What is the recommended treatment for a child with an altered gait following a viral infection?

Management of Altered Gait in Children Following Viral Infection

The most critical initial step is to immediately assess for and exclude life-threatening causes—particularly acute cerebellitis, encephalitis, and anti-NMDA receptor encephalitis—while recognizing that post-infectious cerebellitis is the most common benign cause that typically requires only supportive care. 1, 2

Immediate Assessment and Risk Stratification

Red Flags Requiring Urgent Intervention

• Altered mental status, seizures, or decreased level of consciousness indicate possible encephalitis requiring immediate IV acyclovir (10-15 mg/kg three times daily) and empiric antibiotics until HSV encephalitis and bacterial meningitis are excluded 1, 3
• Severe ataxia with inability to sit or stand, nystagmus, and vomiting suggest acute cerebellitis, which can progress to hydrocephalus requiring neurosurgical intervention 1
• Unilateral lower extremity weakness or refusal to bear weight in children under 3 years, especially with behavioral changes, insomnia, or dyskinesias, should raise concern for anti-NMDA receptor encephalitis 2
• Signs of increased intracranial pressure (severe headache, vomiting, papilledema) warrant immediate neuroimaging before lumbar puncture 3

Specific Historical Features to Elicit

• Recent varicella-zoster virus (VZV) infection within the past 1-3 weeks strongly suggests post-infectious cerebellitis, which is self-limiting and does not require antiviral therapy 1, 4
• Preceding respiratory illness raises consideration for influenza, parainfluenza, or Mycoplasma pneumoniae-associated ataxia 1
• Fever, headache, and personality changes preceding gait disturbance indicate encephalitis rather than isolated cerebellitis 1, 3
• Timing of symptom onset: acute onset (hours to days) suggests infection or stroke; subacute (weeks) suggests autoimmune or metabolic causes 5

Diagnostic Approach

When to Perform Lumbar Puncture

Perform LP immediately if there is any alteration in mental status, seizures, or clinical suspicion for encephalitis, even if the child appears only mildly confused 1, 3. However, if the child has isolated ataxia with normal mental status following recent VZV infection, LP may not be necessary as this presentation is consistent with benign post-infectious cerebellitis 1.

Essential CSF Studies When LP is Indicated

• CSF PCR for HSV-1, HSV-2, VZV, and enteroviruses (accounts for 90% of viral CNS infections) 3
• Bacterial culture and Gram stain to exclude partially treated bacterial meningitis 3
• CSF lactate (levels <2 mmol/L effectively rule out bacterial disease) 3
• Cell count and differential: lymphocytic pleocytosis with low glucose does NOT exclude bacterial meningitis, as TB meningitis and partially treated bacterial meningitis present identically 3

Neuroimaging Requirements

MRI with and without contrast should be obtained in all children with altered gait following viral infection who have any of the following: altered mental status, focal neurological findings, seizures, or progressive symptoms 3, 5. Look specifically for:

• Temporal lobe enhancement (HSV encephalitis) 3
• Cerebellar swelling (acute cerebellitis with risk of hydrocephalus) 1
• Basilar meningeal enhancement (TB or fungal meningitis) 3

Treatment Algorithm

For Suspected Encephalitis (Altered Mental Status + Gait Disturbance)

Start IV acyclovir 10-15 mg/kg three times daily IMMEDIATELY, along with empiric antibiotics (ceftriaxone and vancomycin), without waiting for CSF results 1, 3. This must be initiated within 6 hours of admission, as delays beyond 48 hours significantly worsen outcomes (mortality 70% untreated vs 20-30% with treatment) 3.

• Continue acyclovir for 14-21 days if HSV is confirmed 1
• For children aged 3 months-12 years, use a minimum of 21 days due to higher relapse rates (up to 29%) 1
• Repeat LP at 14-21 days to confirm CSF is negative for HSV by PCR; if still positive, continue weekly until negative 1
• Maintain adequate hydration to prevent acyclovir-induced crystalluria and nephropathy (affects up to 20% of patients after 4 days) 1

For VZV-Associated Presentations

VZV cerebellitis does NOT require antiviral treatment as it is self-limiting 4. However, if there is confirmed VZV encephalitis (altered mental status, not just ataxia), treat with IV acyclovir 500 mg/m² every 8 hours for at least 10 days 1, 4.

For Isolated Ataxia Without Encephalopathy (Post-Infectious Cerebellitis)

Supportive care only is required for most cases 1:

• Monitor closely for signs of hydrocephalus (worsening headache, vomiting, altered consciousness) which occurs in severe cases and requires neurosurgical intervention 1
• Ensure adequate hydration and manage symptoms 4
• Reassure parents that recovery typically occurs over weeks to months 1

For Anti-NMDA Receptor Encephalitis

If gait disturbance is accompanied by behavioral changes, insomnia, dyskinesias, or decreased speech in a child under 3 years, send serum and CSF for anti-NMDA receptor antibodies and initiate immunotherapy (IV methylprednisolone and IVIG) in consultation with pediatric neurology 2.

Common Pitfalls to Avoid

• Never assume lymphocytic CSF means "just viral": TB meningitis, partially treated bacterial meningitis, and listeriosis all present with lymphocytic pleocytosis and low glucose 3
• Never delay acyclovir waiting for HSV PCR results if there is any alteration in mental status 1, 3
• Do not treat post-infectious VZV cerebellitis with acyclovir: it is self-limiting and antiviral therapy is not indicated 1, 4
• Do not miss anti-NMDA receptor encephalitis in young children: gait disturbance may be the presenting symptom before classic features develop 2
• HSV PCR can be negative early in disease course: repeat LP in 24-48 hours if initial PCR is negative and clinical suspicion remains high 3
• Normal or minimally abnormal CSF does not exclude HSV encephalitis: 5-10% of cases present this way 3

Follow-Up and Monitoring

All children hospitalized with neurologic complications of viral infections require systematic outpatient follow-up with comprehensive cognitive testing, as verbal and executive function deficits can persist months after acute illness even in patients without symptomatic complaints 6. This is essential for developing individualized education plans as children return to school 6.