MRI Changes in Guillain-Barre Syndrome (GBS)

Overview

Key MRI Findings

1. Gadolinium Enhancement of Spinal Nerve Roots (Most Important Finding)

• Enhancement reflects breakdown of the blood-nerve barrier at sites of active inflammation and demyelination
• Preferentially involves the anterior (ventral/motor) nerve roots, though posterior roots can also enhance
• Seen as linear, smooth enhancement along the nerve roots within the thecal sac
• Most pronounced in the lumbar and sacral region

"MRI of the lumbar spine with gadolinium...may show nerve root enhancement of the cauda equina, particularly in children with GBS." - Bradley and Daroff's Neurology in Clinical Practice

"Neuroimaging with MRI discloses contrast enhancement of lumbosacral roots in both GBS and CIDP." - Bradley and Daroff's Neurology in Clinical Practice

2. Nerve Root Thickening

• T2-weighted sequences (mildly hyperintense thickened roots)
• STIR sequences

3. Spinal Cord Signal - Usually Normal

• The spinal cord parenchyma is typically normal in classical GBS (AIDP)
• In rare pediatric cases, subtle T2 hyperintensity at the conus medullaris has been reported
• The absence of cord signal change helps distinguish GBS from acute transverse myelitis and compressive myelopathy

4. Brain MRI

• Usually normal in classic GBS
• In Miller-Fisher syndrome (MFS variant - ophthalmoplegia, ataxia, areflexia), the brain is typically normal, though rare reports describe brainstem T2 changes
• In Bickerstaff brainstem encephalitis (overlapping with MFS), T2/FLAIR hyperintensity in the brainstem may be seen
• Rarely, T2 hyperintensity and swelling in the brainstem are found when there is true encephalitic involvement

5. Cranial Nerve Enhancement

Pathological Basis of MRI Findings

• Ventral roots are preferentially affected - explaining why motor deficit predominates
• Segmental demyelination with relative axon sparing (in AIDP)
• The dense inflammatory infiltrate disrupts the blood-nerve barrier - allowing gadolinium to leak into the perineurial space - producing enhancement on MRI

Summary Table: MRI Findings in GBS

Clinical Pearls

• MRI is most useful to rule out cord compression or myelopathy before lumbar puncture
• The finding of cauda equina enhancement is especially helpful in children with GBS, where the diagnosis can be uncertain
• Enhancement findings are non-specific - similar changes are seen in CIDP, sarcoidosis, lymphomatous meningitis, and CMV polyradiculitis (especially in immunocompromised patients)
• A normal MRI does not exclude GBS - the diagnosis remains clinical and electrophysiological
• The extent of nerve root enhancement does not reliably predict severity or prognosis

CSF Findings and Diagnostic Criteria in Guillain-Barre Syndrome

CSF Findings

1. Albuminocytological (Cytoalbuminologic) Dissociation - Hallmark Finding

"CSF findings are distinctive, consisting of an elevated CSF protein level (1-10 g/L) without accompanying pleocytosis." - Harrison's Principles of Internal Medicine, 22e

"Protein values as high as 500 mg/dL are found in exceptional cases of GBS and CIDP." - Adams and Victor's Principles of Neurology

2. Timing of CSF Changes

• First 48 hours: CSF may be completely normal
• End of week 1: Protein usually becomes elevated; albuminocytological dissociation seen in 50-66% of patients
• After 2 weeks: Present in >75% of patients
• Throughout illness: Up to 10% of cases never develop elevated CSF protein

"A CSF profile of albuminocytological dissociation is characteristic of this syndrome and is seen in 50%-66% of patients in the first week of symptoms and in more than 75% of patients 2 weeks after symptom onset." - Bradley and Daroff's Neurology in Clinical Practice

3. CSF Pleocytosis - When to Worry

• A transient, mild CSF pleocytosis (10-100 cells/µL) can occur in otherwise typical GBS
• Sustained pleocytosis (>50 cells/µL) should raise concern for an alternative diagnosis:
  • HIV seroconversion
  • Lyme disease (Bannwarth syndrome)
  • CMV polyradiculitis (immunocompromised patients)
  • Neurosarcoidosis
  • Leukemia/lymphoma with nerve infiltration
  • Tuberculosis or bacterial meningitis

"A CSF cell count greater than 50 WBCs/mL suggests HIV seroconversion or infections such as Lyme disease." - Goldman-Cecil Medicine

4. Why Protein Is Elevated - Pathophysiological Basis

• Inflammatory infiltration of spinal nerve roots disrupts the blood-nerve barrier at the root level
• The high lumbar protein in the face of a normal cisternal protein confirms the source is from the spinal roots
• This is why the finding is called "albuminocytological dissociation" - albumin leaks from inflamed root capillaries but no cellular inflammatory reaction enters the CSF space itself

Diagnostic Criteria

A. Asbury-Cornblath Criteria (1990) - Classic Criteria

Features REQUIRED for Diagnosis:

1. Progressive weakness of both legs and arms
2. Areflexia or hyporeflexia

Clinical Features SUPPORTIVE of Diagnosis:

• Progression over days to 4 weeks
• Relative symmetry of symptoms and signs
• Mild sensory symptoms or signs
• Bifacial palsies
• Autonomic dysfunction
• Absence of fever at onset
• Recovery beginning 2-4 weeks after progression ceases

Laboratory Features SUPPORTIVE of Diagnosis:

• Elevated CSF protein with <10 cells/µL (albuminocytological dissociation)
• Electrodiagnostic features of nerve conduction slowing or block

B. Brighton Collaboration Criteria (Sejvar et al., 2011) - Modern Criteria

Level 1 (Highest Certainty) - ALL of the following:

• Bilateral AND flaccid limb weakness
• Decreased or absent deep tendon reflexes in weak limbs
• Monophasic illness - onset to nadir 12 hours to 28 days, then plateau
• Electrophysiologic findings consistent with GBS
• Cytoalbuminologic dissociation (elevated CSF protein AND CSF WBC <50 cells/µL)
• No alternative diagnosis identified

Level 2:

• Bilateral AND flaccid limb weakness
• Decreased or absent deep tendon reflexes in weak limbs
• Monophasic illness - onset to nadir 12 hours to 28 days, then plateau
• CSF WBC <50 cells/µL (with OR without protein elevation) OR electrophysiologic findings consistent with GBS
• No alternative diagnosis identified

Level 3 (Lowest Certainty - Clinical Diagnosis Only):

• Bilateral AND flaccid limb weakness
• Decreased or absent deep tendon reflexes in weak limbs
• Monophasic illness - onset to nadir 12 hours to 28 days, then plateau
• No alternative diagnosis identified
• (No CSF or electrophysiology required)

Brighton Criteria for Miller-Fisher Syndrome (MFS)

Level 1 (All required):

• Bilateral ophthalmoparesis
• Bilateral reduced or absent tendon reflexes
• Ataxia
• Absence of limb weakness
• Monophasic illness (12h-28 days)
• Neuroalbuminologic dissociation (elevated CSF protein AND WBC <50 cells/µL)
• Normal nerve conduction OR sensory nerve involvement only
• No altered consciousness or corticospinal tract signs

Level 2:

• As above PLUS CSF WBC <50 cells/µL (protein elevation not required)

Level 3:

• Clinical triad (ophthalmoplegia + ataxia + areflexia) + no alternative diagnosis

Features that ARGUE AGAINST GBS (Red Flags)

Summary: CSF in GBS vs. Differential