Spinal Muscular Atrophy

What is spinal muscular atrophy (SMA)?

From: MedlinePlus, National Library of Medicine

Spinal muscular atrophy (SMA) is a group of genetic diseases that damages and kills motor neurons. Motor neurons are a type of nerve cell in the spinal cord and lower part of the brain. They control movement in your arms, legs, face, chest, throat, and tongue.

As the motor neurons die off, your muscles start to weaken and atrophy (waste away). The muscle damage gets worse over time and can affect speaking, walking, swallowing, and breathing.

What are the types of spinal muscular atrophy (SMA) and what are their symptoms?

From: MedlinePlus, National Library of Medicine

There are different types of SMA. They are based on how serious the disease is and when the symptoms start:

• Type l is also called Werdnig-Hoffman disease or infantile-onset SMA. It is the most severe type. It is also the most common. Babies with this type usually show signs of the disease before 6 months of age. In more severe cases, the signs show up even before or just after birth (Types 0 or 1A). The babies may have trouble swallowing and breathing and may not move around a lot. They have chronic shortening of muscles or tendons (called contractures). They usually cannot sit up without help. Without treatment, many children with this type will die before 2 years of age.
• Type ll is a moderate to severe type of SMA. It usually first noticed between 6 and 18 months of age. Most children with this type can sit without support but cannot stand or walk without help. They may also have trouble breathing. They can usually live into adolescence or young adulthood.
• Type lll is also called Kugelberg-Welander disease. It is the mildest type that affects children. The signs of the disease usually show up after age 18 months. Children with this type can walk by themselves but may have trouble running, getting up from a chair, or climbing stairs. They may also have scoliosis (curvature of the spine), contractures, and respiratory infections. With treatment, most children with this type will have a normal lifespan.
• Type IV is rare and often mild. It usually causes symptoms after 21 years of age. The symptoms include mild to moderate leg muscle weakness, tremors, and mild breathing problems. The symptoms slowly get worse over time. People with this type of SMA have a normal lifespan.

What causes spinal muscular atrophy (SMA)?

From: MedlinePlus, National Library of Medicine

Most types of SMA are caused by a change in the SMN1 gene. This gene is responsible for making a protein that the motor neurons need to be healthy and to function. But when part of the SMN1 gene is missing or abnormal, there isn't enough protein for the motor neurons. This causes the motor neurons to die off.

Most people have two copies of the SM1 gene - one from each parent. SMA normally only happens when both copies have the gene change. If only one copy has the change, there usually aren't any symptoms. But that gene could be passed down from parent to child.

Some of the less common types of SMA may be caused by changes in other genes.

How is spinal muscular atrophy (SMA) diagnosed?

From: MedlinePlus, National Library of Medicine

Your health care provider may use many tools to diagnose SMA:

• A physical exam
• A medical history, including asking about family history
• Genetic testing to check for the gene changes that cause SMA
• Electromyography and nerve conduction studies and a muscle biopsy may be done, especially if no gene changes were found

Parents who have a family history of SMA may want to do a prenatal test to check to see whether their baby has an SMN1 gene change. An amniocentesis or in some cases a chorionic villi sampling (CVS) is used to get the sample for testing.

In some states, genetic testing for SMA is part of newborn screening tests.

What are the treatments for spinal muscular atrophy (SMA)?

From: MedlinePlus, National Library of Medicine

There is no cure for SMA. Treatments can help manage symptoms and prevent complications. They may include:

• Medicines to help the body make more of the proteins that the motor neurons need
• Gene therapy for children under 2 years of age
• Physical, occupational, and rehabilitation therapy to help to improve posture and the mobility of the joints. These therapies may also improve blood flow and slow muscle weakness and atrophy. Some people may also need therapy for trouble speaking, chewing, and swallowing.
• Assistive devices such as supports or braces, orthotics, speech synthesizers, and wheelchairs to help people stay more independent
• Good nutrition and a balanced diet to help maintain weight and strength. Some people might need a feeding tube in order to get the nutrition they need.
• Breathing support for people who have muscle weakness in the neck, throat, and chest. The support may include devices to help with breathing during the day and to prevent sleep apnea at night. Some people might need to be on a ventilator.

Which doctor should you see?

The suggested department for discussing Spinal Muscular Atrophy is Neurology, with a neurologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which nervous-system findings help explain the symptoms?
• Would an assessment of walking, communication or daily function be helpful?
• Are rehabilitation or other specialist services relevant?

Treatment discussions and follow-up

Where the source describes treatments, these are an overview of possible care, not a prescription for an individual. Ask which option applies to the confirmed diagnosis, what benefit is expected, what adverse effects to watch for and how progress will be assessed. Availability, approvals and local practice can differ from the country described in the source.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.