Medicine – Epilepsy

Epilepsy is a neurological disorder characterised by an enduring tendency to develop recurrent unprovoked seizures. A seizure results from a sudden episode of abnormal, excessive and synchronous electrical activity within neuronal networks of the brain.

The older classification divides seizures into partial seizures and generalised seizures. Modern terminology uses focal seizures instead of partial seizures and describes them according to whether awareness is preserved or impaired.

1. Basic Mechanism of Epilepsy

Normal brain function depends on a balance between excitatory and inhibitory neuronal activity.

The major excitatory neurotransmitter is:

Glutamate.

The major inhibitory neurotransmitter is:

GABA – gamma-aminobutyric acid.

When excitation becomes excessive or inhibition becomes inadequate, groups of neurons may begin firing abnormally and synchronously.

Therefore:

↑ Excitation or ↓ inhibition → paroxysmal neuronal discharge → seizure.

2. Epilepsy versus a Provoked Seizure

Not every seizure means that a patient has epilepsy.

A seizure may occur because of an acute reversible disturbance such as:

Hypoglycaemia.

Hyponatraemia.

Alcohol withdrawal.

Acute CNS infection.

Acute brain injury.

These are acute symptomatic or provoked seizures.

Epilepsy implies an ongoing predisposition to develop unprovoked seizures.

3. Focal Seizures

The older term partial seizure has been replaced by:

Focal seizure.

A focal seizure begins within neuronal networks in one cerebral hemisphere.

Its manifestations depend on the area of cerebral cortex involved.

Focal seizures can be divided according to awareness into:

Focal aware seizures.

and

Focal impaired-awareness seizures.

They may subsequently spread to both hemispheres and become a focal to bilateral tonic-clonic seizure.

4. Focal Aware Seizures

The older term:

Simple partial seizure

is now called:

Focal aware seizure.

The defining feature is:

Awareness remains preserved throughout the seizure.

The patient knows what is happening and can usually remember the event afterwards.

5. Duration of Focal Aware Seizures

These seizures are usually brief.

They may last:

A few seconds to a few minutes.

The exact clinical manifestations depend on the cerebral region from which the seizure originates.

6. Motor Focal Seizures

If abnormal electrical activity begins in the motor cortex, the patient may develop:

Jerking of one hand.

Jerking of one side of the face.

Movement of one limb.

Tonic posturing.

The patient may remain fully aware during these movements.

7. Sensory Focal Seizures

If sensory regions are involved, the patient may experience:

Tingling.

Numbness.

Visual phenomena.

Abnormal smells.

Abnormal tastes.

These symptoms may occur without loss of awareness.

8. EEG in Focal Seizures

EEG may demonstrate:

Localised or focal epileptiform discharges corresponding to the affected area of the brain.

However:

A normal routine EEG does not exclude epilepsy.

Epileptiform activity may be intermittent and may not occur during the recording.

9. Focal Impaired-Awareness Seizures

The older term:

Complex partial seizure

is now called:

Focal impaired-awareness seizure.

The defining feature is:

Impaired awareness during the seizure.

The patient may appear awake but cannot respond normally to the environment.

10. Duration

A typical focal impaired-awareness seizure lasts approximately:

60–90 seconds, although the duration can vary.

After the seizure, the patient commonly develops a period of:

Post-ictal confusion.

11. Post-Ictal Confusion

After the seizure has stopped, the patient may be:

Confused.

Disorientated.

Drowsy.

Unable to remember the event.

This post-ictal period is particularly useful when distinguishing focal impaired-awareness seizures from typical absence seizures.

12. Aura

A focal impaired-awareness seizure may be preceded by an:

Aura.

An aura is actually a focal aware seizure occurring before further seizure spread.

The symptoms can provide useful information about where the seizure originates.

13. Typical Aura Symptoms

Classic aura symptoms include:

Déjà vu.

A strong or unusual smell.

