Physicians need to obtain patients' medical histories, recognize patterns, consult diagnostic guidelines, consider the possibility of secondary etiologies, and avoid common mistakes to diagnose less common primary headaches accurately.
STOWE, VT—The keys to spotting less common primary headaches include seeing lots of patients with headaches, recognizing patterns, and taking a patient’s medical history—along with “more history” and “when in doubt, repeating the history,” said R. Allan Purdy, MD, at the Headache Cooperative of New England’s 20th Annual Headache Symposium.
Dr. Purdy, a Professor and Head of the Department of Medicine at Dalhousie University, Halifax, Canada, provided an overview of the less common primary headaches, made diagnostic recommendations, discussed common diagnostic mistakes, and described several cases from his own experience—along with clinical pearls based on those cases.
Overview of Less Common Primary Headaches
The International Classification of Headache Disorders (ICHD) includes less common primary headaches in two categories: other trigeminal autonomic cephalalgias (TACs) and other primary headaches, noted Dr. Purdy. The other TACs include paroxysmal hemicrania, short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT), and probable TAC. The other primary headaches include primary stabbing headache, primary cough headache, primary exertional headache, primary headache associated with sexual activity, hypnic headache, primary thunderclap headache, hemicrania continua, and new daily persistent headache.
Diagnosis Recommendations
Diagnosing the less common primary headaches is “highly dependent on the history and the recognition of the disorder in the clinic,” according to Dr. Purdy. He recommended that physicians “spend a lot of time with primary headache patients and learn from the less prominent ones and how to spot them.” In addition, he said they should download the ICHD classification document from the International Headache Society Web site and use it on a daily basis.
Less common headaches often have secondary causes that may be serious, Dr. Purdy cautioned. Also, he said, chronic daily headache may be related in some way to other diseases, as was the case with a patient of his whose headache “completely disappeared following the removal of bile stones.” In the past, binary colic had been misdiagnosed as migraines, he explained.
Dr. Purdy noted that when a lesion is present, physicians should ask, “Where is it?,” “Is it from within or [outside] the nervous system?,” and “What is the lesion?” to determine whether there is a secondary cause. He recommended being “really careful” about the possibility of secondary causes before making a new daily persistent headache diagnosis.
Dr. Purdy emphasized that a patient can have multiple headache diagnoses simultaneously. He also noted that many apparently uncommon headaches actually belong to a very common class: “The diagnosis of migraine is so complex that every new disorder you pick up on and think you’ve discovered … is probably still migraine.”
Diagnostic Mistakes
Some of the most common mistakes that physicians make in diagnosing less common headaches include overreliance on technology, Procrustean thinking, anchoring, and directed history, according to Dr. Purdy.
With regard to technology, he emphasized that “patients with primary headaches can have findings on their MRIs and those with secondary headaches can be normal.” He noted that once a patient and a physician see a “totally benign” pineal cyst, for example, “they focus on that; they never see another thing.”
Dr. Purdy explained that Procrustean thinking refers to Procrustes, an innkeeper in Greek mythology who would ensure that his guests fit in their beds by stretching the bodies of guests who were too short and cutting off the legs of those who were too tall.
Similarly, he said, physicians “may have the diagnosis, but there’s something in the diagnosis that doesn’t fit … and you still make the diagnosis. So if atypical in any way, there may be another diagnosis. Be careful of features that are missing from the diagnosis and those that are present but do not fit—otherwise you might be too Procrustean in your thinking.”
He described anchoring as the tendency to apply the last diagnosis to a new patient: “So I diagnose this guy with abdominal pain with new daily persistent headache, and he has his gallbladder taken out, and he gets better. The next five cases of new daily persistent headache are all going to be abdominal ultrasounds.”
Dr. Purdy said that directed history is the medical equivalent of “leading the witness.” For example, he said, a physician might ask a patient with unilateral headaches whether he or she has experienced drooping eyelids or a small pupil, and the patient might answer affirmatively to please the physician or think it could be true. “So suddenly, you’ve taken them from a common diagnosis into a new disorder,” he said. “The lawyers are cautioned not to do that.... But doctors do it all the time.”