Investigation in Suspected Guillain-Barré Syndrome
| Test | Comment |
|---|---|
| CSF analysis | CSF protein is usually elevated, but may be normal, especially early in the disease course. CSF lymphocyte count >10/mm3 is unusual, and counts >50/mm3 are ‘never’ seen in GBS, such that alternative diagnoses (haematological malignancy, HIV, Borrelia) must be strongly considered in this setting. |
| MRI spine | Mandatory if spinal cord/cauda equina compression is in the differential (see Figure 71.1). |
| Nerve conduction studies/electromyography (NCS/EMG) | Can support the diagnosis by demonstrating an acute neuropathy, and may classify into demyelinating (slowing, temporal dispersion, conduction block) or axonal (reduced amplitudes) subtypes. Electrophysiological studies do not make or break the diagnosis in isolation, however. Interpretation in the context of the clinical presentation, with expert opinion where required, is recommended. |
| Blood tests | All patients Creatinine and electrolytes (including calcium, phosphate and magnesium) (severe electrolyte disturbance may cause flaccid weakness). Liver function tests. Serum protein electrophoresis and immunoglobulin levels (to detect paraproteins and exclude IgA deficiency). Creatine kinase (to exclude rhabdomyolysis). Full blood count. Erythrocyte sedimentation rate and C-reactive protein (usually elevated in vasculitic mononeuritis multiplex, which can mimic GBS). Thyroid function tests. In selected patients Anti-ganglioside antibodies (anti-GQ1b antibodies have 90–95% sensitivity for Miller Fisher syndrome (MFS), anti-GM1 or GD1a may support diagnosis of acute motor axonal neuropathy (AMAN)). Serological tests for prodromal infections (C.jejuni, EBV, CMV, hepatitis E, Mycoplasma pneumonia (before IVIg is given)). ANA/ENA (vasculitis?). Anti-acetylcholine receptor antibodies (myasthenia gravis?). Anti-voltage gated calcium channel antibodies (Lambert-Eaton?). Thiamine/red cell transketolase (dry beriberi?). |
| Stool | Culture for Campylobacter jejuni. |
| Urine | Porphyrins/porphobilogen. |