OBJECTIVE: SCN2A-associated developmental and epileptic encephalopathies (DEEs) 
present with seizures, developmental impairments, and often both. We sought to 
characterize the level and pattern of development in children with SCN2A 
variants, and to address the sensitivity of the Vineland Adaptive Behavior 
Scales (VABS) in measuring changes over time in children with SCN2A-DEEs.
METHODS: Clinical histories for participants with pathogenic SCN2A variants in 
the Simons SearchLight project were analyzed for descriptive purposes. VABS 
scores obtained at study entry and yearly thereafter were analyzed for floor and 
ceiling effects, change with age, and association with epilepsy through use of 
regression and longitudinal regression methods.
RESULTS: Sixty-four participants (50 with epilepsy, 30 [47%] female, median age 
49 months, interquartile range [IQR] 28 to 101) were included. Histories of 
birth complications (N = 34, 54%), neonatal neurological signs (N = 45, 74%), 
and other neurological symptoms (N = 31, 48%) were common and similar in 
epilepsy and nonepilepsy subgroups. Mean standardized VABS scores (Composite 
53.5; Motor, 55.8, Communication, 54.1, Socialization, 59.4, and Daily living 
skills, 55.1) reflected performance ~3 standard deviations below the normative 
test average. In longitudinal regression analyses, standardized scores decreased 
between 1.3 and 2.8 points per year, suggesting regression of abilities. Raw 
score analyses, however, revealed several subdomains with substantial floor 
effects (eg, community use); other raw scores increased with increasing age. 
Participants with epilepsy scored 0.6 to 1 SD lower than those without epilepsy 
(all P's < .05).
SIGNIFICANCE: The VABS, as standardly administered, has shortcomings for 
addressing growth or regression in individuals with SCN2A-DEEs. Some subdomain 
raw scores reflected substantial floor effects. Raw scores increased so slowly 
over time that standardized scores declined. Alternative measures sensitive to 
incremental meaningful change are required if outcomes such as adaptive behavior 
are to be primary outcomes in short-term clinical trials.