Neurology
A 42 year old man presents to the Emergency Department complaining of a 3 day history of progressive muscle weakness and paraesthesia which started in both feet and appears to be spreading up his legs. He is now finding it difficult to walk. On further questioning, you determine that about 2 weeks ago he had a few days illness of bloody diarrhoea following a take away from a chicken shop. Which of the following is the most likely causative pathogen?
Answer:
Guillain-Barre syndrome (GBS) is characterised by an immune-mediated attack on the myelin sheath or Schwann cells of sensory and motor nerves. This is due to cellular and humoral immune mechanisms, frequently triggered by an antecedent infection. Two-thirds of patients with GBS have had infections in the 6 weeks before symptom onset, most commonly upper respiratory tract infection or gastroenteritis. The most commonly identified infectious triggers include C jejuni (in 13% to 39% of cases), cytomegalovirus (CMV) (5% to 22%), Epstein-Barr virus (1% to 13%), and Mycoplasma pneumoniae (5%).Guillain-Barre Syndrome
Neurology
Last Updated: 8th September 2021
Guillain-Barre syndrome (GBS) is an acute inflammatory neuropathy. It is a clinically defined syndrome characterised by motor difficulty, absence of deep tendon reflexes, paraesthesias without objective sensory loss, and increased cerebrospinal fluid albumin with absence of cellular reaction (albuminocytological dissociation). Acute inflammatory demyelinating polyradiculoneuropathy (AIDP) is the most commonly encountered variant.
Pathophysiology
Guillain-Barre syndrome (GBS) is characterised by an immune-mediated attack on the myelin sheath or Schwann cells of sensory and motor nerves. This is due to cellular and humoral immune mechanisms, frequently triggered by an antecedent infection. Two-thirds of patients with GBS have had infections in the 6 weeks before symptom onset, most commonly upper respiratory tract infection or gastroenteritis. The most commonly identified infectious triggers include C jejuni (in 13% to 39% of cases), cytomegalovirus (CMV) (5% to 22%), Epstein-Barr virus (1% to 13%), and Mycoplasma pneumoniae (5%).
Clinical features
Diagnosis is made by pattern recognition.
- The classic presentation is a progressive symmetrical muscle weakness affecting lower extremities before upper extremities, and proximal muscles before distal muscles, accompanied by paraesthesias in the feet and hands. The paralysis is typically flaccid with areflexia and progresses acutely over days, with 73% reaching a lowest point within 1 week and 98% by 4 weeks.
- About 89% of patients experience pain, which typically begins in the back and legs. It occurs at onset and during disease course.
- Facial, oropharyngeal, and extraocular weakness may also occur. These cranial nerve deficits often occur after trunk and limb involvement but precede them in 15% of cases.
- Mild dysautonomia occurs in 70% and causes sinus tachycardia, labile blood pressure, postural hypotension, urinary retention, ileus, and very rarely life-threatening cardiac arrhythmia.
- Up to 30% of patients will develop respiratory muscle weakness requiring mechanical ventilation.
- The progressive phase is followed by a plateau phase of persistent, unchanging symptoms lasting a variable duration before recovery begins.
Investigations
- Nerve conduction studies
- Interpretation of electrophysiology can be difficult, especially in early stages. However, clear electrophysiological evidence of demyelinating polyneuropathy is useful for outcome prediction.
- Lumbar puncture
- Classic finding is elevated cerebrospinal fluid (CSF) protein with normal cell count (albuminocytological dissociation). Occurs in up to 90% of patients at week 1 after symptom onset.
- LFTs
- Hepatic aminotransferases may be elevated during the first few days, and often rapidly normalise by 1 to 2 weeks. Elevation of hepatic enzymes is associated with more severe disease.
- Spirometry
- Should be carried out at 6-hour intervals initially at the bedside.
- Antiganglioside antibody
- Presence of subtype-specific antiganglioside antibodies can differentiate between subtypes and may be useful when the diagnosis remains unclear despite clinical examination, cerebrospinal fluid analysis, and electrodiagnostic tests.
Management
A multidisciplinary approach to the acute phase combining supportive and disease-modifying therapy (with plasma exchange or high-dose intravenous immunoglobulin [IVIG]) is required.
Supportive management includes:
- Respiratory management
- Respiratory failure is common, and up to 30% of patients need ventilatory support or airway protection.
- Risk factors for progression to mechanical ventilation include rapid disease progression, bulbar dysfunction, bilateral facial nerve weakness, and dysautonomia.
- Pulse oximetry and arterial blood gases should not be relied on, as hypoxia or hypercapnia is a late sign and patients will decompensate very quickly.
- Bedside spirometry should be performed every 6 hours initially. Intensive care unit monitoring and elective intubation should be considered if:
- vital capacity is <20 mL/kg (odds ratio 15.0)
- maximal inspiratory pressure worse than -30 cmH₂O
- maximal expiratory pressure <40 cmH₂O
- reduction of 30% or more of vital capacity, maximal inspiratory pressure, or maximal expiratory pressure from baseline
- The mean duration of ventilation is 15 to 43 days, and weaning should be guided by serial pulmonary function tests (PFTs) and assessment of strength. The need for tracheostomy should be addressed from week 2 onwards, especially if PFTs do not show improvement.
- Cardiovascular management
- Haemodynamic monitoring of pulse and blood pressure (BP) should be started on admission. Telemetry is prudent, especially if there is evidence of dysautonomia. If dysautonomia is present, continuous cardiac monitoring and placement of a Foley catheter should be initiated on admission.
- Fluid balance should be monitored carefully, because the autonomic dysfunction renders clinical determination of hydration status very difficult.
- Hypotensive episodes can be managed with fluid boluses. If BP is very labile, intra-arterial BP monitoring should be initiated.
- Hypertensive episodes should be treated with short-acting agents (e.g., labetalol, esmolol, nitroprusside) to prevent abrupt hypotension.
- DVT prophylaxis
- Immobility and hypercoagulability from treatments such as IVIG can increase the risk of DVT in these patients.
- Subcutaneous heparin or enoxaparin and support stockings are recommended for non-ambulatory patients until they are able to walk independently.
- Pain management
- Gabapentin or carbamazepine are generally recommended in the ICU in the acute phase.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
