FUNCTION CHANGES IN SPINAL MUSCULAR-ATROPHY-II AND MUSCULAR-ATROPHY-III

The course of spinal muscular atrophy (SMA) is not well established ex cept for those patients whose age of onset is before 6 months and who achieve only ''sit with support'' as their maximum function (Werdnig-H offmann disease or SMA I). This study shows that there is another grou p of SMA patients whose age of onset and maximum function achieved can be used as prognostic guides. Fifty percent of SMA patients who could walk without assistance and whose onset was prior to age 2 years lost the ability to walk independently by age 12. Fifty percent of SMA pat ients who walked and whose onset was between 2 and 6 years of age lost walking ability by age 44 years. Fifty percent of SMA patients who co uld walk with assistance as their best function ever achieved lost thi s ability by age 7 years, unrelated to age of onset; none could walk w ith assistance after age 14 years. Seventy-five percent of SMA patient s who developed the ability to sit independently as their best functio n were still sitting after age 7 years independent of age of onset; 50 % of this group could sit independently after age 14 years. Eighty-fiv e percent of SMA patients who could walk could not negotiate stairs wi thout holding onto a rail. They could raise their hands above the head ; however, as they lost walking ability, they lost this function as we ll. Only one SMA patient whose maximum function was sitting independen tly could get to the sitting position on his own. Only two of these pa tients could hold their hands above their heads. All patients with SMA lose function over time. This function loss occurs slowly and is rela ted primarily to maximum function achieved; knowledge of age of onset provides helpful information, especially for predicting the loss of in dependent walking.