Guillain-Barré syndrome

Guillain-Barré syndrome
ICD-10	G61.0
ICD-9	357.0
DiseasesDB	5465
MeSH	D020275

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Priyamvada Singh, MBBS [2]

Pathophysiology

All forms of Guillain-Barré syndrome are due to an immune response to foreign antigens (such as infectious agents or vaccines) but mistargeted to host nerve tissues instead (a form of antigenic mimicry). The targets of such immune attack are thought to be gangliosides, which are complex glycosphingolipids present in large quantities on human nerve tissues, especially in the nodes of Ranvier. An example is the GM1 ganglioside, which can be affected in as many as 20-50% of cases, especially in those preceded by Campylobacter jejuni infections. Another example is the GQ1b ganglioside, which is the target in the Miller Fisher syndrome variant (see below).

The end result of such autoimmune attack on the peripheral nerves is inflammation of myelin and conduction block, leading to a muscle paralysis that may be accompanied by sensory or autonomic disturbances.

However, in mild cases, axonal function remains intact and recovery can be rapid if remyelination occurs. In severe cases, such as in the AMAN or AMSAN variants (see below), axonal degeneration occurs, and recovery depends on axonal regeneration. Recovery becomes much slower, and there is a greater degree of residual damage. Recent studies on the disease have demonstrated that approximately 80% of the patients have myelin loss, whereas, in the remaining 20%, the pathologic hallmark of the disease is indeed axon loss.

Physical Examination

The disease is characterized by weakness which affects the lower limbs first, and rapidly progresses in an ascending fashion. Patients generally notice weakness in their legs, manifesting as "rubbery legs" or legs that tend to buckle, with or without dysthesias (numbness or tingling). As the weakness progresses upward, usually over periods of hours to days, the arms and facial muscles also become affected. Frequently, the lower cranial nerves may be affected, leading to bulbar weakness, (oropharyngeal dysphagia, that is difficulty with swallowing, drooling, and/or maintaining an open airway) and respiratory difficulties. Most patients require hospitalization and about 30% require ventilatory assistance. Facial weakness is also commonly a feature, but eye movement abnormalities are not commonly seen in ascending GBS, but are a prominent feature in the Miller-Fisher variant (see below.)

Sensory loss, if present, usually takes the form of loss of proprioception (position sense) and areflexia (complete loss of deep tendon reflexes), an important feature of GBS. Loss of pain and temperature sensation is usually mild. In fact, pain is a common symptom in GBS, presenting as deep aching pain usually in the weakened muscles, which patients compare to the pain from overexercising. These pains are self-limited and should be treated with standard analgesics. Bladder dysfunction may occur in severe cases but should be transient. If severe, spinal cord disease should be suspected.

Fever should not be present, and if it is, another cause should be suspected.

In severe cases of GBS, loss of autonomic function is common, manifesting as wide fluctuations in blood pressure, orthostatic hypotension, and cardiac arrhythmias.

Classification

Although ascending paralysis is the most common form of spread in GBS, other variants also exist.

• Miller-Fisher Syndrome (MFS) is a rare variant of GBS and manifests as a descending paralysis, proceeding in the reverse order of the more common form of GBS. It usually affects the ocular muscles first and presents as ophthalmoplegia, ataxia, and areflexia. Anti-GQ1b antibodies are present in 90% of cases.
• Acute motor axonal neuropathy (AMAN), aka. Chinese Paralytic Syndrome, attacks motor nodes of Ranvier and is prevalent in China and Mexico. The disease may be seasonal and recovery can be rapid. Anti-GD1a antibodies are present. Anti-GD3 antibodies are found more frequently in AMAN
• Acute motor sensory axonal neuropathy (AMSAN) is similar to AMAN but also affects sensory nerves with severe axonal damage. Recovery is slow and often incomplete.

Diagnosis

The diagnosis of GBS usually depends on findings such as rapid development of muscle paralysis, areflexia, absence of fever, and a likely inciting event. CSF and ECD is used almost every time to verify symptoms, but because of the acute nature of the disease, they may not become abnormal until after the first week of onset of signs and symptoms.

• CSF - typical CSF findings include an elevated protein level (100 - 1000 mg/dL) without an accompanying pleocytosis (increased cell count). A sustained pleocytosis may indicate an alternative diagnosis such as infection.

The diagnosis is confirmed by the presence of Albuminocytological dissociation in the CSF

• Electrodiagnostics - electromyography (EMG) and nerve conduction study (NCS) may show prolonged distal latencies, conduction slowing, conduction block, and temporal dispersion of compound action potential in demyelinating cases. In primary axonal damage, the findings include reduced amplitude of the action potentials without conduction slowing.

Diagnostic criteria

• Required
  • Progressive, relatively symmetrical weakness of 2 or more limbs due to neuropathy
  • Areflexia
  • Disease course < 4 weeks
  • Exclusion of other causes (see below)
• Supportive
  • relatively symmetric weakness accompanied by numbness and/or tingling
  • mild sensory involvement
  • facial nerve or other cranial nerve involvement
  • absence of fever
  • typical CSF findings obtained from lumbar puncture
  • electrophysiologic evidence of demyelination from electromyogram