Epilepsy

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

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

Epidemiology

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

Clinical presentation

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

Pathology

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

  • generalised

    • 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

  • generalised

  • combined generalised and focal

  • unknown

• epilepsy syndrome

  • e.g. Dravet syndrome, Lennox-Gastaut syndrome, idiopathic (genetic) generalised epilepsy

Aetiology

There are a myriad of aetiologies, 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 aetiological classification ⁴:

• structural aetiology

  • acquired, e.g. stroke, cerebral palsy, post-meningitis, traumatic brain injury, vascular malformations, mesial temporal sclerosis, meningoencephaloceles, tumours (e.g. gangliogliomas, DNET, PXA, low-grade gliomas)

  • genetic, e.g. focal cortical dysplasia, grey matter heterotopia

• genetic aetiology

  • e.g. channelopathies (e.g. Dravet syndrome), neurocutaneous syndromes (e.g. tuberous sclerosis)

  • note that some genetic aetiologies may also be structural aetiologies in this classification

• infectious aetiology

  • e.g. neurocysticercosis, tuberculosis, toxoplasmosis, cerebral malaria, subacute sclerosing panencephalitis, congenital CMV

  • note that this is not referring to seizures occurring in the setting of an acute CNS infection

• metabolic aetiology

  • e.g. porphyria

• immune aetiology

  • e.g. autoimmune encephalitis

• unknown aetiology

​Radiographic features

MRI

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.

Nuclear medicine

SPECT

If perfuson neuroimaingperfusion neuroimaging is performed during a seizure, it can be useful for localising the epileptogenic focus ^6,7.

FDG-PET

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

PET-TSPO

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.

Treatment and prognosis

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

See also

• epilepsy protocol (MRI)

• status epilepticus