Seizures Flashcards
What is needed for neurons to maintain resting potential, depolarise, and depolarise
Ionic gradient
What maintains ionic gradient in neurones
Ionic channels and pumps
Inhib and excitatory NT
Glutamate excite
GABA inhib
Seizure cellular level
cortical neurons begin to fire in a hypersynchronous manner. This increased rate and sustained network of firing has a characteristic pattern and is called a paroxysmal depolarizing shift. It results in a spreading wave of electrical activity
How does refractory period of neurones change during a seizure
May reduce
Neuronal changes during seizure
Hypersynchronous firing
Sustained incr firing rate
Paroxysmal depolarising shift
Decr refractory period
Loss of surrounding neuronal inhibition
NT imbalance
Initial trigger of seizures
High frequency action potential generation with concurrent hyper polarisation
(Likely mediated by astrocytedps through calcium signalling)
Which cell type is involved in the initial trigger of a seizure via hyper polarisation
Astrocyte
Seizure definition
Transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.
Epilepsy
Conceptually, epilepsy exists after at least one unprovoked seizure, when there is high risk for another.
Epilepsy is considered to be a disease of the brain defined by any of the following conditions:
1. At least two unprovoked seizures occurring >24 h apart
2. One unprovoked seizure and a probability of further seizures similar to the general recurrence risk (at least 60%) after two unprovoked seizures, occurring over the next 10 years
3. Diagnosis of an epilepsy syndrome
Resolved epilepsy
– had an age-dependent epilepsy syndrome but are now past the applicable age
– or who have remained seizure-free for the last 10 years and off antiseizure medicines for at least the last 5 years
How long does a person have to be seizure free and off meds for resolved epilepsy
10 yrs
Off meds 5 yrs
Generalised seizure
Rapid bilateral onset
Always LOC
Convulsive or non convulsive
Generalised seizure subtypes
Tonic clonic
Atonic
Absence
Myoclonic
What parts of the brain are involved in generalised seizure
Originate within brain and quickly engage bilateral networks
Can include cortical and subcortical structures
Focal seizure
Onset within 1 hemisphere
Aura, motor, or autonomic sx
Retained or altered consciousness (stare blankly, grunting, automatisms)
Often progresses to bilateral convulsive in adults
What does a focal seizure often progress to in adults
Bilateral convulsive seizure
Focal seizure parts of brain involved
Originate in networks limited to 1 hemisphere
May be discretely localised or more widely distributed
What is an unknown seizure
Insufficient evidence to characterise as focal, generalised, or both
What type of seizure is a generalised onset non motor presentation
Absence
Which type of seizure may have retained awareness
Focal
