Epilepsy

Question 1

what is the most important excitatory neurotransmitter and receptor, and why?

Answer 1

glutamate via NMDA receptor - cation channel lets in Na, Ca, and lets K out. Depolarises membrane, more likely AP

Question 2

what is the most important inhibitory NT and receptor, and why?

Answer 2

GABA via GABAa receptor - Cl channel, hyper polarises membrane, less likely to fire action potential

Question 3

what is a seizure?

Answer 3

excess excitation and synchronisation of neurones, via loss of inhibitory neurones or too strong excitatory signals.

Question 4

what are some causes of seizures?

Answer 4

genetic differences in brain chemistry/receptor structure, by exogenous activation of receptors (drugs), by acquired brain chemistry changes (drug withdrawal/metabolic changes), or damage to these networks (strokes/tumours)

Question 5

what are signs of a generalised seizure?

Answer 5

LOC often with changes in muscle tone, tongue biting, loss of bladder and bowel control

Question 6

what are signs of a tonic clonic seizure?

Answer 6

initial hypertonic phase followed by rapid clonus (shaking, jerking)

Question 7

what is the post ictal period?

Answer 7

after a seizure, decreased consciousness which can last mins to hours

Question 8

what is the diagnosis criteria for epilepsy?

Answer 8

1) at least 2 unprovoked seizures occurring >24 hrs apart

2) one unprovoked seizure and a probability of further seizures

Question 9

what are different types of reflex seizures?

Answer 9

photogenic, musicogenic, thinking, eating, hot water immersion, reading, orgasm, movement

Question 10

what are the 3 types of classification?

Answer 10

focal onset, generalised onset, unknown onset

Question 11

where do generalised seizures originate?

Answer 11

at some point within and rapidly engage bilaterally distributed networks, can include cortical and subcortical structures but not necessarily the entire cortex

Question 12

where do focal seizures originate?

Answer 12

within networks limited to one hemisphere, may be discretely localised or more widely distributed

Question 13

what can cause a provoked seizure?

Answer 13

as a result of another medical condition - drug use/withdrawal, head trauma, alcohol withdrawal, metabolic disturbances e.g. hyponatraemia, CNS infections, uncontrolled hypertension

Question 14

what is the initial management of a seizure?

Answer 14

airway - is it patent
breathing - sats reading +/- O2
circulation - expect a high HR, wary of BP
disability - may have reduced consciousness depending on type
e - may want to get them in recovery position, look at clock, get help, majority resolve in 5 mins

Question 15

what is status epilepticus?

Answer 15

a seizure lasting more than 5 mins, or multiple seizures without complete recovery in between, is a medical emergency

Question 16

what is the pharmacological treatment for status epilepticus?

Answer 16

wait 5 mins, benzodiazepine, benzodiazepine, phenytoin, thiopentone/anaethesia (call intensive care/anaesthetics)

Question 17

benzodiazepines - mechanism, name ending, side effects

Answer 17

GABAa agonists, increased Cl- conductance = more negative resting potential so less likely to fire

-apam

be aware of addiction, CVS collapse, airway issues

Question 18

what are the benzodiazepine options for SE

Answer 18

IV lorazepam, diazepam rectally, midazolam buccal/intranasally

Question 19

investigations for seizures?

Answer 19

EEG, MRI which can detect vascular/structural abnormalities

Question 20

carbamazepine - mechanism, uses, side effects

Answer 20

Na channel blocker which slows the recovery of neurones from inactive to closed state so reduces neuronal transmission

used for bipolar and chronic pain sometimes

suicidal thoughts, joint pain, bone marrow failure

Question 21

phenytoin - mechanism, uses, kinetics, side effects

Answer 21

Na channel blocker, used mainly in SE or as an adjunct in generalised seizures

exhibits zero order kinetics so care when adjusting doses

bone marrow suppression, hypotension, arrhythmias

Question 22

sodium valproate - mechanism, side effects

Answer 22

mix of GABAa and Na channel blockade

liver failure, pancreatitis, lethargy

Question 23

lamotrigine - mechanism, uses

Answer 23

Na channel blocker, may block Ca channels too

good for focal epilepsy

used where valproate contraindicated in generalised epilepsy

Question 24

levetiracetam - mechanism, uses

Answer 24

synaptic vesicle glycoprotein binder - stops the realise of NTs into the synapse and reduces neuronal activity

option fo focal and generalised

safe in pregnancy

Question 25

what are general side effects of these drugs?

Answer 25

tiredness, n&v, mood changes and suicidal thoughts, osteoporosis, rashes including Steven Johnson syndrome, many can cause anaemia, thrombocytopenia or bone marrow failure

Question 26

which AEDs are CYP inducers/inhibitors?

Answer 26

inducers - phenytoin, carbamazepine, barbiturates

inhibitors - valporate