Epilepsy Flashcards
what is epilepsy
disease characterised by recurring seizures that occur spontaneously and unpredictably
What is the etiology of epilepsy
symptomatic epilepsy which is associated with anatomical or pathological abnormalities or clinical features indicative of an underlying disease such as brain injury, infections
Idiopathic epilepsy is related to genetic inheritance
What is a seizure
a transient occurence of signs and symptoms due to abnomal excessive or synchronous neronal activity in brain
what are the types of seizures
partial seizure in a restricted area and can be divided into simple and complex
generalised seizure involves the whole brain and can be divided into absence, myoclonic, tonic clonic and atonic
What are the types of simple partial seizures
simple motor seizures caused by lesion in the precentral gyrus of frontal lobe
Simple somatosensory caused by lesion near postcentral gyrus
simple visual caused by lesion near the occipital lobe
Describe complex partial seziures
begin with aura in form of illusion and abnormal cognitive state
then second phase with alteration of consciousness
arise in epileptogenic zone in hippocampus, parahippocampus area or amygdala
difference between simple partial seizure and complex partial seizure
in simple, they retain awareness, in complex they loss awareness , and simple seizures originate in the cerebral cortex while complex originate from hippocampus
What types can generalised seizures divide into
convulsive - tonic-clonic seizures
Nonconclusive - absence, atonic, myoclonic
Describe the three phase of tonic-clonic seizure
stage 1 : • loud choking noise as the entire body musculature is contracted
• air is forced out through partially closed vocal cords.
Patients fall to the ground in an unconscious state.
Phase 2 (tonic phase)
• Initial signs : brief flexion of trunk, opening of mouth, elevation of arms
• Rigid muscle extension lasting 15-20 minutes
Respiratory muscle spasm results in suspended breathing and there is often a loss of bowel and bladder control.
stage 3 (clonic phase ): • rhythmic muscle contractions lasting for 20-30 seconds • autonomic signs are present eg. dilated pupils, raised blood pressure, rapid pulse, salivation and sweating.
Describe the EEG of tonic-clonic seizure
in tonic phase, EEG shows decrease in frequency and increase in amplitude then discharges changes from continuous to intermittent burst of activity signalling the beginning
in clonic phase, intermittent burst of activity known as grouped polyspikes and are separated by quiet intervals
Bursts decreased in frequency
Describe absence seizures
involve an interruption to consciousness where the person experiencing the seizure seems to become vacant and unresponsive for a short period of time
divided into typical and atypical
can be treated with ethosuimide
Describe atonic seizure
sudden loss of tone in postural muscles, mild form is head drops, severe form is all postural muscles lose tone and patient collapse
Describe myoclonic seizures
- Consist of bilaterally synchronous involuntary muscle jerks that occur singly or in a brief salvo of repeated jerks
- can be restricted to only one muscle, while others involve large muscle masses including both arms and legs or even the entire body.
- Repetitive massive myoclonic jerks only occur without any alteration in consciousness
- Indicating that mechanism and anatomy underlying myoclonic seizure is different from other types of generalised epilepsy
Effect of status epilepticus
can lead to permanent CNS damage, if lesion in hippocampus can lead to memory los and confusion
What is the pathophysiology of sieuzre
Increase excitatory neurotransmitter input and decreased inhibitory neurotransmitter input or there is alterations in connectivity or in the activity of sodium or calcium channels that lead to hyperexcitable state leading to seizure
Explain the formation of EEG
neurons in epileptic focus can undergo large depolarisation - paroxysmal depolarising shift which cause firing of burst of high-frequency action potentials. After a silent period due to hyperopolarisation, the discharge spread and seizure occur
function of antiseizure drugs
to favour inhibition over excitation and stop or prevent seizure,
glutamate, Na, Ca channel blockers and GABA enhancers
Action of sodium channel blockers
- Prevent the return of the sodium channels to resting state (allow passage of sodium into cell) by stabilizing them in inactive state (channel does not allow passage of sodium)
* Prevent repetitive firing of axons without affecting normal transmission
Action of calcium channel blockers
they inhibit T-calcium channels which are activated at low potential, can induce calcium spike which depolarise neuron further provoking bursts or action potential
used to treat absence seizure
Action of GABA enhancers
drugs positively modulate GABA-A receptor by inhibiting GABA-reuptake (GAT) or metabolism (GABA-T)
• GABA binds to GABA-A receptor -> influx of Cl- into cells via chloride channels
• Increase negativity of cell
• More difficult for cell to reach threshold for firing action potential
Action of glutamate blockers
enhance removal of glutamate from synaptic cleft by excitatory amino acid transporter (EAAT)
when glutamate binds to AMPA, influx of sodium ions allowing depolarisation
What are some alternatives to pharmcological treatements
- Surgery
• Removal of causative lesion (tumour, blood clot), resection of white matter tracts preventing seizure from spreading- Ketogenic diet
• High-fat, low carbohydrate, adequate protein
• Mimic biological adaptions to fasting - Deep brain stimulation (to be explored)
• Increase activity of inhibitory pathways - Stem cell therapy (to be explored)
- Ketogenic diet
