Educationals

Introduction

Convulsions are attacks of involuntary muscle contraction, either sustained, (tonic), or interrupted, (clonic,) e.g. - febrile convulsion, hypoglycemic convulsion.

Epilepsy - In the past term 'epilepsy' was loosely applied to any paroxysmal clinical events and was confused with hysterical fits, syncope, etc.

Epilepsy is a chronic condition characterised by the repeated occurrence of epileptic seizures.

Seizures are clinical events during which abnormal and excessive activity of a group of cerebral neurons occurs.

The excessive activity of cerebral neurons is demonstrated by the paroxysmal change in EEG activity which may be diffuse or localised.

Earlier epileptic seizures were simply described as big (grand mal) or small (petit mal) and later, terms such as psychomotor epilepsy and minor motor epilepsy were coined.

Confusion existed in the minds of physicians regarding the interpretation of these terms and in order to develop a uniform terminology the ILAE published the International Classification of Seizures in 1969.

This was the first time that the concept of relating a clinical event to ictal and inter-ictal EEG was introduced and a clear distinction was made between seizures that were generalised from the beginning to those that were partial or focal at onset and later became generalised.

This was followed by the era of intensive EEG and video monitoring which led to improved descriptive accuracy in the sequence of an individual seizure and a distinction could be made between simple partial (SP) and complex partial (CP) seizures. By repetitive replay of videotapes one was able to discern whether the patient's awareness and responsiveness was maintained or impaired. If a patient is aware and can recall the attack it is a simple seizure and if awareness and responsiveness is altered it is a complex partial seizure.

When we say partial seizures we mean that the initial epileptic discharge originates and remains confined to a restricted area of cerebral cortex. This is so in SP. If this discharge is in parts of limbic system and its projections-then it results in CP.

The epileptic discharge which was initially localized may then spread bilaterally to the entire cerebral cortex to trigger a generalised seizure. (P->GTC)

Simple partial (SP) - consciousness is preserved Complex partial (CP) -consciousness is impaired The seizure may progress from SP - CP - GTC termed as P - GTC

In generalised epilepsy, relatively simultaneous bilaterally large parts of cerebral hemisphere are involved. The genesis of spike and wave activity occurs in cortical structures and spreads via a corticoreticular cortical loop.

Classification of seizures

1. Partial Seizures

Simple (consciousness not impaired)

• With motor, somatosensory, special sensory, autonomic or psychic
  symptoms.

Complex (with impairment of consciousness)

• Beginning as simple partial seizures, progressing to complex
  seizures with or without automatisms.
• May progress to become secondarily generalised.

2. Generalised Seizures

• Absence seizures (typical or atypical)
• Myoclonic seizures
• Clonic, tonic or tonic clonic seizures
• Atonic seizures