What is the appropriate evaluation and management for a patient presenting with sudden onset paresthesia in bilateral feet, with intact bowel and bladder function and no fever?

Evaluation and Management of Sudden Bilateral Foot Paresthesias with Intact Bowel/Bladder Function

Begin with immediate vascular assessment including bilateral pedal pulse examination and ankle-brachial index (ABI) measurement, as sudden bilateral lower extremity paresthesias in the absence of bowel/bladder dysfunction most commonly indicate either peripheral arterial disease or diabetic/metabolic polyneuropathy rather than cauda equina syndrome. 1

Initial Clinical Assessment

Critical Red Flags to Exclude Immediately:

• Rapidly progressive ascending weakness suggests Guillain-Barré syndrome, which reaches maximum disability within 2 weeks and causes respiratory failure in 20% of patients—this requires immediate hospitalization 1
• Motor weakness or paralysis indicates threatened limb viability in vascular disease or spinal cord pathology requiring urgent intervention 2, 3
• Elevation pallor or dependent rubor with absent pulses indicates critical limb ischemia 1

Physical Examination Priorities:

• Remove all lower extremity garments and palpate all four pedal pulses bilaterally (dorsalis pedis, posterior tibial, popliteal, femoral) 1
• Test 10-g monofilament at the dorsal aspect of the hallux bilaterally, moving proximally until threshold is detected 1
• Assess vibration sense with 128-Hz tuning fork, pinprick sensation, and ankle reflexes 1
• Examine for asymmetric hair growth, calf muscle atrophy, and skin temperature changes 1
• Document timing of symptom onset (acute <48 hours vs. subacute) and whether symptoms are progressive or stable 4

Diagnostic Algorithm

Step 1: Vascular Assessment

• Measure resting ABI immediately—ABI ≤0.90 confirms peripheral arterial disease diagnosis 1
• If ABI >1.40 (noncompressible vessels from calcification), obtain toe-brachial index (TBI) with waveforms; TBI <0.70 indicates PAD 1
• If pulses are absent or symptoms suggest acute ischemia (sudden onset, cold extremity, pain), proceed immediately to CT angiography—do not delay with screening tests 3

Step 2: Metabolic/Neuropathic Evaluation

If vascular studies are normal or show chronic stable disease:

• Laboratory testing: HbA1c, vitamin B12, complete metabolic panel, serum protein electrophoresis if indicated 1
• These tests identify diabetic symmetric polyneuropathy (most common cause of bilateral distal paresthesias) and other metabolic neuropathies 1, 4

Step 3: Neurological Localization

Cauda equina syndrome is effectively ruled out by intact bowel and bladder function—this diagnosis requires urinary retention, fecal incontinence, or saddle anesthesia 5, 6, 7

However, if any of the following develop, obtain urgent MRI lumbar spine:

• New onset urinary retention or incontinence 5
• Saddle anesthesia or perineal numbness 7
• Progressive bilateral leg weakness 6
• Severe back pain (though absence of back pain does not exclude spinal pathology) 8

Step 4: Advanced Testing When Indicated

• Electrophysiological testing or neurology referral is rarely needed except when clinical features are atypical or diagnosis remains unclear after initial workup 1
• MRI lumbar spine is indicated if radiculopathy is suspected based on history of back problems and positional symptom variation 1
• Segmental leg pressures with pulse volume recording can delineate anatomic level of PAD if revascularization is being considered 1

Common Pitfalls to Avoid

Do not assume cauda equina syndrome without bowel/bladder symptoms. The presence of intact bowel and bladder function makes CES extremely unlikely, and pursuing this diagnosis without appropriate symptoms leads to unnecessary urgent imaging and potential false-positive diagnoses 5, 9

Do not overlook acute limb ischemia in patients with chronic PAD. Sudden worsening of paresthesias in someone with known vascular disease may represent acute-on-chronic ischemia requiring urgent revascularization within 6 hours 3

Do not delay vascular imaging if acute ischemia is suspected. The principle of "time is tissue" applies—delays beyond 4-6 hours increase risk of permanent damage and limb loss 3

Bilateral symptoms do not exclude vascular disease. Bilateral involvement can occur with aortoiliac occlusion or bilateral embolic events, particularly in patients with atrial fibrillation 2, 3

Management Based on Etiology

For Peripheral Arterial Disease:

• Initiate antiplatelet therapy (aspirin 100 mg daily) unless contraindicated 3
• Optimize cardiovascular risk factors: statin for LDL-C target <55 mg/dL, blood pressure <130/80 mmHg 3
• Consider revascularization if symptoms are lifestyle-limiting or if critical ischemia develops 2

For Diabetic/Metabolic Neuropathy:

• Optimize glycemic control with HbA1c target <7% 1, 3
• Supplement vitamin B12 if deficient 1
• Implement foot protection strategies and regular surveillance 1

For Guillain-Barré Syndrome (if progressive ascending weakness develops):

• Immediate hospitalization with respiratory monitoring 1
• Neurology consultation for consideration of IVIG or plasmapheresis 1