In the end, Tunick went and had a terrific time. But she paid for it later when her body became achy and stiff.
"We were getting ready to leave, but I felt so ill," Tunick recalled. "It was one of the first times I felt really stiff. I thought it was due to the flu, that I was achy and so it was hard for me to move."
But it wasn't a simple case of flu. Soon after Tunick and her fiancé, Brian Mendenhall, returned to their home in southern Nevada, Tunick found she could not stand up and was having trouble breathing. Her doctor sent her to the emergency room.
"Once we got to the hospital, my body had locked up," said Tunick, who had also gone into respiratory failure. "I was unable to move any limb of my body, exactly like a paraplegic. But it's extremely painful. It feels like I'm laying on cement and somebody is crushing me down."
Tunick was experiencing the first of many episodes in which her muscles seized up painfully, a rare neurological condition known as Stiff Person Syndrome (SPS). Though the cause is unknown, SPS has features of an autoimmune disease in which the body's immune system attacks itself, setting off, in this case, muscle spasms.
For some people with the condition, unexpected stimuli -- such as loud noises and emotional distress -- can trigger muscle spasms and falls. Because these stimuli are so prevalent in the outside environment, many SPS sufferers are afraid to leave their homes.
Loud noises do not trigger Tunick's episodes. Rather, Tunick's painful muscle spasms paralyze her anytime her body comes in contact with a hard surface, such as a chair or a hard bed.
And the spasms can be severe.
"When you feel the muscles they're really hard, like rocks," said Dr. William Weiner, chairman of Neurology at the University of Maryland School of Medicine and a member of the American Academy of Neurology. "It's a really abnormal feeling."
Individually, the symptoms of SPS are not diagnostic, meaning they are often too general for doctors to be able to understand much of anything about what condition a patient might have.
And because the syndrome is so rare, it is often mistaken for a variety of musculoskeletal conditions, including Parkinson's disease, multiple sclerosis, fibromyalgia or something of a psychosomatic nature.
"Sometimes people are mistaken for being neurotic or overly anxious," Weiner said. "They complain of intermittent spasms, and doctors won't recognize it."
Weiner added that his clinic may only see one person with SPS every three or four years.
Tunick struggled with autoimmune diseases for years prior to her first SPS episode. Gastroparesis, a disease that paralyzes the stomach muscles, forced her onto a liquid diet. She also suffers from Myasthenia Gravis, which makes her weak and leaves her with little control over her facial muscles.
She has undergone a number of surgeries in the quest to improve her health. She had her gallbladder removed in January 2006 to try and cure her gastroparesis but the operation made her condition worse and she began having long moments when she lost consciousness.