A genetic defect in the SMN1 gene is the main cause of this rare spinal disorder. This gene encodes the protein SMN, without which the motor neurons cannot thrive. A deficiency of this critical protein caused by this genetic flaw results in the loss of motor neurons. The muscles weaken and slowly but surely waste away. This affects all voluntary motor control and can even effect semi-involuntary movements such as breathing and swallowing. SMA is an inherited condition and genetic counselling is important as there is no cure.
Type 1 Spinal Muscular Atrophy
Type 1 is a more severe type of SMA and is additionally known Werdnig-Hoffman disease. The symptoms are present at birth or soon after. Babies born with SMA are unable to sit up or lift their heads and often have problems with swallowing and breathing. Choking is a major hazard for infants born with SMA.
Type 2 Spinal Muscular Atrophy
Type 2 usually presents in infants between 6 and 12 months. The main symptoms are of muscle weakness. These babies are normally able to sit unaided or with minimal assistance, but are generally unable to stand or walk unaided.
Type 3 Spinal Muscular Atrophy
Type 3 is also called Kugelberg-Welander disease is the version of SMA that starts in juveniles and can develop any time from early childhood to adolescence. Many children with SMA will be able to walk and stand unaided, but will find climbing stairs difficult. They will more than likely need aid walking eventually and probably require wheelchair assistance later in life.
Type 4 Spinal Muscular Atrophy
Type 4 does not usually present any symptoms until the sufferer is older than 30. The symptoms can be quite mild to moderate and include tremors, twitching, spasms, muscle weakness and possibly breathing problems. Normally only the upper arms and legs are affected by Type 4.
X-Linked Spinal Muscular Atrophy
X-Linked SMA is characterised by severe muscle weakness and difficulty breathing and the features generally appear in infancy. Babies are often born with broken bones and joint deformities. The muscle tone is very poor and prognosis is generally not good.
Lower extremity Spinal Muscular Atrophy
Lower extremity Spinal Muscular Atrophy is most often characterised by weakness in the thighs and leg muscles. This can start in infancy and tends to progress fairly slowly. The signs of this type of SMA are generally difficulty in climbing stairs and rising from a seated position as well as an unsteady walk.
Adult Onset Spinal Muscular Atrophy
As its name suggests, this form of SMA presents in mid-adulthood. Sufferers experience muscle cramps in the abdomen and limbs, tremors, involuntary muscle contractions, protrusion of the abdomen and weakness in the leg muscles. There can also be problems with voluntary muscle control of the bladder and sphincter as well as difficulty breathing and swallowing.
Complications of SMA are generally related to curvature of the spine and respiratory issues. Scoliosis (spinal curvature) can be uncomfortable and also breathing. This can be treated with a brace and possibly surgery. The respiratory function needs to be monitored and any issues be treated immediately by a qualified specialist.
What is the progression of Spinal Muscular Atrophy?
SMA directly related to chromosome 5 tends to be milder the later in life the symptoms appear. Newborns and infants diagnosed with this illness seldom used to live past their first 2 years of life. The older you are when the symptoms appear, the milder the symptoms tend to be and the longer the life expectancy was predicted to be. With more knowledge and symptomatic treatment, life expectancy is not longer predicted and care is based on the symptoms presented at that stage.
Is there ongoing research to cure, prevent or assist with Spinal Muscular Atrophy?
Although this disease is genetically based, there is more than one gene carrying the information for making the necessary protein. Research is mostly based around getting this 2nd gene to produce the full length, functional SMN protein needed to keep the motor neurons functional.
There is a antisense oligonucleotide therapy currently undergoing clinical trials which is currently at phase 3. If this therapy is approved, it may bring some relief for SMA sufferers. There are a number of other possible research alternatives that may bear fruit in future including drug therapy, early screening, muscle building and neuroprotection. Although there is no cure as yet, research is continuing and hopefully there may be some respite in the near future for SMA afflicted people.
Where can I get more information and support?
Spinal Muscular Atrophy Support UK was established in 1985 and named the Jennifer Trust at that point in time. It was established by a mother who had tragically lost her baby daughter to SMA at the age of 7 months. The disease was considered extremely rare and no research was being conducted to alleviate symptoms or to cure the disorder at that point. Jennifer’s mother Anita set up the trust so that there would be support and information for other families with individuals suffering from SMA.
Spinal Muscular Atrophy Support UK is a charitable organisation which covers the whole of the UK and also supplies information online. This organisation is there to offer personalised support, information and any other services they can to registered SMA suffers, their family and friends. They also hold events where SMA sufferers and their families can meet others in similar situations to share information and support each other as part of a community. Spinal Muscular Atrophy Support UK aims to grow support for the SMA community through partnerships with other charities worldwide as well as local health, social care and research communities.