Scientists in the U.S. say a drug which can reverse some of the early symptoms of Alzheimer's disease takes effect within 10 minutes.

The scientists from the University of California at Los Angeles, and the University of Southern California, say the memory of an 81-year-old man improved dramatically after the drug etanercept, currently used to treat arthritis, was injected into his spine.

Some studies have suggested that too much of a body chemical called tumour necrosis factor-alpha may be at least partly to blame for the advance of the condition.

Etanercept, which is licensed for use as a rheumatoid arthritis drug, works to block this body chemical.

The study highlights the importance of certain soluble proteins, called cytokines, in Alzheimer's disease and the cytokine, tumor necrosis factor-alpha (TNF), is a critical component of the brain's immune system.

In normal circumstances TNF finely regulates the transmission of neural impulses in the brain and the researchers hypothesized that elevated levels of TNF in Alzheimer's disease interfere with this regulation.

The theory was that an injection of etanercept would reduce the elevated levels of TNF.

The scientists Dr. Edward Tobinick and Dr. Hyman Gross have already published a study which suggested that this could benefit Alzheimer's patients.

They had noticed in previous research that injecting the drug into the neck spine seemed to deliver almost immediate effects.

The decided to test the medication on just one patient, a former doctor who had the early stages of the disease.

Before the injection they measured his performance on cognitive tests, and found he performed poorly and was unable to remember the name of the doctor treating him, the date, or the state in which he lived. Neither could he perform simple mental arithmetic, or name more than two animals.

To the astonishment of his family ten minutes after a dose of etanercept, he was noticeably calmer, more attentive, and less frustrated; he also knew he lived in California, knew the day of the week, and the month, could name five animals, and performed better at the arithmetic test.

His wife said he was clearer and more organised and his son declared the change immediately after the drug was administered was the "single most remarkable thing he had ever seen."

The Alzheimer's Research Trust, says the study is promising and innovative but is in the early stages and further work is needed with a larger number of patients before it can be concluded that etanercept could work as a treatment for Alzheimer's.

Experts say it needs to be clear that the benefits were not just due to the placebo effect and established whether any benefit was temporary or whether the disease itself is slowed.

They also warn that a single success did not prove that the drug would work for every dementia patient.

The lead author of the study, Dr. Edward Tobinick, is an assistant clinical professor of medicine at the University of California, Los Angeles and director of the Institute for Neurological Research, a private medical group in Los Angeles.

Co-author Dr. Hyman Gross is a clinical professor of neurology at the University of Southern California.

The authors say though the study discusses just one patient, many other patients with mild to severe Alzheimer's received the treatment and all have shown sustained and marked improvement.

Etanercept acts by binding and inactivating excess TNF and has FDA approval to treat a number of immune-mediated disorders; it was used off label in the study.

The study appears in the Journal of Neuroinflammation.