MCQ: Fever | Rash | Neurological symptoms

Correct Answer: A. Acute disseminated encephalomyelitis

Explanation

Acute disseminated encephalomyelitis (ADEM) is an acute, immune-mediated inflammatory demyelinating disorder of the central nervous system that can occur after viral infections, including measles.

The typical onset is days to weeks after the measles infection, often within 1–2 weeks after the appearance of the rash. The neurological manifestations result primarily from an immune-mediated attack on myelin rather than direct viral invasion of the CNS.

The important clues in this case are:

• Recent measles infection
• Acute encephalopathy
• Seizures
• Multifocal neurological deficits
• Multifocal white-matter lesions on MRI

CSF may show a mild lymphocytic pleocytosis and mildly elevated protein, while glucose is usually normal. CSF findings are nonspecific and are mainly useful for excluding infectious causes of encephalopathy.

Why ADEM is correct

The combination of recent measles infection, delayed neurological deterioration, encephalopathy, seizures, and multifocal MRI abnormalities strongly supports ADEM.

MRI typically demonstrates multiple, bilateral, poorly marginated T2/FLAIR hyperintense lesions involving the cerebral white matter and may also involve the basal ganglia, brainstem, cerebellum, or spinal cord.

Why the other options are incorrect

B. Herpes simplex encephalitis — Incorrect

HSV encephalitis usually causes an acute febrile encephalopathy with seizures and focal neurological abnormalities. MRI classically shows abnormalities involving the temporal lobes and adjacent limbic structures, rather than the widespread multifocal demyelinating lesions characteristic of ADEM.

C. Brain abscess — Incorrect

A brain abscess can cause fever, seizures, headache, and focal neurological deficits. However, MRI typically demonstrates a localized ring-enhancing lesion with surrounding edema, rather than multiple poorly defined inflammatory white-matter lesions.

D. Subacute sclerosing panencephalitis — Incorrect

SSPE is a rare, progressive neurological complication of persistent measles virus infection. It usually develops years after the original measles infection, rather than shortly after the acute illness. Progressive cognitive decline, behavioral changes, myoclonus, and later neurological deterioration are characteristic.

E. Pyogenic meningitis — Incorrect

Bacterial meningitis typically produces neutrophilic CSF pleocytosis, markedly elevated protein, and reduced CSF glucose. The delayed onset after measles together with encephalopathy and multifocal MRI lesions is much more suggestive of ADEM.

Learning Point

Important neurological complications associated with measles include:

• Acute measles encephalitis — occurs during or shortly after the acute infection.
• Acute disseminated encephalomyelitis (ADEM) — an immune-mediated demyelinating complication occurring days to weeks after infection.
• Measles inclusion-body encephalitis — occurs mainly in immunocompromised individuals and has a more subacute course.
• Subacute sclerosing panencephalitis (SSPE) — develops years after measles and causes progressive neurodegeneration.

Exam Pearl

Recent measles + delayed encephalopathy + seizures/focal neurological deficits + multifocal white-matter lesions → think ADEM.

Treatment of significant ADEM generally involves high-dose intravenous corticosteroids. Children who do not respond adequately may require additional immunotherapy such as IVIG or plasma exchange, depending on the clinical situation.

Reference

Royal Children’s Hospital Melbourne. Clinical Practice Guidelines: Common Causes of Ataxia – Acute Disseminated Encephalomyelitis (ADEM).
Read the pediatric clinical guideline

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