Introduction

Epilepsy is a condition that affects the brain and causes repeated seizures.

Epilepsy is estimated to affect more than 500,000 people in the UK. This means that almost one in every 100 people has the condition.

Seizures

The cells in the brain, known as neurons, conduct electrical signals and communicate with each other in the brain using chemical messengers. During a seizure, there are abnormal bursts of neurons firing off electrical impulses, which can cause the brain and body to behave strangely.

The severity of seizures can differ from person to person. Some people simply experience an odd feeling with no loss of awareness, or may have a "trance-like" state for a few seconds or minutes, while others lose consciousness and have convulsions (uncontrollable shaking of the body).

Some people may only have a single seizure at some point during their life. If they do not have a high risk of having further seizures, they would not be regarded as having epilepsy. 

Read more about the symptoms of epilepsy

What causes epilepsy?

Epilepsy can start at any age, but it most often begins during childhood.

It's often not possible to identify a specific reason why someone develops the condition, although some cases – particularly those that occur later in life – are associated with damage to the brain.

For example, epilepsy can be caused by strokesbrain tumours and severe head injuries.

Some cases of epilepsy may be caused by changes in the brain that occur as a result of the genes you inherit from your parents.

Read more about the causes of epilepsy

How epilepsy is diagnosed

Epilepsy is most often diagnosed after you have had more than one seizure. This is because many people have a one-off epileptic seizure during their lifetime.

The most important information needed to make a diagnosis is a description of your seizures from yourself and someone who witnessed the event, but tests may also be carried out to help determine which areas of your brain are affected and look for a potential cause.

Read more about diagnosing epilepsy

How epilepsy is treated

For most people with epilepsy, treatment with medications called anti-epileptic drugs (AEDs) is recommended. These medications cannot cure epilepsy, but they are often very effective in controlling seizures.

It can take some time to find the right type and correct dose of AED before your seizures can be controlled.

In a few cases, surgery may be used to remove a specific area of the brain that is affected or to install an electrical device that can help control seizures.

Read more about treating epilepsy

Living with epilepsy

While epilepsy is different for everyone, there are some general rules that can make living with the condition easier.

It's important to stay healthy through regular exercise, getting enough sleep, eating a balanced diet and avoiding excessive drinking.

You may have to think about your epilepsy before you undertake things such as driving, using contraception and planning a pregnancy.

Advice is available from your GP or support groups to help you adjust to life with epilepsy.

Read more about living with epilepsy

Symptoms

The main symptoms of epilepsy are repeated seizures. There are many different types of seizure, depending on the area of the brain affected.

People with epilepsy can experience any type of seizure, although most people have a consistent pattern of symptoms.

Seizures can occur when you are awake or asleep.

Doctors classify seizures by how much of the brain is affected. There are:

  • partial (or focal) seizures – where only a small part of the brain is affected
  • generalised seizures – where most or all of the brain is affected

Some seizures do not fit into these categories and are known as unclassified seizures.

Partial seizures

There are two main types of partial seizure.

Simple partial seizures

Simple partial seizures are where you remain fully conscious throughout.

Symptoms of a simple partial seizure can include:

  • a general strange feeling that is hard to describe
  • a "rising" feeling in your tummy – sometimes likened to the sensation in your stomach when on a fairground ride
  • an intense feeling that events have happened before (déjà vu)
  • experiencing an unusual smell or taste
  • a tingling sensation, or "pins and needles", in your arms and legs
  • a sudden intense feeling of fear or joy
  • stiffness or twitching in part of the body, such as an arm or hand

These seizures are sometimes known as "warnings" or "auras", because they can be a sign that another type of seizure is on its way. This can give you time to warn people around you and make sure you are in a safe place.

Complex partial seizures

Complex partial seizures are when you lose your sense of awareness and can’t remember what happened after the seizure has passed.

The symptoms of a complex partial seizure normally involve apparently strange and random bodily behaviour, such as:

  • smacking your lips
  • rubbing your hands
  • making random noises
  • moving your arms around
  • picking at clothes
  • fiddling with objects
  • adopting an unusual posture
  • chewing or swallowing

During a complex partial seizure, you will not be able to respond to anyone else, and you will have no memory of the event.

Generalised seizures

There are six main types of generalised seizure.

