The epileptic syndromes and their significance

A major advance in recent epileptology is the recognition of epileptic syndromes that allows an accurate diagnosis and management of seizure disorders.[1-3]

Medical diagnosis is the identification of a disease by investigation of its symptoms and history, which provides a solid basis for the treatment and prognosis of the individual patient. An accurate diagnosis is the golden rule in medicine, and epilepsies should not be an exception to this. Like in any other disease, the recognition of non-fortuitous clustering of symptoms and signs in epilepsies requires the study of detailed clinical and laboratory data.[1-3] However, often in current practice, the diagnosis is limited to either epilepsy or seizures, which is unsatisfactory because this cannot provide guidance on important items such as severity of the disease, prognosis, short- and long-term therapeutic decisions, and genetics (research and counselling), which are all factors that crucially affect personal, family, and social life; education; and career choices of patients. Defining the type of epilepsy should now be considered mandatory as it offers the best guide to both management and prognosis. Most epileptic syndromes and diseases are well defined and easy to diagnose. The benefits of syndromic diagnosis over seizure/symptom diagnosis or an inclusive diagnosis such as epilepsy far outweigh any morbidity from incorrect categorization that may arise in difficult cases.[4]

Important clinical features of a syndrome include the type of seizures, their localization, frequency, sequence of events, circadian distribution, precipitating factors, age at onset, mode of inheritance, physical or mental symptoms and signs, prognosis, and response to treatment.

Epilepsies or epilepsy?

The clinical and practical significance of the syndromic diagnosis of epilepsies is well illustrated by 3 common epileptic disorders. Benign childhood focal epilepsies, juvenile myoclonic epilepsy (JME), and hippocampal epilepsy have nothing in common other than the fact that they may all be complicated by generalized tonic-clonic seizures (GTCS), which are primarily GTCS in JME and secondarily GTCS in benign childhood focal epilepsies and hippocampal epilepsy.

Furthermore, the short-and long-term treatment strategies are entirely different for each disorder: benign childhood focal epilepsies may or may not require medication for a few years, appropriate anti-epileptic drug (AED) treatment is lifelong in JME while neurosurgery may be life-saving for patients with hippocampal epilepsy. What may be a life-saving drug such as carbamazepine for hippocampal epilepsy may be ill-advised for JME.

It should not be difficult to distinguish an intelligent child with benign focal seizures or childhood absence epilepsy from a child with Kozhevnikov-Rasmussen, Lennox-Gastaut, Down, or Sturge-Weber syndrome or a child with severe post-traumatic cerebral damage, brain anoxia, or catastrophic progressive myoclonic epilepsy. Describing all these children as simply having epilepsy just because they have seizures offers no more benefit than a diagnosis of febrile illness irrespective of cause, which may be a mild viral illness, a life-threatening acute bacterial meningitis, or a malignancy. Inappropriate generalizations with regard to terminology, diagnosis, and treatment are the single most important factor of mismanagement in epilepsies.[4]

International Classification of Epilepsies and Epileptic Syndromes [adapted from 2]

  1. Localization-related (focal, local, partial) epilepsies and syndromes
    1. Idiopathic with age-related onset
      1. Benign childhood epilepsy with centrotemporal spikes
      2. Childhood epilepsy with occipital paroxysms
    2. Symptomatic
      1. Chronic progressive epilepsia partialis continua of childhood
      2. Syndromes characterized by seizures with specific modes of precipitation
      3. Temporal lobe epilepsies
      4. Frontal lobe epilepsies
      5. Parietal lobe epilepsies
      6. Occipital lobe epilepsies
    3. Crytopgenic
  2. Generalized epilepsies and syndromes
    1. Idiopathic, with age-related onset (listed in order of age)
      1. Benign neonatal familial convulsions
      2. Benign neonatal convulsions
      3. Benign myoclonic epilepsy in infancy
      4. Childhood absence epilepsy (pyknolepsy)
      5. Juvenile absence epilepsy
      6. Juvenile myoclonic epilepsy (impulsive petit mal)
      7. Epilepsy with grand mal seizures on awakening
      8. Other generalized idiopathic epilepsies not defined above
      9. Epilepsies with seizures precipitated by specific modes of activation
    2. Idiopathic and/or symptomatic (listed in order of age)
      1. West syndrome (infantile spasms)
      2. Lennox-Gastaut syndrome
      3. Epilepsy with myoclonic-astatic seizures
      4. Epilepsy with myoclonic absences
    3. Symptomatic
      1. Nonspecific etiology
        1. Early myoclonic encephalopathy
        2. Early infantile epileptic encephalopathy with suppression burst
        3. Other symptomatic generalized epilepsies not defined above
      2. Specific etiology
        1. Epileptic seizures may complicate many disease states
  3. Epilepsies and syndromes undetermined as to whether they are focal or generalized
    1. With both generalized and focal seizures
      1. Neonatal seizures
      2. Severe myoclonic epilepsy in infancy
      3. Epilepsy with continuous spike waves during slow-wave sleep
      4. Acquired epileptic aphasia (Landau-Kleffner syndrome)
      5. Other undetermined epilepsies not defined above
    2. Without unequivocal generalized or focal features
  4. Special syndromes
    1. Situation-related seizures
      1. Febrile convulsions
      2. Isolated, apparently unprovoked epileptic events
      3. Seizures related to other identifiable situations such as stress, hormonal changes, drugs, alcohol, or sleep deprivation

References

  1. Engel J Jr. A proposed diagnostic scheme for people with epileptic seizures and with epilepsy: Report of the ILAE Task Force on Classification and Terminology. Epilepsia 2001;42:796-803.
  2. Commission on Classification and Terminology of the International League Against Epilepsy. Proposal for revised classification of epilepsies and epileptic syndromes. Epilepsia 1989;30:389-99.
  3. Blume WT, Luders HO, Mizrahi E, Tassinari C, van Emde BW, Engel J Jr. Glossary of descriptive terminology for ictal semiology: report of the ILAE task force on classification and terminology. Epilepsia 2001;42:1212-8.
  4. Panayiotopoulos CP. A clinical guide to epileptic syndromes and their treatment. Second edition. London:Springer; 2007.
Authored by: C. P. Panayiotopoulos | MD | PhD | FRCP on 10/2013
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