Spinal Muscular Atrophy

Spinal Muscular Atrophy (SMA) is a genetic disorder characterized by the progressive weakening and atrophy of muscles due to the degeneration of neurons in the spinal cord and lower brainstem. It presents in various forms, from prenatal onset to late adult onset, with symptoms including muscle weakness predominantly in the lower limbs, respiratory insufficiency, and normal cognitive function. Treatment for SMA involves supportive care to manage nutritional and respiratory needs, physical therapy, and potentially spinal bracing or surgery for scoliosis. Disease-modifying therapies like nusinersen and onasemnogene abeparvovec are used, alongside genetic counseling for affected individuals and their families.

2024-01-05 14:15:37 - Editor

Overview of Spinal Muscular Atrophy (SMA)

Spinal muscular atrophy (SMA) is characterized by the degeneration of anterior horn cells in the spinal cord and motor nuclei in the lower brainstem, leading to progressive muscle weakness and atrophy. SMA typically involves diffuse symmetric proximal muscle weakness, more pronounced in the lower limbs, with markedly decreased deep tendon reflexes. It is associated with respiratory insufficiency, but cognition remains intact. SMA is inherited in an autosomal recessive pattern.

Subtypes of SMA

SMA encompasses various subtypes: SMA type 0 (prenatal onset), SMA type 1 (infantile, severe form), SMA type 2 (intermediate form, onset between 3-15 months), SMA type 3 (juvenile form, onset between 18 months and adulthood), and SMA type 4 (late onset, onset at age ≥30 years).

Treatment Approaches

Treatment of SMA includes supportive measures, disease-modifying agents, and genetic counseling. Supportive Therapy Supportive therapy focuses on preventing complications due to weakness. Nutritional management is crucial, involving food consistency modification and possibly gastrostomy. Respiratory interventions include chest physiotherapy, manual cough assistance, airway secretion management, and respiratory support (noninvasive ventilation or tracheostomy). Physical therapy and spinal bracing (excluding SMA types 1 and 2) are beneficial, and surgical repair for scoliosis may be necessary. Disease-Modifying Therapies Nusinersen, an antisense oligonucleotide, and onasemnogene abeparvovec, a gene therapy, are key disease-modifying treatments. Nusinersen is administered intrathecally with specific dosing schedules. Onasemnogene abeparvovec, administered as a one-time IV infusion, requires pre- and post-infusion liver function monitoring and prednisolone administration. Genetic Counseling Genetic counseling is recommended for individuals with SMA and their families.

Regular Evaluations

Individuals with SMA should undergo routine assessments every six months (or more frequently for severe cases) for nutritional and respiratory status.

References

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