Introduction to Epilepsy

The aim of this article is to give you a broad overview of epilepsy, a neurological condition which affects around 600,000 people in the UK. This article will cover the definition of epilepsy, its symptoms and characteristics, and will discuss the basics of how epilepsy is diagnosed and managed.

What is epilepsy?

Epilepsy describes a condition in which the brain has a predisposition to generate spontaneous, abnormal electrical activity, leading to seizures.

In principle, anyone could have a seizure if their brain is provoked (e.g. with drugs, excess alcohol, or infections such as meningitis), but someone who has a one-off provoked seizure would not be considered to have epilepsy. Epilepsy specifically refers to the brain having an underlying predisposition to generate seizures.

The following practical definition of epilepsy has been suggested: an individual has epilepsy if they have had:

• 2 unprovoked seizures separated by more than 24 hours
• 1 unprovoked seizure, with the risk of having another unprovoked seizure over the next 10 years being greater than 60%

Characteristics of epilepsy

Epilepsy is characterised by seizures (or “fits”), but seizures can present very differently depending on the type of epilepsy that the individual has. For example, seizures may be:

• Focal – abnormal electrical activity that is localised to a particular region of the brain 
  • These seizures tend to cause focal symptoms (symptoms related to the function of a particular brain region) e.g. a seizure in the part of the brain responsible for hand movement may cause twitching or jerking of the hand
• Generalised – abnormal electrical activity that is widespread throughout the brain. Generalised seizures can be further subdivided based on their characteristics. Examples include: 
  • Tonic-clonic seizures (previously called “grand mal” seizures) – begin with muscle stiffening, followed by jerking of the limbs
  • Absence seizures – brief losses of consciousness (for example, the patient may stop talking for a few seconds in the middle of a sentence, then carry on)
  • Atonic seizures (also called drop seizures) – where a patient partially or completely loses muscle tone and sometimes drops to the ground 

There may also be symptoms occurring both before and after a seizure:

• Before a seizure, there may be a prodromal phase, which could last for a few hours or even a few days before the seizure. During this period, the patient may show changes in behaviour or may experience strange sensations (e.g. déjà vu, seeing flashing lights)
• After the seizure, patients usually experience post-ictal phase, where they may have symptoms such as headache, confusion and lethargy. This may last up to 30 minutes. There may also be temporary paralysis of part of the body during the post-ictal phase (referred to as Todd’s palsy)

What causes epilepsy?

The exact cause of epilepsy is unknown in most cases.

Some people have genetic abnormalities which lead to a tendency to have seizures (this typically leads to generalised seizures). Examples of genes associated with epilepsy are:

• SCN8A – encodes a subunit of the voltage-gated sodium channel
• SLC2A1 – encodes the glucose transporter 1

Epilepsy may also have a structural cause (typically causing focal seizures). Examples of structural causes of epilepsy include:

• Head injury (leading to cortical scarring)
• Developmental brain disorders e.g. cortical dysgenesis (abnormal development of the cortex)
• Brain tumours

How is epilepsy diagnosed?

Given the wide range of ways in which epilepsy can present, diagnosis of epilepsy can be difficult. Furthermore, there are other conditions that can present in a similar way to epilepsy (e.g., fainting).

A diagnosis of epilepsy is typically made by a neurologist. Taking a detailed history is essential when determining whether someone might have epilepsy. It is especially helpful if there is a witness to the suspected seizure who can describe exactly what happened. The neurologist will want to know information such as what happened immediately before and after the seizure, and if there were any triggers (e.g., flashing lights). The doctor will also want to know what happened during the seizure and if the patient experienced any symptoms suggestive of a seizure (e.g., faecal or urinary incontinence, tongue biting).

The following investigations may be performed:

• Blood tests – to rule out other causes of the seizure e.g., electrolyte imbalances
• EEG (electroencephalogram) – measures the electrical activity in the brain
• MRI scan – may be considered if a structural cause of epilepsy (e.g. a brain tumour) is suspected
• Lumbar puncture – if an infectious cause (such as meningitis) is suspected

How is epilepsy treated?

Most patients with epilepsy can be managed with anti-epileptic drugs. Examples of these drugs include sodium valproate, carbamazepine and levetiracetam.

Surgery may be considered if a patient’s condition cannot be adequately managed using anti-epileptic drugs. There are several types of epilepsy surgery; for example, surgery may be performed to remove a part of the brain responsible for causing the patient’s seizures, or electrodes may be placed in the patient’s brain (deep brain stimulation).

However, as with all surgery, this does carry some risks. The exact risks depend on the specific type of surgery the patient is having but may include problems with memory, vision or mood, for example.

Summary

• Epilepsy is a neurological condition characterised by spontaneous, abnormal electrical activity in the brain, leading to seizures
• There are many different types of seizures which present in very different ways and can be broadly categorised into focal and generalised seizures
• For most patients the cause of epilepsy is unknown, although epilepsy can be caused by genetic abnormalities and structural abnormalities of the brain
• Epilepsy is diagnosed by taking a thorough history from the patient (and any witnesses to the seizures), supported by investigations such as an EEG, MRI scan and blood tests, for example
• The majority of cases of epilepsy can be managed with anti-epileptic drugs alone, although surgery may be used to treat cases of epilepsy which do not respond well to these drugs

References:

https://www.who.int/news-room/fact-sheets/detail/epilepsy
https://epilepsyresearch.org.uk/about-epilepsy/epilepsy-statistics/
https://www.epilepsy.com/learn/types-seizures
https://www.nice.org.uk/guidance/cg137
https://www.cureepilepsy.org/for-patients/understanding/basics/phases-of-seizures/#:~:text=The prodromal phase is a,more obvious%2C diagnosable symptoms begin.

Fisher RS, Acevedo C, Arzimanoglou A, Bogacz A, Cross JH, Elger CE, Engel J Jr, Forsgren L, French JA, Glynn M, Hesdorffer DC, Lee BI, Mathern GW, Moshé SL, Perucca E, Scheffer IE, Tomson T, Watanabe M, Wiebe S. ILAE official report: a practical clinical definition of epilepsy. Epilepsia. 2014 Apr;55(4):475-82. doi: 10.1111/epi.12550. Epub 2014 Apr 14. PMID: 24730690.