Routine EEG, plus CT or MRI recommended for first unprovoked seizure

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An adult with a first unprovoked seizure should have a routine EEG, augmented by a brain CT or MRI, according to a guideline issued by the American Academy of Neurology. The guideline was issued in response to a study published in the Nov. 20 issue of Neurology.

Evidence shows that these tools can often detect brain abnormalities that caused the seizure and predict seizure recurrence, according to Allan Krumholz, MD, and colleagues at the University of Maryland, co-authors of the study.

The results of the study showed that for adults presenting with a first seizure, a routine EEG revealed epileptiform abnormalities in approximately 23 percent of patients, and these were predictive of seizure recurrence. A brain imaging study, either CT or MRI, was also significantly abnormal in a mean 10 percent of patients, indicating the possible seizure etiology, such as previously unrecognized brain tumors, vascular lesions, and cerebral cysticercosis, or other structural lesions.

Krumholz said that laboratory tests such as blood counts, blood glucose, and electrolyte panels were abnormal in up to 15 percent of individuals, but abnormalities were minor and did not cause the seizure. Overt clinical signs of infection such as fever typically predicted significant CSF abnormalities on lumbar puncture. Toxicology screening studies were limited, but report some positive tests.

According to the results, “EEG should be considered as part of the routine neurodiagnostic evaluation of adults presenting with an apparent unprovoked first seizure (level B). There is also sufficient class II evidence that a brain imaging study, either a CT or MRI, helps determine the presence of a significant abnormality such as a brain tumor. Brain imaging using CT or MRI should be considered as part of the neurodiagnostic evaluation of the adult presenting with a first seizure (level B).”

Krumholz said that CT has a major advantage because of the speed with which it can be used, so its value is mainly in an emergency situation. MRI, however, is regarded as having a higher yield and is preferable in non-emergency or elective situations. Krumholz and his colleagues said both are useful.

To develop the guideline, the authors undertook multiple searches of the medical literature of patients over age 18. The guideline was developed by a subcommittee of the American Academy of Neurology and the American Epilepsy Society.