Diagnosis: Post-Infectious Acute Cerebellitis
The diagnosis is post-infectious acute cerebellitis (Option B), not Guillain-Barré syndrome. The clinical triad of wide-based gait, impaired coordination (abnormal nose-to-finger test), and potential dysarthria following a recent upper respiratory tract infection 3 days prior is pathognomonic for cerebellar dysfunction, not peripheral nerve demyelination 1, 2.
Key Distinguishing Features
Why This is Cerebellitis:
- Cerebellar signs are dominant: Wide-based gait (ataxia), impaired finger-to-nose testing (dysmetria), and dysarthria represent the classic triad of cerebellar dysfunction 2, 3
- Temporal relationship: Symptoms appearing 3 days after URTI is consistent with post-infectious cerebellitis, which typically develops within days to 2 weeks following viral respiratory infections 1, 4, 2
- Viral URTIs are the most common trigger: Up to 80-90% of URTIs are viral, and these infections are well-documented triggers for post-infectious cerebellar inflammation 1, 2, 3
Why This is NOT Guillain-Barré Syndrome:
- Wrong symptom pattern: Guillain-Barré presents with ascending weakness, areflexia, and sensory changes—not cerebellar ataxia 3
- No weakness described: The patient has coordination problems, not motor weakness, which is the hallmark of GBS 2, 3
- Timing is atypical for GBS: GBS typically develops 1-3 weeks post-infection, not 3 days 4, 3
- Cerebellar signs exclude GBS: Dysmetria and truncal ataxia are cerebellar findings that do not occur in peripheral neuropathies like GBS 2, 5
Clinical Reasoning Algorithm
Step 1: Identify the anatomical localization
- Wide-based gait = truncal ataxia (cerebellar midline/vermis) 2
- Impaired nose-to-finger = appendicular ataxia (cerebellar hemispheres) 2
- Dysarthria in this context = ataxic dysarthria (cerebellar speech control) 5
Step 2: Establish temporal relationship
- URTI 3 days ago places this in the acute post-infectious window 1, 4
- Post-infectious cerebellitis occurs in 22-53% of systemic inflammatory conditions following respiratory infections 4
Step 3: Confirm diagnosis
- Brain MRI would show cerebellar edema and white matter changes 2, 3
- CSF analysis may show mild pleocytosis 3
- The combination of cerebellar signs + recent URTI is diagnostic 2
Critical Pitfalls to Avoid
Do not confuse ataxia with weakness: Ataxia is incoordination with preserved strength; weakness is reduced motor power. This patient has the former, pointing to cerebellum, not peripheral nerves 2, 5.
Do not wait for "classic" GBS features: If this were GBS, you would expect symmetric ascending weakness starting in the legs, absent reflexes, and possible respiratory compromise—none of which are described here 3.
Recognize that dysarthria type matters: Ataxic dysarthria (irregular, scanning speech from cerebellar dysfunction) differs from flaccid dysarthria (weak, breathy speech from lower motor neuron disease like GBS) 5.
Management Implications
Post-infectious cerebellitis typically requires supportive care and corticosteroids if severe, with most cases showing complete resolution 2. In contrast, GBS requires IVIG or plasmapheresis and ICU monitoring for respiratory failure 3. Making the correct diagnosis immediately directs appropriate treatment and avoids unnecessary interventions.