SSPE Diagnosis and Cerebrospinal Fluid Findings

Diagnostic Criteria

• The International Encephalitis Consortium recommends measles virus testing for SSPE on CSF when white matter lesions are identified on neuroimaging, particularly in patients presenting with subacute progressive neurological deterioration, myoclonic jerks, and characteristic EEG findings 1, 2, 3
• The hallmark CSF finding in SSPE is dramatically elevated measles-specific antibodies with intrathecal synthesis, demonstrated by a CSF/serum measles antibody index (CSQrel) ≥ 1.5, with typical values ranging from 2.3 to 36.9 in confirmed cases 1, 2, 3
• SSPE may present with minimal or no CSF pleocytosis despite significant CNS pathology, and a normal CSF cell count does not rule out the diagnosis 4

Laboratory Findings

• The CSF cell count in SSPE usually shows mild lymphocytic pleocytosis or may be normal 4
• MRI may demonstrate high signal intensity lesions in subcortical white matter on T2-weighted images, supporting the diagnosis of SSPE 1, 2

CSF Findings in Very Early SSPE

Key Diagnostic CSF Findings

• The protein levels in the CSF of patients with SSPE are generally mildly to moderately elevated, according to the Clinical Infectious Diseases guidelines 5
• CSF PCR for measles virus has unknown sensitivity and specificity in SSPE, which is a critical limitation, as noted by the Infectious Diseases Society of America guidelines 5
• The Infectious Diseases Society of America guidelines recommend that while CSF antibodies are the primary diagnostic tool, PCR results may be variable, in patients with suspected SSPE 5