A 34 year old woman presented to the Emergency Department with a two day history of progressively worsening double vision, followed by ataxia and slurred speech. She reports a diarrhoeal illness eight days ago, though this has now resolved. She is normally fit and well and takes no regular medication.
Today she has noticed difficulty swallowing and feels breathless. Her respiratory rate is 28/min and SpO2 is 94% on 2L/min oxygen. Her GCS is 15/15. A CT head is performed, which is normal. A peak expiratory flow is measured, which is 300L/min.
What is the likely diagnosis?
The likely diagnosis in this case is Miller Fisher syndrome, a variant of Guillain-Barré syndrome, characterised classically by a triad of ataxia, areflexia and ophthalmoplegia.
Guillain-Barré syndrome, and its variants such as Miller Fisher, are the result of an autoimmune response, causing an acute inflammatory polyneuropathy. This autoimmune response is in reaction to a stimulus to the immune system. In this case, it is likely the result of a Campylobacter Jejuni enteritis (accounting for 25-50% of causes). Other causes include viral illnesses such as Influenza, CMV and EBV; Mycoplasma infection; and vaccinations.
Clinical features of Guillain-Barré syndrome include:
- Bilateral ascending motor weakness
- Miller Fisher variant – cranial nerve involvement and bulbar symptoms
- Respiratory failure from muscle weakness
- Autonomic dysfunction – including dysrhythmias, diarrhoea and vomiting, decreased sweating, labile blood pressure
What investigations might be helpful?
- Largely a clinical diagnosis, based on history and clinical examination.
- Guillain-Barré Disability Scale (Hughes disability score) can help stratify risk.
- Lung function tests – Forced Vital Capacity can quantify any deterioration and help inform decisions on critical care referral and requirement for intubation.
- CSF – may show elevated protein count, typically after 5-7 days of disease, or may point to alternative diagnosis.
- Blood tests – raised IgG, antiganglioside GM1 antibody, GQ1b antibody in Miller Fisher variant.
- Nerve conduction studies.
- Infection screen.
What management would be appropriate?
- Up to 25% pf patients with Guillain-Barré will develop respiratory failure. Close monitoring and proactive management are key – however, do not assume all cases are due to neuromuscular dysfunction. Other causes of respiratory failure should be excluded (or treated!).
- There is limited evidence for the use of non-invasive BiPAP or high flow nasal oxygen therapy, but a trial of either may be considered to reduce work of breathing.
- Autonomic dysfunction is a concerning sign and should prompt critical care referral for ongoing management. Fluctuations are common, so caution should be used if treating hypertension, to avoid precipitating subsequent refractory hypotension – short acting agents are advised if the hypertension must be treated.
- Caution with spirometry in cases involving facial weakness, as this weakness can affect the lip-grip on the spirometry mouth piece, causing inaccurate results.
- Specific management involves either plasma exchange or IV immunoglobulins.
- There is no evidence to suggest steroids are effective.
- Critical care admission may be prolonged, so supportive care is vitally important, including nutrition, effective analgesia, early physiotherapy, VTE prophylaxis and psychological support.
When would you consider intubation?
Overall assessment at the bedside and clinical judgement are key. No one test has been shown to reliably predict the need for intubation. However, concerning features which are associated with an increased risk of intubation include:
- Inability to effectively clear secretions or other evidence of bulbar dysfunction.
- Worsening Forced Vital Capacity – less than 15ml/kg or a rapid decline from baseline.
- Worsening respiratory failure on arterial blood gas analysis.
Autonomic instability may be exacerbated in the peri-intubation periods. Hypovolaemia is common, and resuscitation to euvolaemia may mitigate against that instability. Bradycardia may require management with atropine.
Key take home messages
- Guillain-Barré is largely a clinical diagnosis and obtaining a clear history from the patient is vital.
- Forced vital capacity is useful in monitoring respiratory function, and alongside overall clinical assessment, can help assess need for intubation.
- Autonomic dysfunction can be particularly pronounced in the peri-intubation period.
- Critical care length of stay may be prolonged and patients may need extensive supportive care from a multidisciplinary team.