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An arterial blood may be normal in Guillain-Barré Syndrome, with hypoxia or hypercapnoea being a late sign of impending neuromuscular respiratory failure. Spirometry is recommended as a more accurate reflection of a patients requirement for respiratory support
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Arterial blood gas (ABG)
QuestionChoice
In the absence of signs and symptoms of pulmonary embolism, CTPA is unlikely to be of value in this case. A normal CTPA does not preclude the need for intubation in Guillain-Barré Syndrome
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CT pulmonary angiogram (CTPA)
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Whilst a chest x-ray would rule out other causes of breathlessness, this patient is presumed to have Guillain-Barré Syndrome, and a chest x-ray is likely to be normal, and would not help to predict the need for intubation
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Chest x-ray
QuestionChoice
A lumbar puncture in Guillain-Barré Syndrome typically shows an elevated cerebrospinal fluid (CSF) protein with a normal cell count. LP findings do not correlate with severity of illness or need for intubation
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Lumbar puncture (LP)
QuestionChoice
This patient has Guillain-Barré Syndrome (GBS), characterised by the preceding gastrointestinal illness and the pattern of bilateral ascending weakness. Bedside spirometry, particularly forced vital capacity (FVC) has a significant correlation with the risk of respiratory failure and need for intubation. If the FVC < 20mL/Kg, the patient likely needs intensive care, and if <15mL/Kg, likely requires intubation
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Bedside spirometry
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My dude you feel like shit? Here blow into the plastic tube for me.
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User
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Anterior Gallbladder
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See I knew that but I didn't know that
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Serpiginous Defibrillator
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Chapter
## Summary

Guillain-Barré Syndrome (GBS) is an acute inflammatory demyelinating polyneuropathy characterised by a rapid, progressive, ascending symmetrical weakness, often preceded by infection. Diagnosis is largely clinical but supported by specific investigations such as lumbar puncture and nerve conduction studies. Treatment is mainly supportive, with options for disease-modifying treatments like intravenous immunoglobulins (IVIG) or plasmapheresis in severe cases.

## Definition

GBS is an ascending inflammatory demyelinating polyneuropathy, typified by an acute onset of bilateral and roughly symmetric limb weakness. 

## Epidemiology

The prevalence of GBS is approximately 1-2 cases per 100,000 worldwide.

## Aetiology

GBS typically occurs 1-3 weeks following an infection, with common culprits being Campylobacter, mycoplasma, and Epstein-Barr Virus (EBV). 

40% of cases, however, are idiopathic. 

Other potential triggers include infections such as CMV, HIV, Hepatitis A, or following certain vaccinations such as for tetanus, rabies, or swine flu.

## Signs and symptoms

Neurological decline often progresses over days to weeks.

Clinical features of GBS include:

- Progressive ascending symmetrical limb weakness (usually starting with the lower limbs)
- Lower back pain due to radiculopathy
- Paraesthesia, often preceding motor symptoms
- Potential respiratory muscle involvement in severe cases
- Potential cranial nerve involvement leading to diplopia, facial droop
- **Lower motor neurone** signs in the lower limbs: hypotonia, flaccid paralysis, areflexia
- Cranial nerve signs: ophthalmoplegia, lower motor neurone facial nerve palsy, bulbar palsy
- Potential autonomic dysfunction (e.g., arrhythmia, labile blood pressure)

## Variants

Several variants of GBS exist, each presenting with unique characteristics:

- Paraparetic variant
  - Primarily affects the lower limbs

- Miller-Fisher syndrome
  - Presents with ataxia, ophthalmoplegia, and areflexia
  - Associated with **anti-GQ1B antibodies**

- Pure motor variant
  - Ascending weakness without sensory involvement

- Bilateral facial palsy with paraesthesias
  - Affects the cranial nerves

- Pharyngeal-brachial-cervical weakness
  - Results in weakness of the upper limbs
  - Associated with **anti- GT1a antibodies**
- Bickerstaff's Brainstem Encephalitis
  - Presents with encephalitis, ophthalmoplegia, and ataxia

It's worth noting that these variants rarely present purely as described, and there's often overlap in clinical presentation.


