Guillain-Barré syndrome: Clinical sciences

Guillain-Barré syndrome is an acute, monophasic, immune-mediated polyradiculoneuropathy that usually follows a respiratory or gastrointestinal infection. This condition occurs when immune cells inappropriately attack the peripheral nerves and nerve roots, eventually causing demyelination or axonal injury.

Some common pathogens associated with Guillain-Barré syndrome include bacteria like Campylobacter jejuni and Mycoplasma pneumoniae, as well as viruses, such as cytomegalovirus, Epstein-Barr virus, and HIV. Guillain-Barré syndrome is the most common cause of generalized paresis and can also result in sensory loss, autonomic dysfunction, and respiratory failure.

If your patient presents with a chief concern suggesting Guillain-Barré syndrome, first perform an ABCDE assessment to determine if they are unstable or stable. If unstable, stabilize their airway, breathing, and circulation. In some cases, you might need to intubate your patient and provide mechanical ventilation. Next, obtain IV access and consider IV fluids. Finally, put your patient on continuous vital sign monitoring, including blood pressure, heart rate, and pulse oximetry, as well as cardiac telemetry.

Now, here’s a clinical pearl to keep in mind! Because individuals with Guillain-Barré syndrome may present with diaphragm weakness and can quickly progress to respiratory failure, be sure to perform bedside pulmonary function testing! Results will reveal reduced vital capacity, which is the amount of air a patient can exhale after a maximum inhalation. Additionally, you will notice reduced maximal inspiratory pressure, also known as negative inspiratory force; as well as reduced maximal expiratory pressure.

To guide intubation timing in patients with neuromuscular weakness, you can apply the 20, 30, 40 rule. If vital capacity is less than 20 milliliters per kilogram, maximal inspiratory pressure is less than 30 centimeters of water, and maximal expiratory pressure is less than 40 centimeters of water, consider intubating your patient. Because oxygen saturations are often normal in these patients, and hypoxemia is a late finding, do not use PaO2 levels to guide respiratory management. Finally, these patients might present with signs of dysautonomia, including arrhythmias, labile blood pressure, and an exaggerated cardiovascular response to medications.

Okay, now, let’s go back to the ABCDE assessment and take a look at stable individuals. In this case, obtain a focused history and physical exam. The patient will report rapidly progressive tingling, numbness, and weakness that started in the legs and spread upwards over days to involve their trunk, arms, and possibly face. They might also report blurry or double vision, facial weakness, and difficulty swallowing or speaking.

Another common symptom to keep in mind is back pain. History might also reveal a recent respiratory or gastrointestinal infection, usually within the preceding one to three weeks. Finally, in some individuals, influenza vaccination might trigger an aberrant immune response and subsequent Guillain-Barré syndrome.

Now, here’s a high-yield fact! Less common pathogens associated with Guillain-Barré syndrome include Zika and SARS-CoV-2 viruses.

The physical exam will show normal body temperature and mental status. This is important because elevated body temperature is not a feature of Guillain-Barré syndrome, so if your patient is febrile, look for an alternative diagnosis!

Next, peripheral nerve damage results in bilateral, symmetric sensory loss and weakness that is usually more severe in the lower extremities than the upper extremities. Additionally, the exam will reveal decreased muscle tone and reduced or absent deep tendon reflexes. Finally, you may notice evidence of cranial nerve involvement. For example, if the patient’s immune system attacks the facial nerves, you might see bilateral facial palsies; and if it attacks the cranial nerves that innervate extraocular muscles, you might see ophthalmoparesis.

With these findings, suspect Guillain-Barré syndrome, and perform a lumbar puncture to collect and analyze the cerebrospinal fluid, which is also known as CSF. If the presentation is atypical, you should also obtain a nerve conduction study and electromyography.

If the CSF analysis reveals an elevated white blood cell count, and the nerve conduction study or NCS is normal, with abnormal electromyography or EMG showing a myopathic pattern of disease; consider alternative diagnoses.

Conditions that can mimic Guillain-Barré syndrome include active infections of the peripheral nervous system, such as viral myelitis; neuromuscular junction disorders, like botulism; and myopathies.