How should I take a history for a patient presenting with bilateral lower‑limb weakness?

History Taking for Bilateral Lower Limb Weakness

When evaluating bilateral lower limb weakness, immediately assess the time course of symptom onset and check for red flags indicating cauda equina syndrome or spinal cord compression, as these require emergency intervention within hours to prevent permanent disability. 1

Immediate Red Flag Assessment

Begin by determining if emergency conditions are present:

• Ask about bladder and bowel function - New urinary retention, incontinence, or constipation with bilateral leg weakness indicates cauda equina syndrome requiring emergency MRI and surgical consultation within 12-72 hours 1
• Inquire about perineal sensation - Saddle anesthesia or impaired perineal sensation suggests cauda equina syndrome 1
• Assess symptom progression - Rapidly progressive bilateral ascending weakness developing over days to 4 weeks with numbness/tingling suggests Guillain-Barré syndrome, which requires immediate respiratory monitoring as 20% develop respiratory failure 1, 2

Time Course Characterization

The temporal pattern distinguishes between etiologies:

• Hyperacute onset (minutes to hours) - Consider vascular causes (aortic dissection, bilateral emboli), spinal cord infarction, or acute cord compression 1
• Acute-subacute (days to weeks) - Suggests Guillain-Barré syndrome, transverse myelitis, or evolving cord compression 1, 2
• Chronic progressive (months) - Consider degenerative cervical myelopathy, spinal stenosis, or peripheral artery disease 3, 1

Detailed Symptom Characterization

Pattern and Distribution

• Determine if weakness is ascending or descending - Ascending pattern from legs upward suggests Guillain-Barré syndrome 2
• Ask about upper extremity involvement - Hand weakness with leg weakness may indicate cervical cord pathology rather than lumbar disease 2, 4
• Assess symmetry - Though bilateral, note any asymmetry in severity 2

Associated Neurological Symptoms

• Sensory changes - Ask about numbness, tingling, or burning sensations and their distribution; stocking-glove pattern suggests polyneuropathy 5
• Determine if there is a sensory level - A sharp demarcation where sensation changes suggests spinal cord pathology requiring emergency imaging 1
• Back pain - Presence and location may indicate mechanical compression; absence doesn't exclude serious pathology 1

Exertional and Positional Features

Vascular Claudication Assessment

• Characterize leg discomfort with walking - Aching, cramping, or fatigue in buttocks, thighs, or calves that occurs predictably with walking distance suggests peripheral artery disease 3
• Timing of relief - Symptoms relieving within 10 minutes of rest indicate vascular claudication 3
• Effect of position - Vascular claudication improves with rest regardless of position 3

Neurogenic Claudication Assessment

• Positional variation - Pain/weakness worse with standing and lumbar extension, improved with sitting or lumbar flexion suggests spinal stenosis 3, 1
• Relief timing - Neurogenic claudication takes longer to resolve than vascular (often >10 minutes) 3

Functional Impact Assessment

• Walking distance and limitations - Quantify how far the patient can walk before symptoms occur 3
• Rest pain - Leg pain or discomfort present at rest, especially at night, suggests critical limb ischemia or severe neuropathy 3
• Activities of daily living impact - Assess specific functional limitations 3

Risk Factor and Comorbidity Assessment

Atherosclerotic Risk Factors

For patients ≥50 years, assess: 3

• Diabetes mellitus
• Smoking history (current or former)
• Hypertension
• Hyperlipidemia
• Known coronary or cerebrovascular disease

Infectious and Inflammatory Triggers

• Recent infections - Two-thirds of Guillain-Barré syndrome patients report infection within 6 weeks (Campylobacter, CMV, Hepatitis E, Mycoplasma, EBV, Zika) 2
• Vaccination history - Recent immunizations may precede Guillain-Barré syndrome 2

Metabolic and Systemic Factors

• Diabetes history - Diabetic polyneuropathy is a common cause of bilateral leg symptoms 5
• Thyroid symptoms - Weight loss, palpitations, heat intolerance with acute weakness may indicate thyrotoxic periodic paralysis 6
• Renal disease - Uremic neuropathy can cause bilateral weakness 2

Associated Symptoms to Elicit

• Autonomic dysfunction - Orthostatic symptoms, abnormal sweating, or cardiac arrhythmias suggest Guillain-Barré syndrome 2
• Erectile dysfunction - May indicate vascular insufficiency in men with peripheral artery disease 3
• Skin changes - Non-healing wounds, ulcers, or color changes suggest critical limb ischemia 3
• Respiratory symptoms - Shortness of breath or difficulty breathing in the context of progressive weakness is critical in Guillain-Barré syndrome 2

Critical Pitfalls to Avoid

• Do not assume lumbar pathology - Subjective lower limb weakness without upper motor neuron signs can be the presenting feature of degenerative cervical myelopathy; failure to consider cervical spine pathology leads to misdiagnosis and delayed treatment 4
• Do not dismiss normal reflexes - Functional neurological disorder can present with bilateral leg weakness but shows inconsistency on examination with normal reflexes 1, 7
• Do not overlook incomplete cauda equina syndrome - Patients retaining voluntary bladder control can avoid permanent dysfunction if treated urgently, whereas those with retention often have permanent impairment 1
• Do not delay assessment in rapidly progressive cases - Guillain-Barré syndrome requires immediate evaluation including respiratory monitoring, as deterioration can be rapid 1, 2