L17 Seizures and Epilepsy Flashcards
What is a seizure (clinically)? What is the major problem?
Hypersynchronous neuronal discharge, a transient occurrence of signs and symptoms due abnormal excessive synchronous neuronal activity in the brain (usually less than 2 minutes duration)
The major problem is an imbalance between excitation and inhibition
What is the definition of a seizure based on an electrographic?
A clear ictal event comprising of a sudden repetitive, evolving, stereotyped waveform with a definite start, middle and end.
What is involved in a generalized seizure? What is one type of generalized seizure?
Both hemispheres have excessive neuronal activity at the same time and same region (primarily)
One type is an absence seizure (stop and stare, or twitch/stiff)
What is a focal seizure?
Seizure that occurs in one hemisphere, in one region.
The lesion is not necessarily where it will propagate to, and the area it propagates to dictates the symptoms you see
When a focal seizure propagates to both sides of the brain it is called a secondary generalized seizure
What are the three definitions of epilepsy?
- Two or more unprovoked or reflex seizures that are greater than 24 hrs apart (not due to substance or injury)
- A single unprovoked seizure or reflex seizure and a greater than 60% risk of having another seizure over the next 10 yrs
- An epilepsy syndrome
These give a predisposition to seizures
What age range do genetic factors usually affect?
Common in kids
What are the most common causes of epilepsy in adults and kids?
Children and adults show similar proportions of structural, metabolic, immune, and unknown causes
Unknown causes are greatest, about 40%
Children show more genetic causes and adults show more infection causes
What are 5 differences in seizures in children vs adults?
Different mechanisms of epileptogenesis
Different propagation of seizures (usually not generalized in neonates due to decreased myelination)
Unique EEG patterns
Different responses to medication
Different clinical manifestations
What are some things (diagnoses) that can cause seizures, or things that seizures can cause?
Congenital heart disease
Sleep apnea
What is ictal apnea? What can cause it?
Pathophysiology unknown, likely originating in limbic system
Genetic syndromes
Mesial temporal lesions
What are the three key points from the case of a child with ictal apnea?
Apnea can be ictal, especially in young children
Video EEG necessary for diagnosis, and this video EEG can identify subtle non-automatic manifestations
In the case of the child with night time spitting, what lead docs to think it was a behavioural cause? What confirmed it was seizures?
Behavioural: only at night, stereotypical and short, multiple times a night and every night, no recollection
Decided to do an EEG ideally to capture an episode
Diagnosed with focal seizures and ictal hypersalivation, which is an autonomic manifestation during a seizure
What is involved in an autonomic manifestation during a seizure?
Maturation related susceptibility of central autonomic network
Lower threshold for epileptogenic activation
What is the role of GABA and Glutamate in a seizure?
Glutamate: main excitatory NT in the brain, promotes seizures
GABA: main inhibitory NT in the brain, stops seizures
When there is more glutamate than GABA in the brain you may get a seizure
Why does the neonate brain have such a low threshold to seize?
GABA-A receptors are excitatory rather than inhibitory
Developmental imbalance between excitatory and inhibitory mechanisms
High density of NMDA receptors (excitatory) in the hippocampus and neocortex
Delayed maturation of GABA-B, adenosine and 5HT receptors
In the young girl with frequent nighttime arousals, what was used to make a diagnosis of seizures?
Used regular EEG but it was normal, used a video EEG to diagnose with seizures and sleep-related hypermotor epilepsy (previously known as nocturnal frontal lobe epilepsy)
Why is it hard to differentiate between nocturnal seizures and parasomnia?
Ictal and interictal EEGs can be normal or non-specifically abnormal
Etiology: genetic and structural (frontal cortical dysplasia type 2b)
What are three characteristics of frontal sleep related hypermotor epilepsy?
During nREM sleep
Brief, highly stereotypical, occurrence in sleep, overlap with parasomnias
What are some differences between parasomnias and nocturnal seizures?
Parasomnias: pre-school age, childhood, first 1/3 of the night, N3 sleep, 5-30 mins, SINGLE EVENT per night, EEG normal, normal daytime behaviour, respond to benzos at bedtime
Nocturnal seizures: anytime from infancy to adolescents, randomly throughout night, N1/N2 stages of sleep, brief (less than 5 mins), MULTIPLE EVENTS per night, EEG normal or abnormal, irritable/tired/ can have daytime seizures, respond to sodium channel blockers
What is the most important part of evaluating someone for possible seizures?
THOROUGH HISTORY AND EVENT DESCRIPTION
What are three takeaways about video EEG and regular EEG?
Video EEG is a valuable tool in the assessment of children with suspected seizures
EEG can support the diagnosis of epilepsy, and may help in determining the type of epilepsy and guide management
Child with unexplained stereotypical episodes (and seizures are suspected), should have an EEG, ideally both awake and sleeping
What are consequences of overtreatment or undertreatment of seizures?
Overtreatment: neurotoxicity, prolonged NICU stay
Undertreatment: “kindling” of additional seizures, worsen brain injury
Clinical diagnosis of seizures is UNRELIABLE, and seizures are defined by EEG
What are clonic seizures?
Rhythmic jerks, focal or multifocal
What are some similarities and differences between conventional EEG and aEEG.
Both allow continuous bedside assessment of brain function.
Conventional EEG requires an experienced technologist and reader but aEEG is simpler and easy to apply and interpret
Conventional EEG has good spatial coverage, and aEEG has limited spatial coverage
