What is epilepsy?
A group of neurological disorders marked by sudden and recurrent episodes of sensory disturbance, loss of conciousness or convulsions associated with abnormal electrical activity in the brain
On this pet scan which areas are coloured blue?(temporal lobe epilepsy)
The area of hypo-metabolism between seizures
How long between seizures in epilepsy?
It varies -> they are usually intermittent
What causes the seizures?
Excessive and abnormal cortical nerve cell activity
What 6 things can precipitate seizures?
- altered blood glucose and pH
- stress (going to dentist)
- flashing lights
- no apparent cause
How is epilepsy diagnosed (2)?
- ruling out other conditions that might cause similar symptoms
- confirmation with an electroencephalogram (EEG)
What are the major causes of epilepsy (10)?
- birth and perinatal injuries
- congenital malformations
- genetic (ion channels)
- idiopathic (unknown)
- Vascular insults
- Head trauma
- Severe metabolic disturbances
- drug/alcohol abuse
What is the treatment when seizures are caused by something else i.e. tumours/infection?
Treat the underlying cause
What can epilepsy be confused with in children?
What are the NICE guidelines for epilepsy?
You must have 2 seizures and investigations prior to treatment
What are the two types of epilepsy?
What are the different categories of localised seizures?
Simple (no loss of conciousness)
Complex (impairment of conciousness)
What are the different categories of Generalised seizures (6)?
What is a localised seizure?
It affects a specific region of a single hemisphere- includes psychomotor epilepsy
What % of seizures are accounted for by localised seizures?
What can cause localised seizures?
Cortical lesions (tumours, developmental malformation, damage due to trauma or stroke)
What are generalised seizures?
Discharges from both hemispheres
What % of seizures are accounted for by generalised seizures?
What are generalised seizures often caused by?
What are Absence seizures?
= look like daydreaming
What are Myclonic seizures?
= muscle twitch
What are Tonic clonic seizures?
= muscle convulsions
What are Tonic seizures?
= becoming stiff
What are Atonic seizures?
= drop seizures
What is Status epilepticus?
epileptic fits follow one another without recovery of conciousness between them
What are the two proposed mechanisms of epilepsy?
- Decreased inhibitory synaptic activity (insufficient GABA/ GABA-A receptor not working)
- increased excitatory synaptic activity (too much Glutamate (NMDA, Kainate or AMPA receptor)
What are the 3 proposed mechanisms for partial seizures?
- Selective loss of (inhibitory) interneurones = decreased feed forward/backward inhibiton of dendate gyrus cells
- Injury = synaptic reorganisation (axonal sprouting of remaining neurones) & recurrent excitatory connections
- Loss of excitatory neurones =usually inhibit dendate granule cells
What is an epileptic focus?
A high frequency burst of action potentials
(n.b. this is not a problem but its also not quite right)
How do epileptic foci develop into a seizure?
Hyper-synchronisation of neuronal populations = paroxysmal depolarising shift (PDS) = seizure
What is paroxysmal depolarising shift?
activation of AMPA (excitatory) receptors
-> e.g. by glutamate= NMDA receptor activation = increased intracellular K, accumulating Ca in pre-synaptic terminal (enhanced neurotransmitter release) & depolarisation induced NMDA receptor activation (increased Ca influx)