• SMA-Simply Said

• SMA-Scientifically

All SMA Information obtained at www.smasupport.com. 

SMA-SIMPLE VERSION

SMA is a muscular disease passed on genetically to children by their parents.  You can not "catch" SMA by being around someone who has it.  It is a "Recessive" genetic disease, meaning that BOTH parents must carry a copy of the recessive SMA gene.  There is only a 25% chance each pregnancy of the child having SMA and a 75% chance each pregnancy that the child will be healthy.  One out of 40 people is a carrier of this recessive gene.  The brain is not affected, and they have been tested to have at least average to above average intelligence.  Please do not make the mistake of treating them as mentally impaired!!  Their bodies may not be perfect, but their minds are, so be sure to treat them that way!  SMA affects a child's muscular development, and the severity depends on what 'type' of SMA the child has.  There are four "Types" of SMA, Type 1,2,3 & 4.  The earlier  the symptoms are noticed, the more severe the type of SMA.  Type 1 is the most severe, affecting children while still in the womb or shortly after birth.  Type 4 is the least severe, affecting adults.

Type 1 children are diagnosed usually before 6 months of age, more often before 3 months of age.  Symptoms may even start in the womb.  Many mothers later recall the baby not moving as much the last month or so of pregnancy.  They are not able to hold up their heads, roll over, crawl, sit up without support, or walk.  All of their muscles are extremely weak, with the weakest muscles being the legs, upper arms, and neck.  Their chest may appear concave, or very skinny at the top, with a big belly.  Bell-shaped.  SMA affects all muscle systems as well including sucking, swallowing, digesting food, and excretion.  Constipation is a common problem as is being able to control excessive drooling (secretions), and getting proper nutrition and calories for proper weight gain.  A common cold can easily turn into pneumonia which is what usually takes the lives of these children, along with "respiratory failure" or when they no longer have the lung or chest muscles to be able to breathe on their own.  Two major decisions must be made with Type I children...whether or not to insert a feeding tube to prevent pneumonia and prevent starvation when they have lost their ability to suck or swallow; and whether or not to put them on a ventilator or other breathing machine when they experience respiratory failure.  Current statistics show that the average lifespan of a child with SMA Type I, not put on permanent ventilation or "life support", is only 8 months of age, with 80% dying by the age of one, and the majority of the rest dying by age 2.  HOWEVER, these statistics are not a hard and fast rule.  Each child is affected so differently by SMA that they do not all follow the same path or progression.  Also, as more is learned about SMA, the lifespan of a Type 1 child can be lengthened depending on the severity of the symptoms for each particular child.  Last but not least, the line between each Type of SMA is not clearly defined, and it is common for a child to exhibit patterns of two types, thus confusing the issue of "life expectancy" for that child.  

Type I children most often have very little leg movement, very little upper arm movement. Many times their hands remain fisted and their hands/wrists are turned the "wrong" way.  The physical characteristics that often "gives them away" to having SMA is a bell shaped body, legs that stay in the "frog" position, moving the arms from the elbows down only, and the head tilted to the side because of lack of neck muscles. They often have bright, expressive faces and eyes.    

Type 2 children are diagnosed before 2 years of age, usually more like 15 months.  These children are usually able to be in a sitting position without support, but often can not get there by themselves.  They can sometimes crawl with bracing and therapy, and on occasion may stand with braces.  Feeding and swallowing problems are not common in Type 2 children, though they are still possible.  They will usually never walk.  The lifespan of a Type 2 child varies so widely, there isn't one!  They could pass away at an early age or they could live well into adulthood.  As with all forms of SMA, weakness increases over time. 

Type 3 children are diagnosed between 18 months of age and early adolescence.  In the beginning these children are able to stand and walk but usually have difficulty doing so.  They typically have a normal lifespan; however, as with all forms of SMA, weakness gets progressively worse and they usually will be wheelchair bound.

Type 4 SMA is an adult SMA, with symptoms beginning around age 35.   They also usually have a normal lifespan; though, as with all forms of SMA, weakness gets progressively worse.

SMA-THE SCIENTIFIC VERSION

To see the actual medical textbook explanation of each of these types, click on the hyperlinks below associated with each type.

Spinal Muscular Atrophy (SMA) is one of the neuromuscular diseases. Muscles weaken and waste away (atrophy) due to degeneration of anterior horn cells or motor neurons which are nerve cells in the spinal cord. Normally, these motor neurons relay signals, which they receive from the brain, to the muscle cells. When these neurons fail to function, the muscles deteriorate. SMA effects the voluntary muscles for activities such as crawling, walking, head and neck control and swallowing.

