How to diagnose Guillain-Barre syndrome

Guillain-Barre syndrome (GBS) is a demyelinating disease, but rather than affecting the neurons of the central nervous system, it affects peripheral nerves. As with other demyelinating diseases, loss of nerve insulation through demyelination slows conduction through the nerves, resulting in dysfunction.

Guillain-Barre syndrome involves an inflammatory autoimmune attack of peripheral nerve myelin and often follows infection with various viruses, Mycoplasma, Campylobacter jejuni, or after immunization or surgery.

Signs and symptoms of GBS

Guillain-Barre syndrome classically presents with progressive weakness alongside a loss of reflexes that peaks within a few weeks. Fasciculations may also be seen, but are not common in patients with GBS. Because GBS develops rapidly, atrophy is not initially prominent.

Motor findings in patients with GBS are consistent with lower motor neuron lesions:

• Early muscle weakness
• Decreased muscle tone
• Atrophy
• Diminished reflexes

The syndrome can become severe with quadriplegia and respiratory insufficiency; approximately 30% of patients will require ventilatory assistance. These severe symptoms then begin to resolve to a near-total resolution. However, a proportion of the patients can be left with variable degrees of residual weakness.

Differential diagnoses for GBS

There are GBS variants and other diseases that can also cause progressive weakness. You should suspect an alternate diagnosis if your evaluation reveals any of the following:

• The patient is febrile at the onset of symptoms.
• The patient is experiencing significant sensory loss (with or without a sensory level).
• The patient is experiencing bowel or bladder dysfunction.
• The patient demonstrates asymmetrical findings.
• The patient demonstrates central nervous system findings (e.g., aphasia, hemisensory loss, or visual field deficits).
• The patient shows little improvement after four weeks.

Several other differentials should be considered in the diagnosis of Guillain-Bare syndrome:

• Polyneuropathies (including polyneuropathy of critical illness)
• Botulism
• Chronic immune demyelinating polyneuropathy
• Lead neuropathy
• Tick paralysis
• Polio
• Acquired immunodeficiency virus or human immunodeficiency virus neuropathy
• Neurotoxic fish
• Lyme Disease
• Acute myelopathy (e.g., from compression, transverse myelitis, vascular injury)
• Conversion disorder
• Neurotoxic ingestion
• Paraneoplastic syndrome
• Stroke
• Posterior fossa or foramen magnum tumor
• Toxic neuropathy (including hexacarbon syndrome)
• Acute disseminated encephalomyelitis
• Transverse myelitis
• Multiple sclerosis
• Encephalitis
• Vitamin deficiencies
• Cauda equina syndrome
• Myopathy
• Heavy metal toxicity
• Myasthenia gravis

Unfortunately, there are no definitive tests or biomarkers for GBS. It is a clinical diagnosis with the support of diagnostic studies. If you suspect GBS, perform these eight standard evaluations for your patient:

1. Obtain a good history and assess symptoms
2. Perform cognitive, cranial nerve, motor, sensory, reflex, gait, and coordination exams
3. Assess respiratory effort
4. Order blood testing
5. Perform a lumbar puncture
6. Order electromyography and nerve conduction velocity testing
7. Order magnetic resonance imaging
8. Perform a standard peripheral neuropathy battery

Step 1: Obtain a good history and assess symptoms

If you suspect GBS in your patient, find out if they have a history of recent infection, immunization, or surgery. Keep in mind that GBS is more common in patients with lymphoma or lupus.

It is also important to ask how rapidly the symptoms progressed. In GBS, weakness generally progresses over days—not weeks or months. As well, the patient should no longer be actively infected or febrile upon presentation. If they are, they probably don’t have GBS. Look for other clues to explain their neurological dysfunctions.

Step 2: Perform cognitive, cranial nerve, motor, sensory, reflex, gait, and coordination exams

In GBS, there are five expected findings from cognitive, cranial nerve, motor, sensory, reflex, gait, and coordination exams:

1. Proximal weakness
2. Symmetrical weakness
3. Facial weakness and ophthalmoplegia
4. Areflexia or profound hyporeflexia in the major deep tendon reflexes
5. Signs of autonomic dysfunction

Weakness is often more severe proximally than distally in GBS patients (which is unusual for peripheral neuropathy). Severe peripheral neuropathies generally affect distal musculature more than proximal and take much longer to develop; these neuropathies are also associated with definitive muscular atrophy.

Typically, weakness in GBS is relatively symmetrical. Cranial nerve involvement is not unusual, so look for facial weakness and ophthalmoplegia.

As well, look for areflexia or profound hyporeflexia in the major deep tendon reflexes, such as the biceps, triceps, patellar, and Achilles tendons. The lower extremities may be more affected than the upper extremities. Autonomic dysfunction, such as tachycardia, postural hypotension, and other vasomotor symptoms are also not uncommon.

Cognitive function is typically spared in patients with GBS. Sensory loss is unusual, but the patients may feel tingling or other non-descript feelings in the torso and limbs. However, an actual sensory exam should be relatively normal.

Make sure to perform pinprick, light touch, and proprioception exams, and look for a sensory level. If there are definitive sensory findings (particularly at a sensory level), suspect a spinal cord pathology.

Step 3: Assess respiratory effort

During your evaluation, always remember that patients with GBS are at risk of pulmonary failure. When evaluating a patient for suspected GBS, assess respiratory effort early, and consider early formal pulmonary function tests. Be ready to intubate your patient.

Step 4: Order blood testing

Order a complete blood count (CBC) and a metabolic profile. These tests should be negative in GBS, but may implicate other differential diseases.

Also order liver function, creatine phosphokinase, and erythrocyte sedimentation rate (ESR) tests. These are generally negative in GBS, but will help rule out other peripheral neuropathies.

Step 5: Perform a lumbar puncture

Perform a lumbar puncture and look for abnormally elevated protein (greater than 55 g / L) with no elevation in the white blood cell count of the cerebrospinal fluid (CSF); this is known as albuminocytologic dissociation. Although not diagnostic, this finding strongly supports the diagnosis of GBS.

Step 6: Order electromyography and nerve conduction velocity testing

Consider an electromyography (EMG) and nerve conduction velocity (NCV) evaluation to look for evidence of demyelination.

Remember, normal EMG and NCV studies do not rule out the diagnosis of GBS. EMG findings will only be positive if obtained several weeks after the disease onset. Nerve conduction velocity findings will show up earlier and are common in GBS.

Step 7: Order magnetic resonance imaging

Magnetic resonance imaging (MRI) of the spine has been used to rule out other pathologies that may be causing myelopathy, or cauda equina syndrome. With contrast, enhancement of the cauda equina is common in patients with GBS. But, since MRI is not definitively diagnostic, it is generally not ordered.

Step 8: Perform a standard peripheral neuropathy battery

If the diagnosis is not clear, order a standard peripheral neuropathy battery that includes the following measures:

• Thyroid function tests
• Serum protein electrophoresis
• Serum glucose
• Glucose tolerance test
• HbA1c
• Antinuclear antibody
• Extractable nuclear antigens
• Vitamin B12
• Folate
• Vitamin E
• Cryoglobulins
• Hepatitis profile
• Anti-MAG (myelin-associated glycoprotein) antibodies

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