Absences

Absence seizures, which used to be called petit mal, mainly affect children, but they also occur in adults. They cause the person to lose awareness of their surroundings, usually for up to 15 seconds. The person will seem to stare vacantly into space, although some people will flutter their eyes or smack their lips. The person will have no memory of the seizure.

Absences can occur several times a day. They may affect a child's performance at school, and can be dangerous if they occur at a critical time, such as crossing a busy road.

Myoclonic seizures

These types of seizures cause your arms, legs or upper body to jerk or twitch, as if you have received an electric shock. They often only last for a fraction of a second, and you will normally remain conscious during this time.

Myoclonic jerks often happen in the first few hours after waking up and can occur in combination with other types of generalised seizures.

Clonic seizures

These cause the same sort of twitching as myoclonic jerks, except the symptoms will last longer, normally up to two minutes. Loss of consciousness may also occur.

Atonic seizures

Atonic seizures cause all your muscles to suddenly relax, so there is a chance you may fall to the ground and there is a risk you could injure yourself.

Tonic seizures

Tonic seizures cause all your muscles to suddenly become stiff, which can mean you lose balance and fall over. Like atonic seizures, there is a risk of injury.

Tonic-clonic seizures

Tonic-clonic seizures or convulsions, which used to be known as grand mal, have two stages. Your body will initially become stiff and then your arms and legs will begin twitching. You will lose consciousness and some people will wet themselves. The seizure normally lasts a few minutes, but can last longer.

This type of seizure is what most people think of as an epileptic fit.

What to do if someone has a seizure

If you see someone having a seizure, there are simple things you can do to help.

Tonic-clonic seizures

If you are with someone who has a tonic-clonic seizure:

  • protect them from injury by removing any dangerous or potentially harmful objects nearby, and cushioning their head with your hands or soft material
  • do not restrain them or attempt to move them (unless they are in immediate danger) and don't put anything in their mouth
  • stay calm, and stay with them until they regain consciousness

When the convulsions have stopped, put them into the recovery position until they have recovered.

Other types of seizure

If someone is having one of the other types of seizure:

  • protect them from injury by removing any dangerous or potentially harmful objects nearby, and cushioning their head with your hands or soft material
  • only attempt to move them if they are in immediate danger
  • stay with them and comfort them until they have fully recovered

When to call an ambulance

It will not usually be necessary to call an ambulance after a seizure. However, you should call 999 if:

  • the seizure has not stopped after five minutes
  • the person has more than one seizure without recovering in between
  • you know it is the person's first seizure
  • the person is injured, has breathing problems, or needs emergency medical attention for any other reason
  • the person’s behaviour after a seizure is unsafe

Status epilepticus

Status epilepticus is the name for any seizure that lasts longer than 30 minutes, or a series of seizures where the person does not regain consciousness in between. This is a medical emergency and requires treatment as soon as possible.

You can be trained to treat status epilepticus if you care for someone with epilepsy, but if you haven't had any training, it is important to call 999 for an ambulance immediately if you suspect status epilepticus.

If you have been trained to treat the condition, you will usually have been advised to use either:

  • a medication called diazepam that is placed in the person's rectum
  • a medication called buccal midazolam that  comes in liquid form and is given by trickling the liquid onto the inside of the person's cheek

If you have tried one of these treatments and the seizures are continuing, call 999 for an ambulance.

Causes

In over half of epilepsy cases, a cause cannot be found. If there is an identifiable cause, it usually involves the brain being affected by a condition.

The brain is a delicate mix of nerve cells, electrical impulses and chemicals, known as neurotransmitters. Any damage has the potential to disrupt the workings of the brain and cause seizures.

There are two main categories of epilepsy:

  • idiopathic (or primary) epilepsy – where no apparent cause for epilepsy can be found, but there may be a family history, suggesting that the condition is inherited
  • symptomatic (or secondary) epilepsy – where there is a known cause for a person’s epilepsy

Idiopathic epilepsy

In many cases, no cause of epilepsy is found. This may be because medical equipment is not advanced enough to spot some types of damage, or because the epilepsy has a genetic cause.

Many researchers have suggested that small genetic changes in the brain could be the cause of epilepsy. Current research is looking for defects in certain genes that may affect electrical transmission in the brain.

A number of studies have been carried out; however, no strong association has so far been found between any particular genes and the development of epilepsy.

