Will I have another one?
Do I need an EEG?
Do I need an MRI?
Do I need treatment?
Has the patient had an epileptic seizure?
In the assessment of a seizure the most important factor is a good history.
25% of patients seen in a first seizure clinic have not had an epileptic seizure. Most commonly this was a faint.
The diagnosis of a fainting episode versus a seizure should be made on the history.
Epidemiology of the first seizure
In anyone's lifetime the prevalence of a seizure is up to 4%.
30-50% of patients have had prior unrecognised seizures and have not sought medical advice.
After a first seizure the occurrence of a further seizure is 75% at two years; though 40-70% of recurrences occur in the first six months.
The recurrence rate is greater for focal (arising from one part of the brain) than for generalised seizures (Hart Y et al Lancet 336:1271-1274, 1990).
Predictors for recurrence
The risk of recurrence ranges from 24% in subjects with no risk factor profiles to 65% or greater in those with two or more risk factors (focal onset, family history of epilepsy, abnormal neurological examination, or relevant abnormality on neuroimaging or epileptiform abnormalities on an EEG)
A normal EEG following a first seizure is associated with a reduced risk for recurrent seizures.
An EEG with typical features of epilepsy has a 2-3 fold increased risk of relapse.
The recurrence rate is 83% at two years if an EEG shows typical features of epilepsy, but only 12% if an EEG is normal (van Donselaar C et al., Brit Med J 302:620-623,1991; Mackenzie R Clin Neurosc 8(2): 187-189, 2001).
Are you certain of the epilepsy syndrome diagnosis?
The history allows epilepsy syndrome classification after the first seizure in only 47% of patients, whereas the addition of an EEG enables a more accurate diagnosis to be made in 77% of patients.
A subsequent MRI increases the diagnostic yield to 88% (King M et al., Lancet 352; 1007-1011,1998).
The classification of the epileptic syndrome determines the treatment. For example, the syndromes of Idiopathic Generalised Epilepsy, which can present throughout life and not only in younger years, can be made worse with some anticonvulsants (such as Carbamazepine). Treatment of choice is Sodium Valproate, except in women of child bearing age.
Sensitivity of epileptiform changes on an EEG
The yield increases with the number of EEGs. The best rate of yield is between the first and 2nd EEG.
A sleep deprived EEG increases the yield of an abnormal result.
An EEG shows specific epileptiform abnormalities in 25% of adult patients with epilepsy.
Non-specific EEG abnormalities may not be relevant to the question of epilepsy.
Is anticonvulsant treatment necessary after a first seizure?
Anticonvulsant treatment in patients presenting with a first generalised seizure does reduce the risk of relapse. However, 50% of patients who are not treated will never experience a second seizure (Muscco M et al., Neurology 49(4): 991-8,1997). Furthermore the probability of long-term remission is not influenced by treatment. Thus patients treated after seizure relapse have the same time-dependent probability of achieving seizure freedom at two years as those treated after the first seizure.
MRI is the investigation of choice to look for any focal structural abnormality. Imaging should be done for all adult patients except for those with idiopathic generalised epilepsies (EEG with 3Hz spike and wave).
Psychological impact of a first seizure
This involves a loss of perceived control when patients try to deal with their fear of further seizures. Accurate information about natural history and treatment options when an epilepsy syndrome diagnosis is made helps alleviate this psychological impact.
Only start treatment after two or more unprovoked seizures unless there is structural brain disease, epileptiform discharges on an EEG, a specific syndrome associated with recurrence (such as Juvenile Myoclonic epilepsy), or if there are serious social consequences. Most neurologists do not advise treatment after the first seizure only.
Compiled by Stuart Mossman Neurologist FRACP MD