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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
Epidemiology:
- 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
Etiology:
- 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
Pathogenesis:
- 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
Clinical Features:
- 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
Electrodiagnostic findings:
Earliest findings: