The MRC AED Withdrawal Study was sufficiently large to develop and test a predictive model for relapse in patients continuing or stopping their medication (18). The model gives decreasing weight to the following factors: whether or not treatment is withdrawn, period of time seizure-free, taking two or more ASDs, being 16 or older at the time of withdrawal, having myoclonic seizures, and having tonic–clonic seizures of any type. The final factor was an abnormal EEG. While the model does not include the presence of remote symptomatic epilepsy, factors retained in the model may, singly or in combination, provide surrogate measures for symptomatic epilepsy and capture those aspects of remote symptomatic epilepsy that are most associated with an increased risk of relapse. The resulting predictive equation was well calibrated for risks between 10% and 80% and correctly identifies JME as having a high risk of relapse. Table 2 outlines the use of this model which can be downloaded from http://www.liv.ac.uk/neuroscience.
Two groups of investigators have developed simple models to predict relapse in children. Dooley et al. (19) developed a model derived from a study of 97 children in whom drugs were withdrawn after 12 months of remission. A point scoring system was devised in which subjects were allocated 1 point for being female, 1 for seizure onset after 10 years, the presence of neurological abnormality and generalized seizures, and 2 points for partial seizures (other than those of BRE). No subjects with 0 points relapsed (they had BRE by definition). Ninety-five percent of patients with 1 point, 80% with 2 points, 45% with 3 points and 5% with 4 points remained seizure-free. Shinnar et al. (20) determined risk of relapse 2 years after stopping ASDs in 264 children as a function of the number of risk factors for relapse a child had, 0–3. This was done separately for those with cryptogenic/idiopathic versus remote symptomatic epilepsy. In the idiopathic group, predictors of relapse were age at onset >12 years, family history of epilepsy, slowing on the EEG, and atypical febrile seizures. The risk of relapse after 2 years was 12%, 46%, and 71% in children with 0, 1, and 2 of these factors. In remote symptomatic cases, predictors were age of onset >12 years, mental retardation, absence seizures, and atypical febrile seizures. The risk of relapse after 2 years was 11%, 35%, 51%, and 78% in children with 0, 1, 2, and 3 risk factors.