Spinal Muscular Atrophy: Types, Causes, Symptoms, Treatment, Prognosis
What Is Spinal Muscular Atrophy?
Spinal Muscular Atrophy is a genetic neuromuscular disorder characterized by abnormalities in the nervous system which controls voluntary muscle movement. Majority of the nerves that control muscle movements are located in the spinal cord.The condition gets its name as it mainly affects the muscles and the nerve cells majority of which are located in the spinal cord.
What happens in Spinal Muscular Atrophy is that the muscles do not receive signals from the nerve cells to voluntarily move. With passage of time and with less and less movement of the muscles they start getting atrophied meaning that their strength becomes less and less. Spinal Muscular Atrophy is also termed as a motor neuron disease as there is significant loss of nerve cells or motor neurons in this condition.
Types Of Spinal Muscular Atrophy
Spinal Muscular Atrophy is basically classified into four types. The age of onset of symptoms roughly corresponds to the degree of motor function loss in the affected individual meaning that the earlier the onset of symptoms the more will be its effect on the motor function of the individual.
Children who are affected by Spinal Muscular Atrophy at birth have the maximum impact of this condition and tend to have little to no motor function and hence have been categorized as type 1 Spinal Muscular Atrophy.
The types 2 and 3 have generally higher level of motor functioning, although not normal in any way, and are seen in young children and adolescents affected with Spinal Muscular Atrophy.
The type 4 Spinal Muscular Atrophy is seen mostly in adults and the symptoms do not affect the individual much and he or she is able to do most of his or her tasks effectively except for certain tasks like running, jogging, getting up from a seated position and the like but eventually with passage of time and progression of disease they also lose their mobility and ultimately become wheelchair bound due to Spinal Muscular Atrophy.
What Are The Causes Of Spinal Muscular Atrophy?
Spinal Muscular Atrophy is an inherited condition which is passed down through families. It follows an autosomal recessive trait meaning that two copies of the defective gene have been inherited from each parent for the development of Spinal Muscular Atrophy.
Once child has Spinal Muscular Atrophy, due to the defective gene inherited, the body is not able to make proteins that are required for voluntary movement of muscles and due to the lack of protein cell necrosis of the cells that control muscle movement starts.
In case if only one copy of the faulty gene has been inherited, then the child will be a carrier and will have the potency to transmit to his or her offspring this medical condition termed Spinal Muscular Atrophy.
What Are The Symptoms Of Spinal Muscular Atrophy?
The symptoms of Spinal Muscular Atrophy are variable and depend on the type of Spinal Muscular Atrophy.
Symptoms of Type 1 Spinal Muscular Atrophy: The symptoms of this type of Spinal Muscular Atrophy include little to no ability to sit on his or her own, inability to support the head, floppy arms and legs, and dysphagia. This is the severest form of the disease as the muscles that control respiration are also affected by the condition and hence majority of children diagnosed with type 1 Spinal Muscular Atrophy do not cross the 2 year mark.
Symptoms of Type 2 Spinal Muscular Atrophy: The age of onset for this type of Spinal Muscular Atrophy is between 6 to 18 months of age. The symptoms are not as severe as type I but are more in the moderate range. The symptoms are more seen in the lower extremities as compared to the upper extremities but the child may be able to ambulate and sit with assistance.
Symptoms of Type 3 Spinal Muscular Atrophy: In this type, the symptoms start when the child is around 3 years of age. The symptom onset may not begin even when the child reaches puberty and may start as late as when the child is 17 or 18 years of age.
This is the mildest form of Spinal Muscular Atrophy. The child may be able to ambulate, sit and stand without assistance but may have problems with activities like running and jogging, negotiating stairs, or getting up from a seated position. As the disease progresses, the individual may become wheelchair dependent for carrying out activities of daily living.
Symptoms of Type 4 Spinal Muscular Atrophy: The onset of symptoms of this type of Spinal Muscular Atrophy starts when the child becomes an adult. The main symptoms are persistent muscle weakness and in some cases problems with breathing.
The symptoms of Spinal Muscular Atrophy will affect the individual throughout the life but the individual will be able to carry out activities of daily living and will even tend to improve with exercises and physical therapy despite being affected by Spinal Muscular Atrophy.
How Is Spinal Muscular Atrophy Diagnosed?
Spinal Muscular Atrophy is a difficult condition to diagnose due to its similarity with many other medical conditions. In order to diagnose Spinal Muscular Atrophy, the physician may ask the patient some pertinent questions related to growth and milestones and whether he or she had a problem or delay in reaching the milestones.
The patient would be observed for problems with sitting or standing without assistance, any breathing difficulties, and the most important whether any other member of the family has the same symptoms.
Once the physician has a detailed history of the patient certain tests may be conducted to confirm the diagnosis of Spinal Muscular Atrophy. These specialized tests are an electromyography or an EMG test which will give the physician a status of the muscles and whether the muscles are receiving signals from the nerve cells appropriately or not.
Additionally, a genetic testing may also be done to look for any faulty gene which may be responsible for the symptoms.
Muscle biopsy will be conducted to check whether there are any necrotic cells in the muscles which will confirm the diagnosis of Spinal Muscular Atrophy.
How Is Spinal Muscular Atrophy Treated?
As of 2016, there were no specific medications designed specifically for treatment of Spinal Muscular Atrophy. Since that year though, the FDA has approved use of a medication called Spinraza for treatment of this condition which cuts down the risk of fatalities or need for a ventilator in patients suffering from Spinal Muscular Atrophy. This medication has also shown effectiveness in allowing a child to make significant gains at reaching their milestones on time. Other than this, the treatment for Spinal
Muscular Atrophy is symptomatic and supportive and depends on the type of spinal Muscular Atrophy he or she has.
The main aim of treatment is to make the patient as comfortable and as independent as possible despite the symptoms of Spinal Muscular Atrophy. It is important for the child to keep taking part in as many activities as possible even during treatment phase of Spinal Muscular Atrophy to cut down on symptoms severity and prevent the muscles from getting atrophied.
Breathing difficulties is one of the worst symptoms especially in patients with Spinal Muscular Atrophy type 1 and 2 and hence such patients may need a specialized mask for breathing purposes. In severe cases, ventilator may be required for assistance.
In many cases of Spinal Muscular Atrophy, the child may complain of dysphagia because of weak swallowing and throat muscles. In such cases nutrition may become a big problem and for this the patient may require either liquid food or in extreme cases placement of a PEG tube for nutritional purposes as a treatment for Spinal Muscular Atrophy.
For movement, aggressive physical and occupational therapy is quite helpful in strengthening the muscles and allowing the child to move about on his or her own or with minimal assistance. In some cases, a walking aid, brace, or a wheelchair may be required for ambulation purposes.
What Is The Prognosis Of Spinal Muscular Atrophy?
The overall prognosis for Spinal Muscular Atrophy depends on the type of Spinal Muscular Atrophy that the child has. The prognosis for type 1 Spinal Muscular Atrophy is quite poor and the child may not survive beyond two years of age.
The prognosis brightens with type 2 and 3 of this condition. People with type 4 usually live a more or less normal lifespan but in the later years may be completely dependent on wheelchair for ambulation purposes and to carry out their activities of daily living as a result of Spinal Muscular Atrophy.