Epilepsy is a chronic neurological disorder, which is characterised by recurrent seizures.
Epilepsy is characterised by development of multiple seizures.
A seizure refers to a transient neurological change due to synchronous, hyperexcited neuronal activity in the brain. Clinically, this manifests as a transient occurrence of seizure-like activity. This ‘activity’ may refer to a disturbance of consciousness, motor function, emotion, behaviour, cognition or sensation.
Epilepsy is a common neurological disorder that affects > 70 million people globally. The lifetime risk of having a seizure is approximately 1 in 10. The risk of epilepsy, which is the propensity towards recurrent seizures, is 3%.
The cause of epilepsy is unknown in up to one third of patients.
Seizures are common and often occur secondary to an acute insult. These types of ‘provoked’ seizures usually occur at the time of acute illness (e.g. acute stroke, head trauma, hypoglycaemia) or in temporal relationship with the insult.
An acute symptomatic seizure secondary to a defined cause needs to be differentiated from the recurrent, unprovoked seizures that occur in epilepsy.
The cause of epilepsy can be broadly divided into six groups:
Seizures develop due to an imbalance between inhibitory and excitatory signals in the brain.
A seizure may initiate due to high-frequency bursts of excitatory action potentials in neurons. This leads to synchronous, hyperexcitable activity within a neuronal population. If this activity is propagated to other neuronal populations it can lead to clinically apparent seizures. The seizure phenotypes (i.e. clinical features) relate to the location and function off the neuronal network that have been recruited into this abnormal synchronous activity.
In epilepsy, acquired or genetic factors effect the balance between inhibitory (i.e. gabanergic) and excitatory (i.e. glutamatergic) signals.
Overtime, there is transformation within neural networks that promote excitability. This is associated with long-lasting structural and/or biochemical changes that promotes development of epilepsy.
Several known factors increase the risk of developing epilepsy.
The classification of epilepsy is based on recommendations by the International League Against Epilepsy (ILAE).
Classification is based on:
This refers to the exact type of seizure that occurs.
Seizure type can be determined using a three step process that focuses on the area of onset, presence of awareness and associated clinical features.
NOTE: important for focal seizures. All generalised seizures affect awareness in some way.
Following diagnosis, the actual type of epilepsy can be determined.
The development of recurrent seizure types may lead to the diagnosis of epilepsy. Diagnosis is based on one of three criteria (see chapter on diagnosis). If one of these criteria is met, epilepsy can be classified to a particularly type.
Epilepsy may be organised into a specific syndrome.
An epilepsy syndrome is characterised by the recurrent propensity to a specific seizure type or series of seizure types. Determining an epilepsy syndrome is important to guide medical therapy with anti-epileptic drugs (AEDs). Classic epilepsy syndromes include West syndrome, Lennox Gastaut syndrome and juvenile myoclonic epilepsy among many others.
Epilepsy syndromes usually have important characteristics:
Epilepsy is characterised clinically by seizures, which can manifest in numerous ways.
The clinical features associated with a seizure depend on the affected location and function of the brain. This is covered in the chapter on classification.
Each individual seizure is composed into four distinct stages: prodromal, early-ictal, ictal, post-ictal.
This describes a period of subjective feeling or sensation that occurs before the onset of a seizure. It only occurs in some patients and may present with features such as confusion, irritability or mood disturbances.
This phase is characterised by aura. An aura is the earliest sign of seizure activity and refers to subjective symptoms experienced by the patient. These can include sensory, cognitive, emotional or behaviour changes. Not all patients will experience an aura (e.g. generalised seizure onset).
An aura is suggestive of focal epilepsy (occurring in one part of the brain) and may progress to affect a wider area, or develop into a focal to bilateral tonic-clonic seizure.
The ictal phase is highly variable depending on seizure type.
In layman terms, 'seizure' usually refers to a generalised tonic-clonic seizure. This is characterised by stiffening and subsequent rhythmic jerking of the limbs. It may be associated with urinary incontinence and tongue biting, and normally lasts 1-2 minutes.
When a single seizure lasts > 30 minutes in duration, or two seizures occur without regaining consciousness after the first, it is termed status epilepticus or 'status'. Status is broadly divided into convulsive (i.e. movement) and non-convulsive (i.e. no movement). This is a medical emergency and discussed further in our notes on status epilepticus.
