From the Guidelines
Approximately 30-50% of patients with a first unprovoked seizure will have a recurrent seizure within 5 years. This estimate is based on the most recent and highest quality study available, which suggests that the risk of recurrence is significant, but not universal 1.
Key Factors Influencing Recurrence
- The risk of recurrence is highest within the first two years after the initial seizure, with most recurrences happening within the first 6-12 months.
- Certain risk factors, including abnormal EEG findings, structural brain abnormalities (such as tumors, stroke, or traumatic brain injury), nocturnal seizures, or a family history of epilepsy, increase the likelihood of recurrence.
- Other factors that may increase recurrence risk include seizures with focal onset and neurological deficits.
Decision to Start Antiepileptic Medication
- The decision to start antiepileptic medication after a first seizure is individualized and typically not recommended unless specific risk factors are present, as many people will never have a second seizure 1.
- For patients with a first unprovoked generalized seizure, it would be necessary to treat 14 patients to prevent a single seizure recurrence within the first 2 years 1.
Underlying Neurological Predisposition
- The recurrence rate reflects the underlying neurological predisposition to seizures, which varies widely among individuals based on genetic factors, brain structure, and other neurological conditions.
- A history of CNS injury (inclusive of stroke and traumatic brain injury) increases the possibility of further seizures and should be weighed in decision making 1.
From the Research
Risk of Second Seizure
- The risk of a second seizure after a first unprovoked seizure is approximately 36% at 2 years and 46% after 5 years, as reported in the study 2.
- Another study found that the risk of recurrence after a first unprovoked seizure is around 40-50% within 2 years of the initial seizure, and treatment may reduce this risk by as much as half 3.
- Factors that can increase the risk of a second seizure include EEG epileptiform discharges, brain imaging abnormalities, nocturnal first seizure, or prior brain trauma, with the risk being doubled in the presence of these factors 2.
Comparison of Studies
- The studies 2 and 3 provide estimates of the risk of a second seizure, with similar results.
- However, the other studies 4, 5, and 6 focus on the effectiveness of different antiepileptic drugs and do not provide direct estimates of the risk of a second seizure.
- These studies do provide information on the time to treatment failure, remission, and first seizure, but do not address the specific question of the percentage of first-time seizures that have a second seizure.