link Health Link EDI: mossmanI

Epilepsy

First seizure


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 a seizure. Most commonly this was syncope
The differential of a syncopal episode and a seizure should be made on the history
 

Epidemiology of the first seizure 

Lifetime prevalence of any seizure is up to 4%
30-50% of patients have had prior unrecognised seizures and have not sought medical advice  
The occurrence of a further seizure is 75% at 2 yrs though 40-70% of recurrences occur in the first 6/12. Recurrence is greater for partial than for tonic clonic seizures (Hart Y et al Lancet 336:1271-1274, 1990)
 

Predictors for recurrence 

Risk of recurrence ranges from 24% in subjects with no risk factor profiles to 65% or greater in those with 2 or more risk factors (partial onset, FH of epilepsy, abnormal CNS examination, 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 epileptiform abnormalities has a 2-3 fold increased risk for relapse 
Recurrence rate is 83% at 2 yrs if an EEG shows epileptiform activity 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% whereas the addition of an EEG enables a diagnosis to be made in 77%.
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 (Carbamazepine). Treatment of choice is Sodium Valproate except in child bearing females.
 

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 from 49% to 81%
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 tonic-clonic 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. Patients treated after seizure relapse have the same time-dependent probability of achieving seizure freedom at 2 years as those treated after the first seizure
 

Neuroimaging 

MR scanning may take some time and there may be an argument for CT scanning as a routine early investigation with MR reserved for individuals whose epilepsy is not initially controlled by anticonvulsants or if there is a focal abnormality on EEG. 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.
 

Summary 

Only start treatment after 2 or more unprovoked seizures unless there is structural brain disease, epileptiform discharges on an EEG or a specific syndrome associated with recurrence (such as Juvenile Myoclonic epilepsy) or if there are serious social consequences
Nevertheless most neurologists do not advise treatment after the first seizure
 
 
Compiled by Stuart Mossman Neurologist FRACP MD