VALIDATION OF OUTCOME MEASURES FOR SPINAL MUSCULAR ATROPHY USING THE HAMMERSMITH FUNCTIONAL MOTOR SCALE FOR CHILDREN, AND ABDUCTOR DIGITI MINIMI CMAP AMPLITUDE

SMA is a common genetic disorder of children, affecting up to 1 in 6000 children. Approximately half of the number have severe infantile form, termed SMA type 1 of Werdnig Hoffman disease, that is associated with obligatory respiratory problems with use of a ventilator at an average of 8 months, and are never able to sit autonomously. The others have SMA type 2 or type 3, defined by the ability to sit or to stand and walk, at some time in the course of development. The clinical course is unusual for a degenerative disease, with a prolonged plateau or slowly declining phase after an initial more rapid period of declining function. Ideally, treatment that enhances SMN abundance could be used prior to the onset of weakness, or early in the declining phase, to prevent further deterioration and increase the height of the plateau phase. The purpose of this study is to investigate, collecting findings from 10 neuromuscular centers, reliability of new measures which have promise for an outcome measure of a therapeutic trial in SMA patients. We will analyze children aged 2 to12 years, who are not able to walk, and who are affected by SMA type II and type III. We will use to evaluate this population of 60 patients a functional measure, i.e. the Hammersmith Functional Motor Scale for Children, and a neurophysiologic examinations by monitoring of the CMAP amplitude + area of abductor digiti minimi. Our assumption is that without a therapy during the interval of 3 and 6 months there should be little change and hence test-retest will provide a measure of measurement error for . These data can then be used to design properly a study intended to measure improvement during this interval. Data after the period of 1 year will be useful to observe the size of motor deterioration during this time.