Increased Extra‐Axial Cerebrospinal Fluid Volume in Children With Angelman Syndrome: Links to Sleep Problems and Seizures

Background Previous studies demonstrated that children with autism have enlarged volumes of extra‐axial cerebrospinal fluid (EA‐CSF) and an increased ratio of EA‐CSF to brain volume, indicating that EA‐CSF is disproportionally increased beyond macrocephaly often observed in autism. It is unknown whether EA‐CSF is disproportionally enlarged in Angelman syndrome (AS), which shares phenotypic features with autism (sleep problems, seizures) but is characterized by microcephaly. This study examined EA‐CSF and total cerebral volume (TCV) in AS children compared with neurotypical (NT) controls to test whether EA‐CSF is disproportionally enlarged and is associated with sleep problems and seizures. Methods Magnetic resonance imaging scans were acquired in n = 29 AS (M[SD] = 6.95 ± 2.83 years) and n = 27 NT children (M[SD] = 7.96 ± 2.24). EA‐CSF and TCV were compared using analysis of covariance (ANCOVA), controlling for age, sex, and group interactions. In AS, associations between EA‐CSF, sleep quality, and seizure severity were evaluated by linear regression. Results Children with AS had 22% smaller TCV ( p < 0.0001) yet nearly identical EA‐CSF volumes ( p = 0.35). The ratio of EA‐CSF to TCV was 48% higher in AS ( p < 0.0001). Increased EA‐CSF ratio in AS was associated with sleep initiation problems ( p = 0.002) and seizure severity ( p = 0.032). Conclusion Children with AS have disproportionally higher EA‐CSF volume than would be predicted by their smaller brain size. EA‐CSF was associated with sleep problems and seizures, which impact quality of life and are target endpoints of current AS clinical trials. Excessive CSF suggests that CSF circulation might be perturbed in AS, which could have implications for brain waste clearance and impact the biodistribution of AS therapies delivered via CSF.