Approach Considerations
The diagnosis of Guillain-Barré syndrome (GBS) is typically based on the presence of a progressive ascending weakness with areflexia.
Findings on lumbar puncture, electrodiagnostic studies, or occasionally MRI can give support for the diagnosis. However, abnormalities on these studies do not develop until days to weeks after onset of symptoms.
Nearly 2 weeks after presentation of symptoms, lumbosacral MRI can show enhancement of the nerve roots with gadolinium. This imaging study has been described to be 83% sensitive for acute GBS, with nerve root enhancement present in 95% of typical cases. [35]
Lumbar Puncture
Typically, the LP findings are suggestive of demyelination (ie, increased protein >45 mg/dL within 3 weeks of onset) without evidence of active infection (lack of CSF pleocytosis), as originally noted by Guillain, Barré, and Strohl. The CSF findings may be normal within the first 48 hours of symptoms, and occasionally the protein may not rise for a week. Usually by 10 days of symptoms, elevated CSF protein findings will be most prominent.
Most patients have fewer than 10 leukocytes per milliliter, but occasionally a mild elevation (ie, 10-50 cells/mL) is seen. Greater than 50 mononuclear cells/mL of CSF makes the diagnosis of GBS doubtful.
Electrodiagnostic Studies
Within the first week of the onset of symptoms, electrodiagnostic studies in at least two limbs reveal the following:
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A dispersed, impersistent, prolonged, or absent F response (88%)
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Increased distal latencies (75%)
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Conduction block (58%) or temporal dispersion of compound muscle action potential (CMAP)
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Reduced conduction velocity (50%) of motor and sensory nerves
Criteria for axonal forms include lack of neurophysiologic evidence of demyelination, with loss of amplitude of CMAP or sensory nerve action potentials to at least less than 80% of lower limit of normal values for age. It is typically prudent to wait at least 7-10 days for electrical studies to be informative. If electrical studies are performed too early, normal results can be falsely reassuring.
By the second week of illness, reduced compound muscle action potential (CMAP, 100%), prolonged distal latencies (92%), and reduced motor conduction velocities (84%) are prominent.
Serum Anti-Ganglioside Antibodies
In adults with GBS, serum ganglioside antibodies directed against GM1, GM1b, GD1a, and GalNAc-GDIa have been associated with Campylobacter jejuni infection, acute motor axonal neuropathy, a more severe course, and more residual neurologic deficits. The value of these studies as a prognostic marker in children is still under evaluation.
A study of 32 Japanese children diagnosed with GBS identified one or more of these antibodies in 44% and in 64% of those who met the electrodiagnostic criteria for acute motor axonal neuropathy. Those with positive antibodies had a more prolonged recovery with more residual symptoms at the end of the study. [36] However, another study in Western Europe did not find any difference in clinical course or outcome in the 4 patients with positive antibodies out of 63 total children with GBS. [37]
Other antibodies are associated with specific forms of GBS, such as GQ1b with Miller-Fisher syndrome, GD1b with acute sensory neuronopathy, and GT1a with pharyngeal-cervical-brachial variant. Assays for these antibodies may be useful in the diagnostic workup of variant clinical presentations.
Histologic Findings
Although not typically part of routine GBS diagnostic evaluation in pediatric or adult patients, the following are expected findings in GBS:
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In the demyelinating form, demyelination and mononuclear infiltration by lymphocytes and macrophages are seen in peripheral nerves
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Lymphocytes and macrophages surround endoneural vessels and cause an adjacent demyelination
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These lesions can be discrete and are scattered throughout the peripheral nervous system, although they may have a predilection for inflammation of the nerve roots.
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The conduction block and demyelination of the motor nerves result in the progressive weakness that is characteristic of this syndrome. Similarly, the involvement of the sensory nerves leads to pain and paresthesias
Many authors believe that the mechanism of the disease involves an abnormal T-cell response precipitated by a preceding infection. This is thought to give rise to an abnormal immune stimulation. A variety of specific endogenous antigens may be involved in this response, including myelin P-2 and ganglioside GM1, GQ1b, and GT1a.
In this axonal form of GBS, biopsy specimens reveal wallerian like degeneration of fibers in the ventral and dorsal nerve roots, with only minimal demyelination or lymphocytic infiltration. These axonal lesions affect both the sensory fibers and the motor fibers.
Although this form of GBS has been associated with Campylobacter infection, it appears to be a rare complication of such infection.
