418 Seizures and Epilepsy Flashcards
Origin of the word “seizure”
“Sacire” which means “to take possession of”
What is seizure?
A seizure is a transient occurrence of signs or symptoms due to an abnormal excessive or synchronous neuronal activity in the brain
What is epilepsy?
Epilepsy describes a condition in which a person has a risk of recurrent seizures due to a chronic, underlying process (not a single or recurrent seizure that is due to correctable or avoidable circumstances).
Focal vs generalized seizure
Focal seizures
- originate within networks limited to one brain region
- usually associated with structural abnormalities of the brain
Generalized seizures
- arise within and rapidly engage networks distributed across both cerebral hemispheres
- may result from cellular, biochemical, or structural abnormalities that have a more widespread distribution
3 subtypes of Focal seizures
Focal seizures with intact awareness
Focal seizures with impaired awareness
Focal seizures that evolve into generalized seizures
Features of Focal seizures
1) Can have motor or nonmotor manifestations with or without impairment of awareness
2) The abnormal motor movements may begin in a very restricted region such as the fingers and gradually progress (over seconds to minutes) to include a larger portion of the extremity (“Jacksonian march”)
3) May experience a localized paresis (Todd’s paralysis) for minutes to many hours in the involved region following the seizure.
4) May continue for hours or days, in rare instances (“epilepsia partialis continua”)
Term used to denote the phenomenon in which there is gradual progression of a focal seizure from a small region to a larger portion of the extremity
Jacksonian march (described by Hughlings Jackson)
Term used to denote the localized paralysis for minutes to many hours in the involved region following a focal seizure
Todd’s paralysis
Term used to denote a focal seizure that continues for hours or days
Epilepsia partialis continua
Term used to denote subjective, “internal” events that are not directly observable by someone else but may actually be manifestations of a focal seizure
Auras
Illusion that objects are growing smaller
Micropsia
Illusion that objects are growing larger
Macropsia
Typical events in focal seizures with impaired awareness
Frequently begin with an aura that is stereotypic for the patient
Start of the ictal phase is often a motionless stare, which marks the onset of the period of impaired awareness, usually accompanied by automatisms
Confusion after the seizure
Transition to full recovery of consciousness may range from seconds up to an hour or longer. May have anterograde amnesia or transient neurological deficits
Usual variety of generalized seizure when it evolved from a focal seizure
Tonic-clonic variety
Region of the brain from which focal seizures that evolve into generalized seizures usually arise
Frontal lobe
Subtypes of Generalized onset seizures
Typical absence seizures
Atypical absence seizures
Generalized, tonic-clonic seizures
Atonic seizures
Myoclonic seizures
Epileptic spasms
Features of Typical absence seizures
Sudden, brief lapses of consciousness without loss of postural control
Usually lasts for only seconds
No postictal confusion
Usually accompanied by subtle, bilateral motor signs
Main seizure type in 15-20% of children with epilepsy
First clue is often unexplained “daydreaming” and a decline in school performance
EEG hallmark: Generalized, symmetric, 3-Hz spike-and-slow-wave discharges that begins and ends suddenly, superimposed on a normal EEG background
Hyperventilation tends to provoke these electrographic discharges
Features of Atypical absence seizures
Lapse of consciousness is usually of longer duration and less abrupt in onset and cessation
Accompanied by more obvious motor signs
EEG: Generalized, slow spike-and-slow-wave pattern with a frequency of <=2.5 per second
Associated with diffuse or multifocal structural abnormalities of the brain and therefore may accompany other signs of neurologic dysfunction such as mental retardation
Less responsive to anticonvulsants compared to typical absence seizures
Features of Generalized, Tonic-Clonic Seizures
Main seizure type in ~10% of all persons with epilepsy
Most common seizure type resulting from metabolic derangements
Usually begins abruptly without warning, but may sometimes have a prodrome
Phases:
1) Tonic phase 10-20s
2) Clonic phase (total ictal phase usually lasts no more than 1 min)
3) Postictal phase (bladder or bowel incontinence may occur)
Usually with postictal confusion
EEG:
1) Tonic phase - Progressive increase in generalized low-voltage fast activity, followed by generalized high-amplitude, polyspike discharges
2) Clonic phase - High-amplitude activity is typically interrupted by slow waves to create a spike-and-slow-wave pattern
3) Postictal phase - Diffuse suppression of all cerebral activity, then slowing that gradually recovers as the patient awakens
Features of Atonic seizures
Sudden loss of postural muscle tone lasting 1-2s
Consciousness is briefly impaired, but there is usually no postictal confusion
EEG: Brief, generalized spike-and-wave discharges followed immediately by diffuse slow waves that correlate with the loss of muscle tone
Features of Myoclonic seizures
Myoclonus - sudden and brief muscle contraction that may involve one part of the body or the entire body
Most commonly seen in association with metabolic disorders, degenerative CNS disease, or anoxic brain injury
EEG: Bilaterally synchronous spike-and-slow-wave discharges immediately prior to the movement and muscle artifact associated with the myoclonus
Predominant feature of juvenile myoclonic epilepsy
Features of Epileptic Spams
Briefly sustained flexion or extension of predominantly proximal muscles, including truncal muscles
Occur predominantly in infants
EEG: Hypsarrhythmia (diffuse, giant slow waves with a chaotic background of irregular, multifocal spikes and sharp waves). During the clinical spasm, there is a marked suppression of the EEG background (the “electrodecremental response”)
EMG: Characteristic rhomboid pattern
Which type of generalized seizure is associated with a group of genetically determined epilepsies with onset usually in childhood (ages 4-10 years) or early adolescence and are the main seizure type in 15-20% of children with epilepsy?
Typical absence seizures
Most common seizure type resulting from metabolic derangements
Generalized, tonic-clonic seizures
