Abstracts

Rationale: Driving regulations for people with epilepsy or who have had single seizures differ from country to county and form state to state within the USA. Within the European Union a process is ongoing to harmonise driving regulations across member states. Attempts are being made to make policies risk based and an individual will be allowed to regain their ordinary driving license once their risk of a seizure recurrence in the next 12 months has dropped below 20%. EU guidance suggests that an individual should regain their ordinary driving license once they have gone 6 months seizure free following a first seizure, but there are few data in the public domain that inform this policy. Methods: The multicentre study of early epilepsy and single seizures (MESS) was a randomized controlled trial that compared the policies of immediate and deferred antiepileptic drug treatment for patients following a single seizure or with 2 or more seizures where the patient and clinician were uncertain about the need to start antiepileptic drug treatment. The analysis presented here is restricted to MESS patients who had had a single seizure and were 16 year or older. We calculated the risk of a seizure in the next 12 months for patients who had gone 3, 6 and 12 months seizure free following their first seizure. Regression modelling was used to investigate how antiepileptic drug treatment and a number of clinical factors influence the risk of seizure recurrence. Results: 637 of the 1443 patients were included in this analysis. Unadjusted analysis indicate that at six months following a first seizure the risk of a recurrence is significantly below 20% over the next 12 months for patients who start antiepileptic drug treatment, risk 14% (95% CI: 10% to 18%). For patients who do not start treatment the estimate is below 20% but the upper limit of the confidence interval is greater than 20%, risk 18% (95% CI: 13% to 23%). At 12 months the risks are 7% (4% to 11%) and 10% (6% to 15%) respectively. Univariate analyses indicate that the risk of seizure recurrence is higher for patients with a remote symptomatic seizure, neurological deficit, abnormal EEG and a seizure while asleep. Multivariable analyses identify subgroups with an annual recurrence risk significantly greater than 20% after a six month seizure free period. Conclusions: Following a single seizure this reanalysis of MESS provides estimates of seizure recurrence risks that will inform policy and guidance about regaining an ordinary driving license. Multivariate analyses identify the characteristics of patients at higher risk of a seizure recurrence. Further policy guidance is needed as to how such data should be utilised. In particular whether a population approach should be taken with a focus upon the unadjusted results or whether attempts should be made to individualise risk. Guidance is also required as to whether the focus should be upon risk estimates only or upon the confidence interval as well. If the latter, direction is needed as to whether a conservative or liberal approach should be taken.