Symptomatic epilepsy

Causes of symptomatic epilepsy can include:

  • cerebrovascular disease (problems with the blood vessels that supply the brain) – such as a stroke or subarachnoid haemorrhage
  • brain tumours
  • severe head injuries
  • drug abuse and alcohol misuse
  • infections that can damage the brain – such as meningitis
  • problems during birth that cause a baby to be deprived of oxygen – such as the umbilical cord getting twisted or compressed during labour
  • some parts of the brain not developing properly

Although some of these problems can cause epilepsy in childhood, symptomatic epilepsy is generally more common in older people – particularly those over 60 years of age.

Seizure triggers

For many people with epilepsy, seizures can occur without any obvious trigger. However, certain circumstances or the use of certain substances can sometimes precede a seizure. These include:

  • stress
  • lack of sleep
  • drinking alcohol
  • some medications and illegal drugs
  • in women, monthly periods
  • flashing lights (this is an uncommon trigger that affects only 5% of people with epilepsy, and is known as photosensitive epilepsy)

Keeping a seizure diary is a good way to help find out what might trigger your seizures. Every time you have a seizure, record it and make a note of what you were doing. Over time, you might notice some potentially avoidable things that seem to trigger your symptoms.

Diagnosis

Epilepsy is usually difficult to diagnose quickly. In most cases, it cannot be confirmed until you have had more than one seizure.

It can be difficult to diagnose because many other conditions, such as migraines and panic attacks, can cause similar symptoms.

If you have had a seizure, you will be referred to a specialist in epilepsy, normally a neurologist (a doctor who specialises in conditions affecting the brain and nervous system).

Describing your seizures

Some of the most important pieces of information needed to diagnose epilepsy are the details about your seizure or seizures.

The doctor will ask you what you can remember and any symptoms you may have had before it happened, such as feeling strange before the seizure or experiencing any warning signs. It may be useful to talk to anyone who witnessed your seizure and ask them exactly what they saw, especially if you cannot remember the seizure.

The doctor will also ask about your medical and personal history and whether you use any medicines, drugs or alcohol.

The doctor may be able to make a diagnosis of epilepsy from the information you give, but they might run further tests such as an electroencephalogram (EEG) or magnetic resonance imaging (MRI) scan.

However, even if these tests don't show anything, it is still possible that you have epilepsy.

Electroencephalogram (EEG)

An EEG test can detect unusual brain activity associated with epilepsy by measuring the electrical activity of your brain through electrodes placed on your scalp.

During the test, you may be asked to breathe deeply or close your eyes and you may be asked to look at a flashing light. The test will be stopped immediately if it looks like the flashing light could trigger a seizure.

In some cases, an EEG may be carried out while you are asleep (sleep EEG) or you may be given a small, portable EEG recording device to monitor your brain activity over 24 hours (ambulatory EEG).

Magnetic resonance imaging (MRI) scan

An MRI scan is a type of scan which uses strong magnetic fields and radio waves to produce detailed images of the inside of your body.

It can be useful in cases of suspected epilepsy because it can often detect possible causes of the condition, such as defects in the structure of your brain or the presence of a brain tumour. 

An MRI scanner is a large tube that contains powerful magnets. You lie inside the tube during the scan.

Treatment

Most people with epilepsy can be successfully treated with AEDs. AEDs do not cure epilepsy, but can prevent seizures from occurring.

There are many different AEDs. Generally, they work by changing the levels of the chemicals in your brain that conduct electrical impulses. This reduces the chance of a seizure.

The type of AED recommended for you will depend on a number of factors, including the type of seizures you have, your age, whether there are any concerns about a certain AED interacting with other medicines (such as the contraceptive pill), and whether you are thinking of having a baby.

Examples of commonly used AEDs include sodium valproate, carbamazepine, lamotrigine, levetiracetam, oxcarbazepine, ethosuximide and topiramate.

Taking AEDs

AEDs are available in a number of different forms, including tablets, capsules, liquids and syrups.

It is important you follow any advice about when to take AEDs and how much to take. Never suddenly stop taking an AED because doing so could cause a seizure.

Your specialist will start you on a low dose of an AED, then gradually increase it within safe limits until your seizures stop, or if you develop side-effects. If one AED does not control seizures, another will be tried by gradually introducing the new medication and slowly reducing the dose of the old one.

