MRI-identified pathology in adults with new-onset seizures

OBJECTIVE: To determine the frequency and nature of potentially epileptogenic lesions on MRI in adults with new-onset seizures. METHODS: We prospectively studied a consecutive series of 993 patients (597 males [61%]; mean [SD] age: 42.2 [18.8] years, range 14.3-94.3 years) who presented to an adult First Seizure Clinic over a 10-year period. The MRI scans, performed clinically on 3- and 1.5-tesla scanners, were reviewed for their diagnostic yield, nature of abnormalities, and their association with abnormal electrical activity on EEG. RESULTS: MRI scans were acquired in 764 patients (77%); potentially epileptogenic lesions were detected in 177 (23%). The frequency of potentially epileptogenic lesions was higher in patients who were diagnosed as having an epileptic seizure (28%) than in those with a nonepileptic event (8%) (p < 0.001), and highest in those who had focal-onset seizures (53%) (p < 0.001). The most common lesion type in patients with focal seizures was gliosis or encephalomalacia (49%). Other common lesion types were tumors (15%), cavernomas (9%), and mesial temporal sclerosis (9%). Abnormal MRI and EEG were concordant in 18% of patients, with EEG being normal in 55% of patients with epileptogenic lesions. CONCLUSIONS: MRI reveals potentially epileptogenic lesions in a minority of patients with a newly diagnosed seizure disorder. Lesions are most common in patients who have experienced focal seizures. The presence of a potentially epileptogenic MRI lesion did not influence the chance of having an abnormal EEG.