Elaina, 16, suffers from an unusual case of Lyme disease, with symptoms that includes a speech disorder and seizures. (Courtesy Elaina

You'd never know it sitting across from 16-year-old Elaina that she suffers from a rare and debilitating case of Lyme disease. The spark-plug of a teen is bright, bubbly, and optimistic in the face of what she describes as a four-year nightmare.

She believes she was bitten at age 12 by a tick on a soccer field in her New Hampshire town and consequently developed a co-infection of Lyme and another bacterial parasitic illness called Bartonella.

In most, Lyme disease will manifest in fatigue or chronic pain. That's what I experienced when I was infected with Lyme six years ago. A three-day stay in the hospital and a round of antibiotics and I was back to normal.

Not so for Elaina. Her symptoms have ranged from seizures to loss of motor function to light and sound sensitivity. Most unusual of all is what she describes as a tightening of muscles in her throat brought on by stress and fatigue. The result, she says, is an altered spell-like state during which she speaks in what sounds like a Russian accent. Sometimes, she can't even remember what she says or does during those episodes.

We witnessed the speech disorder ourselves when we showed up to interview the teen, whose last name and hometown we're not using.

And here are videos that her mother, Becky, filmed for Elaina's blog.

The symptoms from which she suffers have caused skepticism among medical professionals, some of whom speculate that she is faking it for attention.

But her physician, Dr. Lynn Durand, says that while he can't explain it, he doesn't doubt it either. "Lyme can have some very strange symptoms," he said. "And I think what's so important about Lyme disease is that patients will present with strange symptoms and, we, the medical community, will not know what to make of it, and unfortunately we think, 'If the diagnosis isn't in my head, it must be in the patient's head, so they must be making this up.'

"My feeling is that it's very, very important to take the patients at their word and hear what they have and really try to explore what the causes are."

Watch the whole story on the full episode of "20/20."