The aim is to achieve maximum seizure control with minimum side effects, using the lowest possible dose of a single medicine. Trying a different type of AED is preferable to taking more than one AED, although a combination of medicines may sometimes be necessary to control seizures.

While taking AEDs, do not take any other medicines, including over-the-counter medicines or complementary medicines such as St John's Wort, without first speaking to your GP or epilepsy specialist. Other medicines could have a dangerous interaction with your AED and cause a seizure.

Sodium valproate is not usually prescribed for women of childbearing age because there is a risk it could cause physical defects or developmental problems in an unborn baby.

It can be used if there is no alternative, or if your specialist has assessed you and it's unlikely you'll respond to or tolerate other treatments. Your specialist or GP will also need to check you are using a reliable form of contraception.  Learn more about the risks of valproate medicines during pregnancy.

If you do not have a seizure for more than two years, it may be possible to stop taking your AEDs. Your epilepsy specialist can discuss with you whether this is appropriate and the best way this can be done.

Side effects

Side effects are common when starting treatment with AEDs. However, they are usually short-lived and pass in a few days.

The specific side effects you may experience will depend on the medication you are taking, but general common side effects of AEDs include:

  • drowsiness
  • a lack of energy
  • agitation
  • headaches
  • uncontrollable shaking (tremor)
  • hair loss or unwanted hair growth
  • swollen gums
  • rashes

If you develop a rash, this may mean that you are allergic to the medication. In this case seek medical advice right away.

Sometimes, you may experience symptoms similar to being drunk – such as unsteadiness, poor concentration and vomiting – if your dose is too high. Contact your GP or epilepsy specialist immediately if you experience these side effects so that your dose can be revised.

For information on the side effects of a particular AED, check the information leaflet that comes with your medication.

Brain surgery

If your epilepsy is still poorly controlled after trying treatment with AEDs, you may be referred to a specialist epilepsy centre to see if you are suitable for surgery to remove the part of your brain causing your seizures.

This involves having various types of brain scans to find out where the epilepsy is focused. Memory and psychological tests are also conducted to assess how you are likely to cope with the stress of surgery and how it might affect you.

Surgery is only recommended when:

  • a single area of the brain is causing seizures (partial or focal seizures)
  • removing that part of the brain would not cause any significant loss of brain function

As with all types of surgery, this procedure carries a number of risks. This includes a risk of serious problems such as memory problems and strokes after the operation. However, around 70% of people who have epilepsy surgery become completely free of seizures.

Before having the procedure, your surgeon will explain to you the benefits and risks of the surgery.

Most people normally recover from the effects of surgery after a few days, but it could be several months before you are fully fit and able to return to work.

Alternative procedures

If your epilepsy is still poorly controlled after trying treatment with AEDs, and brain surgery is not suitable for you, your doctor may recommend an alternative procedure.

The most commonly used alternative to surgery is vagus nerve stimulation (VNS), although in a few cases deep brain stimulation (DBS) may be recommended.

Vagus nerve stimulation (VNS)

VNS involves surgically implanting a small electrical device, similar to a pacemaker, under your skin, near your collarbone.

The device has a wire that is wrapped around one of the nerves in the left side of your neck, known as the vagus nerve. The device passes a regular dose of electricity to the nerve to stimulate it. This can help reduce the frequency and severity of seizures.

If you feel the warning sign of a seizure coming on, you can activate an extra "burst" of stimulation, which may prevent the seizure from occurring.

How and why VNS works is not fully understood, but it is thought that stimulating the vagus nerve alters the chemical transmissions in the brain.

Most people who undergo VNS still need to take AEDs.

Some mild to moderate side effects of VNS therapy have been reported, including hoarseness, sore throat and a cough when the device is being used (this normally occurs every five minutes and lasts for 30 seconds).

The battery for the VNS device typically lasts up to 10 years, after which time a further procedure will be needed to replace it.

Deep brain stimulation (DBS)

DBS involves implanting electrodes into specific areas of the brain to reduce the abnormal electrical activity associated with a seizure.

The electrodes are controlled by an external device implanted under the skin of the chest, which is usually permanently switched on.

DBS can help reduce the frequency of seizures, but there are concerns about serious risks associated with the procedure, including bleeding on the brain, depression and memory problems.

