Introduction

Epilepsy is a common neurological condition characterised by recurrent seizures. There are around 500,000 people in the UK with epilepsy, of whom around two-thirds achieve satisfactory seizure control with antiepileptic medication.

Classification

The basic classification of epilepsy has changed in recent years. The new basic seizure classification is based on 3 key features:
  • 1. Where seizures begin in the brain
  • 2. Level of awareness during a seizure (important as can affect safety during seizure)
  • 3. Other features of seizures

Focal seizures
  • previously termed partial seizures
  • these start in a specific area, on one side of the brain
  • the level of awareness can vary in focal seizures. The terms focal aware (previously termed 'simple partial'), focal impaired awareness (previously termed 'complex partial') and awareness unknown are used to further describe focal seizures
  • further to this, focal seizures can be classified as being motor (e.g. Jacksonian march), non-motor (e.g. déjà vu, jamais vu; ) or having other features such as aura

Generalised
  • these engage or involve networks on both sides of the brain at the onset
  • consciousness lost immediately. The level of awareness in the above classification is therefore not needed, as all patients lose consciousness
  • generalised seizures can be further subdivided into motor (e.g. tonic-clonic) and non-motor (e.g. absence)
  • specific types include:
  • → tonic-clonic (grand mal)
  • → tonic
  • → clonic
  • → typical absence (petit mal)
  • → myoclonic: brief, rapid muscle jerks
  • → atonic

Unknown onset
  • this termed is reserved for when the origin of the seizure is unknown

Focal to bilateral seizure
  • starts on one side of the brain in a specific area before spreading to both lobes
  • previously termed secondary generalized seizures

In addition a number of special forms of epilepsy are recognised in children:

SyndromeNotes
Infantile spasms (West's syndrome)Brief spasms beginning in first few months of life
  • 1. Flexion of head, trunk, limbs → extension of arms (Salaam attack); last 1-2 secs, repeat up to 50 times
  • 2. Progressive mental handicap
  • 3. EEG: hypsarrhythmia
  • usually 2nd to serious neurological abnormality (e.g. TS, encephalitis, birth asphyxia) or may be cryptogenic
  • poor prognosis
Lennox-Gastaut syndromeMay be extension of infantile spasms (50% have hx)
  • onset 1-5 yrs
  • atypical absences, falls, jerks
  • 90% moderate-severe mental handicap
  • EEG: slow spike
  • ketogenic diet may help
Benign rolandic epilepsy
  • paraesthesia (e.g. unilateral face), usually on waking up
Juvenile myoclonic epilepsy (Janz syndrome)Typical onset in the teens, more common in girls
  • 1. Infrequent generalized seizures, often in morning
  • 2. Daytime absences
  • 3. Sudden, shock like myoclonic seizure
  • usually good response to sodium valproate

Epidemiology

  • Incidence: 50.00 cases per 100,000 person-years
  • Most commonly see in infants
  • Sex ratio: 1:1
Condition Relative
incidence
Febrile convulsions42.00
Epilepsy: first seizure1
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+

Aetiology

Epilepsy most commonly occurs in isolation although certain conditions have an association with epilepsy:
  • cerebral palsy: around 30% have epilepsy
  • tuberous sclerosis
  • mitochondrial diseases

Clinical features

As well as the seizure activity described above patients who have had generalised seizures may
  • bite their tongue
  • experience incontinence of urine

Asking about such features can be useful way of detecting epileptic seizures when taking a history from a patient who presents with a 'blackout' or 'collapse'.

Following a seizure patients typically have a postictal phase where they feel drowsy and tired for around 15 minutes.

Investigations

Following their first seizure patients generally have both an electroencephalogram (EEG) and neuroimaging (usually a MRI).

Differential diagnosis

It should be remembered that epilepsy is not the only reason people have seizures. The table below shows some of the more common causes of recurrent seizures seen in clinical practice. Patients may of course develop one-off seizures following any insult to the brain, for example infection, trauma or metabolic disturbance.

