Epilepsy

A seizure is an acute alteration in behaviour, consciousness, and muscle movement secondary to excessive and abnormal neuronal discharges. Epilepsy is a condition where patients have a tendency to experience unprovoked seizures.

Seizure Terminology

• Generalised Seizure: Neuronal discharges involves both cerebral hemispheres. Often, patients will lose consciousness.
  • Primary Generalised: When the seizure starts, it starts by simultaneously involving both hemispheres.
  • Secondary Generalised: When the seizure starts, it begins by affecting one hemisphere, and later spreads to involve both hemispheres.
• Focal Seizure: Neuronal discharges are occurring in one part of the brain. Patients may or may not lose consciousness.

The definitions used to classify seizures have gotten somewhat confusing over the years due to frequent changing of terms. Here is a simplified summary so you don’t get confused.

Focal Seizures

 A focal seizure is when there is random, abnormal firing of neurones in one hemisphere of the brain. The symptoms of a focal seizure will depend on which neurones of the brain are abnormally firing i.e. which part of the brain is affected.

Focal seizures can occur with consciousness or without.

• With impaired consciousness (complex): Associated with post-ictal phase (post-ictal means following a seizure - patients tend to be drowsy/confused)
• Without impairment in consciousness (simple): No post-ictal phase

• Temporal Lobe: Auditory, language, emotion, recognition and memory:
  • Automatisms: Automatisms are abnormal repetitive movements that occur without the awareness of the patient. Examples include lip-smacking, chewing movements, rubbing the hands
  • Auditory/olfactory /gustatory hallucinations
  • Emotional disturbances
  • Déja vu: Something that is unfamiliar feels familiar
  • Jamais vu: Something that is familiar feels unfamiliar
• Occipital Lobe – Primary Visual Cortex
  • Visual hallucinations
• Parietal Lobe – Primary Sensory Cortex
  • Tingling and numbness
• Frontal Lobe – Primary Motor Cortex:
  • Abnormal posturing
  • Head movements
  • Eye movements
  • Dysphasia
  • Jacksonian march:
    • To understand the Jacksonian march, you first need to appreciate the concept of the motor homunculus – the idea that specific parts of the brain process information from a particular part of the body e.g. the medial part of the cortex controls the foot
    • A Jacksonian march is when the seizure ‘marches’ through the motor cortex. It spreads from distal to proximal.
    • For example, a Jacksonian march seizure may begin in the fingers, manifesting as paraesthesia in the fingers. The seizure will then progress to involve the hand followed by the wrist, arm, head, neck etc. As you can see, the seizure is moving through the motor cortex.

Todd’s Palsy

This describes weakness or paralysis in a limb, seen following a seizure. The exact mechanism of how it happens isn't fully known. Potential mechanisms are thought to be secondary to a refractory period in neuronal activity following the excessive discharges seen during a seizure, or a self-protective mechanism by the brain to prevent further seizures by inhibiting local neurones.

Generalised Seizure

These seizures simultaneously involve both hemispheres of the brain so you won’t get specifically localising symptoms based on the lobe as you might in partial seizures.

• Absence Seizures
  • Brief interruptions in awareness.
  • A patient may be speaking and will abruptly stop and appear to be vacant or unresponsive, and then continue wherever they had left off.
  • The patient will have impaired consciousness i.e. they will be unaware of having had the seizure. This will usually present in children.
• Tonic-Clonic Seizures
  • There are two phases here.
  • The tonic phase involves stiffening and the patient will appear rigid.
  • This is followed by a clonic phase of jerky muscle contractions.
  • Patients are usually in a post-ictal state following the seizure (ictal meaning seizure). In this state, patients are usually drowsy, confused, may have difficulty speaking, experience amnesia of the seizure, and have a headache.
• Myoclonic Seizures
  • Sudden jerking movements of a part of the body, for example jerking or twitching of the hand.
• Atonic Seizures
  • A sudden loss of muscle tone occurs, and the individual will fall.
  • Patients with atonic seizures tend to maintain their consciousness

Causes

• Structural diseases
  • Scar tissue e.g. childhood febrile seizures are a risk factor for sclerosis of the hippocampus
  • Intracranial neoplasms
• Infections
  • History of meningitis
  • HIV
  • History of encephalitis
• History of traumatic brain injury
• Cerebral Palsy

Triggers for Seizures

• Lack of sleep
• Alcohol excess
• Caffeine
• Dehydration
• Recreational drugs

Investigations

The key difference between epilepsy and other causes of seizures is that epilepsy needs to be a tendency to have unprovoked seizures. It’s important to also ensure someone had a seizure, and not something else during a history.

Bedside

• History and examination: Rule out vasovagal syncope and cardiac syncope. Features more in favour of a seizure include:
  • Deeply bitten lateral border of the tongue
  • Post-ictal confusion
  • Cyanosis during the episode
  • Long time to regain consciousness

Bloods

• FBC, U&E, LFT, Bone, CRP: Baseline
• Blood alcohol levels: ?Alcohol excess as a cause of seizure
• Blood glucose: ?Hypoglycaemia s a cause of seizure

Imaging

• EEG: First done as a routine, but provoking manoeuvres/sleep-deprived EEGs can also be done if patients agree
• MRI: Offered usually within 6 weeks of the referral. A CT can be done if an MRI is contraindicated

Management

The management of epilepsy is primarily with anti-epileptic drugs of which there are several. A lot of these drugs work by targeting voltage gated sodium channels, with some working at other places such as glutamate receptors, GABA receptors, and potassium channels. This usually results in inhibitory action on neurones which helps limit repetitive firing.

The following management is taken from NICE guidelines. Epilepsy management is complex, so this is a heavily simplified version of the full guideline.

Carbamazepine can worsen myoclonic seizures

Pregnancy and Anti-Epileptic Drugs

• Lamotrigine and levetirecatam are safer drugs for use in pregnancy as they haven’t been found to increase the risk of developing congenital malformations compared to the existing risk in the general population
• Phenytoin, Sodium valproate, Phenobarbital and Carbamezapine are associated with increased risk of congenital malformations.

Driving Laws

In the UK, patients are required to notify the DVLA if they have had a seizure or blackout.

Licenses are typically revoked though there are some scenarios where patients can retain their licenses.

Car/Motorbike

• Epileptic seizure while awake + loss of consciousness: License revoked. Can reapply for a license if been on anti-epileptic for 6 months, and seizure free for 6 months
• Seizure whilst asleep and awake: If in the past 3 years all seizures have been whilst asleep, may be able to have license
• Seizures whilst conscious: May still be able to drive if patients are aware of their surroundings and able to move. First seizure needs to have been >12 months ago.

Bus, Coach or Lorry Drivers

• One off seizure: License revoked. Must be seizure free for 5 years and off anti-epileptics for 5 years before they can reapply.
• More than one seizure: License revoked. Must be seizure free for 10 years and off anti-epileptics for 10 years before they can reapply.

Seizure Precautions

If someone comes into A&E with a first-fit, you need to provide them with some safety rules. They are usually as follows:

• Avoid baths
• Avoid swimming alone
• Avoid cycling
• Don’t miss doses of anti-epileptics
• Don’t lock bathroom doors

References

https://www.gov.uk/government/publications/public-assesment-report-of-antiepileptic-drugs-review-of-safety-of-use-during-pregnancy/antiepileptic-drugs-review-of-safety-of-use-during-pregnancy#key-conclusions

https://www.epilepsy.org.uk/living/having-a-baby/sodium-valproate-and-pregnancy

https://epilepsysociety.org.uk/sites/default/files/2020-08/Chapter25Sills2015.pdf