Michael Herndon has had a headache since November 15, 2008. Doctors have ruled out many things, but the cause of his problem is still a mystery. Herndon rubs the area where the pain is the most acute — above and around his eyes and down toward his nose. (Michael S. Williamson/WASHINGTON POST)

Driving south on the Baltimore-Washington Parkway bound for his Adams Morgan home in June 2009, Michael Herndon struggled to cope with the implications of what the doctor had just told him.

For months Herndon had tried to find out why the headache he developed on Nov. 15, 2008 — he remembered the exact date — had not gone away. The 41-year-old had consulted neurologists and ear, nose and throat specialists as well as an allergist and ophthalmologist, but none of them had figured out what was causing his pain.

“I was starting to hit a mental and physical wall,” recalled Herndon, a consumer outreach specialist at the Commodity Futures Trading Commission. “I’d been chasing this for more than six months. No one could tell me what it was. I just remember thinking, ‘How am I going to be able to function if it never goes away?’ ”

He had taken multiple courses of antibiotics and corticosteroids as well as over-the-counter pain relievers, and he had even undergone sinus surgery, all to no avail. Doctors had ruled out a brain tumor and other ailments but had no idea why his head, and increasingly his nose, still hurt.

A month later, Herndon learned the name of his disorder. It would be another year before he found effective help to cope with his chronic, and still largely inexplicable, head pain.

Now a neurologist at a major medical center in Baltimore told him his sinuses looked clear and suggested that the headache might never disappear. But he did not give Herndon a name for his condition or a remedy, suggesting only that he find a headache specialist in the Washington area.

Aftermath of a stress test

In October 2008, after experiencing chest pain, Herndon saw a cardiologist who ordered a variety of tests. During a stress test, which measures the heart’s ability to respond to exercise, “my head felt like I’d had one and a half drinks,” Herndon recalled. Testing revealed nothing amiss with his heart, and the lightheadedness gradually disappeared over the next few days, replaced almost immediately by something else: a dull ache in his upper forehead and between his eyes.

At first Herndon, who rarely got headaches, didn’t think much about it. But after several days, when the pain failed to recede or respond to nonprescription painkillers, he saw his primary-care doctor, who referred him to a neurologist, who ordered various scans.

Herndon’s brain looked normal, but a CT scan revealed a significant sinus infection — his first. Doctors prescribed antibiotics in an effort to knock it out, which would presumably eradicate the headache.

That course of antibiotics was the first of many rounds that failed to vanquish his headache; corticosteroids did nothing, either. After a few months his ENT recommended endoscopic sinus surgery to clean out and open his still-blocked sinuses, a procedure endorsed by a second specialist.

After the operation, which was performed in March 2009, Herndon was optimistic that his headache would finally disappear. But a few weeks later, he said, he had the sinking realization that “nothing felt any different.”

When he told his surgeon, the doctor looked at him with “confusion and some concern,” Herndon recalled. “He told me, ‘It should be better.’ ”

The surgeon prescribed more antibiotics. Herndon also saw an allergist and an ophthalmologist, neither of whom found anything that would account for his pain. He decided to consult a new specialist in Baltimore, particularly because his nose and upper teeth had begun to hurt.

After the Baltimore doctor told him his sinuses weren’t the problem, Herndon decided to regroup. He had lost 15 pounds and had missed a significant amount of work, which worried him despite the support of his supervisor. He flew to Tennessee to spend two weeks visiting his mother and pondering what to do next.

Diagnosis brings little relief

While in Knoxville, he consulted a neurologist who specializes in treating headaches. Armed with his medical records, Herndon recounted his history, and the specialist gave his malady a name: Herndon was suffering from a condition called new daily persistent headache, which sounded more like a description than a diagnosis. The doctor also had sobering news. “He told me that we’re probably never going to cure this, but there are things we can do to try and help you feel a little bit better.”

First described in 1986, new daily persistent headache remains one of the hardest types of headaches to treat. The diagnosis is made on the basis of symptoms and history, not specific lab tests, and after other causes of in­trac­table head pain, including chronic meningitis, a blood clot or an aneurysm, have been ruled out.

Unlike with migraines, the pain of daily headaches tends to affect both sides of the head; there is no aura or vomiting, nor does pain worsen with routine physical activity. Onset is typically sudden, and the disorder often affects those who do not have a history of headaches. Doctors say that patients can often pinpoint the day they developed a headache, unlike with other types, which tend to occur more gradually.

In an article published last year in the journal Headache, Baylor College neurologist Randolph W. Evans and a colleague report that the average age of onset is 35, the disorder is more common in women, and it is rare, affecting less than 1 percent of the population.

Even among neurologists the disorder is little-known. Patients often see “numerous physicians in different specialties, dentists, psychologists and chiropractors in a dizzying and depressing musical chairs of expensive misdiagnoses and sometimes potentially harmful treatments,” the authors write. Common misdiagnoses include sinusitis, eye strain, chronic Lyme disease and temporomandibular joint disorder.

Small studies have found a link with prior infection, including the ubiquitous Epstein-Barr virus, but the cause is unknown. Antidepressants and anti-seizure drugs have not generally proven effective, nor have nutritional supplements, acupuncture, chiropractic ma­nipu­la­tion or yoga.

“It’s very different than migraine,” said neurologist Jessica X. Ailani, director of the headache center at MedStar Georgetown University Hospital, who has been treating Herndon since 2010. “Because the cause is so unclear, treatment ends up being pick and choose.”

Through trial and error, Herndon found a regimen that has diminished his pain: He takes two antidepressants that have been found to quell nerve pain. Once a month when the pain worsens, he adds a common epilepsy drug used to treat chronic pain.

While there’s no way to know for sure, doctors have told Herndon that the sinus infection, which was probably present during his stress test, might have triggered the headache. Whether his surgery helped or hurt is hard to say, Ailani said.

Herndon is grateful that none of his doctors suggested that his problem was psychological, although before his diagnosis he wasn’t so sure. “I wondered whether I was going crazy,” he said, after specialists failed to find an explanation during those first difficult months.

Sometimes, he says, he is able to forget he has had a headache for 31 / 2 years. “It’s like a light on a dimmer switch,” Herndon said. “It never quite goes off.”

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