 2
• Evaluate ankle reflexes bilaterally 1, 2

Vascular Assessment:

• Palpate pedal pulses (dorsalis pedis and posterior tibial) 1, 2
• Assess capillary refill time 2
• Auscultate for femoral bruits if peripheral arterial disease is suspected 2

Foot Inspection:

• Examine skin integrity for ulcers, wounds, or areas of breakdown 1, 2
• Identify foot deformities, calluses, or areas of increased pressure 1, 2

Laboratory Testing

Essential Initial Tests:

• Fasting blood glucose and hemoglobin A1c to screen for diabetes mellitus 2, 4, 3
• Vitamin B12 level with metabolites (methylmalonic acid ± homocysteine) 2, 3
• Serum protein electrophoresis with immunofixation to evaluate for monoclonal gammopathies 3
• Complete blood count to assess for anemia 2
• Thyroid function tests (TSH, free T4) 2, 4

Additional Testing When Indicated:

• Hepatitis B, C, and HIV testing if risk factors present 2, 4
• Anti-ganglioside antibodies if Guillain-Barré syndrome suspected 4
• Anti-MAG antibodies if demyelinating neuropathy suspected 4

Vascular Studies (When Indicated)

• Obtain ankle-brachial index (ABI) if peripheral arterial disease is suspected based on history of leg fatigue, claudication, or absent pulses 1, 2
• Consider exercise treadmill ABI testing if resting ABIs are normal or borderline (0.91-1.00) but symptoms suggest vascular disease 2
• Measure toe-brachial index (TBI) if ABI >1.40, indicating non-compressible arteries 2

Electrodiagnostic Testing

• Reserve nerve conduction studies for atypical presentations, unclear diagnosis, or when considering alternative diagnoses such as carpal tunnel syndrome (if symptoms predominantly affect hands) 1, 5
• Electrodiagnostic testing is not routinely needed for typical distal symmetric polyneuropathy but can distinguish axonal from demyelinating patterns 6

Specialist Referrals

• Refer to endocrinology for diabetes management if newly diagnosed or poorly controlled diabetes 2, 4
• Refer to vascular surgery if significant peripheral arterial disease identified (ABI <0.90 or >1.40) 2
• Refer to podiatry for patients with foot deformities, loss of protective sensation, or history of ulceration 2
• Consider neurology referral for atypical features, rapid progression, or asymmetric patterns 1

Critical Pitfalls to Avoid

• Do not rely on a single neurological test—at least two modalities (e.g., monofilament plus vibration or pinprick) must be performed to accurately diagnose peripheral neuropathy 1, 2
• Do not skip comprehensive foot examination in diabetic patients—this must be performed at minimum annually, and at every visit for high-risk patients 1
• Do not assume diabetes is the only cause in diabetic patients—up to 27% of neuropathy cases have no identifiable cause even after testing, and diabetic patients can have concurrent etiologies 3
• Do not overlook vascular assessment—peripheral arterial disease frequently coexists with neuropathy and requires different management 1, 2
• Do not forget to educate patients with loss of protective sensation about daily foot inspection using visual inspection or mirrors, as they cannot rely on sensation to detect injuries 1