## Differential diagnosis

- Vascular: occasionally, brainstem strokes may present similarly
- Infective/Inflammatory: 
  - Polio: asymmetrical weakness from myelitis
  - Lyme disease
  - CMV
  - HIV
  - TB
  - Transverse myelitis 
  - Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) 
  - Myasthenia gravis
- Traumatic/Structural:
  - Spinal cord compression
- Metabolic:
  - Porphyrias: may result in an acute neuropathy
  - Electrolyte derangements: hypokalaemia, hypophosphataemia, hypermagnesaemia
	

## Investigations

Investigations for GBS include:

- Monitoring of forced vital capacity (FVC) for respiratory muscle involvement
- Cardiac monitoring for autonomic instability
- Blood tests, including arterial blood gas (ABG)
- Serological tests: Anti-ganglioside antibodies
- Lumbar puncture: may show **albuminocytological dissociation** 
	- Increased level of protein (albumin) without a corresponding increase in white blood cells (cytology)
- Nerve conduction studies
	- May show prolongation or loss of the F wave
- Identification of the underlying cause: stool cultures, serology, CSF virology

## Management

Management of GBS is primarily supportive and includes:

- Regular monitoring of FVC
	-  Early involvement of intensive care is essential if any reduction in FVC as deterioration may be rapid
- Venous thromboembolism (VTE) prophylaxis: TEDS + LMWH
- Analgesia: NSAIDs or opiates for radiculopathy-related back pain
- Management of cardiac arrhythmias as per ALS guidelines
- Careful use of antihypertensives due to potential autonomic dysfunction
- Consideration of enteral feeding in those with unsafe swallow

Specific medical management for those with significant disability (e.g., inability to walk) include:

- Intravenous immunoglobulin (IVIG) over a 5-day course
- Plasmapheresis, which has similar efficacy to IVIG but is associated with more side effects.

## Prognosis

While GBS can be life-threatening, particularly when respiratory muscles are affected or in the presence of autonomic dysfunction, the majority of patients experience full recovery. 

However, residual fatigue and weakness can persist in some patients. Certain variants of GBS, like Miller-Fisher syndrome, generally have a good prognosis with full recovery being the norm. 

Prognostic indicators include speed of onset, severity at nadir, age and the presence of preceding diarrhoeal illness.

## References

1. Van den Berg, B., Walgaard, C., Drenthen, J., Fokke, C., Jacobs, B. C., & Van Doorn, P. A. (2014). Guillain–Barré syndrome: pathogenesis, diagnosis, treatment and prognosis. Nature Reviews Neurology, 10(8), 469-482.

2. Yuki, N., & Hartung, H. P. (2012). Guillain–Barré syndrome. New England Journal of Medicine, 366(24), 2294-2304.

3. Hughes, R. A., & Cornblath, D. R. (2005). Guillain-Barré syndrome. The Lancet, 366(9497), 1653-1666.

4. Willison, H. J., Jacobs, B. C., & Van Doorn, P. A. (2016). Guillain-Barré syndrome. The Lancet, 388(10045), 717-727.

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In Guillain-Barré Syndrome (GBS), bedside spirometry is used to assess respiratory function, detecting weakness in respiratory muscles. Reduced vital capacity and peak flow suggest the need for respiratory support or monitoring.
A 65-year-old male attends the Emergency Department complaining of progressive numbness and weakness that started in his legs and moved slowly up his body. He has recently had an episode of diarrhoea and vomiting after eating a "dodgy takeaway".

He has been transferred to the hospital's adjoining tertiary neurology centre with a presumed diagnosis of Guillain-Barré Syndrome (GBS). On arrival in the neurology ward, he appears breathless.

What is the most appropriate investigation to help predict the need for intubation?
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