One day, when Emily Garland was eating her lunch, the 3-year-old grabbed her cheek and started crying.

Her mom, Laurel Garland, a 33-year-old human resources specialist, innocently thought her daughter had simply bitten her cheek.

In reality, that day marked the start of a nightmare, one that drew on for 1` 1/2 years and eluded every local health professional Laurel and her husband, Dave, could throw at it.

As the days passed, Emily kept complaining about the pain, and her parents realized it wasn't just a cheek bite. They thought she had a cavity, but her dentist couldn't find anything.

After a short respite, the pain came back last fall, but worse and more frequent. They took her to another dentist who couldn't find anything wrong.

Next was a pediatrician who thought Emily might have gall stones in her salivary gland. Testing didn't show anything unusual. By this time, if her shirt brushed her cheek as she was getting dressed, or if her hair blew against her face in the breeze, Emily would scream.

The pediatrician suggested perhaps she was faking it to get attention, and her parents considered it. But then Emily started waking up screaming from a dead sleep.

In the spring, Laurel Garland went through the yellow pages to find another dentist. This one, Laila Hishaw, almost immediately suggested Emily might have trigeminal neuralgia, a rare disorder that often triggers a sharp and sudden shock-like stabbing pain in the face.

The trigeminal nerve - the largest of the 12 pairs of cranial nerves - conducts sensations from the face and oral cavity to the brain. The origin of the disorder is still unclear, but doctors suspect the pain may be caused by blood vessels compressing the nerve.

With nerve disorder on their minds, Emily's parents' next stop was a pediatric neurologist, who did tests to rule out multiple sclerosis and brain tumors. Finally, Emily was put on a medication. But to no avail, as the family discovered during their summer boating excursions. Emily - who loves to swim - would enthusiastically jump into the water, only to emerge crying because the water on her face triggered an attack.

Two months ago, Emily's pain was so bad that she had stopped drinking, sleeping, eating and talking. She wouldn't brush her teeth. She started drooling because she didn't want to swallow. "She wouldn't cry; she would scream," remembers Garland, who works for Tucson Newspapers. "She was doing it so much, she lost her voice from all the screaming."

A visit to urgent care left her with large doses of codeine and OxyContin, neither of which dulled the nerve pain. Laurel and Dave Garland, married eight years, were worse than heartbroken - they were panicked. Their formerly exuberant, talkative daughter was gone. Emily was either lethargic from the pain or frozen in place, afraid to do anything because literally everything, even walking, would jostle the pain awake.

Then one day, while searching online, Garland found a support group in Tucson. Charles Panian, a 70-year-old former owner of a dry-cleaning business and leader of the group, said there are 140 people on the mailing list locally.

It's been six years since he was diagnosed and he's largely pain-free now with treatment, but, "I still don't put my head under the shower. That's how bad the pain is."

Through the support group the Garlands found themselves referred to Dr. Abhay Sanan, a neurologist familiar with the disorder. He put Emily on an anti-seizure medication - the same treatment that is working for Panian - and within hours, the pain was improving.

Sanan said he rarely sees children with the disorder. It's rare in the first place - only about 40 patients a year in a community the size of Pima County's will develop it, he estimated, and usually, as adults.

Although anti-seizure medication is often effective, he said, the only cure is a surgical procedure that works in about two-thirds of cases. Surgery involves entering the back of the skull to move the blood vessel away from the nerve and pad it with a piece of Teflon-like material. Another option is a new noninvasive technology that uses radiosurgery to deliver high doses of radiation treatment to the nerve. That's usually reserved for older people though, because over time, the nerve will ultimately heal itself, and the radiosurgery needs to be repeated. Doctors would be reluctant to put that much radiation in someone's system more than twice, Sanan said.

Patients often tell a familiar tale of having a hard time finding a diagnosis: there is no test for the disorder, and it is difficult to diagnose an intermittent pain unaccompanied by any physical changes like redness or swelling. A 1992 study published in The Journal of the American Dental Association tracked 61 patients with trigeminal symptoms. Two-thirds had incorrect diagnoses of dental problems, and as a group, underwent more than 100 dental procedures, including root canals and tooth extractions.

"A lot of times, for people who have this disorder, when it doesn't get diagnosed they get frustrated and think there's no hope," Sanan said, "when in reality, this disorder has very good treatment now and there's much cause for hope."

As for Emily, she will likely eventually build up a tolerance to the medication and her parents are resigning themselves to the likelihood she will someday have surgery. They hope it can wait until she's older and stronger.

But blessedly, for now, she's enjoying a full-blown princess phase, squinching her face up in too-big smiles for photographs, and playing with Sierra, her golden retriever. In other words, she's busy being 4.