CAE

Childhood Absence Epilepsy (CAE) is a common, genetically-linked epilepsy syndrome characterised by frequent, brief absence seizures. It’s now classified by the ILAE as a genetic generalised epilepsy.

Presentation and Clinical Features

• Age of Onset: Typically begins in early school years, between the ages of 4 and 8. It is more common in girls.

• Seizure Characteristics: The core feature is a sudden, brief loss of consciousness, often lasting between 5 and 15 seconds. The child abruptly stops their activity, stares blankly, and may have subtle motor signs.

  • Typical Absences: The child appears unresponsive, with a vacant stare. Common associated features include eye flickering (eyelid myoclonia), upward eye deviation, and lip-smacking or other automatisms.

  • Frequency: Untreated, children can have numerous absences daily, sometimes as many as 20 to 100 or more. This high frequency can lead to a significant impact on learning and attention, as the child “misses” segments of information.

• Triggers: Absence seizures are often precipitated by triggers such as hyperventilation, fatigue, or stress.

• Prognosis: The prognosis is generally good, with most children entering remission by adolescence. However, some may develop other seizure types later in life, particularly if they have an underlying syndrome like Juvenile Myoclonic Epilepsy (JME).

Investigation

• Diagnosis: The diagnosis is primarily clinical and supported by the EEG.

• EEG: The hallmark of CAE is the presence of generalised 3 Hz spike-and-wave discharges on a normal background. The frequency can range from 2.5 to 4 Hz. The discharges are best seen during a state of rest or quiet wakefulness and are reliably provoked by hyperventilation. For this reason, it’s a standard part of the EEG procedure for suspected CAE.

• Neuroimaging: Routine brain MRI is not required for a typical presentation of CAE. It should be considered only if the clinical or EEG findings are atypical or suggest an alternative diagnosis.

Management

• First-Line Treatment: The goal of treatment is to achieve complete seizure freedom to optimise the child’s learning and development.

  • Ethosuximide is now considered the first-line drug of choice for absence seizures in children. Recent studies and ILAE guidelines have shown it to be highly effective with a more favorable side-effect profile compared to other options.

  • Valproate is also highly effective but carries a risk of teratogenicity, weight gain, and hepatotoxicity, limiting its use, especially in adolescent girls.

  • Lamotrigine is an effective option, but some studies show it may be less effective in achieving complete seizure freedom than Ethosuximide or Valproate.

• Monitoring and Follow-up: Regular follow-up is essential to monitor for treatment response and side effects.

• Medication Discontinuation: For children who are seizure-free, medication can often be slowly tapered and discontinued after a period of 1 to 2 years, with the decision based on the child’s overall clinical picture and EEG findings.

• Treatment-Resistant Cases: If seizures are resistant to first-line agents, a re-evaluation of the diagnosis is necessary. This may include considering genetic testing or more advanced neuroimaging. For truly resistant cases, tertiary epilepsy centres may consider other anti-epileptic drugs, the ketogenic diet, or even Vagus Nerve Stimulation (VNS), though these are rarely needed for typical CAE.