Early Diagnosis Key in Spinal Muscular Atrophy

James Wymer, MD, PhD, Professor, University of Florida, Gainesville, FL, highlighted the importance of early diagnosis for spinal muscular atrophy during a virtual presentation at Neurology Week.

Spinal muscular atrophy, a progressive neurodegenerative disease that impacts motor neurons beginning in proximal muscles and voluntary muscle strength, affects patients ranging in age from infanthood to adulthood.

“One of the things that is important about SNA (spinal muscular atrophy) is that we need to individualize therapies, every patient is not the same, we can’t use cookie cutter types of therapy,” Dr Wymer stated.

Spinal muscular atrophy is a spectrum genetic disorder that results from insufficient survival motor neuron (SMN) protein, due to the loss of function of the SMN1 gene.

Symptom onset can be unpredictable. Severity of symptoms vary but can often include muscle weakness or respiratory insufficiency because of the degeneration of motor neurons in the spinal cord.

 Five types of spinal muscular atrophy defined by age of diagnosis were noted in the presentation:

• pre-symptomatic
• infantile-onset type 1
• later-onset type 2
• later-onset type 3
• and later-onset type 4

Dr Wymer’s presentation focused on patients diagnosed as adolescents or adults, classified as later-onset type 4, and talked the audience through a possible patient case scenario. As the presentation of symptoms for later-onset type 4 are milder, making the diagnosis can be more difficult.

In patients with later-onset spinal muscular atrophy, time to significant muscle weakness and loss of motor function is not predictable. Diagnostic delays can cause missed opportunities for therapeutic intervention.

Wymer emphasized the importance of diagnosing this disease early because disease progression can be rapid, and the opportunity for early therapeutic intervention can be missed.

Physical therapy, occupational therapy, speech and language pathology, respiratory therapy and nutrition are all areas of treatment for supporting patients with SMA beyond available medications.

Gene therapy exists for pediatric patients and nusinersen and risdiplam are medications that have been approved in the last 5 years for treatment of SMA.

“The later an individual experiences symptoms, the less severe they are likely to be at presentation, but timely diagnosis and appropriate initiation of therapy remain crucial for optimal outcomes,” Dr Wymer concluded.

—Erin McGuinness

Wymer, J. Early Diagnosis Key in Spinal Muscular Atrophy. Presented at Neurology Week 2021; July 14-18. Virtual.