What are the diagnostic tests and treatments for Multiple Sclerosis (MS) and Guillain-Barre Syndrome (GBS)?

Diagnostic Testing for Multiple Sclerosis and Guillain-Barré Syndrome

Guillain-Barré Syndrome (GBS) Diagnostic Workup

The diagnosis of GBS is primarily clinical, requiring progressive bilateral weakness with absent or decreased reflexes, supported by CSF examination showing elevated protein with normal cell count (albumino-cytological dissociation) and electrodiagnostic studies demonstrating sensorimotor polyradiculoneuropathy. 1

Essential Clinical Features Required for Diagnosis

• Progressive bilateral weakness of arms and legs (may initially involve only legs) 1
• Absent or decreased deep tendon reflexes in affected limbs at some point during clinical course 1
• Progressive phase lasting from days to 4 weeks (usually <2 weeks) 1
• Relative symmetry of symptoms and signs 1

Cerebrospinal Fluid (CSF) Analysis

Perform lumbar puncture during initial evaluation to identify albumino-cytological dissociation (elevated protein with normal cell count), which is the classic finding in GBS 1, 2. However, protein levels are normal in 30-50% of patients in the first week and 10-30% in the second week, so normal CSF protein does not rule out GBS 1, 2.

Critical caveat: Marked pleocytosis (>50 cells/μl) suggests alternative diagnoses such as leptomeningeal malignancy or infectious/inflammatory diseases of the spinal cord or nerve roots 1. Mild pleocytosis (10-50 cells/μl), though compatible with GBS, should prompt consideration of infectious causes of polyradiculitis 1.

Electrodiagnostic Studies (Nerve Conduction Studies and EMG)

Perform nerve conduction studies and EMG to support the diagnosis, particularly in atypical presentations 1, 2. These studies typically reveal:

• Reduced conduction velocities 1, 2
• Reduced sensory and motor evoked amplitudes 1
• Abnormal temporal dispersion and/or partial motor conduction blocks 1
• "Sural sparing pattern" (normal sural sensory nerve action potential while median and ulnar sensory nerve action potentials are abnormal or absent) 1

The H reflex is the most sensitive early test, being absent in 97% of patients within the first week 3. If initial studies are normal (which occurs when performed within 1 week of symptom onset or in patients with proximal weakness), repeat electrodiagnostic studies 2-3 weeks later 1, 2.

Laboratory Investigations

• MRI of spine with and without contrast to rule out compressive lesions and evaluate for nerve root enhancement/thickening 1, 2
• Screen for reversible neuropathy causes: HbA1c, vitamin B12, folate, TSH, HIV 1, 2
• Serum protein electrophoresis and vasculitic/autoimmune screen 1
• Serum antiganglioside antibody testing (limited diagnostic value in typical GBS, but anti-GQ1b antibodies found in up to 90% of Miller Fisher syndrome cases) 1, 2

Respiratory Monitoring

All grades of GBS warrant immediate workup given potential for respiratory compromise 1. Monitor with:

• Pulmonary function testing (negative inspiratory force/vital capacity) 2
• Frequent neurological checks 1, 2
• Assessment for breathlessness at rest, inability to count to 15 in single breath, use of accessory respiratory muscles 2

Multiple Sclerosis (MS) Diagnostic Workup

While the provided evidence focuses primarily on GBS, the following applies to MS based on general medical knowledge and the limited evidence provided:

Neuroimaging

• MRI of brain with and without contrast is the primary diagnostic tool
• Look for demyelinating lesions disseminated in time and space
• MRI of spine may be indicated for suspected spinal cord involvement

Cerebrospinal Fluid Analysis

• Oligoclonal bands present in CSF but not serum
• Elevated IgG index
• Mild lymphocytic pleocytosis may be present

Evoked Potentials

• Visual evoked potentials (most commonly abnormal)
• Somatosensory evoked potentials
• Brainstem auditory evoked potentials

Key Diagnostic Pitfalls to Avoid

For GBS:

• Do not wait for antibody test results before starting treatment 1
• Do not rule out GBS based on normal CSF protein in the first week 1, 2
• Do not rule out GBS based on normal electrodiagnostic studies in the first week 1
• Consider A-CIDP (acute-onset chronic inflammatory demyelinating polyradiculoneuropathy) if progression continues beyond 8 weeks, occurring in approximately 5% of patients initially diagnosed with GBS 4

Features that cast doubt on GBS diagnosis:

• Marked persistent asymmetry of weakness 1
• Bladder or bowel dysfunction at onset 1
• Fever at onset 1
• Sharp sensory level indicating spinal cord injury 1
• Hyperreflexia or clonus 1