emDOCs Podcast – Episode 111: Guillain-Barré Syndrome Part 1

Episode 111: Guillain-Barré Syndrome Part 1

Background:

• GBS is an immune-mediated disease affecting peripheral nerves. 
• An inciting event creates antigens that look like normal host cells or proteins, which confuses the immune system and results in antibodies that attack the myelin sheath of peripheral nerves.  
  • Infectious triggers:  upper respiratory infection or GI illness caused by Campylobacter jejuni,Haemophilus influenzae, E. coli, influenza, HIV, EBV, and COVID-19 have all been implicated.
  • Noninfectious triggers:  vaccinations, checkpoint inhibitors for cancer treatment, surgery, pregnancy, or myocardial infarctions 
• ~100,000 cases occur worldwide annually, making it the most common cause of generalized neuromuscular paralysis. 
• Most patients are 50-70 years old.

Presentation:

• Symptoms start 5 days to 6 weeks after the inciting event.
• The first symptom is a sensory change, such as paresthesias or burning pain in the distal extremities, followed by weakness that progresses proximally.
• Cranial nerve involvement occurs in over half of patients, affecting ocular, facial, or oropharyngeal muscles. 
• The Miller-Fisher syndrome is one of many GBS variants. It is characterized by ophthalmoplegia, ataxia, and areflexia, with less limb weakness.
• Often occurs in four phases:
  • Acute phase (first 2 weeks):  subtle sensory changes/paresthesias
  • Progressive phase (2-4 weeks):  weakness gets worse and spreads proximally
  • Plateau phase (4 weeks):  can last weeks to months
  • Recovery:  can take months to even years

Exam:

• The sensory exam is typically normal, with no numbness.
• Weakness is symmetric and ascending, starting in the feet. It progresses proximally and can involve the abdomen, chest wall, and diaphragm. 
• Hyporeflexia or areflexia are key exam components. ~90% of patients will have a change in their deep tendon reflexes.
• ~⅔ of patients have dysautonomia, resulting in HR and BP fluctuations.

Diagnosis:

• GBS can be a clinical diagnosis, but lab tests and imaging should be performed to rule out other causes of weakness.
• Labs:
  • BMP:  hypokalemia and hypophosphatemia can result in weakness.
  • CSF cell count and protein
    • Albuminocytologic dissociation with elevated protein (50-1,000 mg/dL) and normal cell count suggests GBS. Over half of GBS patients will not have this in the first few days of symptoms. However, after 2-3 weeks, over 80% will.
• Imaging:
  • MRI can show anterior nerve root enhancement and should be obtained of the spine regions corresponding to symptoms.
  • Electromyography is the most sensitive and specific test 1 to 2 weeks from symptoms onset. 

Who needs an LP?  

• Anyone with ascending weakness and/or a change in reflexes should be discussed with neurology, and LP should be completed.
• For patients with symmetrical distal sensory changes that have been getting worse over a week’s time, especially if there is some sort of trigger, discuss the case and the need for an LP with neurology (since LP may be negative at this early stage.)
• For patients with symptoms that have been present for over a month and that haven’t progressed, that’s probably not GBS, and LP is likely unnecessary.

How do I differentiate between GBS and other causes of weakness?

• Rate of symptoms: Symptoms progressing over days to weeks are suggestive of GBS. Faster or slower timelines are not.
• Symmetry: GBS is usually symmetric.
• Sensory involvement: GBS has mild sensory changes and occasionally pain but no severe sensory change.
• Fever: GBS does not usually have fever as symptom onset.
• CSF: Elevated protein after one week with cell count less than 50. 
• Progression: GBS generally is progressive over the first few weeks. If the motor or sensory level is stable, it suggests something other than GBS.
• Bowel/bladder dysfunction: These occur later in GBS and come with severe ascending weakness. If present at onset, it would argue against GBS.

References:

1. Madden J, Spadaro A, Koyfman A, Long B. High risk and low prevalence diseases: Guillain-Barré syndrome. Am J Emerg Med. 2024 Jan;75:90-97. Epub 2023 Oct 28. PMID: 37925758