Abstracts

Rationale: Dravet syndrome (DS) is one of the most well recognized developmental epileptic encephalopathies and is associated with mutations of SCN1A in more than 80% of patients. Poor developmental outcomes are characteristic, with almost all individuals having intellectual disability. Crucial to effective early intervention planning is an understanding of speech and language function in DS patients, yet this has not been characterised to date. We analyze the oral motor, speech and language phenotype in 20 children and adults with DS associated with SCN1A mutations. Methods: DS patients (aged 15 months - 28 years) with SCN1A mutations underwent a tailored assessment battery. Patients were classified as 'Verbal' or 'Minimally verbal'. Results: In children under 2 years, development was normal. In older patients, cognitive skills varied markedly, with intellectual functioning ranging from normal: low average (1) and borderline (1), to intellectual disabled ranging in severity from mild (5) to moderate (2) and severe (9). Of the 15 verbal patients, half had moderate to severely impaired conversational speech intelligibility. Speech was characterized by imprecise articulation, abnormal nasal resonance, breathy or strain-strangled voice, and errors in pitch and prosody. Oral motor impairment was common, compounded by poor postural control, as well as motor planning and programming difficulties. Receptive and expressive language impairment was typical. Non-verbal patients had intentional communication. Conclusions: A distinctive speech and language phenotype was found in twenty patients with DS associated with SCN1A mutations. Recognising this speech and language phenotype will guide therapeutic intervention in DS patients. Funding: S.J.T. supported by National Health and Medical Research Council (NHMRC) Postgraduate Scholarship (101777), Australian National University Gowrie Scholarship and Speech Pathology Australia Nadia Verrall Memorial Research Grant. V.A. supported by NHMRC Senior Practitioner Fellowship (2010-2019). A.T.M. supported by NHMRC Career Development Award (607315, 2010-2015) and Practitioner Fellowship (1105008, 2016-2020). I.E.S. supported by NHMRC Program Grant (628952) and Practitioner Fellowship (1006110). Project also supported by Australian Research Council (ARC) Discovery Project (DP120100285) to A.T.M. and I.E.S.