DisorderNotes
Febrile convulsions
  • typically occur in children between the ages of 6 months and 5 years
  • around 3% of children will have at least one febrile convulsion
  • usually occur early in a viral infection as the temperature rises rapidly
  • seizures are typically brief and generalised tonic/tonic-clonic in nature
Alcohol withdrawal seizures
  • occur in patients with a history of alcohol excess who suddenly stop drinking, for example following admission to hospital
  • chronic alcohol consumption enhances GABA mediated inhibition in the CNS (similar to benzodiazepines) and inhibits NMDA-type glutamate receptors.Alcohol withdrawal is thought to be lead to the opposite (decreased inhibitory GABA and increased NMDA glutamate transmission)
  • the peak incidence of seizures is at around 36 hours following cessation of drinking
  • patients are often given benzodiazepines following cessation of drinking to reduce the risk
Psychogenic non-epileptic seizures
  • previously termed pseudoseizures, this term describes patients who present with epileptic-like seizures but do not have characteristic electrical discharges
  • patients may have a history of mental health problems or a personality disorder

Management

Most neurologists now start antiepileptics following a second epileptic seizure.

Antiepileptics are one of the few drugs where it is recommended that we prescribe by brand, rather than generically, due to the risk of slightly different bioavailability resulting in a lowered seizure threshold.

It is useful when thinking about the management of epilepsy to consider certain groups of patients:
  • patients who drive: generally patients cannot drive for 6 months following a seizure. For patients with established epilepsy they must be fit free for 12 months before being able to drive
  • patients taking other medications: antiepileptics can induce/inhibit the P450 system resulting in varied metabolism of other medications, for example warfarin
  • women wishing to get pregnant: antiepileptics are generally teratogenic, particularly sodium valproate. It is important that women take advice from a neurologist prior to becoming pregnant, to ensure they are on the most suitable antiepileptic medication. Breastfeeding is generally considered safe for mothers taking antiepileptics with the possible exception of the barbiturates
  • women taking contraception: both the effect of the contraceptive on the effectiveness of the anti-epileptic medication and the effect of the anti-epileptic on the effectiveness of the contraceptive need to be considered

Most neurologists now start antiepileptics following a second epileptic seizure. NICE guidelines suggest starting antiepileptics after the first seizure if any of the following are present:
  • the patient has a neurological deficit
  • brain imaging shows a structural abnormality
  • the EEG shows unequivocal epileptic activity
  • the patient or their family or carers consider the risk of having a further seizure unacceptable

Sodium valproate is considered the first line treatment for patients with generalised seizures with carbamazepine used for focal seizures.

Generalised tonic-clonic seizures
  • sodium valproate
  • second line: lamotrigine, carbamazepine

Absence seizures* (Petit mal)
  • sodium valproate or ethosuximide
  • sodium valproate particularly effective if co-existent tonic-clonic seizures in primary generalised epilepsy

Myoclonic seizures**
  • sodium valproate
  • second line: clonazepam, lamotrigine

Focal seizures
  • carbamazepine or lamotrigine
  • second line: levetiracetam, oxcarbazepine or sodium valproate

*carbamazepine may exacerbate absence seizures

**carbamazepine may exacerbate myoclonic seizures



Acute management of seizures

Most seizures terminate spontaneously. When seizures don't terminate after 5-10 minutes then it is often appropriate to administer medication to terminate the seizure. Patients are often prescribed these so family members may administer them in this eventuality, often termed 'rescue medication'. Benzodiazepines such as diazepam are typically used are may be administered rectally or intranasally/under the tongue.

If a patient continues to fit despite such measures then they are termed to have status epilepticus. This is a medical emergency requiring hospital treatment. Management options include further benzodiazepine medication, infusions of antiepileptics or even the use of general anaesthetic agents.