What are the focal neurological symptoms, excluding headache, suggestive of Guillain-Barré (Guillain-Barré Syndrome) syndrome in an otherwise healthy adult patient with influenza?

Focal Neurological Symptoms Suspicious for Guillain-Barré Syndrome (Excluding Headache)

Guillain-Barré syndrome (GBS) is characterized by progressive bilateral ascending weakness with areflexia, not focal neurological deficits—if you see truly focal signs like unilateral weakness, isolated cranial nerve palsies, or a clear sensory level, you should strongly reconsider the diagnosis and look for alternative causes such as stroke, spinal cord compression, or encephalitis. 1

Core Distinguishing Features of GBS

The hallmark presentation of GBS includes:

• Progressive bilateral weakness starting in the legs and ascending symmetrically over days to 4 weeks (typically less than 2 weeks) 1, 2
• Absent or reduced deep tendon reflexes bilaterally (areflexia is a required diagnostic feature) 1, 3
• Symmetrical distribution of motor deficits, not focal or unilateral patterns 1

When "Focal" Signs Actually Suggest GBS Variants

While classic GBS is not focal, certain cranial nerve and regional patterns can occur that might appear focal but are actually part of recognized GBS variants:

Cranial Nerve Involvement (Bilateral Pattern Expected)

• Bilateral facial nerve palsy occurs in approximately 50% of GBS patients and is the most common cranial nerve manifestation 1, 4
• Ophthalmoplegia with ataxia and areflexia defines Miller Fisher syndrome (5-25% of GBS cases), which can present with isolated eye movement abnormalities 1, 4
• Pharyngeal-cervical-brachial weakness (<5% of cases) affects upper body muscles without lower limb involvement 1

Critical caveat: Even when cranial nerves are involved, GBS typically shows bilateral involvement. Isolated unilateral cranial nerve palsies should prompt consideration of other diagnoses like brainstem stroke or structural lesions. 1

Regional Weakness Patterns (Still Bilateral)

• Paraparetic variant (5-10% of cases) restricts weakness to both legs but maintains bilateral symmetry 1, 5
• Pure motor variant (5-70% depending on region) presents without sensory signs but still shows bilateral motor deficits 1, 5

Red Flags That Argue AGAINST GBS

If you encounter these "focal" findings, GBS becomes much less likely and alternative diagnoses must be pursued urgently:

Spinal Cord Pathology Indicators

• Sharp sensory level at a specific dermatome suggests cord compression, not GBS 3
• Hyperreflexia, clonus, or extensor plantar responses indicate upper motor neuron pathology (cord lesion), whereas GBS causes areflexia 3
• Bladder/bowel dysfunction at onset strongly suggests cauda equina syndrome or cord compression rather than GBS 3
• Perineal sensory changes or saddle anesthesia require emergency MRI for cauda equina evaluation 3

Cerebral/Brainstem Pathology Indicators

• Unilateral weakness suggests stroke or focal brain lesion 3
• Focal neurological signs such as paresis, aphasia, choreoathetosis in the context of influenza are more consistent with encephalitis than GBS 1
• Decreased consciousness, seizures, or altered mental status point toward encephalitis/encephalopathy, not GBS 1, 6
• Impaired consciousness with ophthalmoplegia and ataxia suggests Bickerstaff brainstem encephalitis rather than typical GBS 1

Context: GBS as a Rare Complication of Influenza

In patients with influenza presenting with neurological symptoms:

• GBS is a rare manifestation of influenza infection 1, 6
• Encephalitis/encephalopathy is more common than GBS as a neurological complication of influenza, typically presenting 3 days (range 0-7 days) after respiratory symptoms with decreased consciousness and seizures 1
• Focal signs like paresis, aphasia, and cranial nerve palsies in influenza patients are more characteristic of encephalitis than GBS 1

Practical Clinical Algorithm

When evaluating a patient with influenza and neurological symptoms:

1. Check reflexes immediately: Areflexia suggests GBS; normal or hyperreflexia argues against it 3
2. Assess symmetry: Bilateral ascending weakness supports GBS; unilateral or focal deficits do not 1, 3
3. Examine for sensory level: Presence suggests cord pathology requiring emergency MRI 3
4. Evaluate consciousness: Altered mental status points toward encephalitis, not GBS 1
5. Assess respiratory function: 20% of GBS patients develop respiratory failure, which can occur rapidly 5, 3, 2

Bottom line: GBS presents with progressive bilateral symmetrical weakness and areflexia. Truly focal neurological signs—unilateral weakness, isolated cranial nerve deficits, sensory levels, or altered consciousness—should redirect your diagnostic thinking away from GBS toward stroke, cord compression, or encephalitis. 1, 3