What is the typical presentation of Guillain‑Barré syndrome in a previously healthy adult following a recent respiratory or gastrointestinal infection?

Typical Clinical Presentation of Guillain-Barré Syndrome

A previously healthy adult with Guillain-Barré syndrome typically presents with rapidly progressive bilateral ascending weakness starting in the legs, accompanied by diminished or absent reflexes, developing 1–2 weeks after a respiratory or gastrointestinal infection. 1

Antecedent Infection History

• Approximately two-thirds of patients report symptoms of a preceding infection within 4–6 weeks before weakness onset. 1, 2
• Upper respiratory tract infections are the most common antecedent events in Europe and North America, occurring in 22–53% of cases. 2
• Gastroenteritis is the most frequent preceding event in some regions like India and Bangladesh (36–47% of cases), with Campylobacter jejuni being the most commonly identified trigger worldwide (30–32% of cases). 2, 3
• Viral triggers include cytomegalovirus, Epstein-Barr virus, Zika virus, and SARS-CoV-2. 2

Neurological Symptoms at Presentation

• Bilateral ascending weakness is the hallmark feature, typically beginning in the lower extremities and progressing proximally to involve the arms and cranial muscles over hours to days. 1
• Distal paresthesias or sensory loss often precede or accompany the weakness, affecting the hands and feet. 1
• Back and limb pain is an early symptom in approximately two-thirds of patients and can be muscular, radicular, or neuropathic in character. 1
• Diminished or absent deep tendon reflexes are a key diagnostic feature, typically beginning in the lower limbs and progressing upward. 1

Disease Progression Timeline

• Patients typically reach maximum disability within 2 weeks of symptom onset, though progression can continue up to 4 weeks. 1
• The rapidity of progression is a defining characteristic that distinguishes GBS from chronic inflammatory demyelinating polyneuropathy (CIDP). 4

Cranial Nerve Involvement

• Bilateral facial palsy is the most common cranial nerve manifestation, occurring due to the facial nerve's extensive myelin coverage and long intracranial course. 1
• Facial weakness can occur in isolation initially or progress to classic ascending weakness. 1
• Ophthalmoplegia, ataxia, and areflexia characterize Miller Fisher syndrome, a variant seen in 5–25% of cases. 1
• Dysphagia and impaired cough reflex indicate bulbar involvement and increase aspiration risk. 1

Autonomic Dysfunction

• Dysautonomia is common and includes blood pressure instability, heart rate variability, pupillary dysfunction, and bowel or bladder dysfunction. 1
• Cardiovascular complications from autonomic instability contribute to the 3–10% mortality rate even with optimal care. 1

Respiratory Compromise

• Approximately 20% of patients develop respiratory failure requiring mechanical ventilation, which can occur rapidly and sometimes without obvious dyspnea. 1
• The "20/30/40 rule" predicts respiratory failure risk: vital capacity <20 ml/kg, maximum inspiratory pressure <30 cmH₂O, or maximum expiratory pressure <40 cmH₂O. 1
• Single breath count ≤19 predicts the need for mechanical ventilation. 1

Classic Subtypes and Regional Variation

• Acute inflammatory demyelinating polyneuropathy (AIDP) is the most common subtype in Europe and North America (83–90% of cases), presenting with sensorimotor involvement. 2
• Acute motor axonal neuropathy (AMAN) is more prevalent in Asia (30–40% of cases) and presents with pure motor weakness without sensory signs. 1, 2
• The pure motor variant accounts for 5–70% of cases depending on geographic region. 1

Diagnostic Clues on Examination

• Symmetrical weakness is typical, though mild asymmetry can occur; marked persistent asymmetry should prompt reconsideration of the diagnosis. 1
• Weakness is typically more pronounced proximally than distally in the early stages. 5
• Sensory examination may reveal distal sensory loss in a stocking-glove distribution, though pure motor variants lack sensory signs. 1
• Bladder dysfunction at onset is atypical and should raise suspicion for alternative diagnoses such as spinal cord pathology. 1

Pain Presentation

• Pain is often an early and prominent symptom before weakness becomes apparent, affecting approximately two-thirds of patients. 1
• Pain can be neuropathic (burning, shooting), radicular (dermatomal distribution), or muscular (deep aching in limbs and back). 1

Common Pitfalls in Recognition

• Do not dismiss GBS based on normal cerebrospinal fluid protein in the first week, as albumino-cytological dissociation may not yet be present. 1
• Bilateral simultaneous facial weakness is extremely rare in Bell's palsy and should immediately raise suspicion for GBS. 1
• In children, nonspecific features such as irritability and refusal to bear weight may precede obvious weakness. 1
• Electrodiagnostic studies may be normal when performed within the first week; repeat testing in 2–3 weeks if clinical suspicion remains high. 1