Epilepsy Flashcards
Whats the difference between epilepsy and seizures? [2]
Seizures = abnormal, paroxysmal changes in the electrical activity of the brain; they reflect large scale synchronous discharges of neuronal networks
Epilepsy = a neurological disorder that represents a brain state that supports recurrent, unprovoked seizures – it has neurobiological, cognitive, psychological and social consequences
Describe the 3 categories of epileptic seizures? [3]
Focal onset (aka partial seizures)
* Cortical or subcortical effected
* They can remain localized or spread to large areas
* start in one of the brain hemisphere
Generalised onset:
* Both sides of brain at onset
* Cortical or subcortical effected
Unknown onset
* If the beginning of the seizure is uncertain
Define status epilepticus
Status epilepticus
a form of epilepsy which is a life-threatening medical emergency
Seizures which last more than 5 minutes (or more than a seizure in 5 min,
without regain of consciousness)
General features of a tonic-clonic seizure (aka grand mal seizure)
Describe the 5 general features of a tonic-clonic seizure
Premonition (a vague sense that a seizure is imminent)
Pre-tonic-clonic phase (a few myoclonic jerks or brief clonic seizures)
Tonic phase: The muscles will stiffen - causing him/her to fall to the floor (tonic contraction of the axial musculature; upward eye deviation and pupillary dilatation; tonic contraction of the limbs; cyanosis; respiratory muscle contraction - “epileptic cry”; tonic contraction of jaw muscles)
Clonic phase - jerks of increasing amplitude followed by relaxation (sphincter opening may occur) Saliva that has not bene swallowed during the seizure may froth at the mouth. Breathing may be irregular as the respiratory muscles may be affected.
Postictal period (generalized lethargy; decreased muscle tone, headaches, muscle soreness)
Epilepsy diagnosis:
How many seizures are required for an epilipespy diagnosis? [1]
2 or more seizures (from eye witness accounts)
Which part of the brain undergoes structural changes during epilepsy? [1]
Which structural changes occur in this area? [4]
Reorganisation of the hippocampal tissue / hippocampal scleoris:
* Atrophy of CA2 and CA3 hippocampal areas
* Different tract orientation
* Compresion of layers
* Loss of neurones
Strucutral changes in epilepsy (I)
What are the consequences of hippocampal sclerosis / degeneration in epilepsy? [1]
Sprouting of axons & neurogenesis- may lead of excess synaptic conduct between neurons
Aberrant circuits may be created within the hippcampus
Overtime, there is transformation within neural networks that promote excitability.
Strucutral changes in epilepsy (II)
Name [1] and explain [2] which cell type, that if lost, can lead to epilepsy
GABAnergic inhibitory chandelier cells:
- Interneuron cells which synapse onto CNS
- Loss of inhibitory cells increases risk of abnormal excitatory activity
Seconday epilepsy causes:
Lots of epilepsy is idipathic. Name 4 conditions or procedures that may cause epilepsy
Stroke
Brain tumour
CNS infection
Craniotomy
TBI
Aneurysm
Name 3 cellular mechanims that are linked to the developement of epilepsy [3]
Abnormal neuronal excitability (ion channels)
Decreased neuronal inhibition (GABA-dependent) - e.g. loss of chandelier ce
Increased neuronal excitation (glutamate-dependent)
Describe the phenomenon / profile of neurones in an epileptic focus [1]
Describe how this occurs [1]
Burst firing: aka paroxysmal depolarising shift phenomenon
- This leads to synchronous, hyperexcitable activity within a neuronal population
- Particularly NDMA glutamate receptor activation
How do glial abnormalities influence the development of epilepsy? [1]
Astrocytes:
- contain EAAT1 and EAAT2 transporters
- EAAT1 and EAAT2 transporters are key in synaptic glutamate uptake
- A deficiency in EAAT1 and EAAT2 transporters leads to a decrease in glutamate reuptake
- This means there is more glutamate in synapse and increases excitability
Define epileptogenesis [1]
Epileptogenesis is the process by which the previously normal brain is functionally altered and biased towards the generation of the abnormal electrical activity that subserves chronic seizures.
Which physiological changes occur when the body undergoes EPILEPTOGENESIS to create a Hyperexcitable neuronal network in epilepsy [4]
- Neuroinflammation
- Blood- Brain-Barrier breakdown
- Oxidative stress
- Gliosis
- Network and synaptic changes
Which other major pathways may be disregulated in epilepsy? [2]
The mTOR pathway is a major regulator
of growth and homeostasis
The REST pathway leads to negative regulation
of the expression of many genes in the CNS
How do mutations in ion channels change their function to cause epileptic seizures?
paroxysmal electrical activity: hyperexcitable state
Label A&B of the hippocampus [2]
A: CA2
B: CA3
Both undergo atrophy in epilepsy
Label the channels that are abnormally functioning in epilepsy
EAAT1
EAAT2
(causes more glutamate in synapse)
Name this cell [1]
What is the function of this cell [1]
Chanderlier cell
specialized GABAergic interneuron subtype that selectively innervates pyramidal neurons at the axon initial segment (AIS), the site of action potential generation
