EPILEPSY A Brief Overview

                                

Definition

     Epilepsy is a condition of recurring seizures.  A seizure is an abnormal
     firing of cerebral neurons, which may or may not have a clinical 
     manifestation.

Prevalence

     Approximately 4 million Americans have epilepsy.

Classification  

     Partial Seizures - Partial means that the electrical discharge starts
     focally at one point in the brain, e.g., the left hippocampus.  If the
     seizure spreads to other areas of the brain, but does not interfere with
     consciousness, then it is termed Simple.  An example of a Simple Partial
     Seizure is clonic activity of only the right arm.  If the seizure spread
     involves neuronal circuits affecting consciousness, then it is termed
     Complex.  An example of a Complex Partial Seizure is when a person stops
     speaking, smacks his lips and is unresponsive to verbal commands for
     several minutes. Afterwards he will feel tired and not remember everything
     about the preceding seizure.  Either type of partial seizure can go on to
     spread sufficiently so as to result in a generalized "grand mal" seizure.
     Since the seizure first started focally, we say it was a Partial Seizure
     (simple or complex) with secondary generalization.  

     Aura - a simple partial seizure.

Primary Generalized Seizures

     When the abnormal electrical discharges are bilaterally synchronous at the
     onset.  Because these seizures are without a focal onset, there can be no
     "aura," which is a warning sign and actually represents a focal or
     partial seizure.


Etiology

     By and large, the primary generalized epilepsies, such as absence, grand
     mal (tonic-clonic), and myoclonic are genetically determined and present 
     in childhood and adolescence.  The partial epilepsies are more likely to
     be acquired (congenital, posttraumatic, infection, tumor) and present in
     any age.


Natural History

     Although certain stimuli can increase the probability of having a seizure,
     their occurrence is unpredictable.  Many of the patients with primary
     generalized epilepsy will stop having seizures as they enter adulthood
     (independent of treatment).  Medications (anticonvulsants, antiepileptics,
     antiseizure are valid terms to preceed the word medication or drug) help
     prevent seizures but do not cure the patient of his epilepsy. 
     The partial epilepsies are the most difficult to treat.

Treatment

     Rarely can an underlying cause of epilepsy be found in which treatment
     results in a cure.  Rather, antiepileptic drugs are employed to prevent
     the seizure from occurring.  Diagnosing the type of epilepsy is crucial
     in determining which drug to use.  For example, ethosuximide is extremely
     effective in absence, but useless in the partial epilepsies.  Some 
     patients with medically intractable partial epilepsy can benefit from 
     surgical removal of selected areas in the brain.

Prognosis

     Most patients with primary generalized epilepsy can expect to lead 
     productive lives; whereas, one third of the patients with partial 
     epilepsy will suffer social and economic hardships.

References

    Proposal for Revised Clinical and Electroencephalographic Classification of
    Epileptic Seizures, Epilepsia 1981;22:489-501. 
    The Generalized Epilepsies, Ernst Niedermeyer, Charles Thomas Pub., 1972.

    Clinical Electroencephalography, Kiloh, McComas,and Osselton, Butterworths,
    4th Ed., 1982.

    The Diagnosis and Treatment of Convulsive Disorders in Children, S.
    Livingstone, Charles Thomas Pub., 1954.  (Still an excellent text.)