Juvenile Absence EPilepsy (JAE)
Juvenile Absence Epilepsy (JAE) is a form of genetic generalised epilepsy that is distinguished from Childhood Absence Epilepsy (CAE) by its later onset, lower frequency of absence seizures, and the common coexistence of other seizure types. ILAE states that JAE is a well-defined epilepsy syndrome with specific clinical and EEG features.
Presentation and Clinical Features
Age of Onset: JAE typically has a later onset than CAE, with a peak between 10 and 12 years of age, though it can occur anywhere from 8 to 20 years. It is more common in girls.
Absence Seizures:
Semiology: Absences are similar to those in CAE but are generally less frequent, occurring a few times a day rather than dozens. They are characterized by a sudden, brief interruption of consciousness, lasting from 5 to 30 seconds.
Clinical Signs: The blank stare is often accompanied by subtle motor signs such as eyelid myoclonia, mouth automatisms (lip-smacking, chewing), and sometimes head nodding.
Distinguishing from CAE: Unlike CAE, JAE absences are less frequent and can be more difficult to detect without careful observation.
Other Seizure Types:
Generalized Tonic-Clonic Seizures (GTCS): GTCS are a hallmark of JAE and occur in over 80% of patients. They are most common upon awakening.
Myoclonic Seizures: Myoclonic jerks are also common but are less frequent and less severe than in Juvenile Myoclonic Epilepsy (JME). They typically involve the upper limbs, particularly in the morning.
Cognition: Cognitive function is generally not affected, and individuals with JAE have a normal intellectual outcome.
Investigation
Diagnosis: The diagnosis is based on the characteristic clinical history and EEG findings. A detailed history from both the patient and their family is crucial for identifying all seizure types.
EEG: The EEG is key for diagnosis. It shows generalized spike-and-wave discharges, typically at a frequency of 3.5 to 6 Hz. This faster frequency distinguishes it from the 3 Hz pattern seen in CAE.
Provocation: The EEG discharges are enhanced by sleep deprivation and hyperventilation. Photosensitivity (seizures triggered by flickering lights) is also a common finding and should be tested for.
EEG findings in JAE are often more consistent and less dependent on sleep than in other epilepsy syndromes.
Neuroimaging: A brain MRI is not routinely required for a typical presentation of JAE. It should be considered if the clinical history or EEG findings are atypical or suggest an underlying structural cause.
Management and Treatment
Lifelong Condition: Unlike CAE, JAE is considered a lifelong epilepsy in the majority of cases. While seizure control is excellent with medication, the treatment is generally not withdrawn.
Medication Choice: Treatment should address all seizure types (absences, myoclonus, and GTCS).
Valproate is highly effective against all three seizure types and was previously regarded as the first-line choice for males and post-menopausal women.
Levetiracetam and Lamotrigine are also effective and well-tolerated. Levetiracetam is particularly good for myoclonic seizures, while Lamotrigine is a good option for all seizure types in this syndrome.
Considerations for Females: Due to the risk of teratogenicity, Valproate should be used with caution in girls and women of child-bearing potential. In such cases, Levetiracetam, Lamotrigine, or Zonisamide are preferred.
Ethosuximide is effective for absence seizures but has no effect on GTCS and myoclonic jerks, making it a poor choice for monotherapy in JAE.
Treatment-Resistant Cases: For patients with resistant seizures, a combination of AEDs may be necessary, and consultation with a tertiary epilepsy center is recommended. Medications like Clobazam and Topiramate may be considered, though Topiramate can have significant cognitive side effects.
Counseling: Patients and families should be counseled about the lifelong nature of the condition, the importance of medication adherence, and avoiding triggers like sleep deprivation and alcohol.