A genetic neuromuscular disorder, spinal muscular atrophy (SMA) causes muscle atrophy and weakness as motor neurons degenerate in the spinal cord. We will explore SMA's causes, symptoms, diagnosis, treatment, and prevention strategies in this blog post.
Causes
The primary cause of SMA is mutations in the survival motor neuron 1 (SMN1) gene, which produces a protein required for motor neuron function. Motor neurons degenerate over time without adequate levels of this protein, resulting in muscle weakness and atrophy over time. In order to develop SMA, an individual must inherit two copies of the defective gene from each parent.
Symptoms
Symptoms of SMA can vary widely in severity and age of onset, but most commonly include:
-
It leads to difficulty with movement, posture, and motor functions, especially in the proximal muscles (muscles closest to the core).
-
Decreased muscle tone in infants, resulting in poor head control, weak sucking reflexes, and delayed motor milestones.
-
Insufficiency in breathing muscles can lead to respiratory problems, such as difficulty breathing, shallow breathing, or recurrent respiratory infections.
-
Feeding difficulties, aspiration, and choking episodes can be caused by weakness in swallowing muscles.
-
Compared to their peers, infants with SMA may have delayed motor milestones, such as sitting, crawling, or walking.
Diagnosis
There are several common diagnostic methods for diagnosing SMA, including clinical evaluation, genetic testing, and imaging studies.
-
Tests to identify mutations in the SMN1 gene associated with SMA, which can confirm the diagnosis and determine the genetic subtype.
-
Using electromyography (EMG) to assess nerve and muscle function, detect abnormal motor neuron activity, and distinguish SMA from other neuromuscular disorders.
-
To detect signs of muscle degeneration, atrophy, or changes characteristic of SMA, a small sample of muscle tissue is obtained for microscopic examination.
Treatment
Currently, there is no cure for SMA, but treatment is aimed at managing symptoms, improving quality of life, and slowing disease progression. Some common treatment approaches include:
-
SMA can be treated with FDA-approved medications such as nusinersen (Spinraza) or onasemnogene abeparvovec (Zolgensma), which increase SMN protein levels.
-
In order to manage symptoms, maintain function, and optimize overall health, supportive care and interventions, such as physical therapy, occupational therapy, respiratory therapy, and nutritional support, are provided.
-
The use of assistive devices such as braces, orthotics, wheelchairs, or adaptive equipment to improve mobility, independence, and quality of life for individuals with SMA.
Prevention
SMA prevention primarily involves genetic counseling and testing to identify carriers and provide information about the risk of passing the condition on to offspring.
-
Identifying individuals who carry one copy of the defective SMN1 gene, especially among couples with a family history of SMA or those planning to have children.
-
Testing during pregnancy, such as chorionic villus sampling (CVS) and amniocentesis, to detect SMA in the fetus, allowing parents to make informed decisions about pregnancy management and future reproduction.
