Will Subacute Sclerosing Panencephalitis (SSPE) show in Cerebrospinal Fluid (CSF) analysis in the very early stages?

CSF Findings in Very Early SSPE

Yes, SSPE will typically show abnormalities in CSF analysis even in very early stages, most notably dramatically elevated measles-specific antibodies, though the sensitivity of detection may be lower in the earliest phases of disease. 1, 2

Key Diagnostic CSF Findings

The hallmark CSF abnormality 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. 2 This finding is present even when other CSF parameters appear normal. 2

CSF Parameters in Early SSPE:

• Measles antibody titers: Elevated in both serum and CSF, with CSF titers typically ranging from 1/128 to higher levels even in early disease 3
• Cell count: May show mild lymphocytic pleocytosis or can be completely normal despite significant CNS pathology 2, 3
• Protein: Generally mildly to moderately elevated 1
• Oligoclonal IgG bands: Often present on immunofixation electrophoresis, indicating intrathecal antibody synthesis 3

Important Caveats About Early Detection

CSF PCR for measles virus has unknown sensitivity and specificity in SSPE, which is a critical limitation. 1 The Infectious Diseases Society of America guidelines note that while CSF antibodies are the primary diagnostic tool, PCR results may be variable. 1

Timing Considerations:

The diagnosis may be delayed in early stages because:

• Clinical presentation can be atypical with unusual initial symptoms (hemiparesis, headache, generalized seizures) rather than classic myoclonic jerks 4
• Some patients present with focal seizures or altered sensorium before characteristic features develop 5
• The disease can have a highly variable clinical course with periods of stabilization 6

Diagnostic Algorithm for Suspected Early SSPE

When evaluating a patient with subacute progressive neurological deterioration:

1. Obtain CSF for measles antibody testing - this is the single most important diagnostic test 2, 7
2. Calculate CSF/serum measles antibody index - values ≥1.5 are diagnostic 2
3. Check for oligoclonal bands - supports intrathecal antibody production 3
4. Perform EEG - periodic complexes may not appear until later stages but should be obtained 4, 7
5. Obtain brain MRI - T2-weighted images may show high signal intensity lesions in subcortical white matter, though 9 of 26 patients (35%) had normal MRI in one series 4

Critical Clinical Pitfall

A normal CSF cell count does NOT rule out SSPE. 2 SSPE may present with minimal or no CSF pleocytosis despite significant CNS pathology. The key diagnostic finding is the elevated measles antibody titer with intrathecal synthesis, not inflammatory cells. 2, 3

The International Encephalitis Consortium recommends measles virus testing on CSF when white matter lesions are identified on neuroimaging, particularly in patients with subacute progressive neurological deterioration, myoclonic jerks, and characteristic EEG findings. 2 However, given that imaging can be normal early on, clinical suspicion based on history of measles exposure (even congenital) and progressive neurological symptoms should prompt CSF testing regardless of imaging findings. 3, 5