Page 356 - ILAE_Lectures_2015

Chapter 36

The prognosis of epilepsy

AIDAN NELIGAN1 and J.W. SANDER2

1Homerton University Hospital Foundation Trust, London, and 2UCL Institute of
Neurology, Queen Square, London and Epilepsy Society, Chalfont St Peter,
Buckinghamshire

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For patients with seizures, prognosis means the probability of further seizures after a single
unprovoked seizure or the likelihood of achieving seizure freedom or terminal remission after
a pattern of recurring seizures has been established1. It is now accepted that up to 70% of
people with epilepsy will enter remission, usually in the early years of the condition2.
However, in discussing the prognosis of epilepsy, various aspects need to be considered: the
likelihood of recurrence following a single seizure, the impact of early versus late treatment,
the probability of relapse after prolonged remission, the probability of seizure freedom
following epilepsy surgery or relapse following antiepileptic medication withdrawal.

Recurrence after a single unprovoked seizure

Prospective studies of single seizures are difficult, as many events go unrecognised or are
unwitnessed and patients do not usually present to medical attention unless the seizure is
convulsive. The overall risk of recurrence following a single seizure has been reported to be
27−71%. A meta-analysis found that the average risk of seizure recurrence was 40% in
prospective studies and 52% in retrospective studies3. The time interval between the seizure
and inclusion in the follow-up influences recurrence, as many patients have a recurrence
within weeks of the first seizure and are therefore classified as having epilepsy. This
artificially lowers the estimated recurrence rate following a single seizure if there is a long
delay between the initial seizure and recruitment into a recurrence study4. The risk of
subsequent seizures decreases with time, with up to 80% of recurrences occurring within two
years of the initial seizure3.

In the community-based study National General Practice Study of Epilepsy (NGPSE), 67%
of those with a single seizure had a recurrence within 12 months and 78% within 36 months5
which, while high, is within the reported range. In a prospective study of children with a first
unprovoked seizure, 45% had a second seizure with the median time to recurrence being 6.2
months. The cumulative risk of a second seizure was 22% (six months), 29% (one year), 37%
(two years), 43% (five years) and 46% (ten years)6. Another prospective study of adults with
a single seizure found a recurrence rate of 58% at 750 days’ follow-up. No further recurrences
were recorded thereafter during a median follow-up of 10.3 years, underlying the impression
that the risk of seizure recurrence highest in the first 1−2 years following the seizure7.

Recurrence after a second seizure

The risk of recurrent seizures following a second seizure was investigated in a predominantly
adult population8. The risk of a further seizure was 32% at three months, 41% at six months,
57% at one year and 74% at four years. Of those who did not have a