14 - Seizure Disorders Flashcards
1
Q
Define seizure
A
Abnormal, paroxysmal, excessive firing of CNS neurons – transient event
2
Q
Define epilepsy
A
Chronic condition characterized by recurrent seizures which aren’t provoked by systemic or acute neurologic insults
3
Q
Define status epilepticus
A
Seizure lasting >/ 30 minutes or >/ 2 sequential seizures w/o return to normal mental baseline
4
Q
Initial evaluation of seizure
A
- When pt presents w/ first seizure, need to rule out physiologic (and possibly treatable) causes before beginning therapy for seizure disorder, or epilepsy
- This evaluation will help determine the likelihood of future seizures and assist w/ deciding if anti-seizure therapy is warranted
- Hx and physical exam, lab tests (CBC, electrolytes, glucose, hepatic and renal function, etc.), blood/urine tox screen for drugs (to rule out provoked seizure), EEG, CT/MRI to rule out brain tumour or bleeding
5
Q
Diagnosing epilepsy
A
- At least 2 unprovoked (or reflex) seizures occurring > 24 h apart
- Unprovoked = a cause that we can’t fix
- Can also diagnose after 1 seizure based on px hx & risk factors (> 60% chance of having another seizure)
6
Q
Types of seizures
A
- Focal = seizure activity starts in one area of the brain
- Generalized = seizure activity involves both hemispheres of the brain
- Tonic = stiff/flexed; tend to fall backwards
- Clonic = convulsions
- Myoclonic = short muscle twitches
- Atonic = relaxed; tend to fall forward
- Tonic-clonic = tonic phase + clonic phase (alternates between flexion and convulsion)
- Absence = “spaced out”
7
Q
Physiology applicable to seizures
A
- In normal synaptic transmission, there is a balance between inhibitory and excitatory transmission
- Inhibitory = GABA binds to post-synaptic GABAa receptor to open Cl- ion channels & allow influx (hyperpolarized postsynaptic neuron = less likely to “fire”)
- Excitatory = glutamate binds to glutamate receptor (NMDA or non-NMDA type); net result is excitatory postsynaptic potential (ready to “fire)
8
Q
Target for most anti-epileptic drugs (AEDs)
A
- Enhanced excitation (glutamate)
- Membrane depolarization (affecting ion channel Na+, Ca2+, K+ currents)
- Reduced inhibition (GABA)
9
Q
Goals of therapy for seizure disorders
A
- Eliminate seizures (reduce frequency and severity)
- Minimize side effects
- Optimize QOL – address comorbid anxiety, depression
10
Q
Natural hx of treated epilepsy
A
- 60-65% are seizure free (most are w/ one drug but some require more than one)
- Remission: complete cessation of seizures (seizure-free) for at least 1 year
- 30-40% are not controlled
- Refractory: 2 or more AEDs failed to control seizures (appropriate drug, appropriately dosed, tolerated)
- *Majority of px are controlled w/ their first monotherapy, but some require second or third monotherapy or more than 1 drug simultaneously
11
Q
General principles for tx of seizure disorders
A
- Verify diagnosis and determine etiology if possible
- Review seizure description to ensure correct classification
- Match choice of AED to seizure type and to specific pt
- Use monotherapy if possible; polytherapy if necessary
- When adding an AED start low and go slow, but if needed push to max tolerated dose
- Consider changing the timing of dosing to reduce toxicity
- Use clinical response and PK principles to fine-tune dose
- Adjust doses for drug-drug interactions (**AEDs have many interactions)
- Don’t give up
12
Q
Justifying your selection fo AED **know this
A
- Is a drug indicated? (if pt is diagnosed w/ epilepsy)
- Is the selected drug effective? – evidence vs. clinical experience
- Is the selected drug safe? – most common/ serious SE, drug interactions, comorbidities
- Is the selected drug convenient? – available, affordable, relatively easy to take
- Do you have money to pay for this if it isn’t covered?
- Are you likely to remember to take this medication every day?
13
Q
How to determine if an AED is indicated for a pt
A
- Generally, once a pt meets the criteria for diagnosis of epilepsy tx is indicated
- Clinical decision process to treat first-time unprovoked seizures not diagnosed as epilepsy is very pt specific and depends on multiple clinical factors
- Weigh risk of seizure recurrence against adverse effects of AEDs (and consider pt preferences)
14
Q
Recommended drug therapy for different seizure types to know**
A
- Focal (adult) – carbamazepine, levetiracetam, valproic acid
- Generalized tonic-clonic (adult) – carbamazepine, lamotrigine, oxcarbazepine, valproic acid
- Absence (children) – ethosuximide, valproic acid
15
Q
Most common SEs for all AEDs
A
- CNS side effects
- Drowsiness, sedation, fatigue
- Incoordination
- Dizziness
- Cognitive impairment (mental dulling, memory, concentration)
- Diplopia (double vision)
- *May be comparatively worse w/ phenobarbital, carbamazepine, & topiramate
- GI side effects -> diarrhea, cramping
- Toxicities are additive (ie: worse w/ each additional AED added)