An unusual taste.

A rising sensation in the abdomen or epigastrium.

Sudden fear or an unusual emotional sensation.

These are particularly associated with temporal lobe seizures.

14. Temporal Lobe Epilepsy

Temporal lobe seizures commonly produce:

Déjà vu.

Olfactory hallucinations.

Rising epigastric sensations.

Fear.

The seizure may then progress to impaired awareness.

15. Automatisms

Focal impaired-awareness seizures may produce automatisms.

These are repetitive, apparently purposeful movements performed without normal awareness.

Examples include:

Lip smacking.

Chewing movements.

Repeated swallowing.

Picking at clothes.

Hand rubbing.

The patient usually has little or no memory of these behaviours.

16. Focal to Bilateral Tonic-Clonic Seizures

The older term:

Secondarily generalised seizure

is now called:

Focal to bilateral tonic-clonic seizure.

The seizure begins focally in one hemisphere and subsequently spreads to involve both hemispheres.

17. Typical Progression

A possible sequence is:

Aura → focal impaired-awareness seizure → bilateral tonic-clonic seizure.

However, not every patient goes through all of these stages.

Some seizures may progress very rapidly from focal onset to bilateral tonic-clonic activity.

18. Importance of an Aura

If a patient experiences a clear aura before a tonic-clonic seizure, it suggests that the seizure may have:

Focal onset.

Therefore:

Aura before tonic-clonic activity → think focal to bilateral tonic-clonic seizure.

This contrasts with a true generalised-onset tonic-clonic seizure, where a focal aura is absent.

19. Generalised Seizures

Generalised seizures involve neuronal networks in both cerebral hemispheres from the onset.

Important types include:

Absence seizures.

Generalised tonic-clonic seizures.

Myoclonic seizures.

Tonic seizures.

Clonic seizures.

Atonic seizures.

20. Absence Seizures

Absence seizures cause very brief episodes of impaired awareness.

The patient may suddenly:

Stop talking.

Stop an activity.

Stare blankly.

Become temporarily unresponsive.

After several seconds, normal activity resumes.

21. Duration of Absence Seizures

Typical absence seizures are very short.

They usually last:

Less than about 20 seconds.

Because they are so brief, a child may experience many episodes during a single day.

22. No Aura in Absence Seizures

Typical absence seizures begin abruptly.

There is usually:

No aura.

The patient does not experience the warning symptoms typical of some focal seizures.

23. No Post-Ictal Confusion

After a typical absence seizure:

There is no significant post-ictal confusion.

The patient immediately returns to their previous activity.

Therefore:

Brief staring + immediate recovery → think absence seizure.

24. Age of Onset

Typical absence epilepsy generally begins during:

Childhood.

or

Adolescence.

Some syndromes remit with age, while others may persist into adulthood or coexist with other generalised seizure types.

25. EEG in Absence Seizures

The classic EEG finding is:

Generalised 3-Hz spike-and-wave activity.

This is one of the most important examination associations for absence epilepsy.

26. Hyperventilation and Absence Seizures

Hyperventilation can provoke a typical absence seizure.

For this reason, controlled hyperventilation may be performed during EEG testing when absence epilepsy is suspected.

27. Generalised Tonic-Clonic Seizures

The older term:

Grand mal seizure

is now called:

Generalised tonic-clonic seizure.

The seizure begins with loss of consciousness and a tonic phase, followed by a clonic phase.

28. Tonic Phase

During the tonic phase there is:

Sudden loss of consciousness.

Generalised muscle stiffening.

Tonic extension of the limbs.

The tonic phase usually lasts several seconds.

The patient may fall abruptly and sustain an injury.

29. Clonic Phase

The tonic phase is followed by:

Rhythmic bilateral jerking of the limbs.

This represents the clonic phase.

The jerking gradually becomes slower and eventually stops.

30. Other Features During a Tonic-Clonic Seizure

Associated features may include:

Cyanosis.

