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Seizures & Epilepsy

In generalised seizure disorders, there is:

  • always a loss of consciousness
  • no warning
  • symmetrical seizure
  • bilaterally synchronous seizure discharge on EEG or varying asymmetry
  1. Absence seizures
    Transient loss of consciousness, with an abrupt onset and termination, unaccompanied
    by motor phenomena except for some flickering of the eyelids and minor alteration in
    muscle tone. Absences may be typical (petit mal) or atypical and can often be
    precipitated by hyperventilation
  2. Myoclonic seizures – Brief, often repetitive, jerking movements of the limbs, neck or trunk
    Non-epileptic myoclonic movements are also seen physiologically in hiccoughs
    (myoclonus of the diaphragm) or on passing through stage II sleep (sleep myoclonus)
  3. Tonic seizures – Generalized increase in tone
  4. Tonic–clonic seizures
    Rhythmical contraction of muscle groups following the tonic phase.
    In the rigid tonic phase, children may fall to the ground, sometimes injuring themselves.
    They do not breathe and become cyanosed. This is followed by the clonic phase, with
    jerking of the limbs. Breathing is irregular, cyanosis persists and saliva may accumulate in
    the mouth. There may be biting of the tongue and incontinence of urine. The seizure
    usually lasts from a few seconds to minutes, followed by unconsciousness or deep sleep for up to several hours
  5. Atonic seizures
    Often combined with a myoclonic jerk, followed by a transient loss of muscle tone
    causing a sudden fall to the floor or drop of the head


Focal seizures

  • Onset in neural network & limited to one cerebral hemisphere
  • begin in a relatively small group of dysfunctional neurones in
    one of the cerebral hemispheres
  • may be heralded by an aura which reflects the site of origin
  • may or may not be associated with change in consciousness or more generalised tonic-clonic seizure
    Focal seizures


  1. Frontal seizures – motor phenomena
  2. Temporal lobe seizures – auditory or sensory (smell or taste) phenomena
  3. Occipital – positive or negative visual phenomena
  4. Parietal lobe seizures – contralateral altered sensation (dysaesthesia)

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