Antiseizure Drug Helps Optic Neuritis in Multiple Sclerosis
The relationship between seizures, optic neuritis, and multiple sclerosis may seem difficult to fathom, but the results of a new study shed some light on the subject. It appears that the common antiseizure drug called phenytoin has the ability to help prevent the development of acute optic neuritis, an eye condition frequently seen in people who have multiple sclerosis.
Acute optic neuritis involves inflammation of the nerve that transports messages concerning visual stimulation from the eye to the brain. The inflammation can lead to sudden blurry vision, pain, and partial or total blindness. Although individuals can eventually recover from an attack of acute optic neuritis, each episode results in some damage to the eye.
The findings of the latest study, which will be presented at the American Academy of Neurology 67th Annual Meeting by Raju Kapoor, MD, of the National Hospital for Neurology and Neurosurgery in London, United Kingdom, could ultimately make a significant impact on individuals who suffer with this potentially life-altering condition associated with multiple sclerosis. Currently, individuals with acute optic neuritis are treated with steroids, but this approach does not lead to a completely satisfactory result.
Phenytoin, which is an anticonvulsant drug often used to treat individuals with epilepsy, appears to be effective in addressing this visual challenge. This finding comes a study of 86 individuals with acute optic neuritis who were randomly assigned to take either 4 mg/kg/day of phenytoin or a placebo for three months. Treatment was initiated within two weeks of having symptoms.
The researchers used advanced imaging to determine the thickness of the retina and also tested all the patients for color perception and sharpness. They discovered that:
- Generally, individuals who took phenytoin had 30 percent less damage to their retinal nerve fibers than participants who took placebo
- Patients who took phenytoin had 34 percent greater volume of the macula than those who took placebo. The macula, which is extremely light sensitive, is the area of the eye affected by individuals who develop macular degeneration, the leading cause of vision loss among adults older than 50.
In up to 50 percent of people diagnosed with multiple sclerosis, vision problems are a presenting sign. In fact, optic neuritis is the presenting syndrome in 20 percent of MS patients and, according to Edward J. Atkins, MD, “for many people, a diagnosis of optic neuritis is equivalent to having a high risk of MS.”
That the current treatment for acute optic neuritis is usually intravenous steroids (methylprednisolone) followed by an oral steroid (prednisone). This approach has no impact on a person’s final visual outcome and frequently involves side effects such as elevated blood pressure, mood swings, weight gain, and increased risk of infection, among others.
Clearly, other prevention and treatment choices for optic neuritis are needed. Further research is needed to determine whether phenytoin could be such an option.