Clinical Pearls & Morning Reports
Published July 14, 2021
After a first unprovoked seizure, the overall risk of recurrence may be as high as 60%, and this risk is highest within the first 2 years. Read the NEJM Clinical Practice Article here.
Q: How is epilepsy diagnosed?
A: Epilepsy is diagnosed after two unprovoked seizures that occur more than 24 hours apart or after a single event that occurs in a person who is considered to have a high risk of recurrence (>60% risk in a 10-year period). Abnormal findings on electroencephalography (EEG), an abnormal neurologic status, and a second seizure all increase the probability of seizure recurrence. These three factors allow clinicians to stratify low, medium, and high risks and help in guiding decisions about the initiation of antiseizure medication.
Q: What is the role of brain imaging and EEG after a first seizure?
A: Urgent brain imaging is warranted in patients who present with a first epileptic seizure. Computed tomography is useful and widely available. However, in most adults with a first seizure (especially a focal-onset seizure) or early epilepsy, detailed magnetic resonance imaging (MRI; ideally 3-T MRI with <3-mm slice thickness on T2-weighted imaging and fluid-attenuated inversion recovery) is warranted to identify more subtle underlying causes such as hippocampal sclerosis, focal cortical dysplasia, or tumor that may be treated surgically. Interictal EEG that is performed in a patient who has had a first seizure is unlikely to capture another seizure, although the procedure may provoke psychogenic nonepileptic seizures. EEG is most informative in patients younger than 25 years of age because these patients are most likely to have subclinical interictal generalized activity that may confirm a generalized seizure tendency and that strongly predicts further seizures (70% positive predictive value).
A: Antiseizure medication is primarily indicated when the risk of further spontaneous seizures is judged to exceed 60% over the next 10 years. The initiation of long-term use of antiseizure medication is a major decision that is made by the patient and clinician. This decision requires reasonable certainty of an epilepsy diagnosis; the use of medication for a trial period in patients in whom the diagnosis is uncertain should be avoided. The Medical Research Council Multicentre Trial for Early Epilepsy and Single Seizures showed that the risk of seizure recurrence was lower in the first 2 years after the first seizure among patients who received immediate initiation of medication (generally carbamazepine or sodium valproate) than among those who received delayed treatment pending a second seizure (32% vs. 39%), but earlier initiation of treatment did not affect longer-term seizure remission. Adverse events were significantly more common with immediate treatment than with delayed treatment (in 39% and 31% of the patients), and quality-of-life measures were similar in the two groups. Therefore, clinicians usually advise withholding medication in patients who have had a single seizure unless the recurrence risk is particularly high.
A: Data from long-term pragmatic trials suggest that the first-line medication for patients with focal-onset seizures is either lamotrigine or levetiracetam, although other reasonable options are available; for patients with generalized-onset seizures, the first choice is sodium valproate, except for women of childbearing potential, in whom the first-line medication is usually levetiracetam. Sodium valproate carries high risks in pregnancy. Approximately 10% of babies exposed to sodium valproate in utero have major congenital anomalies, and up to 40% have measurable neurodevelopmental delay. Thus, valproate should generally be avoided in women of childbearing potential; if valproate is used, effective measures should be taken to prevent pregnancy unless the woman is fully informed about the risks.