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Acute Inflammatory Demyelinating Polyradiculoneuropathy

Introduction:

Classified under the eponym Guillain-Barre syndrome (GBS)
Other variants of GBS include Acute Motor Axonal Neuropathy (AMAN), Acute Motor and Sensory Axonal Neuropathy (ASMAN), and the Miller Fisher syndrome (MFS).
AIDP is acute monophasic immune-mediated polyradiculoneuropathy provoked by a preceding infection

Mean age of onset of 40 years affecting slightly more males than females of all ages, races and nationalities
Worldwide incidence of GBS ranges from 0.6 to 4.0/100,000 people

AIDP is most common form of GBS in North America, Europe and most of the developed world representing about 85% to 90% of cases
⅔ patients give history of antecedent respiratory tract or GI tract infection
Campylobacter infection is most commonly observed in upto 30% cases
Campylobacter associated GBS has worse prognosis, manifests slow recovery and with greater residual neurologic disability.
Other precipitants include EBV, CMV, mycoplasma, pneumonia, and influenza-like illnesses
Also has an association with HIV infection; predominantly in those who are not profoundly immunocompromised

Molecular Mimicry: auto-antibodies cross-react with peripheral nerve components because of sharing of cross-reactive epitopes
Immune response can be directed towards myelin or axon of peripheral nerve
Acute Inflammatory Demyelinating Polyradiculoneuropathy (AIDP): When directed against epitopes in myelin or schwann cell membrane; cellular + humoral immune responses are involved
Progression of disease for about two weeks
Nadir of disease reaches 4 weeks after initial symptoms in 90% patients
If disease progression is more than 8 weeks, it is classified as chronic inflammatory demyelinating polyradiculoneuropathy or CIDP

Weakness starts in the legs (90%)
Decreased or absent reflexes in affected arms or legs (90%)
Paresthesias accompanying weakness (>80%)
Dysautonomia (~70%)
Pain due to nerve root inflammation, typically in the back and extremities (two thirds of patients)
Facial nerve Palsies (>50%)
Oropharyngeal weakness (50%)
Severe respiratory muscle weakness requiring ventilatory support (10%-30%)
Oculomotor weakness (15%)
Weakness begins in arms and facial muscles (10%)
SIADH (5%; more in hospitalized patients)

Unusual clinical features of GBS include: papilledema, facial myokymia, hearing loss, meningeal signs, vocal cord paralysis, and mental status changes.
Posterior reversible encephalopathy syndrome, also called reversible posterior leukoencephalopathy syndrome has been associated with GBS in children and adults likely related to acute hypertension from dysautonomia

Earliest findings: