Guillain-Barré syndrome (GBS) represents a spectrum of rare, acute, immune-related polyneuropathies with varying features and presentations. It is divided into 2 main subtypes: demyelinating and axonal. Demyelinating forms include acute inflammatory demyelinating polyneuropathy (AIDP) and the clinical variant Miller Fisher syndrome (MFS). Axonal forms include acute motor axonal neuropathy (AMAN) and acute motor-sensory axonal neuropathy (AMSAN).

The exact etiology is unclear, but GBS typically presents days to weeks after an infection, most commonly Campylobacter jejuni. Other reported triggers include cytomegalovirus (CMV), influenza, Epstein-Barr virus, HIV, and Japanese encephalitis. GBS has also been reported in patients with probable Zika virus infection in French Polynesia, Brazil, and Colombia and in patients with Oropouche virus infection in Cuba. Rarely, GBS has been associated with surgery or immunization. There have been rare reports of GBS occurring about 2 weeks after having the Johnson & Johnson (Janssen) COVID-19 vaccine.

AIDP is the most common form of GBS reported in the United States. It is a rapidly progressive autoimmune disorder of the peripheral nervous system characterized by limb paresthesias, areflexia, and generalized symmetrical muscle weakness or paralysis, usually beginning in the extremities and spreading to the torso, facial, respiratory, and bulbar muscles. MFS is characterized by ophthalmoplegia, ataxia, and absence of the tendon reflexes. Patients with MFS usually demonstrate serum anti-GQ1b immunoglobulin G (IgG) antibodies.

Common clinical findings of AIDP:

• Progressive (typically over 2 weeks), symmetric muscle weakness in more than 1 limb (can range from mild weakness to total paralysis of all 4 limbs, bulbar muscles, and/or trunk)
• Absent or depressed deep tendon reflexes
• Accompanying signs and symptoms may include mild paresthesias in the hands and feet accompanying the weakness, pain in the back and extremities (seen in two-thirds of patients), and dysautonomia (tachycardia, urinary retention, orthostatic hypotension, etc). There is often lack of fever at onset.

Common presenting symptoms in children:

• Neuropathic pain, typically bilateral leg pain and lower back pain
• Gait unsteadiness and/or refusal to walk
• Facial weakness
• Autonomic dysfunction

Recovery may take weeks to years. About two-thirds of individuals make a full or near full recovery. Approximately 10%-15% have residual weakness, numbness, or pain. Mortality rate is generally < 5%. Poor prognostic factors include age older than 60 years, rapid nadir within first 7 days, ventilator dependency, and preceding infection with CMV or C jejuni.