A Muscular Dystrophy Support Group

What is SMA?

 Spinal Muscular Atrophy (SMA) is a disease of the anterior horn cells. These horn cells are located in the spinal cord. SMA affects the voluntary muscles for activities such as crawling, walking, head and neck control and swallowing.

It mainly affects the muscles closest to the point of origin , and in this case those closest to the trunk of one's body. Weakness in the legs is generally greater than in the arms. Some abnormal movements of the tongue (tongue fasciculation) is also common. The senses/feelings are normal as is intellectual activity. It is often observed that patients with SMA are unusually bright and sociable.

The diagnosis of children with this type is usually made before 6 months of age and in the majority of cases before 3 months, there may be a lack of foetal movement in the final months of pregnancy. Usually a child with SMA Type I is never able to lift his/her head or accomplish normal physical milestones. Swallowing and feeding may be difficult and the child may show difficulties with there own secretions. There is a general weakness in the intercostals and accessory respiratory muscles (muscles between the ribs). The chest may appear concave (sunken in) due to the diaphragmatic (tummy) breathing.

Diagnosis is almost always made before 2 years of age with the majority of cases diagnosed by 15 months. Children with SMA Type II may sit unsupported although they are usually unable to come to sitting position without assistance. Feeding and swallowing problems are not usually characteristic, although in some patients this can occur and a feeding tube may become necessary. Tongue fasciculation is less found in children with SMA Type II but a fine tremor in their outstretched fingers is common. Children are also diaphragmatic breathers.

Diagnosis is made sometime after 18 months of age and as late as adolescence. the patient with SMA TYPE III can stand alone and walk, but may show difficulty with walking and/or getting up from sitting or bent over position. With SMA Type III,  fine tremor can be seen in the outstretched fingers but tongue fasciculation is seldom seen.

SMA Type IV (ADULT ONSET)

Typically in the adult form symptoms begin after age 35. It is very rare for Spinal Muscular Atrophy to begin between ages of 18 and 30. Adult SMA is characterized by insidious onset and very slow progression. The bulbar muscles, those muscles used for swallowing and respiratory function, are rarely affected in SMA Type IV.

Courtesy FSMA.ORG