SMA mainly affects the proximal muscles, or in other words the muscles closest to the trunk of the body. Weakness in the legs is generally greater than weakness in the arms. Some abnormal movements of the tongue, called tongue fasciculation's may be present in patients with Type I and some patients with Type II. The brain and the sensory nerves (that allow us to feel sensations such as touch, temperature, pain etc.) are not affected. Intelligence is normal.  In fact it is often observed that patients with SMA are unusually bright and sociable.

Type 1 Severe Infantile SMA, or Werdnig-Hoffman disease

• Infantile spinal muscular atrophy (Werdnig-Hoffman disease) is the most severe form of SMA. It usually becomes evident in the first six months of life. The child is unable to roll or sit unsupported, and the severe muscle weakness eventually causes feeing and breathing problems. There is a general weakness in the intercostals and accessory respiratory muscles (the muscles situated between the ribs). The chest may appear concave due to the diaphragmatic breathing. These children usually do not live beyond about 24 months of age, though those numbers are changing.
  

Type 2 Intermediate type (this does not have a hyperlink so it is spelled out below instead.)

• What are the features of intermediate (type 2) SMA?

  A child with the intermediate form of SMA often reaches six to twelve months of age, sometimes later, and learns to sit unsupported, before symptoms are noticed. Weakness of the muscles in the legs and trunk develops and this makes it difficult for the child to crawl properly or to walk normally, if at all. Weakness in the muscles of the arms occurs as well although this is not as severe as in the legs. Usually the muscles used in chewing and swallowing are not significantly affected early on. The muscles of the chest wall are affected, causing poor breathing function. Parents notice that the child is "floppy" or limp, the medical term for this being hypotonia.  Tongue fasciculations are less often found in children with Type II but a fine tremor in the outstretched fingers is common. Children with Type II are also diaphragmatic breathers.  Physical growth continues at a normal pace and, most importantly, mental functions is not affected. The children are bright and alert and it is important that they receive all the available opportunities to develop their intellectual capacities to their fullest extent. Integration into a normal school environment gives them the best chance to mature intellectually and emotionally.

  What does the future hold?

  The course of the disease is quite variable, and difficult to precisely predict from the start.  Children with the intermediate form of SMA usually sit unsupported. Weakness of the legs and trunk usually, but not always, holds the child back from standing and walking alone. Sometimes the muscle weakness can seem to be non-progressive, but in most cases weakness and disability will increase over many years. Severe illness with prolonged periods of relative immobility, putting on excessive weight or growth spurts may contribute to deterioration in function.  Due to weakness of the muscles supporting the bones of the spinal column, scoliosis (curvature of the spine) often develops in children who are wheelchair bound. If this becomes severe it can cause discomfort and can have a bad influence on breathing function as well. An operation can be done to straighten the spine and prevent further deterioration.  Recurrent chest infections may occur, because of decreased respiratory function and difficulty in coughing. Parents will have been shown how to encourage their child to maintain his/her maximum respiratory function as well as how they can perform postural drainage of the chest. They should start this as the first sign of any chest problem. Antibiotics and inhalation therapy may also be needed. Sometimes hospitalization is required to best manage and care for the child.  The long term outlook depends mainly on the severity of weakness of the muscles of the chest wall and on the development of scoliosis. Lifespan is always difficult to predict. Mildly affected children may live into adult years. The more severely affected children may die, due to pneumonia and other chest problems, before or in their teens.
  

Type 3 Mild Juvenile SMA, or Kugelberg-Welander disease

• Juvenile spinal muscular atrophy (Kugelberg-Welander disease) usually has its onset after 2 years of age. It is considerably milder than the infantile or intermediate forms. In juvenile spinal muscular atrophy children are able to walk, although with difficulty.  The patient with Type III can stand alone and walk, but may show difficulty with walking and/or getting up from a sitting or bent over position. With Type III, a fine tremor can be seen in the outstretched fingers but tongue fasciculations are seldom seen.

Type 4 Adult Onset

• Typically in the adult form symptoms begin after age 35. It is very rare for Spinal Muscular Atrophy to begin between the 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 Type IV.
  

Type 5 Kennedy's Syndrome or Bulbo-Spinal Muscular Atrophy

• This form also known as Adult Onset X-Linked SMA, occurs only in males, although 50% of female offspring are carriers. This form of SMA is associated with a mutation in the gene that codes for part of the androgen receptor and therefore these male patients have feminine characteristics, such as enlarged breasts. Also noticeably affected are the facial and tongue muscles. Like all forms of SMA the course of the disease is variable, but in general tends to be slowly progressive or non-progressive.