Overview
Generalised Epilepsy (GTC)
1. Clinical Overview
Summary
Generalised epilepsy involves seizures affecting both cerebral hemispheres from onset. Generalised tonic-clonic (GTC) seizures are the most dramatic type, characterised by loss of consciousness, tonic stiffening followed by clonic jerking, and a post-ictal recovery phase.
Key Facts
| Aspect | Detail |
|---|---|
| Definition | Seizures involving both hemispheres from onset |
| Most Common Type | Generalised tonic-clonic (GTC) |
| Duration | 1-3 minutes typically (status if > min) |
| Post-ictal | Confusion, drowsiness, headache |
| First-Line Treatment | Valproate (males), Lamotrigine/Levetiracetam (females) |
Clinical Pearls
- Lateral tongue bite: Highly specific for GTC (vs tip bite in syncope)
- Eyes OPEN: During seizures (vs CLOSED in psychogenic non-epileptic seizures)
- Valproate in pregnancy: Highly teratogenic - AVOID in women of childbearing age
- SUDEP: Sudden unexpected death in epilepsy - major concern with uncontrolled GTC
2. Epidemiology
Prevalence
| Population | Prevalence |
|---|---|
| All epilepsy | 1% of population |
| Generalised epilepsies | ~30% of all epilepsies |
| Idiopathic generalised | Peak onset adolescence |
Risk Factors
| Risk Factor | Association |
|---|---|
| Family history | Genetic component |
| Brain injury | Structural epilepsy |
| Maternal Hx of epilepsy | Inherited syndromes |
| Alcohol withdrawal | Provoked GTC |
3. Pathophysiology
Mechanism
Abnormal Neuronal Excitability
(Genetic or Acquired)
↓
Imbalance: Excitation (Glutamate) > Inhibition (GABA)
↓
Hypersynchronous Discharge
↓
Both Hemispheres Simultaneously
↓
GENERALISED SEIZURE
Seizure Phases
| Phase | Features | Duration |
|---|---|---|
| Aura | May be absent in generalised | Seconds |
| Tonic | Stiffening, apnoea, cyanosis, "cry" | 10-20 seconds |
| Clonic | Rhythmic jerking, slowing frequency | 30-60 seconds |
| Post-ictal | Unconscious → confused → recovery | Minutes to hours |
4. Clinical Presentation
Tonic-Clonic Seizure
| Feature | Description |
|---|---|
| Loss of consciousness | Immediate, no warning (vs focal → bilateral) |
| Tonic phase | Sustained contraction, fall, apnoea, cyanosis |
| "Epileptic cry" | Air forced through closed cords |
| Clonic phase | Rhythmic jerking of limbs |
| Incontinence | Urinary (sometimes faecal) |
| Tongue bite | Lateral (highly specific) |
| Post-ictal confusion | Minutes to hours |
| Todd's paresis | Temporary weakness (suggests focal onset) |
Other Generalised Seizure Types
| Type | Features |
|---|---|
| Absence | Brief staring spells, immediate recovery |
| Myoclonic | Sudden jerks, especially morning |
| Atonic | Sudden loss of tone ("drop attacks") |
Common Triggers
| Trigger | Mechanism |
|---|---|
| Sleep deprivation | Lowers seizure threshold |
| Alcohol (withdrawal) | GABAergic rebound |
| Flashing lights | Photosensitive epilepsy |
| Missed medication | Subtherapeutic levels |
| Stress/illness | Metabolic changes |
5. Clinical Examination
Between Seizures
- Often entirely normal
During/After Seizure
| Finding | Significance |
|---|---|
| Lateral tongue bite | Highly specific for GTC |
| Urinary incontinence | Supportive of seizure |
| Post-ictal confusion | Duration correlates with seizure severity |
| Elevated CK | May be raised post-GTC |
6. Investigations
First-Line
| Investigation | Purpose |
|---|---|
| EEG | May show generalised spike-wave (3Hz in absence) |
| MRI brain | Exclude structural cause |
| Blood tests | Glucose, U&E, calcium, magnesium |
Additional
| Test | Indication |
|---|---|
| Video EEG | Diagnostic uncertainty |
| Genetic testing | Suspected syndrome (JME, CAE) |
| Drug levels | If breakthrough seizures |
7. Management
Lifestyle Measures
| Measure | Rationale |
|---|---|
| Regular sleep | Avoid sleep deprivation |
| Limit alcohol | Lower seizure threshold |
| Medication adherence | Critical |
| Avoid triggers | Photosensitivity if relevant |
Pharmacotherapy
| Patient | First-Line | Notes |
|---|---|---|
| Males / not of childbearing potential | Sodium Valproate | Broad-spectrum efficacy |
| Females of childbearing age | Lamotrigine or Levetiracetam | Avoid valproate (teratogenic) |
| Alternative | Topiramate, Zonisamide | Valproate caution also applies |
Important Drug Considerations
- Valproate: Highly teratogenic (neural tube defects, IQ reduction) - Pregnancy Prevention Programme
- Lamotrigine: Slow titration to avoid Stevens-Johnson syndrome
- Levetiracetam: Mood changes, aggression possible
- Carbamazepine/Phenytoin: AVOID in generalised epilepsy (may worsen)
Status Epilepticus Protocol
Seizure >5 minutes
↓
Step 1: IV Lorazepam 4mg (or Buccal Midazolam)
↓ (wait 5 min)
Repeat if no response
↓ (wait 5 min)
Step 2: IV Phenytoin (or Levetiracetam)
↓
Step 3: (Refractory) RSI + Anaesthesia
8. Complications
| Complication | Notes |
|---|---|
| Injury from falls | Common |
| Tongue laceration | Lateral bite |
| Aspiration | Post-ictal |
| SUDEP | 1:1000/year - major concern |
| Status epilepticus | Medical emergency |
| Driving restrictions | Cannot drive for 12 months seizure-free |
| Occupational impact | Some jobs restricted |
9. Prognosis & Outcomes
| Factor | Outcome |
|---|---|
| Seizure-free on medication | 70% achieve control |
| Drug-resistant epilepsy | ~30% |
| SUDEP risk | Higher with uncontrolled nocturnal GTC |
| Quality of life | Good with treatment adherence |
10. Evidence & Guidelines
| Organisation | Key Points |
|---|---|
| NICE NG217 | Valproate restriction in females, AED choice |
| ABN | Pregnancy and epilepsy guidance |
| ILAE | Classification and management recommendations |
11. Patient / Layperson Explanation
What is a tonic-clonic seizure? It's the type of seizure most people picture - you lose consciousness, your body stiffens then shakes, and you may bite your tongue or be incontinent. Afterwards, you'll feel confused and tired.
What causes it? Your brain has too much electrical activity all at once. It can run in families or develop after brain injury. Often no cause is found.
How is it treated?
- Daily medication (anti-epileptic drugs) - very effective for most people
- Avoiding triggers like lack of sleep or excess alcohol
- Not driving until seizures are controlled (usually 12 months seizure-free)
What should someone do if I have a seizure?
- Stay calm
- Protect my head (cushion it)
- Don't put anything in my mouth
- Put me in recovery position after jerking stops
- Call 999 if seizure lasts over 5 minutes, or if it's my first
12. References
- NICE NG217. Epilepsies: diagnosis and management. 2022.
- Fisher RS, et al. ILAE Official Report: Classification of Epilepsies. Epilepsia. 2017.
- Harden CL. Pregnancy and epilepsy. Continuum. 2019.