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• Seizure


  A transient occurrence of signs or symptoms due to abnormal, excessive, or synchronous neuronal activity in the brain

  
• Before attempting to classify a seizure, a physician must first determine that the event has the characteristics of a seizure and not of the many imitators of seizure, such as convulsive syncope, parasomnias, movement disorders, and other nonepileptic events

  
• Provoked seizures


  Caused by a transient factor that acts on an otherwise normal brain and temporarily lowers the seizure threshold

  
• Transient factors


  • Acute insults to the nervous system (eg, acute intracerebral hemorrhage) and acute systemic metabolic derangements (eg, hypoglycemia, hyponatremia, or substance intoxication or withdrawal)
• Unprovoked seizures


  May have an unknown cause or a known remote cause (eg, prior stroke, head trauma, metabolic disorder, or developmental abnormality)

  
• Epilepsy


  A condition in individuals who experience recurrent seizures or are at risk of recurrent seizures

  
• Epilepsy is defined as a disease in which seizures tend to recur and a patient meets at least 1 of the following criteria: 1) Two or more unprovoked seizures occurring more than 24 hours apart; 2) One unprovoked seizure and a probability of further seizures similar to the general recurrence risk after 2 unprovoked seizures (≥60%) over the next 10 years; 3) An epilepsy syndrome

  
• Drug-resistant epilepsy


  Epilepsy that persists despite adequately dosed trials of 2 different, tolerated, and appropriately selected antiepileptic medications (either alone or in combination)
• The International League Against Epilepsy (ILAE) first developed classifications for seizures and epilepsy in 1981 and has revised them several times. The most recent revision, from 2017, has continued to shift seizure classification toward a descriptive and operational naming system to be more understandable to providers and the public

  
• Seizure classification


  • Mode of onset (focal, generalized, or unknown), level of awareness (aware or impaired), and semiology (motor or nonmotor)

  
• Mode of onset


  The first step in seizure classification is to determine whether onset is focal, generalized, or unknown

  
• Level of awareness


  Refers to the perception or knowledge of self and environment during a seizure
• Semiology


  The systematic classification and analysis of symptoms and signs
• Generalized seizures


  • Arise in both hemispheres simultaneously, resulting in impaired awareness, with or without bilateral motor manifestations

  
• Focal seizures


  • Semiology depends on the location of the seizure focus, and different clinical features may appear as the ictal activity spreads to adjacent brain regions

  
• The most common type of focal epilepsy is mesial temporal lobe epilepsy, often caused by mesial temporal sclerosis
• Seizure semiology


  • Can help in lateralizing the seizure, such as an early, nonforced head turn often localized to the ipsilateral temporal lobe, and a forced head turn usually due to a seizure focus in the contralateral hemisphere

  
• Seizure semiology


  • The figure of 4 sign, characterized by unilateral tonic arm extension with flexion at the elbow of the opposite arm, is associated with a seizure focus in the hemisphere contralateral to the extended arm

  
• Seizure semiology


  • The fencer's posture, another finding when patients have a seizure focus contralateral to the extended arm, often arises from the frontal lobe

  
• Epilepsy type


  Refers to the type of seizures occurring in a patient (focal, generalized, combined generalized and focal, or unknown)

  
• Epilepsy etiology


  The 2017 ILAE classification defined 6 etiologic categories (but >1 may apply): structural, genetic, infectious, metabolic, immune, and unknown
• Epilepsy syndrome


  A cluster of clinical features that occur together, incorporating seizure types, EEG features, and imaging findings, generally categorized according to the typical age of the patients at onset

  
• About 10% of people in the United States have 1 seizure in their lifetime; less than 4% have recurrent seizures or epilepsy. Currently, more than 3.4 million people in the United States have active epilepsy, making it one of the most common neurologic disorders

  
• Acute symptomatic seizures


  Also called provoked seizures or reactive seizures, result from new and active insults to the central nervous system, such as toxic, metabolic, infectious, inflammatory, or structural causes

  
• Unprovoked seizures


  Seizures without an acute symptomatic cause

  
• Epilepsy is typically defined as the occurrence of 2 or more unprovoked seizures

  
• Factors such as sleep deprivation, exposure to flashing lights, or illness may lower the threshold for a seizure to occur, but seizures associated with these mechanisms should not be considered provoked since they would not be expected to occur under typical circumstances

  
• Between 30% and 40% of unprovoked seizures and epilepsy have a remote symptomatic cause, which is lower among young children and higher among the elderly

  
• Remote symptomatic causes


  • Cerebrovascular disease, hypoxic-ischemic injury, neurodegenerative conditions, traumatic brain injury, prior central nervous system infection or inflammation, neoplasm, and developmental abnormalities (eg, congenital brain malformations, intellectual disability, and cerebral palsy)
• Compared with idiopathic seizures, seizures with a remote symptomatic cause are more likely to recur, are less likely to remit once established, and are associated with greater long-term mortality

  
• Cognition


  The mental process of knowing things
• Cognitive functions


  • Memory
  • Language
  • Perception
  • Executive function (planning, initiating, and reasoning)
• Dysfunction of cognition without a change in consciousness may result in various disorders, including aphasia, apraxia, agnosia, executive dysfunction, and memory disorders such as dementia and amnesia

  
• Transient dysfunction of cognition associated with a change in level of consciousness or attention may be due to delirium or confusional states
• Cognitive domains


  • Learning and Memory: Acquiring, storing, and retrieving information
  • Language: System of structured communication
  • Executive Function: Managing and regulating cognitive abilities
  • Complex Attention: Focusing on multiple tasks simultaneously
  • Perceptual Motor Cognition: Integrating sensory and motor skills
  • Social Cognition: Understanding and interacting with others
• Cognitive dysfunction syndromes


  • Aphasia: Loss of ability to understand or express speech, caused by brain damage
  • Apraxia: Trouble performing movements when asked, even though the desire and physical ability are present
  • Agnosia: Difficulty recognizing objects, people, or sounds, despite having functioning senses
  • Executive Dysfunction: Difficulty with tasks that require planning, decision-making, and task management
  • Memory Disorders: Disruptions in the ability to remember information, affecting learning and daily functioning
• Delirium


  A fluctuating level of consciousness with impairment in behavior and mental function caused by a physical disease

  
• Delirium is characterized by disturbance in attention (ie, reduced ability to direct, focus, sustain, and shift attention) and awareness (reduced orientation to the environment)

  
• The disturbance in delirium develops over a short period (usually hours to a few days), represents an acute change from baseline attention and awareness, and tends to fluctuate in severity during the course of a day

  
• Delirium may also be accompanied by psychomotor behavioral disturbances, emotional disturbances, and hallucinations