Last revised by Rohit Sharma on 23 Feb 2024

Epilepsy is a common neurological disorder that is characterized by a predisposition to having epileptic seizures and can take many clinical forms and have a veritable Augean stable of etiologies.

Epilepsy is defined by the International League Against Epilepsy (ILAE) as 1:

  • at least two or more unprovoked (or reflex) seizures occurring more than 24 hours apart; or

  • one unprovoked (or reflex) seizure and a probability of further seizures similar to the general recurrence risk after two unprovoked seizures, occurring over the next 10 years; or

  • diagnosis of an epilepsy syndrome

Epilepsy is very common, with approximately 3% of the population affected at some point in their life 2.

The hallmark clinical feature of epilepsy is that of epileptic seizures, which may have a variety of semiologies depending on the type of seizure and epilepsy. However, there are other important clinical features that may accompany epileptic seizures in epilepsy 3:

  • psychiatric co-morbidity, e.g. anxiety, depression

  • physical effects/complications of epileptic seizures, e.g. injury, death, neurocognitive deterioration

  • social effects/complications: e.g. lower education levels, lower employment rates with fewer options, limitations on recreational activities, stigmatisation

  • medication side-effects, e.g. neurocognitive deterioration, weight gain, rash, osteoporosis

Epilepsy is classified by the International League Against Epilepsy (ILAE) according to a three-level framework 4:

  • seizure type 5

    • focal (preferred term to 'partial') onset

      • may have awareness (preferred term to 'simple partial') or impaired awareness (preferred term to 'complex partial' or 'dyscognitive')

      • may be motor onset or non-motor onset (e.g. sensory, autonomic)

      • may progress from focal to bilateral tonic-clonic seizures

    • generalized

      • may be motor seizures, e.g. tonic-clonic (preferred term to 'grand mal') seizure, clonic seizure, tonic seizure, myoclonic-tonic-clonic seizure, myoclonic-atonic seizure, atonic seizure

      • may be non-motor or absence (preferred term to 'petit mal') seizure

    • unknown

  • epilepsy type

    • focal

    • generalized

    • combined generalized and focal

    • unknown

  • epilepsy syndrome

There are a myriad of etiologies, however, in adults with new onset of seizures ~50% will not have a determinable cause 2. The International League Against Epilepsy (ILAE) have proposed the following etiological classification 4:

MRI brain is the radiographic modality of choice 2. Please see articles on specific conditions listed above for imaging features. There are a number of MRI protocols that can be used to investigate patients with seizures.

If perfusion neuroimaging is performed during a seizure, it can be useful for localizing the epileptogenic focus 6,7.

May show an area of hypometabolism corresponding to the epileptogenic focus. Largely replaced by MRI but can be used in conjunction for localization of the epileptogenic foci 8.

Translocator protein (TSPO) is a molecular marker for glial activation and neuroinflammation. Quantification of TSPO using PET has been recently used to study epileptogenic foci. For example, increased TSPO levels can be seen in the epileptogenic foci within temporal lobes in patients with temporal lobe epilepsy 9,10.

Management of epilepsy is potentially complex, and may involve 2,3:

  • lifestyle restrictions, e.g. driving restrictions, restrictions on employment, limiting exposure to drugs and alcohol

  • antiseizure medications, either as monotherapy or in combination, and ketogenic diet

    • note that describing these medications as 'antiseizure' is the ILAE preferred terminology to 'antiepileptic' or 'anticonvulsive' 11

  • epilepsy surgery, e.g. stereo EEG, surgical resection, neuromodulation therapies

  • specific management of psychosocial effects/complications

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Cases and figures

  • Case 1: tuberous sclerosis
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  • Case 2: heterotopia / polymicrogyria
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  • Case 3: grey matter heterotopia
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  • Case 4: band heterotopia
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  • Case 5: focal cortical dysplasia
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  • Case 6: polymicrogyria
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