Measles CNS Invasion: Clinical Manifestations
Yes, when measles virus crosses the blood-brain barrier, it causes severe neurological symptoms including fever, altered mental status, seizures, and potentially permanent brain damage or death. 1
Acute Neurological Manifestations
When measles virus invades the central nervous system, the clinical presentation is dramatic and occurs in approximately 1 per 1,000 infected persons:
- Fever is typically the initial manifestation, often reaching ≥103°F (≥39.4°C), appearing during or shortly after the acute measles illness around 10 days post-infection 1
- Altered mental status ranging from drowsiness to coma develops as a cardinal feature of encephalitis 1, 2
- Seizures occur frequently, representing direct CNS involvement rather than simple febrile convulsions 1, 2
- Behavioral changes and confusion manifest as the encephalitic process progresses 1
- Vomiting is among the most frequent presenting symptoms alongside drowsiness 2
The CDC emphasizes that these symptoms represent true encephalitis with direct brain involvement, not merely systemic illness, and carry a case fatality rate of 1-2 per 1,000 measles cases. 1
Delayed Neurological Complications
Beyond acute encephalitis, measles virus persistence in the CNS causes devastating late complications:
Subacute Sclerosing Panencephalitis (SSPE)
SSPE is invariably fatal and appears years after the initial infection, caused by persistent mutant measles virus in the brain with a risk of 4-11 per 100,000 measles-infected individuals, particularly those infected at young ages. 1
The clinical progression follows a characteristic pattern:
- Insidious personality changes and intellectual decline progressing to dementia 1
- Myoclonic jerks with characteristic 1:1 EEG periodic complexes 1
- Motor deterioration leading to coma and death 1
Measles Inclusion Body Encephalitis (MIBE)
This occurs specifically in immunocompromised patients and represents chronic CNS infection with measles virus. 3, 4
Diagnostic Approach
When CNS involvement is suspected:
- Obtain CSF analysis for measles-specific antibody testing showing intrathecal synthesis to confirm diagnosis 1
- Perform MRI imaging as the preferred modality, which is more sensitive than CT for detecting encephalitic changes 5
- Order EEG to assess for abnormalities, which are present in most cases though nonspecific 5, 2
- Monitor for fever, altered mental status, seizures, or focal neurological signs during or shortly after measles illness 1
Critical Context: Wild-Type vs. Vaccine-Strain Risk
The risk differential is stark and clinically crucial:
- Wild-type measles encephalitis: 1 per 1,000 cases 1
- MMR vaccine-associated encephalopathy: approximately 1 per 2 million doses 1
The CDC and ACIP definitively state that MMR vaccine does not increase SSPE risk, and measles vaccination has essentially eliminated SSPE in countries with high vaccination coverage. 1
Management Priorities
Treatment is primarily supportive as no proven antiviral therapy exists for acute measles encephalitis in immunocompetent patients:
- Vitamin A supplementation: 200,000 IU orally for children over 12 months, repeated on day 2 for complicated measles 5
- Aggressive fever control with acetaminophen or ibuprofen 1
- Seizure management with standard anticonvulsant protocols 1
- Monitor for increased intracranial pressure and treat secondary bacterial infections with antibiotics 5
- Consider intravenous ribavirin for immunocompromised patients, though evidence is limited 5
Aciclovir is not indicated for measles encephalitis. 5
Prognosis
The outcomes are sobering:
- Permanent brain damage occurs in survivors of measles encephalitis 1, 6
- Death rate: 1-2 per 1,000 reported measles cases in the United States 1, 6
- SSPE is uniformly fatal once clinical manifestations appear, typically 6-8 years after initial infection 5
Before vaccine introduction in 1963, approximately 3,500 cases of measles encephalitis occurred annually in U.S. children, making this a devastating and preventable complication. 1