Epilepsy

A tendency to recurrent, usually spontaneous, epileptic seizures

Aetiology

  • Occurs at any age, most common in infancy and old age
  • Genetic, aquired brain, metabolic, toxic and environmental factors
  • Generalised epilepsy presents in childhood and adolescence, most have genetic predisposition
  • Focal epilepsy - localisation-related, can generalise laterally

Pathophysiology

  • An epileptic seizure is abnormal synchronisation of neuronal activity
    • Usually excitatory with high frequency action potentials
    • Sometimes predominantly inhibitory
  • Interruption of normal brain activity - focally or generalised
  • Usually brief (secs-mins)

Primary generalised epilepsy

  • Often presents in childhood/teens
  • Early morning jerks
  • Generalised seizures
  • Risk factors - sleep deprivation, flashing lights

Focal onset epilepsy

  • Underlying structural cause
  • Focal onset, can then generalise
  • Onset at any age
  • Hippocampal sclerosis can occur
  • Frequently involves complex partial seizures

Types of seizures

Generalised tonic-clonic seizures

  • Loss of consciousness and tonic (muscle tensing) and clonic (muscle jerking) episodes
  • May be associated tongue biting, incontinence, groaning and irregular breathing
  • After the seizure there is a prolonged post-ictal period
     where the person is confused, drowsy and feels irritable or depressed

Focal seizures

  • Start in the temporal lobes
  • Affect hearing, speech, memory, and emotions
  • Can present as: hallucinations, memory flashbacks, deja vu, doing strange things on autopilot

Absence seizures

  • Typically happen in children, 90% stop as they get older
  • The patient becomes blank, stares into space and then abruptly returns to norma
  • During the episode they are unaware of their surroundings and won’t respond
  • These typically only lasts 10-20 seconds

Atonic seizures - ‘drop attacks’

  • Characterised by brief lapses in muscle tone
  • These don’t usually last more than 3 minutes

Myoclonic seizures

  • Present as sudden brief muscle contractions, like a sudden ‘jump’

Investigations

  • ECG - to rule out prolonged QT syndrome
  • Imaging - MRIb
    • CTb may be indicated in some acute cases e.g. clinical or radiological skull fracture, deteriorating GCS, head injury with seizure - bascially to look for other causes of fall that require immediate intervention
  • EEG
    • Consider if trying to distinguish between non-convulsive status and encelopathy
    • Generalised epilepsy will show generalised spike-wave abnormalities

Management

  • Lamotrigine, levetiracetam and valproate are good for all seizure types
  • Carbamazepine, gabapentin and phenytoin are better for focal (including secondary generalised) seizures
  • Ethosuximide is the drug of choice for absence seizures
  • Carbamazepine may worsen myoclonic seizures
  • Issues regarding teratogenicity should also be considered, particularly in the context of valproate use which has a high risk of neural tube defects - lamotrigine is a good choice for women of childbearing age