53 Pseudo-obstructive events in Spinal Muscular Atrophy as a potential marker for disease progression

Introduction Sleep disordered breathing (SDB) is common in children with spinal muscular atrophy (SMA) as a result of respiratory muscle weakness. However, SDB events are currently scored according to criteria created for healthy children. This study aims to add to previous evidence 1,2 that SMA type II patients have respiratory events (we defined them as ‘pseudo-obstruction’) which do not conform to the current AASM guidelines for obstructive or central events. They are the result of paradoxical breathing and REM-related shallow breathing. Methods Respiratory events were defined as either ‘obstructive apnoea’ (OA), ‘central apnoea’ (CA), ‘central hypopnoea’ (CH), ‘obstructive hypopnoea’ (OH) as per AASM guidelines. We additionally defined the criteria for ‘pseudo-obstruction’ (PO) based on previous publications (figure 1).1 Trained sleep physiologists were provided 8 ‘test’ epochs randomly chosen from either SMA II or other patients. Physiologists were asked to designate the respiratory events they deemed most appropriate for each epoch, blind to diagnosis of the patient. Interscorer reliability tests were performed against the gold standard for each event. Results The average concordance with the gold standard was 75% overall. It was mildly reduced to 67% when looking specifically at POs. We are currently evaluating whether disease progression is associated with an increase in POs by looking at subsequent yearly sleep studies of 10 SMA II and 1 SMA I patient, self-ventilating in room air, across a 3-year period. Discussion Future efforts will aim to look more closely at inter scorer reliability. Recognising these pseudo-obstructive events may influence treatment.2 Additionally, if these events correlate along the motor and respiratory deterioration, they can be used as markers of response to overnight ventilation and, more importantly, to new available treatments. References Chacko A. Sleep Medicine 2020. Kouri l. Journal of clinical neuromuscular disease, 2020. Berry. AASM manual 2020.