Tonic-clonic Seizure
A tonic-clonic seizure is the classic convulsive episode most people picture when they think of epilepsy. It unfolds in two phases: a brief tonic phase in which muscles stiffen and consciousness is lost, followed by a clonic phase of rhythmic, jerking limb movements lasting one to three minutes. Afterwards, the person typically feels confused, exhausted, or drowsy for up to an hour.
Key points
- The episode moves through a stiffening phase followed by rhythmic limb jerking that can last up to three minutes.
- Confusion, tiredness and drowsiness lasting up to an hour commonly follow once the movements stop.
- Anticonvulsant treatment is usually started after more than one seizure without a clear trigger, aiming to calm abnormal brain electrical activity.
- Phenytoin, an established option, works by stabilising the sodium channels in nerve membranes that carry these electrical signals.
Managing tonic-clonic seizures long-term
Once a person has had more than one unprovoked tonic-clonic seizure, most neurologists begin anticonvulsant therapy. The goal is to suppress abnormal electrical firing in the brain enough to prevent further episodes. Phenytoin is one of the older, well-studied anticonvulsants used for this purpose, working by stabilising voltage-gated sodium channels in nerve membranes. It is often used in acute settings and for longer-term control in patients who tolerate it well. For a broader view of conditions and medicines in this field, see the neurology category.
If someone has a seizure lasting more than five minutes, or has repeated seizures without regaining consciousness, seek emergency help immediately.