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Risk of recurrence after a first seizure and implications for driving: further analysis of the Multicentre study of early Epilepsy and Single Seizures

BMJ 2010; 341 doi: https://doi.org/10.1136/bmj.c6477 (Published 08 December 2010) Cite this as: BMJ 2010;341:c6477
  1. L J Bonnett, statistical research assistant1,
  2. C Tudur-Smith, senior lecturer in medical statistics1,
  3. P R Williamson, director and professor of medical statistics1,
  4. A G Marson, professor of neurology2
  1. 1Department of Biostatistics, University of Liverpool
  2. 2Clinical and Molecular Pharmacology, University of Liverpool
  1. Correspondence to: A G Marson A.G.Marson@liverpool.ac.uk
  • Accepted 22 September 2010

Abstract

Objective To determine for how long after a first unprovoked seizure a driver must be seizure-free before the risk of recurrence in the next 12 months falls below 20%, enabling them to regain their driving licence.

Design Randomised controlled trial: Multicentre study of early Epilepsy and Single Seizures (MESS).

Setting UK hospital outpatient clinics from 1 January 1993 to 31 December 2000.

Participants People entered MESS if they had had one or more unprovoked seizures and both the participant and the clinician were uncertain about the need to start antiepileptic drug treatment. The subset of people used for this analysis comprised participants aged at least 16 years with a single unprovoked seizure.

Main outcome measure Risk of seizure recurrence in the 12 months after a seizure-free period of 6, 12, 18, or 24 months from the date of the first (index) seizure. Regression modelling was used to investigate how antiepileptic treatment and several clinical factors influence the risk of seizure recurrence.

Results At six months after the index seizure the risk of recurrence in the next 12 months for those who start antiepileptic drugs was significantly below 20% (unadjusted risk 14%, 95% confidence interval 10% to 18%). For patients who did not start treatment the risk estimate was less than 20% but the upper limit of the confidence interval was greater than 20% (18%, 13% to 23%). Multivariable analyses identified subgroups with a significantly greater than 20% risk of seizure recurrence in the 12 months after a six month seizure-free period, such as those with a remote symptomatic seizure with abnormal electroencephalogram results.

Conclusion After a single unprovoked seizure this reanalysis of MESS provides estimates of seizure recurrence risks that will inform policy and guidance about regaining an ordinary driving licence. Further guidance is needed as to how such data should be utilised; in particular, whether a population approach should be taken with a focus on the unadjusted results or whether attempts should be made to individualise risk. Guidance is also required as to whether the focus should be on risk estimates only or on the confidence interval as well. If the focus is on the estimate only our unadjusted estimates suggest that treated and untreated patients are eligible to drive after being seizure-free for six months. If the focus is also on confidence intervals, direction is needed as to whether a conservative or liberal approach should be taken.

Trial registration Current Controlled Trials ISRCTN98767960.

Footnotes

  • We thank C Warlow and M Walker for their comments on the manuscript.

  • Contributors: LJB analysed the data and drafted and revised the paper. CT-S and PRW provided support for statistical analyses and drafted and revised the paper. AGM joint coordinated the MESS trial, provided clinical input, and drafted and revised the paper. AGM is guarantor.

  • Funding: This study (RP-PG-0606-1062) was supported by the National Institute for Health Research programme grants for applied research funding scheme. The original trial was funded by the Medical Research Council. The views and opinions expressed within this paper do not necessarily reflect those of the National Health Service, the National Institute for Health Research, or the Department of Health. The researchers are independent from the funders.

  • Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any company for the submitted work; no financial relationships with any companies that might have an interest in the submitted work in the previous 3 years; no other relationships or activities that could appear to have influenced the submitted work. PRW and AGM sit on the Secretary of State for Transport’s Honorary Advisory Panel on Driving and Disorders of the Nervous System.

  • Ethical approval: Not required as this was a reanalysis of data.

  • Data sharing: Statistical code and dataset are available from the corresponding author at A.G.Marson@liverpool.ac.uk.

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