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Electroencephalographic Normalization as a Biomarker of Clinical Recovery in Down Syndrome Regression Disorder
Jonathan D Santoro1,2, Mackenzie Silverman1, Maeve C Lucas1
1Division of Neurology, Department of Pediatrics, Children's Hospital Los Angeles, Los Angeles, California, USA.
Objective:
Down syndrome regression disorder is a syndrome characterized by subacute loss of cognitive, behavioral, and functional abilities in individuals with Down syndrome. Electroencephalography abnormalities are frequently observed during evaluation, but it remains unclear whether these findings represent a dynamic marker of disease activity. We evaluated longitudinal changes in electroencephalography and examined whether normalization is associated with clinical improvement.
Methods:
We conducted a retrospective longitudinal cohort study of individuals with Down syndrome regression disorder who underwent electroencephalography within 2 months of symptom onset and repeat studies at six and 12 months. Active epilepsy, antiseizure medication use, or seizures during follow-up were exclusionary. Changes in electroencephalography were assessed over time. Among participants with abnormal baseline electroencephalography, associations between treatment exposures, electroencephalography normalization, and changes in clinical severity were evaluated.
Results:
Among 589 eligible individuals, 181 met inclusion criteria and 69 (38.1%) had abnormal baseline electroencephalography. Abnormal electroencephalography prevalence decreased to 20.4% at 6 months and 16.6% at 12 months (both p < 0.001 versus baseline). Among participants with abnormal baseline electroencephalography, normalization occurred in 49.3% by 6 months and 56.5% by 12 months. Immunotherapy exposure during the first 6 months was associated with higher odds of normalization (p < 0.001, 95% CI: 20.0-676.1) and faster time to normalization (HR: 15.35, p < 0.001, 95% CI: 4.90-48.09). Normalization was associated with reduced disease severity (all p ≤ 0.01).
Interpretation:
Electroencephalography abnormalities frequently improve over time in Down syndrome regression disorder. Normalization is associated with greater clinical recovery, supporting serial electroencephalography as a potential biomarker of neurophysiologic recovery in this condition.