GBS is an acute, inflammatory, demyelinating polyneuropathy. Key points:
It occurs when the immune system attacks the myelin sheath of the peripheral nerves. This is thought to develop because the infective trigger provided an antigen that was similar to ‘antigens’ of the patient’s myelin. This results in an immune response developing. Activated macrophages destroy the myelin sheath in patches, resulting in impaired neuronal conduction.
Paraesthesia, areflexia, pain
Can involve resp muscles
The presentation is variable. Weakness and sensory disturbance are usually the presenting features.
Weakness is progressive and described as ascending, starting in the lower limbs and progressing upwards. The exact presentation of this may vary depending on the speed e.g. gradually increasing difficulty in walking. Cranial nerve involvement is common, resulting in disturbances of speech and swallowing, and visual disturbance from ophthalmoplegia. Respiratory muscle involvement can lead to respiratory failure. The weakness is flaccid and areflexic. Muscle wasting will often occur after a few weeks. Weakness will often begin within 3 weeks of the triggering illness and reach peak severity after a further 2 weeks.
Sensory involvement also commonly presents in an ascending pattern. The sensory disturbance can be numbness, paresthesia or pain. The pain is more common in the legs and back.
Autonomic dysfunction is common. It may include:
Acute inflammatory demyelinating polyradiculoneuropathy (AIDP) is the most common and the form described here.
Acute motor axonal neuropathy (AMAN) is another form. It is more common in Japan and China and in younger patients. The pathophysiology and resulting symptoms are different. Here antibodies bind to ganglioside antigens on the axon membrane itself (GM1 GD1a), resulting in selective motor nerve involvement.
Miller Fisher Syndrome (MFS) is quite a different variant. The key features are:
There is limb weakness in 25% of patients as well. It is associated with autoantibodies against the ganglioside GQ1b.
Acute motor and sensory axonal neuropathy (AMSAN) is another variant. The pathophysiology is similar to AMAN bit there is also sensory nerve involvement. It can be more severe with slower and incomplete recovery.
A chronic form of the disease, chronic inflammatory demyelinating polyneuropathy (CIDP) is also described.
There is often a potential trigger for GBS in the recent history (about ⅔ of patients), particularly:
Resp tract infection
Pathogens that have been particularly linked include:
There have been some links to vaccinations.
This will be directed at identifying other potential diagnoses, and searching for evidence of GBS as the diagnosis.
Electrolytes - Calcium, potassium
SIADH may occur in some patients
ESR/CRP - may be raised
Serology - EBV, HSV, CMV, HIV
Raised protein in 90% (may be delayed)
Normal WBC and glucose
Nerve Conduction studies
Pattern primarily of demyelination
May vary depending on type of GBS (and thus aid differentiation)
This will generally be divided into specific and supportive treatment.
Specific This comprises of immunomodulation:
Intravenous immunoglobulin (IVIg) therapy
IVIg is an effective treatment for GBS. It involves IV administration of pooled donor IgG, which blocks the patient’s autoimmune process. It is most effective if administered within the first 2 weeks. In general it is easier to administer than plasmapheresis. A dose of 0.4g/kg is given IV for 5 doses over 5 days.
Plasmapheresis involves removing the patients blood and applying a filtering process, replacing the plasma fraction with FFP or HAS (which may be better). Therefore, the relevant autoantibodies are removed. It is also an effective treatment, though most effective if undertaken within the first week of the disease. The general course will be replacement of 1-2 times the plasma volume, 4 times over 1-2 weeks.
Steroids are no longer used as part of treatment due to lack of benefit. There is no benefit from combining plasmapheresis or IVIg. There can be some treatment related fluctuations that occur following successful treatment where there is a deterioration - repeated IVIg may be indicated.
Supportive This aims to be alert to and minimise the impact of the disease on the patient. MDT input is essential.
Respiratory support is needed in around 30% of patients. Deterioration can be rapid and needs observation to detect. Measurement of respiratory parameters can give useful, objective information e.g. changes in vital capacity, ABGs. Features that are suggestive of a need for respiratory support include:
Vital capacity < 1L (15ml/kg)
Bulbar involvement impairing airway safety
ABG evidence of respiratory failure
Inability to lift head
Respiratory support may need to be prolonged (several weeks) although there is quite a degree of variation. Consideration should be given to early tracheostomy.
Cardiovascular support may be needed due to autonomic dysfunction. This may simply be a case of appropriate observation. Abnormalities include:
Sinus tachycardia (most common)
Conduction disturbances e.g. blocks
Instability can be particularly common at induction of anaesthesia (suxamethonium should probably be avoided at all stages).
Pain can be a common problem in GBS. Escalation up the analgesic ladder is appropriate but neuropathic agents e.g. gabapentin, may be needed. There is a high incidence of depression in GBS.
Feeding may need to be supported in patients with impaired swallowing or requiring respiratory support. Autonomic dysfunction may result in ileus and benefit from prokinetics.
Epidemiology & Prognosis
The incidence is 1-2 per 100,000. It is more common in males. The incidence is bimodal with younger (15-35) and older (50-75) peaks.
Recovery is often the case but may be prolonged. An average time until return to walking is 3 months. Neurological problems persist in 20% and can be severe. Patients are at risk of the complications of critical care and so need careful attention paid to mitigating these risks. Poor prognostic features include: