By Dr Kausik Mandal
Spinal Muscular Atrophy (SMA) is a rare genetic disorder that affects the motor neurons in the spinal cord, resulting in muscle weakness and progressive loss of movement. It is caused by a mutation in the survival motor neuron 1 (SMN1) gene, leading to a deficiency in the survival motor neuron protein (SMN) which is critical for the normal functioning and survival of motor neurons. SMA is the cause of the most infantile deaths worldwide than any other genetic disorder. According to a study, the incidence of SMA in India is one in 7,744 live births, which is approximately 3,200 Indian babies each year.
The severity of SMA can vary depending on the specific type, with Type I generally considered the most dangerous and severe form of the condition. Each variant/type of SMA has a different set of symptoms.
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Significant symptoms of SMA disease occur between six months and one year after birth. It is essential to recognise the symptoms of SMA early to facilitate timely diagnosis and intervention.
Here are 6 most common symptoms associated with SMA.
Muscle Weakness
SMA is a genetic disorder that primarily affects the motor neurons in the spinal cord, which are responsible for controlling muscle movement. As a result of the loss of motor neurons, individuals with SMA experience progressive and often severe muscle weakness. This weakness typically begins in the lower limbs and can spread to other muscle groups, impacting mobility and motor function. Infants with SMA may exhibit poor head control, difficulty moving limbs, or a weak grasp.
Difficulty Moving
SMA can lead to difficulty in moving the limbs, which can be particularly noticeable in infants and young children. The specific impact on mobility and the ability to move can vary depending on the type and severity of SMA, but in general, individuals with SMA experience muscle weakness and a decrease in muscle function, which can lead to challenges in moving and performing everyday tasks. In infants and young children with SMA, this may manifest as difficulty achieving motor milestones like sitting, crawling, and walking. As the condition progresses, individuals with SMA may require assistive devices such as wheelchairs to maintain mobility.
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Respiratory Issues
Respiratory issues are one of the common and significant symptoms of SMA. SMA can impact the muscles used for breathing, leading to respiratory problems. Individuals with SMA may have very weak intercostal muscles, which compromises this normal breathing rhythm. This can result in weak respiratory muscles and underdeveloped lungs, a weak cough, severe risk of decreased respiratory muscle strength during viral respiratory infections—even infections that only cause minor illness for healthy individuals, increased risk of pneumonia, aspiration of food or drink, hypoventilation, or shallow breathing, especially during sleep.
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Difficulty Swallowing (Dysphagia)
SMA can impact the muscles used for swallowing, resulting in difficulty feeding or an increased risk of aspiration (inhaling food or fluids into the airways). This can lead to weight loss and respiratory issues. Problems sucking and swallowing for people with SMA are usually caused by muscle weakness in the throat and mouth. SMA also causes damage to bulbar motor neurons, which impacts chewing, speech, and swallowing and leads to fasciculations (quivering) of the tongue.
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Scoliosis
Scoliosis is the most common symptom that SMA patients may encounter, and its severity is linked to SMA type 1. Scoliosis can cause breathing difficulties, because the lungs have less room to expand and allow for deep breathing. The condition also reduces patients’ mobility, which causes joints to stiffen or become displaced, especially those placed under stress by the bending spine, such as the hip joints. Patients who are unable to stand straight often must support their weight with their arms, further limiting their mobility.
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Sensory and Cognitive Function
In some cases, SMA can lead to sensory and cognitive symptoms. These may include difficulties with speech, hearing, and in rare cases, mild cognitive impairment. However, cognitive function remains intact for most individuals with SMA.
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Management & Treatment
Early diagnosis of SMA is crucial for initiating appropriate medical and therapeutic interventions. It’s important for individuals with SMA to receive appropriate medical care and physical therapy to help manage their mobility challenges and optimize their quality of life.
The management of SMA necessitates employing a variety of strategies designed to address symptom control, slow down the advancement of the disease, and enhance the well-being of individuals afflicted by SMA. These approaches target the root cause—a deficiency of survival motor neuron (SMN). Early treatment not only enhances quality of life but also extends lifespan.
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(The author is an additional professor at the Medical Genetics Department, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow).
[Disclaimer: The opinions, beliefs, and views expressed by the various authors and forum participants on this website are personal].
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