Ch26+27 Seizures and Special Seizures Flashcards
What’s the definition of a seizure
an abnormal paroxysmal neuronal discharge that results in abnormal sensation, motor function, behaviour, or consciousness.
What’s a primary generalized seizure
Bilaterally symmetric and synchronous, involving both cerebral hemispheres as the onset, consciousness lost from the start. Approx 40% of all seizures.
What’s a partial/focal seizure
Implies one hemisphere involved a onset, about 57% of all seizures.
What’s a complex partial/focal seizure
Focal onset followed by either delayed impairment of consciousness, immediate impairment of consciousness, secondary generalisation
How does the 2017 International Leagues Against Epilepsy Classify Seizures?
Give three features that are typical of mesial temporal lobe epilepsy?
Aura (epigastric, emotional, olfactory, gustatory)
Complex partial oftern begin with arrest and stare
Postictal disorientation, recent-memory deficit and amnesia of ictus
Describe the feauture of juvenile myoclonic epilepsy
Myoclonic jersk
GTCS
Absence
Polyspike discharges on EEG
What’s West Syndrome?
Seizure disorder that begins in the first year of life
Recurrent gross flexion and occational extenstion of trunk and limbs
Seizures diminish with age
[responds to ACTH or corticosteroids]
EEG - hypsarrythmia
What’s Lennox-gastaut syndrome? And what is the surgical option?
Atonic seizures of childhood ‘ drop attacks’
Corpus Callosotomy
What factors lower the seizure threshold?
Sleep deprivation
Hyperventilation
Photic stimulation
Systemic infection
Metabolic derangement
Name two AEDs that interfere with platelet function?
Valproic acid
Phenytoin
What’s the dose of phenytoin for status? (BNF)
20mg/kg loading
Then 100mg TDS
What are the signs of phenytoin toxicity?
Nystagmus, diplopia, ataxia, asterixis, slurred speech, confusion, CNS depression
For a woman of childbearing age requiring an AED what is tradtional first choice?
carbamazepine
What birth defect is valproate associated with?
NTD (1-2%)
What’s the incidence of early (<7 days) post traumatic seizures in severe head injury? (severe e.g. LOC>24 hours, amnesia<24 hours, focal deficit, confusion, haematoma)
vs mild./moderate
30% severe
1% n mild to moderate
What’s the cindence of late post traamatic seizures (>7 days) in patients with significant head trauma (LOC>2 mins, GCS<8, epidural haematoma etc) within 2 years of HI?
10-13%
What the incidence of post traumatic seizures in penetrating head injuries (followed to 15 years)?
50%
Describe the evidence for the use of phenytoin for prophylaxis of post-traumatic seizures?
Temkin (1990) NEJM - Phenytoin reduces the risk of early but not late post traumatic seizures
Describe some features suggestive of pseudo/non-epileptic seizures
Arching of the back
Asynchnous movement
Stop and go (seizures usually build gradually)
Forced eye closure
Provoked with atypical stimuli
Bilateral shaking with preserved awareness (exception SMA seizures)
Weeping (whining)
Multiple or variable seizures types
What’s the most common type of seizure? What’s the prevalence?
Febrile convulsion. 2.7% prevalence in developmentally and other wise neurologically normal children
Define status epilepticus
Sz>5mins
Or persistent seizure activity with no neurological recovery in between (Not greenberg!)
What percentage of seizures that persists over 5 mins will continue over 1 hour?
61%
How do you manage status epilepticus?
ABCs
Benzodiazepine (e.g. lorazepam 4mg IV, midazolam 10mg IM, diazepam (can be rectal)
Load with phenytoin
Alternatives to phenytoin - valproate, phenobarbital, levetiracetam
If seizures continue >30 mins and are refractory - intubate and propofol or midazolam infusion
In an unknown patient presenting with status and hypoglycaemia what drug must you give before bolusing glucose?
Thiamine (giving glucose first in thiamine deficiency can precipitate Wernicke’s encephalopathy)
What’s the incidence of birth defects to mother’s with a known seizure disorder?
4-5% (double normal) - effect due to AED vs genetic vs environment unknown
What’s the mechanism of action of phenytoin?
Voltage-dependent block of sodium channels (prevents high-frequency repetitive firing)
What’s the mechanism of levetiracetam?
It inhibits Synaptic Vesicle 2A (SV2A) protein inhibitor (via calcium) reducing neurotransmitter release and acting a neuromodulator
What’s the mechanism of benzodiazepines?
They increase the affinity of GABA(A) receptor for GABA
What’s the mechanism of carbamazepine?
Sodium Channel Blocker
What’s the mechanism of valproate?
Believed to be mixed (sodium channels and increases GABA)
