Natural History Study of STXBP1-Developmental and Epileptic Encephalopathy into Adulthood

Hannah Stamberger*, David Crosiers, Ganna Balagura, Claudia M. Bonardi, Anna Basu, Gaetano Cantalupo, Valentina Chiesa, Jakob Christensen, Bernardo Dalla Bernardina, Colin A. Ellis, Francesca Furia, Fiona Gardiner, Camille Giron, Renzo Guerrini, Karl Martin Klein, Christian Korff, Hana Krijtova, Melanie Leffner, Holger Lerche, Gaetan LescaDavid Lewis-Smith, Carla Marini, Dragan Marjanovic, Laure Mazzola, Sarah McKeown Ruggiero, Fanny Mochel, Francis Ramond, Philipp S. Reif, Aurélie Richard-Mornas, Felix Rosenow, Christian Schropp, Rhys H. Thomas, Aglaia Vignoli, Yvonne Weber, Elizabeth Palmer, Ingo Helbig, Ingrid E. Scheffer, Pasquale Striano, Rikke S. Møller, Elena Gardella, Sarah Weckhuysen

*Corresponding author for this work

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Abstract

Background and ObjectivesPathogenic STXBP1 variants cause a severe early-onset developmental and epileptic encephalopathy (STXBP1-DEE). We aimed to investigate the natural history of STXBP1-DEE in adults focusing on seizure evolution, the presence of movement disorders, and the level of functional (in)dependence.MethodsIn this observational study, patients with a minimum age of 18 years carrying a (likely) pathogenic STXBP1 variant were recruited through medical genetics departments and epilepsy centers. Treating clinicians completed clinical questionnaires and performed semistructured video examinations while performing tasks from the (modified) Unified Parkinson Disease Rating Scale when possible.ResultsThirty adult patients were included for summary statistics, with video recordings available for 19 patients. The median age at last follow-up was 24 years (range 18-58 years). All patients had epilepsy, with a median onset age of 3.5 months. At last follow-up, 80% of adults had treatment-resistant seizures despite long periods of seizure freedom in 37%. Tonic-clonic, focal, and tonic seizures were most frequent in adults. Epileptic spasms, an unusual feature beyond infancy, were present in 3 adults. All individuals had developmental impairment. Periods of regression were present in 59% and did not always correlate with flare-ups in seizure activity. Eighty-seven percent had severe or profound intellectual disability, 42% had autistic features, and 65% had significant behavioral problems. Video examinations showed gait disorders in all 12 patients able to walk, including postural abnormalities with external rotation of the feet, broad-based gait, and asymmetric posture/dystonia. Tremor, present in 56%, was predominantly of the intention/action type. Stereotypies were seen in 63%. Functional outcome concerning mobility was variable ranging from independent walking (50%) to wheelchair dependence (39%). Seventy-one percent of adults were nonverbal, and all were dependent on caregivers for most activities of daily living.DiscussionSTXBP1-DEE warrants continuous monitoring for seizures in adult life. Periods of regression are more frequent than previously established and can occur into adulthood. Movement disorders are often present and involve multiple systems. Although functional mobility is variable in adulthood, STXBP1-DEE frequently leads to severe cognitive impairments and a high level of functional dependence. Understanding the natural history of STXBP1-DEE is important for prognostication and will inform future therapeutic trials.

Original languageEnglish
JournalNeurology
Volume99
Issue number3
Pages (from-to)E221-E233
Number of pages14
ISSN0028-3878
DOIs
Publication statusPublished - 19. Jul 2022

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© American Academy of Neurology.

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