Ketogenic diet

A ketogenic diet a diet high in fats and low in carbohydrates and protein, and it is thought that it may make seizures less likely by altering the chemical composition of the brain.

It was one of the main treatments for epilepsy used before AEDs were available, but is no longer recommended for adults with the condition because a high-fat diet is linked to serious health conditions, such as diabetes and cardiovascular disease (CVD).

However, a ketogenic diet is sometimes advised for children with seizures that are difficult to control and have not responded to AEDs because it has been shown to reduce the number of seizures in some children. It should only be used under the supervision of an epilepsy specialist with the help of a dietitian.

Good epilepsy care

The Department of Health has developed a National Service Framework (NSF) for long-term conditions.

This gives guidance to doctors, nurses and healthcare staff on how to provide care to patients. It was developed in consultation with people with long-term neurological conditions, including epilepsy. It tells staff how to give services that are co-ordinated, matched to people’s needs, and easy to use.

Patients can also use the National Service Framework. It can:

  • provide information and support to help you make decisions about your care
  • give you a choice about how and where you get treatment and care
  • help you live more independently

The National Institute for Health and Care Excellence (NICE) has also published guidelines on the diagnosis and management of the epilepsies in adults and children

The guidelines give comprehensive and objective information on the benefits and limitations of the various ways of diagnosing, treating and caring for people with epilepsy. They can help health professionals and patients decide on the most appropriate treatment.

Complementary therapies

There are several complementary therapies that some people with epilepsy feel work for them. However, none has been shown conclusively in medical studies to reduce seizures.

Therefore, you should treat with caution advice from anyone other than your GP or epilepsy specialists to reduce or stop taking your anti-epileptic medication and try alternative treatments. Withdrawing anti-epileptic medication without medical specialist supervision may result in seizures.

Herbal remedies should also be used cautiously because some of their ingredients can interact with anti-epilepsy medication. St John’s Wort, a herbal remedy used for mild depression, is not recommended for people with epilepsy because it can affect the blood levels of anti-epilepsy medication and may affect seizure control.

For some people with epilepsy, stress can trigger seizures. Stress-relieving and relaxation therapies such as exercise, yoga and meditation may help.

Living with

Regular exercise and a healthy diet are recommended for everyone, not just people with epilepsy. They can help prevent many conditions, including heart disease and many forms of cancer.

Try to eat a balanced diet, containing all the food groups, to give your body the nutrition it needs. Exercising regularly can increase the strength of your bones, relieve stress and reduce fatigue.

Drinking

Heavy drinking can cause seizures, as well as interact with anti-epileptic drugs (AEDs). AEDs can heighten the effects of alcohol, while alcohol can make the side effects of AEDs worse and make the medication less effective.

Heavy drinking is also associated with disrupted sleep patterns, and this may increase your chances of having a seizure. Drinking no more than the recommended daily limits may help reduce this risk.

The recommended daily limits for alcohol are three to four units for men and two to three units for women. A unit of alcohol is equal to about half a pint of normal strength lager or a pub measure (25ml) of spirits.

Read more about drinking and alcohol

Women and epilepsy

There are some aspects of epilepsy and epilepsy treatment that women with the condition need to be particularly aware of.

Contraception

Some anti-epileptic drugs (AEDs) can reduce the effectiveness of some types of contraception, including:

If you are sexually active and are not planning a pregnancy, ask your GP or epilepsy specialist whether your AEDs could affect your contraception.

You may need to ensure you or your partner use another form of contraception such as a condom or intrauterine device (IUD).

Also, the effectiveness of the AED lamotrigine may be reduced if you are taking the combined oral contraceptive pill.

Some AEDs have also been known to make the emergency contraceptive pill less effective. If you require emergency contraception, you may need an IUD. Your GP, family planning clinic or pharmacist should be able to advise you.

Pregnancy

There is no reason why women with epilepsy cannot have a healthy pregnancy. However, it is always preferable if the pregnancy is planned because there is a slightly higher risk of complications developing during pregnancy. With forward planning, these risks can be minimised.

The main risk is that some AEDs are known to increase the chances of a serious birth defect occurring, such as spina bifida, cleft lip or congenital heart disease. The risks depend on the type of AED and the dose you are taking.

The UK Epilepsy and Pregnancy Register can provide more information and advice about the use of AEDs during pregnancy.

