What is the recommended management for a pediatric patient diagnosed with Acute Disseminated Encephalomyelitis (ADEM)?

ADEM Diagnosis and Management in Pediatrics

Immediate First-Line Treatment

High-dose intravenous methylprednisolone (20-30 mg/kg/day, maximum 1 g daily) for 3-5 days, followed by oral corticosteroid taper over 4-6 weeks minimum, is the recommended treatment for pediatric ADEM. 1, 2, 3, 4

Critical Initial Management Steps

Start Empirical Acyclovir Immediately

• Never delay empirical acyclovir while awaiting diagnostic confirmation, as HSV encephalitis cannot be excluded initially and requires immediate antiviral therapy 1, 2, 3
• Continue acyclovir until infectious encephalitis is definitively ruled out by CSF PCR and clinical course 1
• This dual approach (steroids + acyclovir) protects against both ADEM and infectious encephalitis until diagnosis is confirmed 1, 2

Diagnostic Confirmation Requirements

• MRI is the imaging modality of choice, revealing large confluent T2 hyperintense brain lesions, multifocal subcortical white matter abnormalities, thalamic/basal ganglia involvement, and longitudinally extensive spinal cord lesions 2, 5
• CSF analysis typically shows lymphocytic pleocytosis with elevated protein but normal glucose 2, 5
• Oligoclonal bands are typically absent or transient (unlike MS) 6
• Encephalopathy is required for diagnosis, ranging from confusion to coma, accompanied by multifocal neurologic deficits 2, 5

Treatment Algorithm by Response

Days 1-5: Initial Pulse Therapy

• Administer IV methylprednisolone 20-30 mg/kg/day (maximum 1 g/day) for 3-5 days 1, 2, 3, 4
• Continue empirical acyclovir until infectious causes excluded 1, 2
• Monitor for clinical improvement in consciousness, motor function, and other neurologic deficits 4, 7

After Day 3-5: Assess Response

If good response:

• Transition to oral corticosteroid taper over minimum 4-6 weeks 1, 2, 3, 4
• Steroid tapers shorter than 4-6 weeks lead to symptom recurrence and must be avoided 2, 3, 8
• If flaring occurs during taper, extend duration or temporarily increase dose 2

If poor response or worsening after 3-5 days:

• Add IVIG (2 g/kg divided over 2-5 days) OR plasma exchange 1, 2, 3, 4
• Critical timing consideration: Do not perform plasmapheresis immediately after IVIG, as it will remove the administered immunoglobulin 2
• Plasma exchange should be considered early in severe or life-threatening cases 1, 4

Refractory Cases (Third-Line)

• Consider rituximab or cyclophosphamide in consultation with pediatric neurology for truly refractory cases 2, 3
• Evidence for these agents is limited but may be necessary for severe, non-responsive disease 2, 4

Common Clinical Presentations to Recognize

Typical Features

• Acute hemiparesis (76% of cases), bilateral long tract signs (85%), and altered mental status (69%) are most common 6
• Ataxia, headache, and weakness are frequent presenting symptoms 7
• Behavioral changes including confusion (76%), disorientation (41%), and speech disturbances (59%) 5
• Seizures occur in approximately one-third of patients 5
• Optic neuritis (often bilateral) and myelitis (frequently longitudinally extensive) 2, 5

Temporal Pattern

• Symptoms typically develop 1-14 days after vaccination or 1 week after rash in exanthematous illness 2
• Preceding viral illness or vaccination occurs in 74% of cases 6
• Fever is usually absent at onset of neurological illness 2

Critical Pitfalls to Avoid

Never Delay Acyclovir

• HSV encephalitis requires immediate treatment and cannot be clinically distinguished from ADEM initially 1, 2, 3
• Two negative CSF PCRs for HSV make HSV encephalitis very unlikely 1

Never Rush Steroid Taper

• Tapers shorter than 4-6 weeks cause relapse 2, 3, 8
• Treatment with methylprednisolone tapering over more than 3 weeks is associated with lower relapse rates 8
• Symptoms may flare during tapering, indicating steroid-dependence in some cases 2, 5

Transfer Considerations

• Patients with declining consciousness require urgent PICU assessment for airway protection, ventilatory support, and raised intracranial pressure management 1, 3
• Transfer to pediatric neurological unit should occur within 24 hours if diagnosis not established or patient fails to improve 1
• Extensive white matter changes on MRI indicate longer recovery time and worse outcomes 3

Prognosis and Follow-Up

Expected Outcomes

• 89-90% of children show monophasic course with excellent recovery (EDSS 0-2.5) 6
• 10-13% have biphasic or relapsing disease 6, 8
• Complete clinical recovery is common, but 11% may have ongoing disability (EDSS 3-6.5) 6
• Disability is most strongly related to optic nerve involvement at presentation 6

Long-Term Monitoring

• MRI lesions may persist even in asymptomatic patients; periventricular lesions disappear later than others 8
• Consider MOG antibody testing, as anti-MOG antibodies influence treatment decisions and indicate potential for relapsing course 2, 9
• In children with relapsing demyelinating events, consider chronic autoimmune CNS diseases like MS or NMO 4
• Never discharge without definite or suspected diagnosis and clear follow-up plans, as sequelae may not be immediately apparent 3