This is the recovery period, when the seizure has abated. There may be an extended recovery period, which is dependent on seizure type. During the period of recovery there may be altered consciousness, confusion, memory loss, drowsiness or general malaise.
This period may last hours, particularly with tonic-clonic seizures.
The diagnosis of epilepsy is based on one of three criteria.
A diagnosis of epilepsy is made if any of the following three criteria apply:
There are numerous epilepsy mimics, which can be grouped into several categories:
NOTE: non-epileptic seizures resemble epileptic seizures but with no electrophysiological correlation or clinical evidence for epilepsy.
Neuroimaging and an EEG can help support the diagnosis of epilepsy.
Following a seizure, baseline investigations should be used to look for a precipitating cause. In adults, a series of baseline investigations including an ECG and bloods is essential.
A non-invasive method of assessing and recording the electrical activity of the brain. Epilepsy, or the propensity towards seizures, is associated with particular waveform activity on an EEG. They are usually analysed by neurophysiologists.
It is not used as a sole diagnostic tool and cannot be used to exclude epilepsy, particularly if the clinical presentation supports a diagnosis of epilepsy.
Typically involves magnetic resonance imaging (MRI), but computed tomography (CT) can be used where MRI is not available or suitable. Able to look for structural abnormalities that cause certain epilepsies.
MRI essential in patients who develop epilepsy before two years old, there is a suggestion of focal onset seizures or poor seizure control with anti-epileptics.
Management of epilepsy is broadly divided into acute control of seizures and long-term prevention of seizures with AEDs.
The overall goal for managing a patient with epilepsy should be for no seizures and no side-effects from medications. This will not be possible in every patient due to the complexity of epilepsy.
The key aspects of management are education and safety, treating acute seizures, role of the first fit clinic and long-term treatment with AEDs.
It is vital to educate patients, family and carers about epilepsy, provide information regarding safety precautions and how to provide pre-hospital care for seizures. This may be in the form of a formal first-aid course or guidance on epilepsy society websites.
After initial presentation and management of a suspected epileptic seizure, patients should be referred to a 'first fit' clinic where they will be seen by a specialist who manages patients with epilepsy (i.e. neurologist).
The clinic involves formal assessment (history and examination) and organisation of relevant investigations (e.g. MRI, EEG) to determine whether the seizure is likely to represent epilepsy. If the diagnosis of epilepsy is made, patients are given education and started on AEDs.
As a general rule, following a single seizure patients are not routinely started on AEDs unless there is felt to be considerable risk for another seizure.
AEDs are the hallmark of long-term treatment of epilepsy. They reduce the risk of developing seizures. There are different choices, which depends on the type of epilepsy, patient demographics, side-effect profiles and patient choice.
NOTE: sodium valproate is highly teratogenic (30-40% developmental disorder / 10% congenital malformation) and should NOT be given to women and girls of childbearing potential. This includes girls who are likely to need treatment into their childbearing years.
The NICE CG137 guidelines provide guidance on the first-line and adjuvant medications that can be used for different types of epilepsy. The general rule is initiation of monotherapy at the lowest possible dose to control seizures. Doses can be increased, and if ineffective, can be weaned down and a new medication introduced. Combination (i.e. adjunctive) therapy may be needed.
*NOTE: only offered to males or females without childbearing potential.
The two major complications of epilepsy are status epilepticus and sudden unexpected death in epilepsy (SUDEP).
Several complications may develop due to seizures including trauma, drowning, road traffic accidents and falls. A sustained seizure > 30 minutes or recurrent seizures without regaining consciouses describes status epilepticus. This is a life-threatening medical emergency. For more details see our notes on status epilepticus.
Sudden unexplained death in epilepsy is the result of sudden death in a patient with epilepsy with no identifiable cause. It is the most common cause of death in young adults with epilepsy. SUDEP has been linked to uncontrolled epilepsy and nocturnal seizures. Seizure control is pivotal to reduce risk.
Following a seizure, patients need to stop driving and inform the DVLA.
There are certain rules to driving in the context of having a seizure. These depend on the timing of the seizure(s) (i.e. day or night) and whether the person has a group 1 (cars, motorcycles) or 2 (large lorries, buses) license. Always consult the DVLA for further advice.
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