If you are planning a pregnancy, talk to your epilepsy specialist. It may be possible to change the AED you are taking to minimise risks. Taking 5mg of a folic acid supplement each day can also help reduce risks of birth defects.

If you discover you are pregnant, do not stop taking your medicine. The risks to your baby from uncontrolled seizures are far higher than any risks associated with your medicines.

There are no risks associated with breastfeeding while taking an AED.

Children and epilepsy

Many children with well-controlled epilepsy can learn and participate in their school’s activities completely unaffected by their condition. Others may need extra support to get the most out of their time at school.

Make sure your child’s teachers know about their condition and the medication they need to control it.

Epilepsy is more common among children with learning disabilities and special educational needs. These children are entitled to extra help to overcome their difficulties. Each school will have at least one member of staff with responsibility for children with special educational needs. The law says that all state schools must do their best to meet special educational needs, sometimes with the help of outside specialists.

If your child needs a lot of extra help, the local education authority may carry out an assessment. This will outline the help your child needs, set a number of long-term goals, and ensure your child is regularly reviewed.

Talk to others

If you have any questions about your condition, your GP or nurse may be able to advise you. You may also find it helpful to talk to a trained counsellor or psychologist, or to someone at a specialist helpline. Your GP surgery will have information on these.

Some people find it helpful to talk to other people who have epilepsy, either at a local support group or in an internet chat room.

Driving

If you have a seizure, you have a legal responsibility to inform the Driving and Vehicle Licence Authority (DVLA).

You will usually not be able to hold a group one driving licence, required for private cars and motorcycles, until:

  • you have not had a seizure for one year, or
  • you have at least one year where you have only had seizures while asleep, and you have never had seizures when awake before, or
  • you have had seizures while awake in the past, but you have only had seizures while asleep for at least three years

You will also need to meet all the other minimum driving standards, including being able to read a number plate from 20 metres and having at least 6/12 vision (with glasses or contact lenses if necessary). Having 6/12 vision means you can see at six metres what someone with standard vision could see from 12 metres away.

The DVLA may issue a licence if your seizures have never caused you to lose awareness or affected your ability to safely control a vehicle.

You will not usually be able to hold a group two driving licence, required for heavy goods vehicles and passenger carrier vehicles that are more than 7.5 tonnes, until:

  • you have not had a seizure for the past 10 years and have not been taking AEDs during this period, and
  • your epilepsy specialist confirms there is no likelihood of seizures occurring

You will need to apply to the DVLA for the return of your licence. They will only return your licence when they are satisfied your epilepsy is under control. As part of this process, they may wish to contact your GP or epilepsy specialist. You will not have to retake a driving test when your licence is returned.

You have the right to appeal against their decision at a magistrates' court.

If you ignore these regulations, you will be liable for prosecution. Your GP also has a legal responsibility to inform the DVLA if it is felt that your driving is putting both you and others at risk.

Money and finances

If you have to stop work or work part time because of your epilepsy, you may be entitled to one or more of the following types of financial support:

Free prescriptions

If you take anti-epileptic drugs, you are entitled to get all your prescriptions (not just those for AEDs) free of charge. 

Sudden unexpected death in epilepsy (SUDEP)

When somebody with epilepsy dies and no apparent cause can be found, it is known as sudden unexpected death in epilepsy (SUDEP).

Although the risk of SUDEP for someone with epilepsy is low, SUDEPs are estimated to cause between 500 and 1,000 deaths in the UK every year.

The exact causes of SUDEP are unknown, and it is not possible to predict who will be affected. One theory is that seizures could affect the person's breathing and heartbeat.

Things that may lead to SUDEP include:

  • having seizures which cause loss of consciousness and the body to go stiff and start jerking (tonic-clonic seizures)
  • poorly controlled epilepsy, such as not using anti-epileptic drugs (AEDs) as prescribed or to control seizures
  • having sudden and frequent changes to AEDs
  • being a young adult (in particular male)
  • having sleep seizures
  • having seizures when alone
  • drinking large amounts of alcohol

If you are worried that your epilepsy is poorly controlled, contact your epilepsy specialist. It may be possible to refer you to a specialist epilepsy centre for further treatment.

A charity called SUDEP Action can offer advice and support on SUDEP, as well as a helpline for people who have lost a loved one as a result of epilepsy.