The researchers from the Oregon Health & Science University School of Medicine's department of neurology and the OHSU MS Center of Oregon presented the study this month at the American Academy of Neurology's 57th Annual Meeting in Miami Beach, Florida.
In addition to ginkgo biloba's potential to improve attention, the natural medicine also appeared to have minimal side effects.
The study's lead author, Dr Jesus Lovera, a research fellow in neurology at OHSU School of Medicine, said those receiving ginkgo "performed better on a test that measures a person's ability to pay attention and to sort conflicting information."
Thirty-nine patients completed the study, with 20 receiving ginkgo biloba and 19 receiving placebo. The researchers recorded that there were no differences in results between the two groups in the areas of gender, education, type of MS, years since onset, or baseline performance after a series of neuropsychological tests.
However, the ginkgo group was found to be four seconds - about 13 per cent - faster than the placebo group on a timed colour and word test that measured attention and "executive functions" such as planning, decision making and controlling goal-directed behavior and execution of deliberate actions.
During the so-called "Stroop" test, patients were shown coloured boxes and asked to name the colours. They were then shown the names of colours printed with different-colored inks, such as the word "green" printed in red, and asked to read the word. Finally, patients were asked to describe the ink used for each word.
Lovera said the differences in the Stroop result would be comparable to differences in scores between healthy people aged 30 to 39 and those aged 50 to 59.
The researchers found that Ginkgo appeared to be more beneficial for MS patients who were having specific problems with Stroop exercies. Hence, Lovera said: "we would like to do another study in which we choose patients that are impaired in this particular test".
Ginkgo is derived from the leaves of the ginkgo tree and has been used for thousands of years by the Chinese as a herbal remedy for a variety of ailments. It contains potent antioxidants called flavoglycosides that have been shown to have neuroprotective effects in animal models of spinal cord injury.
It also has terpene-lactones that block a substance known as platelet activitating factor, which is important in regulating blood vessel function as well as the mediating inflammation and the sticking of inflammatory cells to blood vessels.
Many MS patients have long suspected that ginkgo improves disease symptoms. In a recent survey of nearly 2000 patients in Oregon, 20 per cent reported using the supplement and 39 per cent found it to be beneficial. However, until now, there was no evidence the supplement had any effect on memory.
"It has been shown to be of benefit in Alzheimer's, but we did not know if it would work for MS," Lovera said. "We wanted to see if there was any suggestion that it could help patients with MS that are having cognitive problems."
Lovera said the study results demonstrate that ginkgo should not be discounted for treating MS, but its safety and efficacy must be tested in much larger clinical trials before doctors should recommend it to their patients.
"The study suggests that for cognitive problems, it may only help a certain group of patients," he said. "We need to study this further."
Ginko biloba is among several complementary and alternative medicine therapies being investigated by OHSU's Department of Neurology for their effects on symptoms of neurological disease. Studies have ranged from clinical trials of lactoferrin for treating Alzheimer's disease to the use of yoga as a therapy for MS fatigue.