CNS Infections and Inherited Conditions with Neurological Manifestations

Priority 1: Life-Threatening CNS Infections

The American College of Radiology recommends that viral or bacterial meningitis/encephalitis must be ruled out first given the classic presentation of fever with headache, vomiting, and altered neurological function (blurred vision) 1, 2
Fever with altered mental status, behavior changes, or focal neurological signs (including visual disturbances) strongly suggests encephalitis 1
Headache with nausea, vomiting, and fever represents the classical triad of CNS infection 2, 3
Visual disturbances occur from dural irritation and localized encephalitis affecting cranial nerves or visual pathways 2
The presence of nuchal rigidity, photophobia, or altered consciousness would further support this diagnosis 4
The Centers for Disease Control and Prevention recommends that empiric antimicrobial therapy should not be delayed while awaiting diagnostic confirmation, as delays worsen outcomes and increase mortality 5
Blood cultures, complete blood count, hepatic transaminases, and serum sodium should be obtained before antibiotics 5
Neuroimaging (CT or MRI) should be performed before lumbar puncture if focal neurological signs, altered consciousness, or concern for increased intracranial pressure 2, 3

A positive family history is a critical red flag that must be explored for inherited conditions that may predispose to intracranial pathology 1
Acute Disseminated Encephalomyelitis (ADEM) can present with encephalopathy, fever, and visual disturbances (optic neuritis) 6
Bilateral optic neuritis is common in ADEM 6
ADEM often follows viral infections or vaccinations 6
MRI shows large, confluent T2 brain lesions in ADEM 6
Family history may indicate inherited migraine variants with severe aura, but fever is not typical of primary migraine and should raise suspicion for secondary causes 7, 8

Brain abscess, subdural empyema, or epidural empyema can present with fever, headache, vomiting, and visual changes 3, 4
Subdural empyema in older children often results from sinusitis or otitis media extension 3
Rocky Mountain spotted fever presents with fever, headache, and can mimic meningitis 5
The American College of Radiology recommends that CT has 98% sensitivity for acute subarachnoid hemorrhage 4
Thunderclap headache with vomiting should trigger immediate CT evaluation 4

The American College of Radiology recommends that MRI with and without IV contrast is preferred for suspected CNS infection, showing superior sensitivity for encephalitis, meningeal enhancement, and abscess formation 2, 3
Non-contrast CT should be performed if MRI is unavailable or if immediate imaging is needed before lumbar puncture 3, 4
MRI sequences (T2 FLAIR, DWI, post-contrast T1) help identify vasogenic/cytotoxic edema and meningeal enhancement 2
Lymphocytic pleocytosis and elevated protein suggest viral encephalitis or ADEM 6