L12 - Brain rhythms: epilepsy Flashcards
what is a seizure?
The clinical manifestation of abnormal and excessive excitation of cortical neurones
What is epilepsy?
A tendency towards recurrent seizures unprovoked by systemic or neurological insults
What is epileptogenesis?
Sequence of events that convert a normal neuronal network to a hyperexcitable one.
What are some causes of symptomatic or provoked seizures?
Drugs Intracranial surgery Hypoglycaemia Sleep deprivation Cardiac disease Low Na+, Ca2+ and Mg2+ Within 24 hours of a stroke
What are the different types of generalised and focal epilepsies?
Generalised:
- Convulsive (tonic-clonic, clonic-tonic-clonic)
- Absense
- Atonic (lapse in muscle tone)
- Myotonic (brief muscle spasms)
Focal:
- Simple - no altered consciousness
- Complex - altered consciousness
What are some of the characteristics of generalised seizures?
Not localised to one hemisphere
Cortical and subcortical nuclei can be involved
Can be symmetric or asymmetric
What is a tonic-clonic seizure?
A generalised seizure with almost all of the cortical neurones involved. The seizures involves a tonic phase in which the muscles stiffen for a few seconds and then a clonic phase where there are radpid repeated contractions of muscles.
What is a generalised absense seizure?
A seizure where the patient has an abrupt and offset sense of awareness. This typically causes memory impairment and the seizure is often accompanied by clonic movements of the eyelids, chin and face. Associated with a sharp synchronous spike seen all over the brain.
What is the mechanism behind a generalised absence seizure? How is it treated?
A series of glutamatergic and GABAergic synapses firing synchronously between the thalamus and the cortex. This causes the synchronous spike and waves during the seizure. It is treated by Ca2+ T-type channel blockers (ethosuximide).
What are the characteristics of a focal seizure?
60% of adult epilepsy
Usually last 50s to 3mins
Originates in a specific part of the brain and localised to one hemisphere
May be impairment of awareness
Type of seizure associated with location in brain.
What is SUDEP?
Sudden unexpected death in epilepsy
What are the risk factors for SUPED?
Poor seizure control
Young male
Seizures when alone
Large amounts of alcohol
What is status epilepticus?
An epileptic seizure that lasts for 10 mins or longer, this means mortality approaches 50% in some cases.
What normally prevents the chain reaction between neurones that is seen in epilepsy?
Inhibition normally stops this happening
What are the causes of epilepsy?
Normally there is no known cause (idiopathic epilepsy) and it is just thought that the individuals brain has a lower seizure threshold.
In rare cases there is a known case such as a tumour
Estimated that 40% of epilepsy has a genetic link however it is a complex mode of inheritence
