Abstracts

Rationale: In the initial assessment of patients with new-onset seizures, electroencephalography (EEG) and magnetic resonance imaging (MRI) are indicated. Together with a careful history and examination, they are performed with the idea of obtaining information about the epilepsy syndrome and help assess the individual risk for seizure recurrence. But, there is heterogeneity of first seizure studies, and even though EEG and etiology are consistently found to be the best predictors for seizure recurrence and prognosis, there are contradictory results in the literature. There is a striking lack of systematic studies using early EEG and MRI in order to better characterize epileptogenic areas and elucidate the mechanisms of seizure recurrence. The purpose of this study was to describe the frequency of EEG abnormalities and explore relationships between MRI and EEG findings, as well as prognosis of seizure recurrence to determine their relevance in the assessment of patients with new-onset seizures. Methods: All patients with a newly diagnosis of seizures or epilepsy seen since the new-onset seizure clinic (since inception until April 30th, 2009) at the University of Western Ontario Epilepsy Programme were included. As part of the assessment patients had a history and physical examination, blood work, outpatient EEGs, and 1.5 T MRI of the Brain. The EEG studies were performed using the 10-20 international system, using a XLTEK program (Ontario, Canada). Results of these studies were systematically entered into a database. The analysis was done using MS Excel 2003. Results: Of 163 patients with newly diagnosed epilepsy, 46 presented after a single unprovoked seizure. 26 were male, mean age was 39 (range: 10-81), and 39 were right-handed. In terms of risk factors for seizures: 12 had head trauma, 10 had family history of seizures, and 3 febrile seizures. An abnormal MRI was found in 19 patients. In terms of EEG results: 15 had epileptiform discharges (9 focal and 6 generalized), 10 showed slowing (8 focal and 2 generalized) and 21 had normal EEG. In terms of outcome, 47% of those with epileptiform abnormalities continue to have seizures (44% focal EEG abnormalities and 50% generalized EEG abnormalities), while 40% of those with slowing in the EEG have continued to have seizures (all of them with focal slowing), and of the ones with normal EEG, 43% continued to have seizures. Conclusions: Taking into account that this cohort of patients is small, we found that approximately 50% of new-onset seizure patients have abnormal EEGs, and the results did not influence prognosis.