Epilepsy

Epilepsy is a common neurological disorder that hasis characterised by a varied presentation and requirespredisposition to having epileptic seizures.

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

• at least two or more unprovoked (or reflex) seizures at leastoccurring more than 24 hours apart for diagnosis. MRI is; or
• one unprovoked (or reflex) seizure and a probability of further seizures similar to the; or general recurrence risk after two unprovoked seizures, occurring over the modalitynext 10 years
• diagnosis of choice foran epilepsy, most often investigating for an underlying cause, especially in adults.  syndrome

Epidemiology

Epilepsy is very common, with approximately 3% of the population affected at some point in their life ^1,52.

Pathology

Epilepsy syndromes can be generally divided into two broad categoriesis classified by the International League Against Epilepsy (ILAE) according to a three-level framework ^1,54:

• 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 to focal to bilateral tonic-clonic seizures
  • generalised
    • may be motor seizures, e.g. absence epilepsy, tonic-clonic (preferred term to 'grand mal') seizure, myoclonic clonic seizure, tonic seizure, myoclonic-tonic-clonic seizure, myoclonic-atonic seizure, atonic seizure
    • focal, can progressmay be non-motor or absence (preferred term to 'petit mal') seizure
  • unknown
• epilepsy type
  • focal
  • generalised
  • combined generalised (focal-to-bilateral)and focal
  • unknown
• epilepsy syndrome
  • e.g. Dravet syndrome, Lennox-Gastaut syndrome, idiopathic (genetic) generalised epilepsy

Aetiology

There is a wide range of causes, however, in adults with new onset of seizures ~50% will not have a determinable cause ^1-52. The International League Against Epilepsy (ILAE) have proposed the following classification ⁶⁴:

• idiopathic: epilepsy due to an underlying single gene condition or complex inheritance (seizures as the only manifestation)
• cryptogenic: unknown cause
• provoked epilepsy: e.g. secondary to fevers, head trauma, drug-induced
• predominantly genetic/developmental causationstructural aetiology
  • childhood epilepsy syndromes
  • progressive myoclonic epilepsies
  • neurocutaneous syndromesacquired, 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)
  • chromosomal disorders, e.g. Down syndrome
  • single gene disorders
  • developmental cortical abnormalitiesgenetic, e.g. focal cortical dysplasia, grey matter heterotopia
• genetic aetiology
  • e.g. channelopathies (e.g. Dravet syndrome), neurocutaneous syndromes (e.g. tuberous sclerosis)
  predominantly acquired
• infectious aetiology
  • e.g. neurocysticercosis, tuberculosis, toxoplasmosis, cerebral malaria, subacute sclerosing panencephalitis, congenital CMV
  • mesial temporal sclerosis, meningoencephaloceles
  • tumours, e.g. gangliogliomas, DNET, PXA, low-grade gliomasnot 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 choice². 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 perfusion brain

If performed during the crisisan epileptic seizure, it can be useful for localising the epileptogenic focus ^6,7,8.