Country music legend Kris Kristofferson, who has battled memory problems for years, is apparently among many Americans who have been misdiagnosed with Alzheimer's disease, only to learn later that they actually have a treatable illness – in this case, Lyme disease, a top expert says.

“I think that it’s possible for Lyme disease to be misdiagnosed as Alzheimer’s and Kris Kristofferson’s story speaks to the importance of an accurate diagnosis,” Dr. Gary Small, director of the University of California-Los Angeles Longevity Center, tells Newsmax Health.

Kristofferson, 79, was under the belief that his longstanding memory problems stemmed from Alzheimer's, but now his wife says that the iconic singer, songwriter, and award-wining actor actually had untreated Lyme disease. After just a few weeks of treatment, he turned around, she says.

"All of a sudden he was back,” Lisa Kristofferson tells Rolling Stone. “There are still bad days. [But] some days he's perfectly normal and it's easy to forget that he is even battling anything.”

For years, doctors had been telling Kristofferson that his increasingly debilitating memory loss was due to either Alzheimer's or to dementia brought on by blows to the head from boxing, football, and rugby he played in his teens and early 20s. Some days, Kristofferson couldn't even remember what he was doing from one moment to the next, the article says.

But, earlier this year, a doctor decided to test Kristofferson for Lyme disease, and the test came back positive. After three weeks of treatment for the ailment – along with getting off the drugs for Alzheimer’s and depression that he was taking – the singer's memory problems have largely disappeared, the article indicates.

According to Small, while Alzheimer's disease is often under diagnosed,  it can also be misdiagnosed.

“Severe anemia, thyroid disorders, and depression are all treatable conditions that can produce symptoms that look like Alzheimer's,” he says.

It’s also been estimated that up to 5 percent of those misdiagnosed with Alzheimer’s or Parkinson’s disease have a treatable brain condition known as "normal pressure hydrocephalus.”

“The take home message for all of this is that Alzheimer’s disease has to be diagnosed only after a thorough investigation, which includes the patient’s history, as well as blood tests, and often brain imaging as well,” adds Small, author of the Mind Health Report newsletter.

Such tests can include Lyme disease, especially if the patient lives in or has traveled to an area known to be tick infested, he notes.

Kristofferson’s wife also says that her husband's going off of drugs for Alzheimer's and depression have  made a great difference.

“Many medications can cause problems with cognition that are similar to Alzheimer’s, particularly those given for depression,” notes Small.

Kristofferson’s wife believes that the singer must have been infected with Lyme disease by a tick bite when he was in Vermont, crawling around the woods while filming the movie “Disappearances,” which was released in 2006.

The issue over whether untreated Lyme disease can cause chronic medical problems is one of the hottest debates in medicine, says Dr. Michael Zimring, director of the Wilderness and Travel Medicine Center at Mercy Medical Center in Baltimore.

“Acute Lyme disease, which is diagnosed clinically, can cause complications involving the heart, nervous system, muscles, and joints, but whether this can occur later on as chronic Lyme disease  is very controversial," says Zimring, who stresses he is discussing the topic only in general terms, as he prefers not to discuss specific cases.

The Centers for Disease Control and Prevention does not acknowledge the existence of chronic Lyme disease, preferring the term "post treatment chronic Lyme disease syndrome" for people who have been treated for Lyme disease but are beset with lingering, debilitating symptoms.

Clouding the problem is the issue of Lyme disease testing. People who have Lyme disease can test negative for it until their body builds up antibodies. But people who don’t have it can also test positive for other reasons, including autoimmune disorders, which is why the CDC recommends a two-tier testing process.

Regardless, the change in diagnosis – and treatment – has made a huge difference in Kristofferson's day-to-day life, as well as his future plans. The singer, who will turn 80 this month, recently traveled to Canada to record with fellow legends Gordon Lightfoot and Ronnie Hawkins, and also plays the lead in the movie “Traded,” which will be released this week.