Neuroimmunology and Neuroinfectious Diseases
What to know
ADEM is a post-infectious, multifocal demyelinating illness in which encephalopathy is a required feature, along with white matter lesions; treat with high-dose steroids. Pediatric MS requires two episodes separated in space and time, with periventricular lesions and CSF oligoclonal bands; start disease-modifying therapy early. Neuromyelitis optica spectrum disorder (AQP4-IgG) causes longitudinally extensive transverse myelitis, bilateral optic neuritis, and area postrema syndrome; treat with rituximab rather than interferon. MOG antibody disease causes optic neuritis with disc swelling, ADEM-like presentations, and transverse myelitis, and is often monophasic.
Anti-NMDA receptor encephalitis affects young people, often girls, with psychiatric symptoms, choreoathetosis, seizures, and autonomic instability; search for an ovarian teratoma and treat with steroids, IVIG or plasma exchange, and tumor removal. Opsoclonus-myoclonus in a toddler warrants neuroblastoma screening.
Bacterial meningitis: empiric vancomycin plus a third-generation cephalosporin, with dexamethasone given with or before the first antibiotic dose. Herpes simplex encephalitis affects the temporal lobes with fever, seizures, and altered mentation; start IV acyclovir immediately because CSF PCR can be negative in the first 72 hours. Congenital infections: CMV (periventricular calcifications, hearing loss), toxoplasmosis (diffuse calcifications, chorioretinitis, hydrocephalus), Zika (microcephaly).
Traps
Do not delay antibiotics or acyclovir for a lumbar puncture in an unstable child. ADEM requires encephalopathy; without it, consider MS or another process. Bilateral facial palsy in an endemic area suggests Lyme disease.
Rule of thumb
Fever, seizures, and temporal lobe signal change equals acyclovir now; adjust later when PCR and MRI return.