A seizure as defined by the eminent British neurologist Gordon Holmes is a "sudden, involuntary, time limited attenuation in function, secondary to an abnormal discharge of neurons in the central nervous system". They may be due to an acute systemic or focal neurologic lesion. Idiopathic seizures have no known underlying definitive cause. Modern imaging techniques and volumetric analysis are now revealing various migrational disorders and focal microdysgenesis of the cortex which is shrinking the percentage of truly idiopathic patients.
Epileptic Seizures
Discrete epileptic events due to transient hypersynchronous abnormal neuronal discharges
Epilepsy: recurrent unprovoked seizures
General Epidemiology
Overall incidence: 40–70: 100,000 in developed countries
Single seizure; 0.5–5% of the population over a lifetime
Greatest incidence occurs during the first year of life
Western Europe and USA:
By the age of 20, 3% of children may have had a seizure; 25% of these will develop epilepsy
80% of these children are seizure free within five years; most by one year
Approximately 20–30% of newly diagnosed epilepsy patients will develop medically refractory seizures
Secondary rise in incidence after 60 years of age
Risk factors for epilepsy:
Mental retardation
Perinatal disorders
Cerebral palsy
Cerebrovascular disease
Infection of the central nervous system
Neoplasm
Neurodegenerative disease
Drug abuse
Men 1–2.4 times at greater risk than women
Classification of Epilepsy
The International Classification of Epileptic Seizures
Partial Seizure: The first clinical and or EEG changes indicate initial involvement of one hemisphere. Partial seizures are classified on the basis of impairment of consciousness.
Simple partial: No impairment of consciousness
Complex partial: Impairment of consciousness
Partial with secondary generalization
Generalized Seizures: The first clinical and or EEG changes indicate initial involvement of both hemispheres. Consciousness is impaired.
Tonic clonic
Absence
Clonic
Myoclonic
Tonic
Atonic
Unclassified:
Neonatal seizures
Epileptic Syndrome:
Heterogeneous groups of disorders with specific manifestations. Classification is based on:
Cluster of signs and symptoms
Seizure type
Age at onset
EEG findings
Prognosis
Response to antiepileptic drugs (AED)
Seizures Classified by Etiology
Idiopathic: Seizures that occur in the absence of an acute precipitating central nervous system insult, systemic metabolic dysfunction or a history of prior neurologic insult.
Acute Symptomatic: Seizures that occur only during the first week after an acute central nervous system lesion or are concurrent with:
Metabolic disturbance
Febrile episode
Alcohol withdrawal
Remote Symptomatic: Seizures in a patient with a history of central nervous system insult associated with an increased risk of seizure.
Epilepsies, Epileptic Syndromes and Related Seizure Disorders: International League Against Epilepsy Classification
Localization-Related (focal or partial)
Seizure semiology, EEG or MRI implicate a focal origin
Primary Idiopathic:
Definition: an idiopathic disorder is one not preceded by another disorder
Benign childhood epilepsy with Centro-temporal spikes
Childhood epilepsy with occipital paroxysms
Primary reading epilepsy
Secondary symptomatic:
Secondary to a known or suspected central nervous system disorder
Chronic progressive epilepsia partialis continua of childhood:
Rasmussen's Syndrome
Epilepsies by cortical localization:
Temporal lobe epilepsy
Frontal lobe epilepsy
Parietal lobe epilepsy
Occipital lobe epilepsy
Generalized Epilepsies and Syndromes
Idiopathic generalized epilepsies:
Benign neonatal familial convulsions
Benign neonatal convulsions
Benign myoclonic epilepsy in infancy
Childhood absence epilepsy (pyknolepsy or petit mal)
Juvenile absence epilepsy
Juvenile myoclonic epilepsy
Epilepsies with grand mal seizures
Generalized tonic clonic seizures (GTCS) on awakening
Epilepsies with Seizures Characterized by Specific Modes of Presentation
Reflex epilepsies: Specific mental or somatic events that trigger seizures:
Temperature change
Photic stimulation
Math (simple calculations)
Chess
Somatic (proprioception or touching the skin surface)
Reading
Auditory (specific tones)
Chemical smells
Eating
Walking
Singing
Symptomatic (age-related)
West Syndrome (infantile spasms)
Lennox–Gastaut Syndrome (infancy)
Epilepsy with myoclonic-astatic seizures
Epilepsy with myoclonic absence
Symptomatic Generalized Epilepsies and Syndromes: Often Associated with Diffuse Encephalopathy
Generalized seizures
Supportive EEG findings
Many different types of seizures in the same patient
Neuroradiological signs may be positive
Non-Specific Etiology (age-related)
Early myoclonic encephalopathy
Early infantile epileptic encephalopathy with suppression bursts
Specific Syndromes
Malformations
Inborn errors of metabolism
Seizures with both Generalized and Focal Features
Neonatal seizures
Severe myoclonic epilepsy in infancy
Epilepsy with continuous spike-and-waves during slow wave sleep
Seizures occurring only when there is an acute metabolic or toxic event
Alcohol
Drugs
Eclampsia
Nonketotic hyperglycemia
Isolated Seizures or Isolated Status Epilepticus
The major problems in the epilepsies suffered by adult patients are major motor seizures and complex partial seizures. The varying auras and descriptions of complex partial seizures make them difficult to diagnose in many instances. Occasionally primary childhood seizure types extend into adolescence and adulthood and will be discussed. Congenital and pediatric seizures will not be discussed in detail, but may be mentioned for completeness.