OUTCOME MEASURES: P.189Measuring fatigability during real-life assessment in spinal muscular atrophy

Abstract

Fatigability is a key component of several neuromuscular disorders and constitutes for some patients the main burden of the disease. Fatigability can be more severe when there is an impairment of the neuromuscular junction, such as in auto-immune or congenital myasthenia, but also in non-myastenic syndrome such as spinal muscular atrophy (SMA). In a controlled environment, fatigability can be measured using the 6 minutes walking test, by comparing the number of meters walked during the first and the last minute of the test. This method has demonstrated a clear fatigability component in SMA patients. Actimyo is a movement Holter monitoring that allows upper and lower limb movement capture and analysis during real life. On the lower limb, any individual stride can be detected and measured. On the upper limb, any active movement of the patients can also be detected and quantified. The distribution of movements and movements characteristic is studied over a 180-hour-period during which the patients follow their usual lifestyle, which allows a good representation of patient performance in real life. In order to understand how fatigability can be quantified in SMA patients, we compared the data recorded in the morning and in the afternoon during 2 weeks in 24 non-ambulant SMA patients, 9 ambulant SMA patients, and 70 age-matched controls. We did not observe any significant difference in stride velocity in controls, but patients with SMA experienced a drop in all walking parameters (stride speed, stride length and total number of meters walked) that reached statistical significance for median stride speed and stride length. Overall, patients with SMA walked 23% less in the afternoon than in the morning period. In non-ambulant patients, we observed a significant drop of 5% in the median power of upper limb movements when comparing the afternoon and the morning period. These data illustrate a first method to objectively assess fatigability in neuromuscular patients by using a continuous measure of movements.