Seizures Flashcards
Pathogenisis of seizures
Abnormal electrophysiolgical ctivity (cellular dysfunction)
Distribution of seizures
Focal or diffuse
Focal: seizures starts at 1 site, often spreads, can become diffuse
Diffuse: seizure activity starts with a diffuse distribution
Localization of seizures
Some common focal origins but also diffuse types
Temporal profile of seizures
Transient (except status epliepticus)
Clinical presentation of seizures
- hyperactivity or hypoactivity of cortical neurons
- convulsive (involuntary) motor movements
- stereotypies: repetitive movements
- loss of consciousness, with ot without later awareness of loss
- aura: sometimes preceded by sensory hallucinations (blue to focal origin)
What can be a clue to focal origin
Aura
Scalp electrodes detect synaptic potentials in cortex
EEG
What does EEG detect
A population of neurons as generated by the excitatory or inhibitory post synaptic response of pyramidal neurons to excitatory or inhibitory input form DENDRITES
Positive signal in EEG
The EPSP occurring near the cell body generates inward electrical current (into the cell) and outward current (out of cell) near the cortical surface
Negative signal one EEG
The EPSP occurring near the tip of the dendrite generates inward electrical current (into the cell) and outward current (out of cell) near the cell body
What is the arrangement of electrodes
Standardized arrangement
Beta wave on EEG
Wake state: eyes open, active
Alpha EEG
Wake state, eyes closed, relaxed
Theta EEG
Drowsy/sleep
Delta EEG
Sleep
What is a normal EEG
Beta or alpha waves
Goes from frontal lobe down to occipital
Gerenalized (diffuse/bilateral) seizures
Sudden and widespread cortical origin ( no neuroanatomical focus)
What are the two different types of generalized (diffuse/bilateral) seizures
Tonic clonic (grand mal) Absence (petit mal)
Tonic clonic seizures
- grand mal
- consciousness interrupted
- convulsive
- too much firing, sometimes disoriented afterwards
Absence seizures
- generalized (bilateral/diffuse)
- petit mal
- consciousness interrupted (unaware during seizure)
- mostly blank stare
- can show some subtle muscle contractions
Partial (focal) seizures
Cortical origin in one lobe or part of a lobe *neuroanatomical focus)
What subgroup of seizures has a neuranatomical focus
Partial (focaL)
What are the two different types of partial (focal) seizures
Simple focal
Complex focal
Simple focal seizure
- partical (focal) seizure
- consciousness maintained (aware during seizures)
- common origin sites are motor and sensory regions (parahippocampus region)
Complex focal seizure
- partial (focal) type of seizure
- consciousness interrupted (unaware during seizure)
- common origin: temporal lobe
- spreads and beceoms generalized
What is the most common origin of complex focal seizures
Temporal lobe
Neural mechanism of tonic clonic seizures
Simultaneous “burst-firing” and synchronization of cortical neurons across cerebral cortex
Temporal profile of tonic clonic seizures
Sudden onset, renascent course (minutes)
Initial stage of tonic clonic seizures
Tonic
-stiffening, bilateral extension, often arched back
Second stage of tonic clonic seizures
Clonic
- rhythmic
- conclusive felxion/extension or ‘shaking’
- chewing or biting motions
Consciousness in tonic clonic seizures
Loss of consciousness and initial post-vital phase
What do tonic clonic seizure EEGs lack
Beta and alpha waves
Pre-ictal waves for clonic tonic
Alpha and beta