Clinical Scenario:
A 4-year-old unimmunized boy is admitted with fever, cough, coryza, conjunctivitis, and a generalized maculopapular rash. He recovers with supportive treatment. Ten days after the onset of the rash, he develops generalized tonic-clonic seizures followed by altered consciousness. Cerebrospinal fluid examination reveals 18 lymphocytes/mm³, mildly elevated protein, and normal glucose. MRI brain shows multiple bilateral white matter lesions.
What is the most likely diagnosis?
A. Acute disseminated encephalomyelitis
B. Herpes simplex encephalitis
C. Brain abscess
D. Subacute sclerosing panencephalitis
E. Pyogenic meningitis
Correct answer & Explanation:
Correct Answer: A. Acute disseminated encephalomyelitis
Explanation: Measles / ADEM
Acute disseminated encephalomyelitis (ADEM) is an immune-mediated demyelinating disorder that occurs 2–30 days after the onset of the measles rash, most commonly within 1–2 weeks. It results from an autoimmune response against myelin rather than direct viral invasion of the central nervous system.
Typical features include:
- Recent measles infection
- Acute onset of encephalopathy
- Seizures
- Focal neurological deficits
- Multifocal white matter lesions on MRI
CSF usually shows mild lymphocytic pleocytosis with mildly elevated protein and normal glucose.
Why the other options are incorrect
A. Acute disseminated encephalomyelitis
Correct. The delayed onset after measles, encephalopathy, seizures, and multifocal white matter lesions are characteristic of ADEM.
B. Herpes simplex encephalitis
Usually presents with fever, altered consciousness, and focal seizures, but MRI typically shows temporal lobe involvement rather than multifocal white matter lesions.
C. Brain abscess
Usually presents with persistent fever, focal neurological deficits, and ring-enhancing lesions on imaging rather than diffuse demyelinating lesions.
D. Subacute sclerosing panencephalitis
Occurs several years after natural measles infection with progressive cognitive decline, behavioral changes, and myoclonus, not within days of acute measles.
E. Pyogenic meningitis
Typically causes neutrophilic CSF pleocytosis, low CSF glucose, and markedly elevated protein, which are absent in this case.
Learning Point
Neurological complications of measles include:
- Acute measles encephalitis (during the acute illness due to direct viral invasion)
- Acute disseminated encephalomyelitis (2–30 days after rash; immune-mediated)
- Measles inclusion body encephalitis (in immunocompromised patients)
- Subacute sclerosing panencephalitis (years after infection)
ADEM is treated with high-dose intravenous corticosteroids, and most children recover with timely treatment.
