Guillain-Barré syndrome
Overview
Two forms of acutely presenting neuropathies:
- Demyelinating, typically Guillain-Barré syndrome (GBS), also called acute inflammatory demyelinating polyneuropathy – importantly, because it is inflammatory, it responds to immune-modulating therapy.
- Axonal. Notably, the immune-mediated axonopathies, which are most commonly due to the primary vasculitis (eg, polyarteritis nodosa) and secondary vasculitis (eg, rheumatoid arthritis).
Guillain-Barré syndrome: acute inflammatory demyelinating polyneuropathy
Overview
- This acute polyneuropathy characteristically presents with ascending numbness and weakness and lower motor neuron findings (eg, muscle cramps).
- They occur one to two weeks following a viral respiratory or GI illness (~70% of the time).
- Campylobacter jejuni, which causes diarrhea, is the most common infectious agent (up to 40% of cases in the US are due to Campylobacter jejuni).
Presenting Pattern: Ascending Numbness/Weakness
- Low back (and/or thigh pain) is one of the most common presenting features.
- Rule out spinal cord compression or cauda equina syndrome in patients with GBS-like presentations.
- The classic pattern in GBS is symmetric, ascending numbness, followed by severe weakness (often to the point of paralysis) and diminished or absent muscle stretch reflexes over a 2 – 4 week time period.
- Note that because GBS is actually a polyradiculopathic neuropathy (meaning that both the nerve roots and nerves are affected), it can present with proximal (rather than distal) weakness. - As well, note that the large fiber sensory exam, itself, can be surprisingly preserved in patients despite the prominent numbness, which can be misleading.
- Autonomic dysfunction (gastric hypomotility, urinary retention, cardiac dysrhythmias, and blood pressure swings) can plague patients with GBS.
- There can be rapid swings in heart rate and blood pressure.
- To remember these swings, it's helpful to imagine competing vagal nerve dysfunction and surges in the sympathetic nervous system.
- Facial weakness and bilateral ptosis represent the oculobulbar palsies that occur in roughly half of GBS cases.
- In addition to this ptosis, patients can have ocular dysmotility and pupillary changes.
- Respiratory failure.
- Almost one-third of patients will develop phrenic nerve failure with resultant diaphragmatic paralysis and require mechanical ventilation.
- Even in the absence of diaphragmatic paralysis, patients can require intubation for airway protection from the bulbar dysfunction, itself.
Treatment
- Plasmapheresis or IVIG are immunotherapies.
- The argument as to which is more preferred is beyond our scope here but it should be noted that to date there is not evidence for the combined use of these treatments (although this is often done in clinical practice) and it's also important to realize that steroids have been shown to be detrimental in GBS treatment.
- Most importantly, management involves monitoring for respiratory failure with frequent respiratory measurements (forced vital capacity and negative inspiratory force).
- And monitoring for other aspects of autonomic dysfunction, as well. These include:
- Cardiovascular swings, which can occur rapidly, so we have to be careful not to overcorrect any single finding because the pendulum can rapidly swing the other way.
- Cardiac dysrhythmias, which can be so severe as to require a temporary pacemaker to avoid asystole and sudden cardiac death.
- Ileus, which is so common, that all patients require a good, proactive bowel protocol.
Laboratory Testing in Guillain-Barré Syndrome
Cerebrospinal Fluid (CSF)
- CSF testing is the primary, key helpful diagnostic test; it demonstrates a mildly elevated protein (~ 60) in the setting of a normal WBC (<50), which is called cytoalbuminologic dissociation.
- CSF protein is elevated because the attack affects proximal roots, which lie within the spinal canal, thus the proteinaceous debris increases the CSF protein level.
Electromyography(EMG)/Nerve Conduction Studies (NCS)
- EMG/NCS testing shows demyelination.
- Take note, however, that the classic changes, such as prolonged distal onset latency, reduced conduction velocity, and conduction block can take several days to a couple of weeks to appear, so we look for other changes early on such as abnormal F-waves and H reflexes.
Imaging
- Imaging of the spine (ideally, MRI) (and brain), mostly to rule-out other potential mimickers such as cord compression and carcinomatous meningitis but also to assess for evidence of cranial nerve or nerve root enhancement.
HIV
- Indicate that HIV testing is warranted in GBS because HIV seroconversion, itself, can trigger an acute inflammatory demyelinating polyneuropathy (AIDP).
Key Mimickers
- Compressive myelopathy, which can present with an acute/subacute flaccid paraparesis (spinal shock).
- Tick paralysis, which typically manifests with an abrupt (sometimes overnight) development of severe weakness (which can be asymmetric) or ataxia.
- Less commonly, it can manifest with a GBS-like ascending paralysis.
- Like GBS, tick paralysis will often cause sensory symptoms with negligible sensory exam findings and loss of muscle stretch reflexes.
- Viral myelitis, which can initially present with a flaccid paralysis.
- As well, consider that, especially in the immune-suppressed, CMV can cause an associated a radiculomyelitis that mimics GBS very closely: ascending flaccid paralysis with sensory loss. Prominent bladder and bowel incontinence is an associated finding.
- Critical illness neuropathy can mimic GBS.
- As its name suggests, it occurs in the setting of severe physiological stress.
- Acute intermittent porphyria can cause an acute attack of cranial neuropathies and quadriparesis that resembles GBS.
- It is preceded by a few days of colicky abdominal pain and behavioral disturbance.
- Distinguishing features are the marked asymmetry found in porphyria; predilection for proximal muscles; and a characteristic shield-like sensory loss over the chest.
- Screening involves 24-hour testing looking for abnormal levels of porphyrin in the urine or feces.
- Numerous medications are implicated as the cause of a porphyria attack, they include: barbiturates, sulfonamides, and certain antiepileptics (eg, valproic acid, carbamazepine, and primidone).
- Alcohol is also an important potential trigger.
- Lastly, always consider B12 deficiency myelopathy, especially given its treatability.
Guillain-Barré Syndrome Variants
- Acute motor axonal neuropathy (AMAN) (aka Chinese paralytic illness), which has a more rapid and severe progression than AIDP, and acute motor and sensory axonal neuropathy (AMSAN): both of these axonal variants are highly associated with Campylobacter Jejuni infection.
- Miller Fisher Syndrome (MFS), which consists of the triad AOA, which stands for ataxia, ophthalmoplegia, and areflexia and highlights the prominent, early oculobulbar involvement, ataxia out of proportion to weakness, and lower motor neuron findings of areflexia (rather than upper motor neuron signs found in cerebellar disorders). Anti-GQ1b IgG testing is a helpful diagnostic tool in this disorder.