EEG Scoring Systems in Developmental Epileptic Encephalopathies With and Without Epileptic Spasms: A Comparative Analysis of Reliability and Diagnostic Clarity.

Background: The Burden of AmplitudeS and Epileptiform Discharges (BASED) and "Hypsarrhythmia Scoring System" (HSS) serve to evaluate the interictal EEG in infantile epileptic spasms (ES) syndrome (IESS). We aimed to assess these scoring systems' reliability and diagnostic utility in infants with IESS and other developmental and epileptic encephalopathies (DEEs) without ES.

Methods: Three epileptologists from a single medical center scored the deidentified EEG tracings of 110 infants, 58 with IESS, and 52 with other DEEs (of similar age and sex distributions), according to the BASED and HSS scoring systems. Inter-rater agreement (IRA) for both scoring systems was assessed.

Results: High-severity BASED and HSS scores (suggesting epileptic encephalopathy or hypsarrhythmia) were noted in 76% and 78% of the IESS infants and 44% and 56% of the other DEE infants, respectively. In IESS, the IRA of BASED was "excellent" (Intraclass correlation coefficient 0.91 [95% confidence interval (CI) 0.87-0.94]) and of HSS "good" (intraclass correlation coefficient 0.85 [95% CI 0.75-0.87]). IRAs for high-severity scores were "good" for BASED (Ƙ 0.72 [95% CI 0.58-0.86]) and "fair" for HSS (Ƙ 0.59 [95% CI 0.43-0.75]).

Conclusions: High-severity BASED and HSS scores, traditionally associated with IESS, may appear in nearly half of infants with DEEs without ES and be absent in a quarter of infants with IESS. Clinical judgment is essential for IESS-related diagnostic and therapeutic decision-making in infants with DEEs who present with abnormal undiagnosed movements and high-severity scores on EEGs (indicating epileptic encephalopathy or hypsarrhythmia). In IESS, the BASED scoring system shows better inter-rater reliability than HSS.