What is Subacute Sclerosing Panencephalitis (SSPE)?
Subacute sclerosing panencephalitis (SSPE) is a rare, fatal, progressive neurological disorder caused by persistent measles virus infection of the central nervous system that typically develops years after the initial measles infection and almost invariably leads to death. 1
Disease Pathophysiology
SSPE results from chronic measles virus infection that causes encephalitis and demyelination of neurons throughout the brain, hence the term "panencephalitis." 2
The disease is caused by persistent measles virus infection, not by measles vaccination—vaccination actually prevents SSPE. 1
Measles virus remains in the CNS and can be detected by PCR and antibody testing, with viral load potentially correlating with disease progression. 3
Clinical Presentation and Stages
SSPE typically presents 7-10 years after the initial measles infection, with insidious onset of subtle personality changes and declining intellectual performance. 4
The disease progresses through four distinct stages: personality changes → mental deterioration with seizures and myoclonic jerks → motor signs → coma and death. 4, 2
Characteristic myoclonic jerks occur with a 1:1 relationship to periodic EEG complexes, which is a distinctive diagnostic feature. 5, 4
Additional manifestations include ocular pathology leading to blindness and psychiatric illnesses. 2
Diagnostic Approach
Detection of intrathecal synthesis of measles-specific antibodies in CSF is the crucial diagnostic criterion for SSPE. 4
EEG reveals well-defined periodic complexes that correspond with myoclonic jerks. 5, 4
Consider PCR testing of CSF for measles virus RNA, though antibody testing is often more reliable. 4
Look for oligoclonal bands in CSF with immunoblotting against measles virus proteins. 4
Treatment Options
Intrathecal ribavirin is the recommended treatment, though there is no established curative therapy. 5
Combination therapy with interferon alpha, inosine pranobex, and ribavirin shows the most potential for prolonging survival beyond three years. 6
Symptomatic control with antiepileptic drugs is necessary for seizure management. 2
Additional treatment modalities include interferon combined treatment, vitamin A, and ketogenic diet for disease modification. 2
Prevention
Measles vaccination is the only effective prevention strategy for SSPE and has led to near elimination of cases in countries with high vaccination coverage. 1, 5
The administration of live measles vaccine does not increase the risk for SSPE, even among persons who have previously had measles disease or received live measles vaccine. 1
Evidence indicates that children who developed SSPE after vaccination likely had unrecognized measles infection before vaccination, and the SSPE was directly related to the natural measles infection, not the vaccine. 1
Important Clinical Caveats
SSPE can present with atypical brainstem involvement in rare cases, which may lead to misdiagnosis and poor outcomes. 7
Brainstem presentations may include absence seizures and pronounced ataxia rather than typical cortical features. 7
Recent surges in SSPE cases in developed countries have been attributed to reduced vaccination coverage, aggravated by misinformation and declining immunization after the COVID-19 pandemic. 2, 8
The disease affects the brain within 9 months or less once symptoms begin, hence the term "subacute." 2