NEW YORK (AP) _ Lyme disase can produce severe nervous system disorders that look like brain tumors, Alzheimer's disease and multiple sclerosis, condemning patients to years of needless suffering because of misdiagnosis, doctors said Monday.

In addition, such disorders can occur years after exposure to Lyme disease, which often is curable, said researchers at the International Conference on Lyme Disease and Related Disorders, sponsored by the New York Academy of Sciences.

Lyme disease was identified in 1975 by Dr. Allen Steere, formerly of Yale University, who noted an unusually large number of cases of arthritis in young people in Lyme, Conn.

In 1982 a corkscrew-shaped bacteria of the kind known as spirochetes was discovered to be the cause of the disease, and it was found to be usually treatable with antibiotics. The disease is transmitted by ticks, which carry the spirochete.

However, a disturbing number of cases of Lyme disease are being misdiagnosed, although no one knows precisely how many, said Dr. Andrew Pachner, a neurologist and Lyme disease specialist at Georgetown University in Washington, D.C.

He suggested that in areas where Lyme disease is most common - the northeastern United States, Wisconsin and Minnesota - hospitals should routinely test all admitted patients for evidence of infection, just as many of them do for evidence of syphilis.

''Anybody in an area endemic for Lyme disease who develops neurological problems should consider that as Lyme disease and be tested,'' Pachner said.

Prompt diagnosis and treatment is important, he said, because the bacterium that causes the disease can lie dormant in the body for many years and when it finally becomes active it may no longer be treatable.

''At some point this disease flips in at least some people to an untreatable phase,'' said Pachner.

In 1982, 491 cases of Lyme disease were reported to the federal Centers for Disease Control in Atlanta. The figure climbed to 1,498 cases by 1984. More recent figures will be released by the Centers for Disease Control later this week at the conference.

In the wake of the discovery of the Lyme disease spirochete, it became possible to test people to see whether they'd been exposed to it. Such testing soon made it clear that the organism causes a wider spectrum of illness than arthritis, said Steere, now at Tufts University's medical center in Boston.

''There is an increasing awareness at this point of the neurological part,'' of the illness, he said. Lyme disease can also cause a fatal inflammation of the heart and inflammation of the optic nerves that can lead to blindness, Steere said.

Dr. John Halperin of the State University of New York at Stony Brook said Lyme disease also can cause milder neurological problems, leading not to severe illness but to loss of memory, concentration and other intellectual functions.

He found that 60 of 85 Lyme disease patients who came to his clinic had electrical abnormalities of the nervous system.

A group of 17 patients given a battery of a dozen psychological and neurological tests were found to have problems with immediate and delayed recall, the ability to learn and solve problems, and maintaining attention and concentration.

When the patients were treated with antibiotics, their mental functions generally returned to normal, he said.