Children with SMA type II may eventually be able to sit, but they are unable to learn to stand or to walk.
I used two male-male couplers here plus a short length of semi rigid coax to reach the bulkhead mounted SMA output socket.
There are several different types of SMA with varying severity; see the website below for more details.
These include SMA type I, also called Werdnig-Hoffmann; SMA type II; SMA type III, also called Kugelberg-Welander disease; Kennedy syndrome, or progressive spinobulbar muscular atrophy; and congenital SMA with arthrogryposis.
Parents of children with SMA usually carry the gene for the disease but have no symptoms themselves.