Spinal Muscular Atrophy - Diagnosis

Diagnosis

Prenatal screening is controversial, because of its cost on the one hand, and the severity of the disease on the other hand. Some researchers have concluded that population screening for SMA is not cost-effective, at a cost of $5 million per case averted in USA. Others conclude that SMA meets the criteria for screening programs and relevant testing should be offered to all couples.

Very severe SMA (type 0/I) can be sometimes evident before birth - reduction in fetal movement in the final months of pregnancy; else, it manifests within the first few weeks or months of life when abnormally low muscle tone is observed (the "floppy baby syndrome").

Further, for all SMA types,

• Patient will present hypotonia associated with absent reflexes
• Electromyogram will show fibrillation and muscle denervation
• Serum creatine kinase may be normal or increased
• Genetic testing will show bi-allelic deletion of exon 7 of the SMN1 gene – this is conclusive of the disease.