Generalised Epilepsy Syndromes
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Direct answer
Generalised epilepsy syndromes are epilepsies in which seizures involve both hemispheres from onset, with generalised spike-and-wave discharges on EEG. The three classic examples are childhood absence epilepsy, juvenile myoclonic epilepsy and Lennox-Gastaut syndrome, each with a characteristic age, seizure type and EEG pattern. Sodium channel blockers such as carbamazepine can worsen absence and myoclonic seizures, so they are avoided in these syndromes.
What you must remember
- Childhood absence epilepsy: Onset in childhood with brief staring spells, a generalised 3 Hz spike-and-wave pattern and provocation by hyperventilation.
- Juvenile myoclonic epilepsy: Adolescent onset with morning myoclonic jerks, generalised tonic-clonic seizures and 4 to 6 Hz polyspike-and-wave discharges.
- Lennox-Gastaut syndrome: Childhood onset with multiple seizure types, drop attacks, intellectual disability and slow spike-and-wave under 2.5 Hz.
- First-line for absence: Ethosuximide, a T-type calcium channel blocker, with valproate or lamotrigine as alternatives.
- Valproate in JME: Effective for generalised tonic-clonic and myoclonic seizures, but teratogenic and needing caution in women of childbearing potential.
- Avoid in generalised epilepsy: Carbamazepine, phenytoin and oxcarbazepine, which can aggravate absence and myoclonic seizures.
- Photosensitivity: Flickering light can trigger myoclonus in juvenile myoclonic epilepsy, with a photoparoxysmal response on EEG.
Recognising the syndrome from age, seizure and EEG
Each syndrome is recognised by putting the age at onset, the seizure type and the EEG pattern together. The table lists the three syndromes in order of typical age.
| Syndrome | Age and seizures | EEG | First-line drugs |
|---|---|---|---|
| Childhood absence | Age 4 to 10, staring spells | Generalised 3 Hz spike-and-wave | Ethosuximide, valproate |
| Juvenile myoclonic | Adolescence, myoclonus on waking | 4 to 6 Hz polyspike-and-wave | Valproate, levetiracetam (lamotrigine may worsen myoclonus) |
| Lennox-Gastaut | Childhood, drop attacks and tonic seizures | Slow spike-and-wave under 2.5 Hz | Valproate, lamotrigine, rufinamide, clobazam |
Age at onset is often the first clue in a case vignette, so note it before reading the drug options. Lennox-Gastaut syndrome is usually drug resistant, which is why early specialist referral matters. The EEG pattern should always be read alongside the clinical seizure description rather than in isolation.
Prognosis also differs between the syndromes, since childhood absence epilepsy often remits in adolescence while juvenile myoclonic epilepsy usually needs lifelong treatment.
Where the exam tries to catch you
Examiners test whether you avoid the drug that worsens the syndrome.
- Trap: Choosing carbamazepine for absence seizures Correct: carbamazepine can worsen absence and myoclonic seizures, so ethosuximide or valproate is preferred.
- Trap: Using valproate without counselling in a young woman with juvenile myoclonic epilepsy Correct: valproate carries a major teratogenic risk, so alternatives such as levetiracetam or lamotrigine are considered when pregnancy is possible.
- Trap: Labelling a slow spike-and-wave pattern as typical absence Correct: slow spike-and-wave below 2.5 Hz with multiple seizure types and learning difficulty points to Lennox-Gastaut syndrome.
Frequently asked questions
Which EEG pattern is typical of childhood absence epilepsy?
Childhood absence epilepsy shows generalised 3 Hz spike-and-wave discharges on EEG, with bursts that correspond to brief staring spells. Hyperventilation often provokes the pattern during the recording. The background EEG is usually normal between the bursts.
Why is valproate used in juvenile myoclonic epilepsy despite its teratogenicity?
Sodium valproate is effective against generalised tonic-clonic and myoclonic seizures in juvenile myoclonic epilepsy, which is why it is often the most effective single drug. Its teratogenic risk, including neural tube defects and lower cognitive scores in exposed children, requires careful counselling in women of childbearing age. Levetiracetam and lamotrigine are considered when pregnancy is planned.
What drugs are used for Lennox-Gastaut syndrome?
Lennox-Gastaut syndrome is treated with valproate, lamotrigine, rufinamide, clobazam and topiramate, often in combination, because it is usually drug resistant. Carbamazepine, phenytoin and oxcarbazepine can worsen the seizures and should be avoided. Early specialist referral improves the chance of finding an effective regimen.
Why should carbamazepine be avoided in generalised epilepsy?
Carbamazepine is a sodium channel blocker that can aggravate absence seizures and myoclonic jerks in generalised epilepsy. It can also precipitate tonic and atonic seizures in Lennox-Gastaut syndrome. Its use is therefore reserved for focal epilepsy and trigeminal neuralgia rather than generalised syndromes.