Excessive salivation.

Tongue biting.

Urinary incontinence.

Transient abnormal breathing.

Lateral tongue biting is particularly supportive of a generalised convulsive seizure.

31. Post-Ictal Phase

After the seizure, the patient usually develops a significant post-ictal period.

Features include:

Prolonged confusion.

Drowsiness.

Headache.

Muscle aches.

Fatigue.

The patient may subsequently sleep for some time.

32. No Aura in Primary Generalised Tonic-Clonic Seizures

A truly generalised-onset tonic-clonic seizure generally has:

No focal aura.

If a clear aura such as déjà vu, an abnormal smell, or a rising epigastric sensation occurs first, consider:

Focal onset with subsequent bilateral spread.

33. Focal Aware Seizure – Note Form

Old name: simple partial seizure.

Onset: one cerebral hemisphere.

Awareness: preserved.

Duration: seconds to a few minutes.

Symptoms: depend on cortical area involved.

EEG: may demonstrate a focal discharge.

34. Focal Impaired-Awareness Seizure – Note Form

Old name: complex partial seizure.

Awareness: impaired.

Duration: commonly around 60–90 seconds.

Aura: may precede the impairment of awareness.

Typical aura: déjà vu, unusual smell or rising abdominal sensation.

Automatisms: lip smacking, chewing, picking movements.

Afterward: brief post-ictal confusion.

35. Focal to Bilateral Tonic-Clonic Seizure – Note Form

Old name: secondarily generalised seizure.

Starts: focally.

May begin with: aura.

May progress through: focal impaired awareness.

Then: spreads to both hemispheres.

Result: bilateral tonic-clonic seizure.

36. Absence Seizure – Note Form

Onset: generalised.

Main feature: brief impairment of awareness/staring.

Duration: usually less than 20 seconds.

Aura: absent.

Post-ictal confusion: absent.

Typical onset: childhood or adolescence.

EEG: generalised 3-Hz spike-and-wave.

37. Generalised Tonic-Clonic Seizure – Note Form

Old name: grand mal seizure.

Onset: generalised from the beginning.

Awareness: lost.

Tonic phase: generalised stiffening and extension.

Clonic phase: rhythmic jerking.

Aura: absent in a true generalised-onset seizure.

Afterward: prolonged post-ictal confusion and drowsiness.

38. Focal Impaired Awareness versus Absence Seizure

Focal impaired-awareness seizure:

Usually lasts around 1–2 minutes.

Aura may occur.

Automatisms are common.

Post-ictal confusion is common.

Often associated with temporal lobe epilepsy.

Absence seizure:

Usually lasts only seconds.

No aura.

Abrupt staring and impaired awareness.

Immediate recovery.

No significant post-ictal confusion.

Classic 3-Hz spike-and-wave EEG.

39. Modern Terminology

For current terminology, remember:

Simple partial → Focal aware seizure.

Complex partial → Focal impaired-awareness seizure.

Secondarily generalised → Focal to bilateral tonic-clonic seizure.

Grand mal → Generalised tonic-clonic seizure.

Key Clinical Pattern

The easiest way to classify a seizure is to ask:

WHERE DID IT START, AND WAS AWARENESS PRESERVED?

One hemisphere + awareness preserved → Focal aware seizure.

One hemisphere + awareness impaired → Focal impaired-awareness seizure.

Focal onset followed by bilateral convulsion → Focal to bilateral tonic-clonic seizure.

Both hemispheres from onset → Generalised seizure.

For rapid examination recall:

ABSENCE = brief staring + <20 seconds + no aura + no post-ictal confusion + 3-Hz spike-and-wave.

FOCAL IMPAIRED AWARENESS = aura ± automatisms + 60–90 seconds + post-ictal confusion.

GENERALISED TONIC-CLONIC = tonic stiffening → clonic jerking → prolonged post-ictal confusion.