Neurology · Year 3 · from Neurology

Case 3: Acute Disseminated Encephalomyelitis (ADEM)

Patient Demographics

• Age: 8 years
• Sex: Male
• Occupation: 3rd grade student

Chief Complaint

Mother: "He had a cold last week, now he's confused and can't walk."

History of Present Illness

The patient had a viral upper respiratory infection 2 weeks ago with fever, cough, and runny nose, which resolved. Four days ago, he developed headache and low-grade fever. His mother noticed he became increasingly confused - not recognizing family members and speaking incoherently. He became progressively weaker and ataxic, unable to walk by day 3. He has been more drowsy than usual. No prior neurological history. Immunizations are up to date (no recent vaccines). No travel or tick exposure.

Neurological Examination Findings

Mental Status:

• Drowsy, arousable to voice
• Oriented to name only
• Confused, inattentive
• Encephalopathy present (required for ADEM diagnosis)

Cranial Nerves:

• Pupils equal, reactive
• Bilateral CN VI palsy (abducens - sign of increased ICP)
• Fundoscopy: Mild bilateral papilledema
• Facial weakness (bilateral, suggesting brainstem involvement)

Motor Examination:

• Upper extremities: 4/5 bilateral
• Lower extremities: 3/5 bilateral
• Hypotonic

Sensory Examination:

• Decreased sensation to pinprick below T6

Reflexes:

• Upper extremities: 3+ bilateral
• Lower extremities: 3+ bilateral
• Bilateral Babinski positive

Coordination:

• Finger-to-nose: Dysmetria bilaterally
• Unable to assess gait (cannot stand)

ADEM vs First Attack of MS

Neuro Workup

• MRI Brain:
• Bilateral, asymmetric, large, poorly-demarcated T2 hyperintensities
• Involvement of subcortical white matter, deep gray matter (thalami, basal ganglia)
• Some lesions enhance with gadolinium
• No periventricular Dawson's fingers pattern
• MRI Spine:
• Long segment thoracic cord T2 hyperintensity
• LP:
• Opening pressure: 28 cm H2O (elevated)
• WBC: 120 (lymphocytic pleocytosis)
• Protein: 85 (elevated)
• Glucose: Normal
• Oligoclonal bands: Absent (present in only 10% of ADEM)
• MOG antibody (serum): Positive
• AQP4 antibody: Negative
• EEG: Diffuse slowing consistent with encephalopathy, no seizures
• Labs: Respiratory viral panel positive for rhinovirus

Diagnosis

Acute Disseminated Encephalomyelitis (ADEM) - MOG antibody-associated

• Post-infectious (following viral URI)
• Meets diagnostic criteria: Encephalopathy + multifocal CNS demyelination + supportive MRI

Management

Acute Treatment:

1. IV methylprednisolone 30 mg/kg/day (max 1 g) for 5 days

• High-dose steroids are first-line

1. If no improvement: IVIG 2 g/kg divided over 2-5 days
2. If still refractory: Plasmapheresis

Supportive Care:

1. ICU monitoring given encephalopathy and signs of increased ICP
2. Seizure precautions (ADEM can present with seizures)
3. Fever management
4. DVT prophylaxis (mechanical)
5. Physical therapy early mobilization

Monitoring for MS:

1. ADEM is usually monophasic, but some children develop MS
2. Follow-up MRI at 3-6 months
3. If new lesions or clinical relapse: Consider MS diagnosis
4. MOG-positive ADEM may have relapses (MOGAD)

Prognosis:

1. Generally good - 70-90% full recovery
2. Recovery over weeks to months
3. Cognitive deficits may persist in some
4. MOG-positive cases may relapse (need close follow-up)

Long-term Management (if MOG antibody positive):

1. No consensus on maintenance therapy after first ADEM
2. If relapse occurs: Consider IVIG, steroids, rituximab, mycophenolate
3. Regular neuro-ophthalmology follow-up (optic neuritis common in MOGAD)

Clinical Image

Image Description: Axial T2-weighted MRI of the brain showing bilateral, asymmetric, large white matter and deep gray matter lesions characteristic of acute disseminated encephalomyelitis (ADEM).

Attribution: Image from Radiopaedia.org, Case courtesy of Dr. Bruno Di Muzio. Licensed under CC BY-NC-SA 3.0. Source: https://radiopaedia.org/cases/acute-disseminated-encephalomyelitis-adem-6

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