Epilepsy
A tendency to recurrent unprovoked seizures caused by abnormal, excessive, hypersynchronous electrical discharge of cortical neurons, with seizure semiology directly reflecting which part of the cortex fires and how far the discharge spreads.
In a nutshell
Epilepsy is an enduring tendency for cortical neurons to discharge synchronously and excessively; where the discharge starts and how far it spreads determines the seizure semiology, and treatment works by raising the threshold for that synchronous firing.
Classic presentation
A witnessed tonic-clonic convulsion with loss of consciousness, rhythmic limb jerking, tongue biting and a period of post-ictal confusion.
Key points
- Seizure semiology maps directly onto the cortical region discharging: this is how focal seizures are localised clinically.
- Focal seizures start in one region and may spread to become bilateral; generalised seizures start simultaneously across both hemispheres.
- Diagnosis rests primarily on eyewitness history; EEG and MRI support the diagnosis and find a cause but do not make it alone: a normal EEG never excludes epilepsy.
- A single provoked seizure, such as with fever, hypoglycaemia or alcohol withdrawal, is not epilepsy; epilepsy requires an enduring unprovoked tendency.
- Anti-seizure drug choice depends on seizure type, focal versus generalised, not on the underlying cause.
First-line investigation
A detailed eyewitness account of the event, supported by EEG for interictal epileptiform activity and MRI to look for a structural cause.
First-line management
Confirm the diagnosis with specialist assessment, then start an anti-seizure medication chosen according to whether seizures are focal or generalised.
Exam traps
- A normal EEG does not exclude epilepsy: the diagnosis is clinical, not electrophysiological.
- Not every convulsion is epilepsy: syncope can produce brief jerking (convulsive syncope) and is a key differential the stem may be testing.
- Sodium valproate is avoided in women of childbearing potential because of teratogenicity, a very common exam trap despite being broad-spectrum and effective.
Educational content pending clinical review. Not medical advice.