Abstracts

Unlike in chronic epilepsy, the role of MRI in management of adult patients presenting with a first seizure is uncertain. No evidence is available to determine which patients should receive an MRI following a first epileptic seizure. A clinical algorithm to determine which patients may gain benefit from MRI following a first seizure was developed based on findings in 105 consecutive adult patients from a hospital-based First Seizure Clinic. Data from a second First Seizure Clinic cohort, of 100 patients from a different hospital, was used to validate the predictive value of the algorithm. In the development cohort, MRI provided useful information additional to CT in 16.2% (17/105) of patients, identifying six lesions missed by CT, and clarifying the nature of the CT lesion in 11, including three CT lesions which were shown to be artifactual. Predictors of added value from MRI were (i) a CT showing a lesion that required clarification (p[lt]0.001), (ii) a partial or unclassifiable seizure type (p=0.001), and (iii) a history of head-injury (p=0.011). Based on these findings a clinical algorithm was proposed where MRI was only offered to patients with a CT lesion needing clarification, a partial or unclassifiable seizure type, or a history of head-injury. In the development cohort the algorithm had a sensitivity of 100%, and a specificity of 79.6%.
In the validation cohort, 9% (9/100) of patients gained additional value from MRI. When the algorithm was applied to the validation cohort, no patient not offered a MRI, would have gained value from this test. The algorithm had a sensitivity of 100%, and a specificity of 47.25%. The results of this study identify subgroups of patients presenting following a first seizure in whom MRI has a high yield for adding value to CT and a group in whom the yield is low. This algorithm may be useful in clinical practice to guide selection of which patients should be referred for MRI.