Early life seizures and epileptic spasms in STXBP1-related disorders

BACKGROUND AND OBJECTIVES: Individuals with disease-causing variants in STXBP1 frequently have epilepsy onset in the first year of life with a variety of seizure types, including epileptic spasms. However, the impact of early-onset seizures and anti-seizure medication (ASM) on the risk of developing epileptic spasms and impact on their trajectory is poorly understood, limiting informed and anticipatory treatment, as well as trial design. METHODS: We retrospectively reconstructed seizure and medication histories in weekly intervals for individuals with STXBP1-related disorders with epilepsy onset in the first year of life and quantitatively analyzed longitudinal seizure histories and medication response. RESULTS: We included 61 individuals with early onset seizures, 29 of whom had epileptic spasms. Individuals with neonatal seizures were likely to have continued seizures after the neonatal period (25/26). The risk of developing epileptic spasms was not increased in individuals with neonatal seizures or early infantile seizures (21/41 vs. 8/16; OR 1, 95% CI 0.3–3.9, p = 1). We did not find any ASM associated with the development of epileptic spasms following prior seizures. Individuals with prior seizures (n = 16/21, 76%) had a higher risk to develop refractory epileptic spasms (n = 5/8, 63%, OR =1.9, 95% CI 0.2–14.6, p = 0.6). Individuals with refractory epileptic spasms had a later onset of epileptic spasms (n = 20, median 20 weeks) compared to individuals with non-refractory epileptic spasms (n = 8, median 13 weeks; p = 0.08). When assessing treatment response, we found that clonazepam (n = 3, OR 12.6, 95% CI 2.2–509.4; p < 0.01), clobazam (n=7, OR 3, 95% CI 1.6–6.2; p < 0.01), topiramate (n=9, OR 2.3, 95% CI 1.4–3.9; p < 0.01), and levetiracetam (n=16, OR 1.7, 95% CI 1.2–2.4; p < 0.01) were more likely to reduce seizure frequency and/or to maintain seizure freedom with regards to epileptic spasms than other medications. DISCUSSION: We provide a comprehensive assessment of early-onset seizures in STXBP1-related disorders and show that the risk of epileptic spasms is not increased following a prior history of early-life seizures, nor by certain ASM. Our study provides baseline information for targeted treatment and prognostication in early-life seizures in STXBP1-related disorders.