Tonic-clonic seizures: what they look like, first aid and when to call 999

Epilepsy Action describes tonic-clonic seizures as the type of epileptic seizure most people recognise. In the past they were called grand mal seizures, and they are sometimes called convulsive seizures. The NHS lists them among the main types of epileptic seizure, defined as a seizure where you become unconscious and may fall, your muscles get stiff and your body jerks and shakes.

They can have a generalised onset, meaning they appear to involve both sides of the brain from the start, or they can begin as a focal seizure in one area and spread to both sides. Epilepsy Action calls the latter a focal to bilateral tonic-clonic seizure. Where a seizure begins is not always known, particularly when nobody saw it and the person cannot recall the onset.

In the tonic phase, according to Epilepsy Action, the person loses consciousness and is not aware of what is happening. All their muscles go stiff, and if they are standing they fall to the floor. Air may be pushed past the voice box, which can make a sound like crying out, and they may bite their tongue or the inside of their mouth.

In the clonic phase the limbs jerk quickly and rhythmically. The person may lose control of the bladder or bowels, and breathing may be affected, causing a blue tinge around the mouth. On black or brown skin the colour may look grey, and it can be easier to see on the lips, gums, inside the eyelids, palms or soles of the feet.

Some people have an aura beforehand, such as a feeling of deja vu or a flash of light. Epilepsy Action explains that an aura is actually a focal seizure, and that it can act as a warning that a tonic-clonic seizure is about to follow. Not everyone gets one.

Epilepsy Action sets out the steps for helping someone having a tonic-clonic seizure. They are designed to be easy to remember and to keep the person safe rather than to stop the seizure.

• Protect them from injury by removing harmful objects from nearby.

• Cushion their head.

• Look for an epilepsy identity card or identity jewellery, which may say what to do.

• Time how long the seizure lasts.

• Once the jerking has stopped, help their breathing by gently placing them in the recovery position.

• Stay with them until they are fully recovered, and be calm and reassuring.

Epilepsy Action says not to hold the person down or put anything in their mouth, not to move them unless they are in danger, not to try to bring them round, and not to give them anything to eat or drink until they are fully recovered. The person may wet themselves, and a light blanket or piece of clothing over the lower body can help preserve their dignity, as can moving bystanders away.

The NHS says to call 999 if you think someone is having a seizure and it is the first time it has happened, it lasts longer than is usual for them or longer than 5 minutes if you do not know how long their seizures usually last, they do not recover as usual afterwards or have another seizure without recovering in between, or they have now had 3 or more seizures in 24 hours. Epilepsy Action adds seriously injuring themselves and having trouble breathing after the seizure has stopped to its list of reasons to call an ambulance.

The NHS also notes that people with epilepsy do not always need to go to hospital when they have a seizure. They usually have a care plan that says what to do, such as giving emergency medicine and when to call 999, and a trained person can follow it.

The time afterwards is called the post-ictal phase and it varies. Epilepsy Action says the person might have a headache and feel sore, tired and very unwell; feel confused or have memory problems; or go into a deep sleep. Breathing may sound heavy and laboured, with a deep snoring sound. Some people feel confused and scared and may act in unusual ways. Recovery may take an hour or two, or several days.

Some people have temporary weakness or cannot move part of their body after a seizure, known as Todd's paralysis. Epilepsy Action says it can last from a few minutes up to 36 hours and goes away by itself, and that a brain scan is usually done the first time it happens to rule out a stroke.

The NHS says anyone who has had a seizure needs to see a specialist, who will ask what happened before, during and after, and ideally speak to someone who saw it. Tests can include an electroencephalogram (EEG), an electrocardiogram (ECG), a CT or MRI scan, blood tests and genetic testing. You will usually be diagnosed with epilepsy if you have had more than 1 seizure, or if tests show a risk of more seizures.

The main treatment is anti-seizure medicine, and emergency medicine may be prescribed for seizures that last longer than usual. Epilepsy Action recommends keeping a seizure diary, taking medicines as prescribed without missing doses, carrying medical ID, and checking that rescue medicine is in date. The NHS says if you have had any type of seizure you must not drive and must tell the DVLA. Uncontrolled tonic-clonic seizures increase the risk of sudden unexpected death in epilepsy (SUDEP), which Epilepsy Action says affects around 1 in every 1,000 people with epilepsy each year, so the aim of treatment is to reduce them as far as possible.