Spinal Muscular Atrophy (SMA)

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Introduction

Spinal Muscular Atrophy (SMA) is a genetic condition under the scope of the neuromuscular disorders. It is characterised by degeneration of alpha motor neurons in the spinal cord.

Spinal Muscular Atrophy affects ...

Clinically Relevant Anatomy

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Mechanism of Injury / Pathological Process

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Clinical Presentation

Spinal Muscular Atrophy (SMA) is the second most common neuromuscular disorder of childhood. People affected by the mildest types of SMA have proximal weakness and impaired ambulation. Furthermore, fatigue is a symptom to present in almost every case of SMA which may also lead to impaired function and endurance. Current research in the area shows that there is good correlation between upper and lower limb function in patients with the disease. There are several types of SMA, which start at different ages and may present with various phenotype.

Types of SMA:

• SMA type I - affects babies less than six months old and is the most severe type of the disease
• SMA type II - develops in babies between 7 and 18 months old. This type is less severe than type I and most children survive into adulthood and can live long, fulfilling lives.
• SMA type III - appears after 18 months of age and is the least severe type affecting children. SMA type III has been divided into two further sub-categories: SMA IIIa and SMA IIIb - according to the time when the first symptoms of the condition appears (if before or after 3 years of age).
• SMA type IV - this type of SMA patients are diagnosed in adulthood and they present with only mild problems.

Diagnostic Procedures

Diagnoses could be made by prenatal screening or by gene panel investigation/ observational

Outcome Measures

There are several outcome measures which can be used to detect changes in the natural history of the patients with SMA. These tools should be appropriate selected according to the age and severity of the disease.

Six-Minute Walking Test (6MWT)

The Six-Minute-Walking-Test can be safely performed in ambulant patients with SMA. It has been proven to detect fatigue-related changes in this population of patient and correlates with other established outcome measures for patients with spinal muscular atrophy.

Management / Interventions

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Differential Diagnosis

Neuromuscular conditions:

• Duchenne Muscular Dystrophy
• Charcot-Marie-Tooth
• Amiotrophic Lateral Sclerosis
  

Resources and Useful Links

SMA REACH UK - Information Page

Spinal Muscular Atrophy Support UK