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Imaging important for secondary headache Dx: pathologic organic processes account for up to 16% of emergency visits attributable to headaches.

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 1.5 of 100,000 vertebral dissections. There are multiple causes, which include an underlying arteriopathy (Ehlers-Danlos and Marfan syndromes); fibro-muscular dysplasia; minor trauma, hyperextension, or rotation of the neck; major trauma or sports injuries; and possibly even chiropractic manipulations.

In vertebral dissections, the headache usually precedes neurologic symptoms by about 15 hours. Neck pain is also common in these patients, and there is the possibility of a brain stem infarct, as well. "Any time you have neck pain [or] headaches, and the patient might have a risk factor, consider dissection in your differential diagnosis," Dr. Mechtler said.

MRI of possible dissections involves the use of special fat-suppression protocols that allow visualization of the double lumen. Magnetic resonance angiography has been very useful in the diagnosis of dissections, particularly vertebral artery dissections, he said.

Cerebral venous thrombosis can have several variations. The classic CT scan sign is the empty delta sign, Dr. Mechtler said. The sign consists of a triangular area of enhancement or high attenuation with a relatively low-attenuating center on multiple contiguous transverse CT images obtained in the region of the superior sagittal sinus.

It's not uncommon for the findings to consist of an atypical arterial distribution vascular event. Often, this type of case is sent on to a neurooncologist for evaluation of a possible glioblastoma multiforme.

Most adult patients with intracranial neoplasms don't have headaches initially. "It's a myth that brain tumors cause headaches often," Dr. Mechtler said. Headache is present in only about 50% of cases of intracranial neoplasm.

Headache frequently does occur when there is a mass in the posterior fossa or around the meninges, he said.

In children, though, headaches are associated with intracranial neoplasms--two-thirds of childhood tumors are intratentorial.

When a glioblastoma multiforme spreads across the corpus callosum to the contralateral side, a butterfly shape can be seen on a coronal view MRI. Dr. Mechtler also noted that headaches are associated with glioblastoma multiforme when subependymal spread can be seen on MRI.

BY KERRI WACHTER

Senior Writer
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Title Annotation:Pain Medicine
Author:Wachter, Kerri
Publication:Clinical Psychiatry News
Geographic Code:1U5FL
Date:Jun 1, 2005
Words:698
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