Epilepsy Flashcards
Define seizure
The clinical manifestation of an abnormal and excessive excitation of a population of cortical neurones
An abnormal, synchronous, paroxysmal neuronal discharge in the brain causing abnormal function
Sudden, transient and disorderly
Define epilepsy:
Tendency towards recurrent seizures unprovoked by a systemic or neurological insults
Define epileptogeneis
Sequence of events that convert a normal network into a hyper excitable network
Symptomatic provoked seizures caused by:
Drugs: stimulant intoxication or sedative withdrawal
Severe sleep deprivation
Cardiovascular disease: ‘reflex anoxic seizures’
Seizures within 24hrs of stroke of TIA
Seizures with intracranial surgery
Seizures due to hypoglycaemia
Seizures provoked by low Na+, Ca2+, Mg2+
What are the types of seizures
Focal/ partial seizure: no altered consciousness complex, altered consciousness - one part of the brain, one hemisphere
Generalised seizures: convulsive (tonic clonic; tonic-clonic-tonic; absence, atonic, myoclonic
Generalised facts
Site of onset cannot be determined to either hemisphere Can be asymmetric or symmetric Can include cortical and subcortical structures, but not necessary the entire cortex Types: Convulsive (tonic clonic) Absence Atonic Myotonic
What happens In the tonic stage of the seizure
Muscles stiffen
Lose consciousness
May fall down
What happens In the clonic stage of the seizure
Rapid muscle contractions sometimes called convulsions
Happens in a generalised absence seizure
Abrupt onset and offset of altered awareness
Memory impaired
Clonic movements of eyelids, chin and face
Synchronous 3Hz ‘spike and wave’ recorded over most of the scalp
Associated with awareness that can be mistaken for day dreaming
What is the mechanisms and treatment for absence seizures
Interactions between the thalamus and cortex
Glutamatergic and GABAergic synapses generate rhythmicity
Treatment: ethosuximide
Focal seizures facts
Originate in specific part of the brain - 1 hemisphere
Duration ~10 seconds to 2-3mins
60% of adult epilepsy
Maybe an impatient of awareness
Features dependent on the localisation of the seizure
E.g. Focal motor seizure
Most new adult onset epilepsy presenting to secondary generalisation
Is epilepsy life threatening
Seizure activity can change HR /breathing
Status epilepticus - epileptic seizure for more than 30mins or a series of seizures without regaining consciousness
Mortality 50%
What are the EEG spikes caused by in epilepsy
Areas working synchronously which do not usually work together
What normally happens when cells are excited
When neurones reach a certain excitatory threshold it then triggers sufficient inhibition to put a brake on the system this brake is from GABAergic neurones which connect to many excitatory neurones and when a threshold is reached this leads to inhibition
What happens to the excitatory and inhibitory neurones in epilepsy
In epilepsy there are more excitatory neurones these networks are enlarged so there is less inhibitory to go around excess excitation leads to a seizures
