GBS

Question 1

Variants of GBS and pathophysiology

Answer 1

Question 2

Clinical Features
-preceeded by
-neurological features

Answer 2

i)* Usually preceded by a viral illness
ii)* Common triggers: CMV, HSV, EBV, vaccination, Campylobacter Jejuni
iii)* Weakness- Symmetrical, progressive, Ascending weakness (starts distally and progresses proximally)
iv)* Distal muscles affected > proximal
v)* Areflexia (loss of deep tendon reflexes)
vi)* Sensation: typically intact
vii)* May have autonomic instability
viii)*Cranial Nerve Involvement
- Occurs in ~45% of cases
- Especially facial nerve (VII)
- May be bilateral facial palsy

Question 3

Autonomic Instability
Signs

Answer 3

=> Common in ventilated patients
-> Parasympathetic/sympathetic imbalance:
* Persistent tachycardia
* Postural hypotension
* Bradycardia, asystole
* Wide BP swings, sinus node arrest
* Delayed gastric emptying/Paralytic ileus
* Urinary retention
* May mimic brainstem stroke or poisoning

=> Autonomic dysfunction m/c in Demyelinating variant tather than axonal.

Question 4

Pathogenesis

Answer 4

• Autoimmune-mediated demyelination/ axonal degeneration that is :
• Triggered by infection →** macrophage activation** which leads to myelin stripping from Schwann cells and sometimes direct axonal damage

Question 5

Investigations

Answer 5

a. CSF (Lumbar Puncture)
* Classic: Albuminocytologic dissociation
(↑ protein with normal WBC)
* Seen >1 week after onset

b. Nerve Conduction Studies (NCS)
* Slowed conduction velocity
* Prolonged F-waves
* Helps differentiate:
- AIDP (demyelinating) vs
- AMAN/AMSAN (axonal variants)

c. EMG
* ↓ Motor unit recruitment
* Denervation findings in axonal variants

d. Spirometry- Particularly Vital capacity
- T/F to ICU when <20ml/kg,
- Consider intubation when < 15ml/kg

e. Neuroimaging- CT/MRI to exclude underlying organic pathology

f. Search for underlying cause
-Serological Markers(10 tests)
* Anti-ganglioside antibodies (e.g., GM2, GQ1b)
* Anti-GQ1b seen in Miller Fisher variant
* Stool for C jejuni
* Serology for viral hepatitis, atypical pneumonia

g. Other tests:
* B12, Folate, TFTs, Urinary porphyrins, Drug screen

F wave is a late muscle response to electrical stimulation of a peripheral nerve.
Assesses the function of proximal part of motor neuron(unlike M wave which is the primary muscle response

Question 6

Invx cont..
Timing and importance of NCS and CSF

Answer 6

=>Nerve conduction studies:
* Most useful around 2 weeks after symptom onset
* Helps distinguish between AIDP vs AMAN/AMSAN
* Important for prognostication

CSF- 2nd week

Question 7

Management

Answer 7

=>Specific:
I) Plasma exchange:
* 4–5 exchanges of 1–2 plasma volumes each
*
Evidence:
->Two trials have shown:
* ↓ Requirement for mechanical ventilation
* ↓ Duration of mechanical ventilation in those who require it
* ↓ Time to motor recovery
* Mortality = NOT affected
* Most effective when started within 7 days of symptom onset
* Replacement fluid = Albumin

ii) Immunoglobulin therapy (IVIg):
* As effective as plasma exchange
* Total dose = 2 g/kg IV over 2–5 days
* No benefit in combining PE + IVIg

*	Steroids:
*	High or low dose = NO value
*	May be harmful

Question 8

Management cont..

Answer 8

Monitor for
* Regular measurement of vital capacity (VC):
-VC < 15 mL/kg or
- <30% predicted → high risk of mechanical ventilation
* Pain:
* Often limb pain, may precede weakness
* Warning sign for bulbar involvement and aspiration risk

Question 9

Mx cont…

Answer 9

🔹 Indications for Mechanical Ventilation (MV)
* Bulbar involvement
* Respiratory insufficiency:
- VC < 15 mL/kg or <30% predicted
- Signs of fatigue: dyspnoea, tachypnoea, exhaustion

⸻

🔹 Airway & Ventilation
* Early tracheostomy should be considered if prolonged MV likely

⸻

🔹 Intubation Considerations
* Induction:
* Avoid suxamethonium: ↑ risk of hyperkalaemia, arrhythmias
* Prefer non-depolarising NMBDs
* Bradycardia risk: particularly with endotracheal suctioning

Question 10

Mx cont…

Answer 10

🛌 Supportive:
* VTE prophylaxis:
* Use naso-enteric anticoagulation or heparin
* DOACs can be used
* Chest and limb physiotherapy → maintain joint mobility
* Repositioning to prevent pressure area care
* Use ankle splints to avoid foot drop
* NG feeding or gastrostomy for nutrition if needed
* Change CVC to PICC for IVIg/PLEX
* Watch for nosocomial infections
* TV, radio, music, hearing aids, family input — for Delerium prevention

Question 11

📈 Recovery Timeline

Answer 11

• Nadir typically reached in ~2 weeks
• Gradual recovery follows over weeks to months
• ~70% recover to functional independence within 1 year

Question 12

⚠️ Poor Prognostic Features

Mnemonic from your notes:
MV
Age > 60
Early quadraparesis
Non-motor symptoms (e.g., dysautonomia)
Delay in treatment > 7 days

Answer 12

• Rapidly progressive disease, especially with quadriparesis
• Requiring mechanical ventilation (except in children)
• Preceding diarrhoeal illness
• Age > 60 years

MEAN- MV, Elderly, Axonal variant, significant Neurology on presentation

Question 13

🕒 Long-term Outlook

Answer 13

• Gradual improvement may continue for 12 months to 2 years

⚰️ Mortality
* Overall mortality: 5–8%
* Usual causes:
- Respiratory complications
- Autonomic instability