Many medications and therapies for spinal muscular atrophy (SMA) need to reach the spinal cord to be effective. However, this can be quite difficult to achieve as many medications have trouble crossing the blood-brain barrier that protects the spinal cord. Some drugs and therapies are able to cross the barrier, but others such as stem cell therapy or Spinraza, need to be delivered directly into the central nervous system to bypass it.
According to the SMA Foundation, this can be achieved in three different ways.
- Intraparenchymal delivery: Drugs and therapies can be delivered directly to the spinal cord tissue using the intraparenchymal route, where the drug is infused into either the inner or outer layer of spinal cord tissue.
- Intrathecal delivery: Delivery of the drug or therapy into the subarachnoid space in the lumbar area of the spine, which is filled with cerebrospinal fluid. Spinraza is delivered through this method.
- Intracerebroventricular delivery: Delivery of the drug or therapy into the subarachnoid space in the ventricles of the brains which are filled with cerebrospinal fluid, allowing the medication to reach the brain and the spinal cord.
Cerebrospinal fluid is replaced several times a day when it exchanges with the bloodstream. Most drugs and therapies delivered directly into the spinal cord will need repeated administrations and different drugs need different routes into the cerebrospinal fluid to be effective.
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