Spinal Muscular Atrophy and Breathing — What Families Need to Know

When I started in pediatric respiratory medicine, a diagnosis of SMA type 1 usually meant a conversation about how long a baby had. That conversation is different now. Nusinersen (Spinraza), onasemnogene abeparvovec (Zolgensma) and risdiplam (Evrysdi) have given many children strength and milestones we never used to see. What has not changed is that the breathing muscles, the cough and the swallow need close attention, and that is where most of the serious illness in SMA still comes from.

Why SMA affects breathing

SMA weakens the muscles controlled by the spinal cord. In most children the diaphragm is relatively spared, but the muscles between the ribs are weak. The result is a very recognisable pattern: the tummy rises with each breath while the chest sinks inwards, and over time the chest can become narrow and bell-shaped.

Three problems follow from this:

• A weak cough. Children cannot clear secretions properly, so an ordinary cold can settle on the chest and turn into pneumonia or a collapsed segment of lung.
• Breathing that fails first during sleep. Muscle tone drops in dream sleep, and shallow breathing, low oxygen and a rising carbon dioxide level usually appear overnight long before they show during the day.
• Swallowing difficulty. Saliva or feeds can go into the airway, which adds aspiration to the infection risk.

Sitters, non-sitters and walkers

We still talk about SMA types 0 to 4, but for day-to-day respiratory planning it is more useful to think about what a child can do now. A child who cannot sit independently has the highest respiratory need. Children who sit but do not walk often need airway clearance support and overnight monitoring. Children who walk usually have milder respiratory involvement but still need regular review, particularly once scoliosis develops or if motor function starts to change. Treatment can move a child between these groups, so the respiratory plan should be reviewed as they progress.

What regular respiratory monitoring looks like

• Clinic review with a respiratory history focused on infections, sleep, headaches, feeding and weight.
• Lung function and cough strength in children old enough to do the tests, including peak cough flow.
• Sleep studies to pick up night-time hypoventilation early. In non-sitters this is often done in infancy; in older children it is guided by symptoms and lung function.
• Swallow assessment when there is coughing with feeds, wet breathing or recurrent chest infections.
• Scoliosis follow-up, because a curving spine reduces lung volume and matters before any spinal surgery.

Airway clearance: the most important daily treatment

For many children with SMA, a good airway clearance routine does more to prevent hospital admissions than anything else. That usually means chest physiotherapy techniques, suction for younger children and a mechanical insufflation–exsufflation device, often called a cough assist. The device gives a deep breath in and then quickly reverses to pull secretions out, doing the job a strong cough would do.

The routine should be taught properly, with settings adjusted to the child, and families need a written plan for stepping it up when their child has a cold. That plan is often what keeps a child at home rather than in intensive care.

Non-invasive ventilation

Night-time NIV through a nasal or full-face mask supports weak breathing muscles, allows the child to sleep deeply and can reduce chest deformity in younger children. In non-sitters it is often started early, sometimes proactively. For others it is started when a sleep study shows hypoventilation, or when a child has repeated infections. Some children also use it during illness or for part of the day.

I have written more about how NIV is set up and managed at home in home NIV for children.

Protecting against infection

• All routine immunisations, plus yearly influenza vaccination for the child and household.
• Pneumococcal vaccination as recommended for children with chronic respiratory conditions.
• RSV protection in infancy where it is available and appropriate.
• Early review with any chest infection, with a low threshold for antibiotics and intensified airway clearance.

Where gene therapy fits

Disease-modifying treatment and respiratory care are not alternatives. Children who receive Zolgensma, Spinraza or risdiplam still need the same respiratory surveillance, and the respiratory plan is updated as their strength changes. Some children improve enough to come off night-time support. Others remain stable on it. Both outcomes are much better than the natural history of the condition, and both depend on the basics being done well.

About Dr Omi Narayan

Consultant Pediatric Pulmonologist and Sleep Physician based in Dubai. Trained for 16 years in the UK's NHS, including as Consultant at Royal Manchester Children's Hospital. Dual UK board certification (CCT) in Pediatrics and Pediatric Pulmonology. 57 peer-reviewed publications.

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