Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a genetic condition that is characterized by the degeneration of alpha motor neurons in the spinal cord (these affect the control of voluntary movements). This causes weakness and wasting of muscles. The weakness tends to be more severe in the muscles that are closest to the center of the body. The symptoms usually worsen with age. In most cases, the condition appears at birth but can appear in adulthood in rare instances. The prevalence of SMA is 1 in 6,000-10,000 births and 1 in 57 people are carriers of the gene. Spinal Muscular Atrophy (SMA) is the second most common neuromuscular disorder of childhood. The course of SMA varies and the severity of the disease ranges from mild muscle weakness to total paralysis and the need for support to breathe. The condition does not affect a child’s intelligence, a child, or an adult with SMA can socialize normally and partake in society.

Causes of Spinal Muscular Atrophy

SMA is caused by a deficiency of a motor neuron protein called survival motor neuron (SMN). This protein is essential for normal motor function and the lack of it is caused by genetic flaws in the gene SMN1. The neighboring gene SMN2 can compensate for some of the functions of SMN1. Typically, people have two copies of the SMN1 gene and one to two copies of SMN2 genes in each cell. The number of copies of the SMN2 gene modifies the severity of the condition and helps to determine which type of SMA is developed. Having multiple copies of the SMN2 gene is usually associated with less severe features of the condition that later develops in life.

Signs and Symptoms of Spinal Muscular Atrophy

Muscle weakness is the major feature of SMA. The muscle weakness is associated with other impairments such as:

  • Muscle wasting (atrophy).
  • Low muscle tone that makes the child’s body feel loose or “floppy” (hypotonia).
  • Absent or markedly decreased deep tendon reflexes (eg, knee-jerk reflex).
  • Involuntary tongue movements.
  • Hand tremors.
  • Tight joints that do not bend or stretch all the way, or possibly don’t move at all.
  • Spinal deformity (scoliosis).
  • Respiratory infections and lung disease.

Types of Spinal Muscular Atrophy

There are many types of SMA, they differ in age of onset and severity of weakness. There is overlap between the types but they are categorized as follows;

  • SMA type I- affects babies less than six months and the most severe type of the disease.
  • SMA type II- develops in babies between 7 and 18months old. This type is less severe than type I and most children survive into adulthood.
  • SMA type III- appears after 18months of age and is the least severe of the symptoms.
  • SMA IV- this type of SMA patient is diagnosed in adulthood and they present with only mild problems.

How Can Physiotherapy Help?

The goal of physiotherapy is to help a child with SMA to achieve the highest level of independent living and mobility possible and to prevent or delay the development of complications. Evaluation of the child is the first and most important step to determine the treatment goals of a child. Therapy will help in;

  • Strength training and exercises to improve and maintain mobility
  • Improving developmental skills such as head and trunk control
  • Management of respiratory complications
  • Management of scoliosis and skeletal deformity
  • Providing and modifying assistive devices
  • Prevention of joint contracture.

The progression of the disease varies, but generally, as individual ages, muscle strength decreases, and symptoms progress. However, some people with SMA live a normal lifespan. If your child is experiencing any of these symptoms, consult a physician for a proper diagnosis and advice.  If you have concerns about your child’s growth and development, give us a call at PCA, we have pediatric specialists on hand to help your child achieve their full potential.                            

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