Epilepsy Flashcards
How does epilepsy occur?
As a result of abnormal electrical activity originating in brain which give rise of electrical storm that produces seizures
What is a seizure
Seizure is the abnormal movement/behaviour as a result of epilepsy
What are the types of seizures?
- Epileptic seizure
- Non-epileptic seizure (psychological/stress-induced)
- Provoked seizure (trauma/hypoglycaemia/drug-abuse)
When do idiopathic generalised seizure occur?
During childhood/adolescence (but may not be diagnosed till adulthood)
*can be EEG seizure but no nervous system abnormalities and normal intelligence
What are the types of idiopathic generalised seizures?
- General tonic-clonic (unconscious > muscle stiffening [tonic phase] > violent jerking [clonic phase] > deep sleep [post ictal phase])
- Absence (brief LOC; interrupts an activity & stares blankly; may occur several times a day)
- Myoclonic (sporadic jerking, both side of body jerking movements - jerks are described as electrical shocks)
- Clonic (rhythmic jerks of both sides of body - *may not be full body)
- Tonic (muscle stiffness/rigidity)
- Atonic (loss of muscle tone in all 4 limbs)
What is the difference between generalised and partial epilepsy?
Generalised = entire brain
Partial = small part of a brain
When do idiopathic partial epilepsy occur?
Begins in childhood and may be a part of fam hx
- outgrown by puberty and nvr diagnosed in adult
- seizure tends to happen during sleep
- partial motor seizure that involve face
*diagnosed by EEG
What are the types of idiopathic partial epilepsy?
- Simple (awareness intact)
a) motor (jerking, muscle rigidity, spasms, head turning)
b) sensory (unusual sensations involving 5 senses - vision, hearing, smell, taste, feel)
c) psychological (memory/emotional disturbances) - Complex (awareness impaired)
- automatism (lip smacking, chewing, fidgeting, walking, other repetitive, involuntary coordinated movements)
- Partial seizure with secondary generalisation
- conscious > LOC and convulsions
What is an aura?
- a warning sign of an impending seizure/feeling that seizure is coming
- not always present
- experience immediately before seizure
- a sensation (specific taste/smell)
What are the some triggers of epilepsy?
- Hypoglycaemia
- Alcohol
- Sleep deprivation
- Pyrexia
Who has a lower risk of recurrent seizures?
Patient who has
- a single seizure
- a normal EEG
- a normal brain scan
Who has a higher risk of seizures?
Patient who has
- previous/hx of undiagnosed seizures
- epileptiform EEG
- abnormal brain scans
What is the pathophysiology behind epilepsy?
Unbalanced excitatory and inhibitory receptor/ion channel function which favour depolarisation
Dysregulated discharge/synchronous firing of multiple neurons tgt from one region of a brain
What are the investigations for epilepsy?
- Electroencephalogram (EEG)
- May show normal waves between seizures so will need to use triggers like sleep deprivation and hyperventilation to elicit pathological mechanism
- Blood tests (LFT, blood chemistry)
- MRI/CT (May show abnormal brain structures)
*others - lab, spinal punctures
What are the main goals of antiepileptics?
To reduce membrane excitability by:
1. Altering Na+ and Ca2t (excitatory NT) conductance during action potentials
2. Enhance effects of inhibitory GABA NT (mainly signal through GABA receptors)
*not all compounds are effective against all types of seizures
What are the first-line anti-epileptics for newly diagnosed generalised and partial tonic-clonic seizures?
- Phenytoin
- Carbamazepine
- Valporate
Which of the first line antiepileptics are not for pregnant women and why?
Phenytoin - AE: tetragenic (birth defect: malformation of fetus/baby)
Which of the first line antiepileptics cause an accelerated elimination of other drugs, resulting in a need for an increased dosage of such drugs?
Carbamazepine
What is the MOA of phenytoin and carbamazepine?
Block voltage dependent Na channels = reduce excitatory Na signals
Which antiepileptic can be used for absence seizure?
Valporate
What is the implication of phenytoin?
Need to titrate and monitor phenytoin doses due to its narrow therapeutic index
Why do the dosage of other medications increase when taking carbamazepine?
Carbamazepine is a hepatic enzyme induce (CYP450), causing a med half life to shorten with repeated doses and accelerated elimination of other drugs (even carbamazepine)
What is the AE of carbamazepine?
Aplastic anaemia (bone marrow cannot produce all kinds of blood cells - potentially fatal)
What is the MOA of valporate?
Block voltage-dependent Na and Ca channels + inhibit GABA transaminase = increase GABA
