Doctors often initially misdiagnose people with Jakob-Creutzfeldt disease, a rare brain disorder caused by misfolded, infectious prion proteins, according to new research.

Jakob-Creutzfeldt disease, or CJD, is marked by rapid brain wasting and dementia and typically kills patients within a year after symptoms appear. According to the National Institutes of Health, there are about 200 cases each year in the United States.

In the new study, researchers found 97 people with CJD received an average of almost four different diagnoses each before doctors made the correct call. Those alternate diagnoses included autoimmune disorders, Alzheimer's and depression.

Researchers said the early symptoms of CJD can vary widely, depending on where in the brain infected proteins accumulate.

"There's a lot of other things it could be, literally any disease that could affect the brain in a relatively rapid way," said Dr. Richard Caselli, a neurologist from the Mayo Clinic Arizona in Scottsdale, who wrote a commentary accompanying the study in the Archives of Neurology.

He said the search for a correct diagnosis, with multiple failed attempts along the way, is "obviously a very traumatic thing for families to endure." It can also be expensive.

CJD is not treatable, so although catching it early prevents patients from having to undergo more tests, it won't change the course of the disease.

On the other hand, Caselli said a number of other conditions that may come with similar symptoms, such as infectious meningitis, can be treated if they're diagnosed quickly. That's why neurologists try to exhaust every possible curable option before landing on a diagnosis of CJD.

Dr. Michael Geschwind of the University of California, San Francisco, and colleagues found it took CJD patients almost eight months from the onset of symptoms until they were correctly diagnosed, on average. By then, most only had a few months left to live.

The study included 97 people, age 26 to 83, referred to the UCSF Memory and Aging Center between 2001 and 2007. Seventeen of them had been correctly diagnosed with CJD at their first assessment - but it took much longer for others.

Caselli said that because symptoms of different brain-related disorders often overlap, magnetic resonance imaging, or MRI, is typically the best way to see what's going on in the brain and make a diagnosis. But even so, that doesn't always work.

"The challenge comes when the MRI findings are not as definitive as you'd like them to be," he told Reuters Health.

Some other invasive tests, such as spinal taps, can differentiate meningitis from CJD.

Geschwind said he often tests for infections such as syphilis and HIV in people with early symptoms similar to CJD. Dementia that comes on quickly can also be caused by cancer antibodies that attack the nervous system, he said.

A small fraction of CJD cases are passed down in families and the disease can be transmitted through infected brain tissue. But most cases occur when normal proteins in the brain spontaneously become infectious, for no clear reason.

"Any time there's a patient with a rapidly progressing dementia, I mean going from completely normal function to not being able to function in a few months to less than a year, I think CJD should be (considered)," Geschwind told Reuters Health.

"But so should many of these other conditions, some of which are treatable."

"It still is true that one should not accept the diagnosis without being sure that one has had a thorough evaluation," Caselli said.

"The more definitive one can be, the more one can save the patient who's pretty oblivious through all this from getting dragged from one doctor to another," he added.

"Once the diagnosis is credibly established, it really probably is best to start thinking about palliative care hospice, the comfort of the patient and the family so that people can start to deal with this diagnosis and the time they have left."