The initial step in diagnosing SMA begins with parental concerns about their children's strength and gross motor abilities. These concerns usually occur early in life in children with SMA Type I and II, where as children with SMA III may not show any clinical symptoms for many years. It is important that a physician knowledgeable about pediatric neuromuscular diseases examine these youngsters. Some of these alternative diagnoses required different diagnostic tests and may warrant different forms of treatment. Typically, the child with SMA Type I and II will exhibit his or her most dramatic weakness in the proximal muscles of the legs and arms.
Sensation is normal and children always appreciate feelings like tickling and light touch.
Although the clinical examination is critically important, the fact that other neuromuscular disease can present with the same symptoms and show some of the same physical features makes additional diagnostic testing necessary. Most children with muscular dystrophy have very high CPK levels, where as children with SMA have normal or only slightly elevated CPK levels. The physician administers a small electrical stimulus to the nerves of a child's arm and legs to determine how quickly electrical messages are carried by the motor and sensory nerves. The second part of the test requires the insertion of a very fine electrical probe into several muscles. Characteristic abnormalities show that the muscle has lost nerve supply because of the malfunction of the motor neuron.