Imaging Important for Secondary Headache Dx: Pathologic Organic Processes Account for Up to 16% of Emergency Visits Attributable to Headaches

Article excerpt

ORLANDO, FLA. -- Neuroimaging is key to diagnosing relatively rare secondary headaches, one expert said at the annual meeting of the American Society of Neuroimaging.

"Secondary headaches are where neuroimaging is of paramount importance," said Laszlo L. Mechtler, M.D., director of the headache center at Dent Neurologic Institute in Buffalo, N.Y.

Secondary headaches represent a symptom of a pathologic organic process and are associated with more than 316 disorders and illnesses, posing a diagnostic challenge. The causes of these headaches can be serious and life threatening. Secondary headaches account for up to 16% of annual emergency department visits that are attributable to headaches, according to Dr. Mechtler.

Physicians should rely on several red flags to trigger an imaging study to investigate the possibility of secondary headache, he pointed out.

Dr. Mechtler discussed the use of neuroimaging in diagnosing several types of secondary headaches.

Subarachnoid hemorrhage is classically described as the "worst headache of my life," but be careful when patients say that. Only 12% of the patients who present to the emergency department with this type of headache actually have subarachnoid hemorrhage, if the neurologic examination is normal. The percentage jumps to 25% if the neurologic examination is abnormal, Dr. Mechtler said. "So even with the worst headache of your life, we're still talking primary headaches."

For a patient presenting with "the worst headache of my life," in the first 24 hours, CT is the study of choice, Dr. Mechtler said. According to the literature, the probability of recognizing a subarachnoid hemorrhage on CT during the first 24 hours is 95%. At 1 week post onset, that probability drops to 50%.

"Interestingly, FLAIR [fluid-attenuated inversion recovery] MRI has really changed our perception of subarachnoid hemorrhage," he said. Recent studies have shown that FLAIR MRI is as sensitive as CT between 1 and 7 days. "After 4 or 5 days, FLAIR is probably even more sensitive than CT itself."

Neuroimaging is very important in the diagnosis of carotid/vertebral arterial dissections, in which headache is the most common symptom. "But this headache has no classic symptoms," Dr. Mechtler said.

This condition is relatively rare, occurring in only 3 of 100,000 carotid dissections and 1. …