AIDP
I'll look up AIDP (Acute Inflammatory Demyelinating Polyneuropathy) from the medical library right away.
Reading File
Now let me search the medical library for AIDP content in parallel:
Finding Sources
Searching PubMed
"acute inflammatory demyelinating polyneuropathy" OR "Guillain-Barre syndrome"
Good. Now let me read the most authoritative sources - Bradley's Neurology and Harrison's, plus Robbins for pathology, in parallel:
Reading File
Reading File
Reading File
Now let me get more detailed content from Bradley's Neurology on pathophysiology, treatment, and nerve conduction findings, and also Miller's Anesthesia for the full clinical picture:
Reading File
Reading File
I now have rich, comprehensive content. Let me compile a thorough answer.
AIDP - Acute Inflammatory Demyelinating Polyneuropathy
AIDP is the most common subtype of Guillain-Barré Syndrome (GBS) and the predominant form seen in Europe and North America. It is the prototypical immune-mediated demyelinating neuropathy affecting peripheral nerves and spinal roots.
Definition & Classification
AIDP is one of several distinct GBS subtypes:
| Subtype | Feature |
|---|---|
| AIDP | Demyelinating; most common in Western countries |
| AMAN | Pure motor axonal; common in China/Asia; linked to C. jejuni |
| AMSAN | Motor + sensory axonal; severe, poor recovery |
| Miller-Fisher Syndrome | Ophthalmoplegia + ataxia + areflexia; anti-GQ1b antibodies |
Epidemiology
- Incidence: 1.8 per 100,000 per year (stable over decades)
- Affects all ages; males > females (1.5:1)
- Incidence rises with age: 0.8 in <18 yrs to 3.2 in >60 yrs
- The leading cause of acute paralytic disease in Western countries after polio eradication
Pathophysiology
The injury is triggered by a preceding infection (in ~2/3 of cases), which provokes generation of microbe-specific T cells and antibodies that cross-react with antigens in the nerve sheath (molecular mimicry):
- Both T cell-mediated and antibody-mediated responses are involved; T cells are thought to play the dominant role
- Injury is most extensive at nerve roots and proximal nerve segments
- Pathology: multifocal inflammatory demyelination of spinal roots and peripheral nerves, with mononuclear cell infiltrates rich in macrophages
- Motor conduction blocks and reduced conduction velocities confirm widespread demyelination on NCS
Common triggers:
- Campylobacter jejuni (most common bacterial trigger)
- Epstein-Barr virus (EBV)
- Cytomegalovirus (CMV)
- HIV
- Zika virus
- SARS-CoV-2
- Vaccinations, immune checkpoint inhibitors (non-infectious triggers)
Clinical Features
Onset: Symptoms begin 1-2 weeks after exposure, progress over days, reach nadir at 2-4 weeks, then plateau.
Classic presentation (ascending weakness):
- Symmetrical weakness beginning in the lower limbs, ascending proximally
- Hyporeflexia or areflexia (invariable feature)
- Mild sensory symptoms (paresthesias); vibration sense impairment distally
- Pain in extremities, back, or interscapular area in ~70% of patients
- Severity ranges from mild gait difficulty to nearly total quadriplegia
Cranial nerve involvement (45-75% of cases):
- Bilateral facial paresis in at least 50%
- Less common: extraocular muscle involvement, lower cranial nerve palsy, facial myokymia
Respiratory failure:
- Occurs in 20-30% of cases; 9-30% require mechanical ventilation
- Mortality with mechanical ventilation is ~14.3% vs. <3% overall
Autonomic dysfunction (65% of hospitalized patients):
- Orthostatic hypotension, urinary retention, GI atony
- Episodic hypertension, sinus tachycardia, arrhythmias
- Bradycardia, heart block, asystole (vagal spells - can be triggered by tracheal suctioning)
Diagnostic Criteria
Required Features:
- Progressive bilateral weakness of upper and lower limbs
- Areflexia or hyporeflexia in the weak limbs
Supportive Clinical Features:
- Progression over days to 4 weeks
- Relative symmetry
- Mild sensory symptoms
- Bifacial palsies
- Autonomic dysfunction
- Absence of fever at onset
- Recovery beginning 2-4 weeks after progression ceases
Laboratory/Investigations:
- CSF: Albuminocytological dissociation - elevated protein with <10 cells/µL (cytoalbuminologic dissociation)
- Nerve conduction studies (NCS): Conduction slowing or block, prolonged distal latencies, absent/prolonged F-waves, indicating demyelination
- ECG (autonomic complications)
- Antibody titers (anti-GM1 = worse prognosis in AMAN)
- Screening for causative pathogens
Respiratory Monitoring
Ventilatory failure is the main reason for ICU admission. Key thresholds ("20-15-30 Rule"):
| Parameter | Threshold |
|---|---|
| Forced Vital Capacity (FVC) | <20 mL/kg - requires close monitoring |
| FVC | <15 mL/kg - probable intubation needed |
| Maximal Inspiratory Pressure (MIP) | <-30 cm H₂O - worrisome |
- The Erasmus GBS Respiratory Insufficiency Score (EGRIS) predicts who may need ICU admission
- Hypercarbia is a late sign - do not rely on it
- Early tracheostomy is appropriate for prolonged respiratory failure
Treatment
Immunotherapy (start as soon as possible; effective within ~2 weeks of first motor symptoms):
-
IVIg (Intravenous Immunoglobulin) - preferred first-line due to ease of administration and safety
- Dose: 2 g/kg total, given as five daily infusions
- Mechanism: Anti-idiotypic antibodies in IVIg neutralize GBS autoantibodies
-
Plasmapheresis (PLEX) - equally effective as IVIg
- Removes offending antibodies from circulation
- Combination of IVIg + PLEX is not significantly better than either alone
- Corticosteroids alone are NOT effective in GBS/AIDP
Supportive care:
- Ventilatory support (as above)
- Pain management
- DVT prophylaxis
- Autonomic monitoring and management
- Rehabilitation
Prognosis
- Most patients (who survive acute phase) recover over months to years
- ~5% have rapid progression to maximal deficit within 72 hours
- Axonal degeneration on NCS = poorer recovery
- GM1 antibody positivity = worse recovery
- Mortality: <3% overall; rises to ~14.3% with mechanical ventilation
- Pain may persist for >1 year in a third of patients
- Mortality was 33% before the introduction of positive-pressure ventilation; now 1-5%
AIDP vs. CIDP (Key Distinction)
| Feature | AIDP | CIDP |
|---|---|---|
| Time course | Acute, monophasic; nadir by 4 weeks | Chronic, progressive or relapsing (>2 months) |
| Treatment | IVIg or PLEX | IVIg, PLEX, or corticosteroids |
| Associations | Preceding infection | Paraproteinemias, lymphoid neoplasms, HIV |
Sources:
- Bradley and Daroff's Neurology in Clinical Practice, Chapter 106
- Harrison's Principles of Internal Medicine, 22E (2025)
- Robbins & Kumar Basic Pathology
- Miller's Anesthesia, 10e
This is a shared conversation. Sign in to Orris to start your own chat.