What is Spinal Muscular Atrophy?​

3D image of spinal pain

Spinal muscular atrophy (SMA) is a genetic disorder that affects the control of muscle movement.

It is caused by a loss of specialized nerve cells, called motor neurons, in the spinal cord and the part of the brain connected to the spinal cord.

It leads to weakness and wasting (atrophy) of muscles. In severe cases, the muscles used for breathing and swallowing are affected.

Many types of spinal muscular atrophy are distinguished by the pattern of features, the severity of muscle weakness, and the age when the muscle problems begin.

Spinal muscular atrophy affects one in 6,000 to one in 10,000 people.

How is Spinal Muscular Atrophy Diagnosed?

The first steps in diagnosing a neuromuscular disease are usually an in-office physical examination and family history, with some simple tests to distinguish spinal muscular atrophy (SMA) from similar conditions, such as muscular dystrophy.

Genetic testing will be recommended if SMA is suspected because this is the least invasive and most accurate way to diagnose. In rare cases, doctors may order a muscle biopsy.

3d image of a spine with Spinal Muscular Atrophy

How is Spinal Muscular Atrophy Inherited?

Spinal muscular atrophy (SMA) is inherited in an autosomal recessive manner.

It occurs when a person inherits two copies of a defective gene, one from each parent. The gene associated with SMA is called SMN1.

Most SMA cases involve a mutation or deletion in this gene, resulting in a deficiency of the survival motor neuron (SMN) protein. Motor neuron degeneration occurs due to insufficient SMN protein, leading to muscle weakness and atrophy.

Both parents of an affected individual are usually carriers of a mutated SMN1 gene.

When two carriers have a child, there is a 25% chance of SMA, a 50% chance of being a carrier, and a 25% chance of having two normal copies of the gene.

Types of Spinal Muscular Atrophy

There are several types of spinal muscular atrophy (SMA), which are classified based on the age of onset and the severity of symptoms.

The primary types of SMA include:

  1. Type 1 (Werdnig-Hoffmann disease): The most severe form, appearing in infancy, with significant muscle weakness and limited life expectancy.
  2. Type 2: Usually appears between 6 and 18 months of age, with moderate muscle weakness and difficulty walking.
  3. Type 3 (Kugelberg-Welander disease): Begins in early childhood or adolescence, characterized by milder muscle weakness and variable progression.
  4. Type 4 (adult-onset SMA): The mildest form, starting in adulthood with mild muscle weakness and a relatively normal life expectancy.

It’s worth noting that these classifications are based on general patterns, and there can be some variation in symptoms and disease progression among individuals.

Genetic testing and clinical evaluation are crucial for an accurate diagnosis and for determining the specific type of Spinal Muscular Atrophy in each case.

Child in Wheelchair sports court

The Prognosis for Spinal Muscular Atrophy

Recently, survival has increased in severe spinal muscular atrophy patients with aggressive and proactive supportive respiratory and nutritional support.

With proper care, Type I cases (which account for approx. 10% of all SMA1 cases) live into adulthood.

In type II, the course of the disease is slower to progress, and life expectancy is less than in the general population. Death before age 20 is frequent, although many people live to become parents and grandparents.

Type III has normal or near-normal life expectancy if standards of care are followed.

Type IV, adult-onset spinal muscular atrophy usually means only mobility impairment and does not affect life expectancy.

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ICON Rehab Powerchair

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Quantum Q6 Edge 2 Powerchair

Mobility for Those With Spinal Muscular Atrophy

Many with spinal muscular atrophy experience the progressive loss of the ability to walk and position themselves, necessitating the use of a specialized power wheelchair.

Powerchairs incorporate power-adjustable seating for user repositioning and comfort; speciality drive controls, including those requiring minimal hand strength; and a highly adaptable design to meet an individual’s current and future needs.

Powerchairs feature the latest advanced technologies to increase the independence of those with spinal muscular atrophy.

iLevel seat elevation technology allows users to operate the powerchair seated or standing.

Bluetooth is also integrated into Quantum’s Q-Logic 3 electronics, so those with spinal muscular atrophy can operate much of their environment with the powerchair drive control.

Powerchairs are designed to provide optimal medical comfort and maximum independence.

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