Spinal muscular atrophy type 2 is a genetic disease that causes muscle wasting and coordination problems in infants. A genetic mutation affects the production of a specific type of protein that spinal cord nerve cells need to survive. As neurons die, muscles in the shoulders, arms, and legs become weaker and weaker. Children with the disorder typically cannot stand or use their arms without assistance. There is currently no cure for spinal muscular atrophy type 2, but bracing devices, surgeries, physical therapy, and support from family members can help patients reach some degree of independence in their lives.
Most doctors recognize three or four types of spinal muscular atrophy, and patients are categorized based on age at the time of the disease's onset and the severity of their symptoms. Type 2 generally appears when an infant is between six and 18 months old. It is a rare autosomal recessive disorder, and both parents must be carriers of a specific mutated gene in order to pass the disease on to their offspring. The damaged gene fails to produce working survival motor neuron proteins (SMNs) in the spinal cord. Neurons in the spine that control voluntary muscles quickly degenerate without sufficient levels of SMNs.
Spinal muscular atrophy type 2 has its largest effects on large muscles in the back, shoulders, arms, and legs. Children with the disorder are usually unable to sit upright without assistance. They typically do not have the strength to learn to crawl or hold themselves up with their arms when lying face down. The disorder can also prevent young children from feeding themselves because of a lack of coordination and strength in arm muscles. In some cases, serious respiratory problems develop due to weakness in the chest, throat, and mouth.
Doctors can usually diagnose spinal muscular atrophy type 2 based on physical symptoms and the results of blood tests. Genetic testing of both the patient and his or her parents is performed to confirm the disease. An exam called electromyography may be performed to gauge the severity of muscle wasting. Electromyography involves sending small electrical impulses to various muscle groups and measuring their reactions.
Treatment for spinal muscular atrophy type 2 typically involves a multifaceted approach. Children as young as two may be fitted with leg braces or standing wheelchairs to help them develop some mobility. Physical therapy in the form of water exercises can help to strengthen and preserve remaining muscles. As children get older, ongoing therapy, powered wheelchairs, and special education arrangements offer them a chance to go to school. Most children with the disorder have normal intelligence and are able to learn and socialize as well as their peers.
Spinal muscular atrophy type 2 can cause scoliosis in later childhood or adolescence. Spinal fusion surgery may be considered to improve a patient's posture and make it easier for him or her to get around. With treatment and the proper support from loved ones, most people with the disorder can have long, productive lives.