What finding would support the diagnosis of a 34-year-old man with progressive lower extremity weakness, recent history of diarrhea, and absent ankle reflexes with intact sensation?

Albuminocytologic Dissociation is the Key Diagnostic Finding in Guillain-Barré Syndrome

Albuminocytologic dissociation in cerebrospinal fluid is the most supportive laboratory finding for diagnosing Guillain-Barré syndrome (GBS) in this patient with progressive lower extremity weakness following diarrhea. 1

Clinical Presentation Analysis

The patient presents with classic features of GBS:

• 34-year-old man with progressive lower extremity weakness over 2 days
• Recent history of diarrhea (2 weeks) that has resolved
• Symmetric lower extremity weakness
• Absent ankle reflexes
• Intact sensation

This presentation strongly suggests GBS, particularly the pure motor variant, which is characterized by motor weakness without sensory signs and occurs in 5-15% of GBS cases in most regions 2.

Diagnostic Findings in GBS

Cerebrospinal Fluid Analysis

• Albuminocytologic dissociation: Elevated CSF protein with normal cell count is a hallmark finding in GBS 1
• This finding may be normal in 30-50% of patients in the first week of symptoms and 10-30% in the second week 1
• CSF examination is particularly valuable when the diagnosis is less certain 3

Other Diagnostic Tests

• Electrodiagnostic studies: Show reduced conduction velocities, reduced sensory and motor evoked amplitudes, and abnormal temporal dispersion 1
• Anti-ganglioside antibodies: Limited clinical value in typical motor-sensory GBS but may be helpful in specific variants 3

Why Albuminocytologic Dissociation is the Correct Answer

Among the options provided:

1. Albuminocytologic dissociation: Characteristic CSF finding in GBS, supporting diagnosis 2, 1
2. Improvement with steroids: Incorrect - corticosteroids are not recommended as monotherapy for idiopathic GBS 1, 3
3. Increased forced vital capacity: Incorrect - GBS typically causes decreased vital capacity due to respiratory muscle weakness 1
4. Low CSF glucose: Incorrect - CSF glucose is typically normal in GBS; low glucose suggests infection 1
5. Selective enhancement of dorsal root ganglion on MRI: Incorrect - GBS typically shows enhancement of anterior nerve roots and cauda equina 4

Treatment Considerations

While not directly related to the diagnostic question, it's important to note:

• First-line treatment is intravenous immunoglobulin (IVIg) 0.4 g/kg/day for 5 consecutive days, initiated as soon as possible after diagnosis 1, 3
• Plasma exchange is an alternative to IVIg, with 12-15 L in 4-5 exchanges over 1-2 weeks 1, 3
• Corticosteroids are not recommended as monotherapy for idiopathic GBS 1, 3

Monitoring and Prognosis

• Respiratory function should be closely monitored as 15-30% of GBS patients require ventilatory support 2
• The modified Erasmus GBS outcome score (mEGOS) can help predict recovery 1, 3
• Approximately 60-80% of patients are able to walk independently 6 months after onset 1
• About 20% of patients remain unable to walk after 6 months, with mortality rates of 3-10% despite optimal treatment 1

Common Pitfalls in Diagnosis

• Waiting too long to initiate treatment - IVIg should be started as soon as possible after diagnosis
• Misdiagnosing GBS as other conditions like botulism, myasthenia gravis, or acute myelopathy 1
• Failing to consider acute-onset chronic inflammatory demyelinating polyradiculoneuropathy (A-CIDP) if progression continues after 8 weeks 1, 3