CNS Week 5 Epilepsy Flashcards
Define seizure
A transient occurrence of signs and or symptoms due to abnormal excessive or synchronous neuronal activity in the brain
Define epilepsy
A pathologic and enduring tendency to have recurrent seizures
And
By the neuro-biologic, cognitive, psychological and social consequences of this condition
What is the difference between seizures and epilepsy
Seizures are a pathological pattern of neural activity and epilepsy is a tendency to recurrent seizures
What are the 2 main types of seizure
Generalised seizures: starts simultaenously in both hemispheres
Focal seizures: seizure starts in a focus and then spreads
What are the 3 types of common generalised seizures
Typical absence
Myoclonic
Tonic- clonic
What are absence seizures
Mainly childhood in onset
Frequent brief attacks (1-30s)
Sudden loss and return of consciousness
No aura and no post-ictal state
Some involuntary movements
Respond to some anti-epileptic drugs and not others
What are myoclonus seizures
Sudden brief shock like muscle contractions
Usually bilateral arm jerks
Often worse in the mornings
Precipitated by sleep deprivation and alcohol
Respond to particular anti epileptics
Describe tonic clonic seizures
Sudden onset, gasp, fall
Tonic phase with cyanosis
Clonic phase
Post-ictal phase (recovery is not instant)
Tongue bitten and incontinence, fractured shoulder
Noisy breathing
Headache and muscle pain afterwards
What are focal seizures
Often aura or warning at onset
As seizures spreads -> loss of awareness and involuntary movement
Often caused by brain lesions -> tumour, abscess, trauma
Describe temporal lobe seizures
Auras: rising sensation in stomach, olfactory and gustatory hallucinations, deja vu
As the seizure spreads the person suddenly stops and blank stares, loss of responding and awareness, mouth movements, fidgeting or postures- automatisms
What is idiopathic epilepsy
No brain lesions, no intellectual impairment, often generalised seizures
Easy to treat, seizures usually controlled
What is symptomatic epilepsy
Sign of underlying lesion or brain disorder, often cognitive problems, abnormal MRI common
Seizures not controlled
What are the key regulators of neuronal excitability
Non gated ion channels
- resting membrane potential
Voltage gated ion chanels
- Na+, K+, Ca2+, Cl-
Dendrite information processing
Action potential and repolarisation
What are epileptiform discharges due to
Neuronal bursting (an ion channel property)
Synaptic effects (both glutamate and GABA)
Glia effects
Non synaptic effects (eg extracellular K+)
What is epileptogenesis
The process following an injury that leads to the first of a series of spontaenous and recurring seizures
What structural changes occur in epileptogenesis
Cell loss inhibitory
Axonal sprouting
Neurogenesis
Gliosis
Neuro - inflammation
BBB breakdown
What molecular changes occur in epileptogenesis
Neuronal changes (Na, K, Ca, Cl, HCO3)
Neurotransmitter transporters
Neuro-modulators
What functional changes occur in epileptogenesis
Gap junctions
Glia: buffering of extracellular environment
How was the first anti epileptic drug developed (phenytoin)
Electrodes to rodents head
Shocked with electricity to induce seizure
Loaded with drug beforehand to see if it prevents electrical current from causing a seizure
Mode of action of vigabatrin
GABA transaminase inhibitor
Higher GABA levels prevent fading of inhibiton
Mode of action of tiagabine
GABA reuptake inhibitor
Higher GABA levels prevent fading of inhibition
In summary what are seizures caused by
Abnormal burst firing and synchronisation in normal / modified neural circuits
Steps for the management of epilepsy
Ensuring a correct diagnosis
Determining the cause
Deciding on treatment
Advising on lifestyle issues
4 different types of seizures
Absences
Myoclonus
Tonic clonic
Focal
Differentials for blackouts and funny turns
Epilepsy
Fainting
Cardiac causes
Psychological causes
Why is valporate a risk in women
Has a 6-10% malformation rate in pregnancy with subtle facial abnormalities
30-40% associated with low IQ and autism
Never give valporate to a woman 12-55 without specialist adivce
There is a valporate pregnancy prevention program where it is not prescribed unless the woman is fitted with a highly active contraceptive coil