Academy calls for emergency CT for some seizure patients

November 16, 2007

New American Academy of Neurology guidelines recommend immediate CT brain scans for some patients who arrive in the emergency room with seizures.

New American Academy of Neurology guidelines recommend immediate CT brain scans for some patients who arrive in the emergency room with seizures.

The AAN appointed a panel of experts from several U.S. academic institutions to redefine neuroimaging's value in the management of this patient population and reassess clinical features traditionally associated with abnormal imaging studies. The Therapeutics and Technology Assessment Subcommittee, led by Dr. Cynthia L. Harden of Cornell University, reviewed all the clinical evidence related to neuroimaging of ER patients available online through the National Library of Medicine from 1966 to November 2004.

Investigators found head CT scans useful in this setting, especially for young children and patients presenting with their first seizure, a history of AIDS, or a predisposing condition. They published a report with the new guidelines in the Oct. 30 issue of Neurology.

"Infants under six months old with seizure may have brain abnormalities on their CT scans 50% of the time," Harden said.

The guidelines are based on clinical evidence of management changes due to CT in about 20% of adults and up to 8% of children presenting to the emergency room with first seizure. Patients with AIDS and first seizure show high rates of abnormalities and toxoplasmosis, an infectious disease of the central nervous system caused by a parasite.

Researchers also found that a predisposing clinical history, an abnormal neurologic exam, or focal seizure onset can predict an abnormal CT study. Abnormalities found on CT that lead to change in treatment include tumors, traumatic brain injury, and stroke.

ER patients with first seizures represent a particularly common incidence, according to Dr. Nancy J. Fischbein, an associate professor of radiology at Stanford University. Most patients with chronic seizures do not end up in the ER unless they have a seizure in an unfamiliar locale or when they are away from family or friends.

"A noncontrast CT scan is an excellent screening study. For example, just because a patient who has a seizure happens to be an alcoholic doesn't mean that the person didn't suffer an intracranial hemorrhage as the cause of the seizure, rather than because of alcohol use or withdrawal," Fischbein said.

The guidelines did not make recommendations regarding the use of brain MR imaging in the emergency room to screen people with seizure because of insufficient data. But CT should not be seen as competing against MRI in this setting. If a noncontrast CT screening shows negative, it does not mean an MR might not turn something up, Fischbein said.

"The guidelines are catching up with current clinical practice," she said.

For more information from the Diagnostic Imaging archives:

MR imaging reveals signs of temporal lobe epilepsy

CT for mild head injury shines in triage

MR arterial spin labeling proves feasible, safe in children

High-field scanners assume routine clinical caseloads