Clues Pointing TO This Diagnosis

Antecedent GI illness ("stomach bug"/bad chicken sandwich) two to three weeks before onset — a preceding infection (often Campylobacter jejuni from undercooked poultry) occurs in up to ~76% of cases and is the classic GBS trigger
Ascending weakness starting in the feet/calves and climbing to thighs — progressive weakness that begins distally in the legs and ascends is the hallmark pattern
Bilateral, relatively symmetric involvement — GBS characteristically produces symmetric limb weakness rather than a focal or one-sided pattern
Distal tingling/paresthesias in both feet preceding weakness — early sensory symptoms increase the likelihood of GBS
Rapid progression over days (Sunday to Thursday) — GBS progresses over 12 hours to 28 days before reaching a plateau
Absent knee reflexes/global areflexia — decreased or absent deep tendon reflexes is a required diagnostic feature
CSF showing high protein with normal cell count (albuminocytologic dissociation) — the classic CSF finding in GBS
Nerve conduction studies showing slowing "at the roots" — electrodiagnostic evidence of a polyradiculoneuropathy supports and classifies GBS
Monitoring of respiratory status (serial FVC) — GBS threatens respiratory muscles, so vital capacity is followed closely, a key feature of the illness course
Response to IVIG with gradual recovery over months — the monophasic, treatment-responsive course fits GBS

Why It's NOT the Similar Diseases

NOT transverse myelitis/spinal cord compression — cord lesions produce a sensory level, upper motor neuron signs (eventual hyperreflexia), and early prominent bladder/bowel dysfunction; Gilbert has areflexia and an ascending peripheral pattern without a sensory level
NOT myasthenia gravis — MG causes fatigable weakness with ocular/bulbar predominance and preserved reflexes and sensation; Gilbert has areflexia, sensory symptoms, and an ascending course with an antecedent infection
NOT botulism — botulism causes descending paralysis with early cranial nerve involvement, pupillary changes, and no sensory symptoms; Gilbert's weakness is ascending with sensory paresthesias
NOT poliomyelitis/West Nile anterior myelitis — these cause asymmetric, purely motor weakness with fever and no sensory loss; Gilbert has symmetric weakness with sensory paresthesias and no fever at onset
NOT hypokalemic (electrolyte) paralysis — electrolyte disturbances can mimic acute weakness but lack the antecedent infection, distal paresthesias, and CSF albuminocytologic dissociation; a normal potassium excludes it

Differential Diagnosis List

Transverse myelitis/spinal cord compression — ruled out by absence of a sensory level and bladder/bowel dysfunction, with areflexia rather than UMN signs
Myasthenia gravis — ruled out by areflexia, sensory involvement, and preceding infection rather than fatigable ocular/bulbar weakness
Botulism — ruled out by ascending (not descending) weakness and presence of sensory paresthesias
Poliomyelitis/West Nile virus — ruled out by symmetric weakness with sensory symptoms and no fever at onset
Hypokalemic periodic paralysis/electrolyte disturbance — ruled out by normal electrolytes and the CSF albuminocytologic dissociation

Key Distinguishing Test

GBS is primarily a clinical diagnosis (progressive symmetric limb weakness plus hyporeflexia/areflexia after excluding alternatives), supported by two confirmatory tests. Lumbar puncture classically shows albuminocytologic dissociation—elevated CSF protein with a normal white cell count—though protein is often normal in the first week and rises in >90% by the end of week two. Nerve conduction studies demonstrate a polyradiculoneuropathy and help classify the demyelinating versus axonal subtype, but are not required for diagnosis.

Board Note

Classic association: an antecedent infection (most commonly Campylobacter jejuni, also viral respiratory illnesses) 1–4 weeks before the ascending, symmetric weakness with areflexia
Diagnosis is clinical; support with LP (albuminocytologic dissociation) and nerve conduction studies—remember early CSF protein can be normal
First-line treatment is IVIG or plasma exchange (equally effective); start early in patients who are progressing or unable to walk. Corticosteroids alone are not effective. IVIG is preferred with autonomic instability
The most important acute complication is respiratory failure—monitor serial vital capacity/FVC and transfer to a high-dependency/ICU setting when respiratory or autonomic compromise is a concern
Also watch for autonomic dysfunction (blood pressure/heart rate lability, arrhythmias); provide DVT prophylaxis, pain management, and early physiotherapy
Most patients recover over weeks to months, but GBS remains serious—about 5% die and up to 20% cannot walk independently at one year, so refer promptly to neurology and hospitalize for monitoring

“Gilbert’s Story”