What Is Spinal Muscular Atrophy?

Spinal Muscular Atrophy: Genetic Diagnosis, Therapy & Multidisciplinary Care

Spinal muscular atrophy (SMA) is a severe and uncommon genetic neuromuscular illness caused by the death of the motor neurones of the spinal cord. It results in progressive muscle weakness and atrophy. Nevertheless, even with some improvement in therapy, early detection and offering a complete range of care are essential to maximise the results.

This article will act as a guide to enlighten people about spinal muscular atrophy. It aims to provide the most essential points that families and healthcare providers should be aware of to manage the condition successfully and outline a detailed description of the condition.

What Is Spinal Muscular Atrophy Disease?

SMA entails a collection of hereditary ailments that affect lower motor nerve cells or nerve cells that carry messages between the spinal cord and muscles. The destruction of such neurones causes progressive degeneration of the muscles, especially of the proximal muscles (those nearest to the centre of the body).

Why Does Spinal Muscular Atrophy Occur?

SMA is generally caused by mutations in the SMN1 gene on chromosome 5q. SMN1 encodes a protein called survival motor neuronee (SMN) that is involved in motor neuronee survival. A defective SMN1 gene suppresses or destroys the synthesis of the SMN protein, causing neuronal degeneration.

The inheritance is autosomal recessive. That is, both parents have to be carriers of a mutated copy of SMN1 to have an affected child. The risk of acquiring it is roughly one baby in 10,000, so it is essential to conduct carrier screening.

What are the Types of Spinal Muscular Atrophy?

Depending on the age of onset and severity, SMA is categorised into these types:

What are the symptoms of spinal muscular atrophy?

The general signs among types entail:

• Gradual muscle weakness, especially in the shoulders, hips, thighs, and back
• Hypotonia (reduced muscle tone)
• Twitching of the muscles (fasciculations)
• Scoliosis and contractures of the joints in severe conditions
• Feeding and breathing difficulties, particularly infantile-onset types
   

How Is Spinal Muscular Atrophy Diagnosed?

Diagnosis is made by:

1. Clinical evaluation: Neurologists evaluate motor milestones, muscle strength, reflexes, tone, and breathing function.
2. Genetic testing: Blood tests detect SMN1 mutations and determine SMN2 copy number, aiding in type and prognosis classification.
3. Electromyography (EMG)and nerve conduction studies (NCS): Identify motor neurone pathology.
4. Muscle biopsy: Rarely used due to the diagnostic simplicity of genetic tests.
5. Newborn screening: Implemented in many jurisdictions to enable pre-symptomatic intervention.
    

What are the treatment options for spinal muscular atrophy?

Although SMA remains incurable, several disease-modifying therapies have dramatically altered its course:

• Nusinersen (Spinraza)
  
  
  • Antisense oligonucleotide delivered intrathecally.
  • Enhances SMN protein production from the SMN2 gene
  • Improves motor milestones
     
• Onasemnogene abeparvovec (Zolgensma)
  
  
  • Single-dose intravenous gene therapy delivering a functional SMN1 copy
  • Approved in 2019–2021 across multiple regions, used primarily in infants with up to 3 SMN2 copies
     
• Risdiplam (Evrysdi)
  
  
  • An oral daily small molecule that modulates SMN2 splicing to increase SMN protein
  • FDA-approved in 2020; tablet form approved in February 2025

These medications are most effective when administered early, ideally before irreversible motor neurone loss.

What is the supportive care and long-term management for spinal muscular atrophy?

Holistic care is critical and typically includes:

• Respiratory support: Non-invasive ventilation, airway clearance, suctioning, and tracheostomy when necessary.
• Nutritional support: Monitoring for swallowing difficulties and aspiration risk and maintaining appropriate caloric intake.
• Physical and occupational therapy: Stretching, strengthening, positioning, and mobility maintenance.
• Orthopaedic interventions: Bracing or surgery to manage spinal deformities and joint contractures.
• Psychosocial and palliative support: Counselling for patients and families; planning for advanced care.
   

Regular multidisciplinary follow-up ensures proactive management as symptoms evolve.

Can Spinal Muscular Atrophy Be Prevented?

While SMA cannot be prevented once a child inherits both mutated genes, prevention strategies focus on:

• Carrier screening for couples with a family history or those of reproductive age.
• Genetic counselling to assess recurrence risks and inform pregnancy planning.
• Preimplantation genetic diagnosis (PGD) during IVF to select embryos without the SMN1 mutation.
   

These measures help reduce incidence but do not alter the disease course in affected children.