3 electrophysiology of epilepsy Flashcards
(29 cards)
What is the general neuronal organization in the cortex?
large pyramidal neurons in vertical columns, with apical dendrite perpendicular to surface
What does EPSP stand for?
excitatory post-synaptic potential
What does IPSP stand for?
inhibitory post-synaptic potential
What are the EEG recordings of?
cell membrane depolarization [Na channels]
cell membrane hyper polarization [Cl channels]
In the special circuit (hippocampus) the perforate path was the input…what is the output?
subiculum
Excitatory output of the pyramidal cells in the hippocampus are opposed by what?
recurrent inhibitory interneurons (GABA)
What does the intralaminar thalamic cell inhibit? what does this cause?
- Thalamic relay neuron
- leaves the thalamic neuron primed for bursting activity
The bursting activity of TRNs is mediated by what?
calcium channels
What does electroencephalography record?
the extra-cellular voltage potential of a population of cortical neurons
–6 cm/electrode
In the normal EEG what does the alpha rhythm represent?
Awake state
In the asleep EEG what stage is the vertex sharp waves?
Stage N1
What asleep EEG stage is the sleep spindles, K-complexes, and positive occipital sharp transients?
Stage N2
What asleep EEG stage is the slow wave sleep?
Stage N3
What EEG stage is low voltage EEG, no muscle tone, and SAW TOOTH WAVES?
Stage REM
In an abnormal EEG, what does focal slowing imply?
focal cerebral dysfunction
In the abnormal EEG, what does generalized slowing imply?
diffuse cerebral dysfunction or deep dysfunction (thalamic or ARAS)
What are the abnormal EEG forms of paroxysmal activity?
spikes, spike-wave (imply seizure tendency)
These can be focal or generalized
In the US what percentages—
- will have 1 seizure?
- Will have Recurrent Seizures?
- Lifetime risk?
- Current active epilepsy?
- 10%
- 4%
- 3%
- 1%
What is the dormant basket cell hypothesis?
Inhibitory interneuron feedback is lost and excitation is unopposed creating prolonged depolarization. A population of neurons experiences repetitive action potentials—->seizure
What is the mossy fiber sprouting hypothesis?
mossy fibers synapse back on themselves producing a positive feedback loop and CA3 cells undergo sustained depolarization —-> seizure
What do we see in the neocortical pyramidal cell and the TRN in absence seizure pathophysiology? what is recorded from cortex?
hyperexcitable cortex and thalamus produce and excessive reverberating loop
generalized spike wave is recorded
What is the pathophysiology of the complex partial seizure?
abnormality of hippocampus with aberrant dendritic sprouting of excitatory neurons and loss of inhibitory
What are the clinical signs of complex partial seizure?
staring, unresponsive, automatic movements, lasts 30-120 seconds
What does the EEG look like in a complex partial seizure?
focal, rhythmic sharp activity
