The child with SMA will experience impairment of crucial functions such as breathing, sucking and swallowing. Additional conditions can develop out of such impairment. For example, abnormal spinal curves may develop due to weak back muscles, further complicating the breathing process by compressing the lungs.
Prior to the advent of feeding tubes, interruption in swallowing often caused death in cases of SMA type 1 (the most severe kind). There are now many assistive devices to help keep children with SMA alive (and comfortable, at least relative to years past). However, risks still exist. One is choking. Choking is possible because a child with SMA has weak swallowing and chewing muscles. Another risk is aspiration, or inhaling of food. Aspiration can block the airway as well as be a source of infection.
SMA manifests in many ways, which will vary especially according to type. In all types of SMA, you can expect muscle weakness, wasting and atrophy, as well as muscle coordination problems. The reason for this lies in the nature of the disease itself: SMA affects nervous control of voluntary muscles.
There is no cure for SMA. The most promising prognosis comes about with early detection. Advances in medicine can help manage the complications associated with SMA.