Each optic nerve contains approximately one million nerve cells (neurons) that connect the eye to the brain. Inflammation from multiple sclerosis (MS) can affect the optic nerves. Therefore, it is very common for people with MS to have vision problems.
When MS inflammation affects optic nerve neurons, they may lose their protective myelin coating, a process called demyelination. This caused signals through the neurons to slow down, resulting in blurred vision.
Medications may repair myelin, but studies are limited.
4-aminopyridine (4-AP) is a medicine used to treat symptoms of MS caused by demyelination. It stabilizes movement of potassium ions through the surface of demyelinated neurons, making it easier for them to conduct signals.
Historically, 4-AP has only been available through compounding pharmacies, so studies of its use have been small and not rigorously designed. More recently, studies of a pharmaceutically manufactured form of 4-AP, dalfampridine (Ampyra®), found it to be effective at improving walking in patients with MS in a number of ways.
New research suggests vision benefits.
The Department of Neurology and Neurotherapeutics at the University of Texas Southwestern Medical Center in Dallas recently studied 4-AP in people with MS who have optic nerve damage.
Researchers tested the vision of a small group of patients with vision problems caused by MS before administering 4-AP or a placebo. After five weeks, one-third of the patients taking 4-AP had improved vision, compared to just 14 percent taking a placebo. They found that those with the least damage to optic neurons particularly benefited from 4-AP.
Next steps for a potential new therapy.
This research suggests that 4-AP may be somewhat beneficial for people with vision problems caused by MS. While none of the subjects in the study had serious complications of treatment from 4-AP, seizures may result from treatment with similar medications, so they need to be used cautiously. Further studies with more patients are necessary to learn if Ampyra may be best used to treat vision changes and what types of patients would find it most beneficial.
