Exam 3 lecture 6 Flashcards
Define myoclonic, tonic, clonic, atonic, tonic-clonic seizures
Myoclonic- shock-like contraction of muscles, isolated jerking of head, trunk and body
tonic- these seizures occur in children. involve rigidity as a result of increased tone in exterior muscle.
clonic- these seizures occur in babies and young children. Involve rapid, repetitive motor activity
Atonic- Sudden loss of muscle tone. Pt fall (drop attacks)
tonic-clonic- life threatening
Define seizure, epilepsy, convulsion (!!!)
Seizure- abnormal neuronal discharge with or without loss of consciousness
Epilepsy- repeated seizure due to damage, irritation, and/or chemical imbalance in the brain which leads to a sudden excessive, synchronous electrical discharge
Convulsion- specific seizure type where the attack is manifested by involuntary muscle contractions.
What are seizures a result of (!!!)
Seizures are a result of disordered, synchronous, and rhythmic firing of populations of brain neurons (synchronized hyperexcitability)
Prolonged seizure can lead to _______. Why?
Ischemia.
During a seizure, the brain uses more energy than it can manufacture, so prolonged seizure can result in cell eschemia.
Classify seizures (!)
focal onset
generalized onset
unknown onset
Define the types of seizures (!!!)
Focal onset- known spot where neurons fire to cause seizures. Classified into either aware or impaired awareness. Has motor onset and non motor onset. May progress to focal to bilateral tonic-clonic
Generalized onset- Classified to either motor (tonic clonic) or non motor (abscence seizures)
unknown onset- Classified into motor or non motor
compare focal and generalized seizures
focal- starts in temporal lobe. May progress to bilateral tonic clonic.
generalized- most are assumed to be genetic
difference in propagation between focal seizure and primary generalized seizures
focal- frequently progress to secondary generalized seizures via projections to the thalamus (focal to bilateral)
Primary generalized seizures- propagate via diffuse interconnections between thalamus and cortex. (no discrete focus) (involves both hemispheres of the brain)
focal seizures can be either ______ or _______
Focal seizures can be aware or impaired awareness
describe aware and impaired awareness focal seizures
Aware- 25% of focal seizures
no loss of consciousness
impaired awareness- most common focal seizure.
Clouding of consciousness, staring
Aura
postictal state due to impaired awareness
What is Postictal state? symptoms.
postictal state- After a seizure, a patient will not recover a normal level of consciousness immediately. May last seconds to hours depending on (area of brain affected, length of seizure, use of antiepileptic drugs, age)
symptoms- confusion, disorientation, anterogate amnesia
Describe generalized seizures (absence types)
Can be typical or atypical
typical- No convulsions, aura, or postictal period
atypical- slower onset than typical
Describe the generalized seizures
Generalized tonic-clonic-
1st phase- tonic phase- no aura
2nd phase- clonic phase
Focal-to-bilateral tonic-clonic seizures start out as a focal seizure
(this type of seizure was previously referred to as a ‘secondarily
generalized attack’). In this case there can be a brief aura.
Understand the characteristic properties of status epilepticus and the therapeutic goals in treating this state.
repetitive seizure activity in which the patient does not regain consciousness between seizures or a continous single seizure episode lasting >30 mins. could be life threatening.
Therapeutic goal is to bring seizures under control wiyhin 60 mins.
What is PDS? understand the electrophysiological basis of
depolarization and hyperpolarization.
The PDS consists of a large depolarization that triggers a burst of action potential
Depolarization- Involves activation of AMPA and NMDA channels by excitatory neurotransmitter glutamate and voltage gated calcium channels leading to an influx of cations.
depolarization if followed by hyperpolarization
Involving the activation of GABA receptors (influx of Cl- ions) and voltage and calcium dependent K channels leading to an efflux of K+
Neuronal signaling (depolarization) is normally dampened by
feed forward and feedback inhibition.
Does one seizure make an epilepsy? When can we dx therapy for epilepsy
No!
Drug therapy can be gradually withdrawn in
patients who have been clinically-free of
seizures for 2-5 years.
Which of the following types of convulsions can be preceded by
an aura phase?
(A) typical absence (petit-mal)
(B) primary generalized tonic-clonic (grand-mal)
(C) focal to bilateral (secondary generalized) tonic-clonic
(D) all of the above
Focal to bilateral (secondary generalized) tonic clonic
Define inhibitory surround
Electrical discharge spreads through the seizure focus but is contained as a result of inhibition in a neighboring zone called inhibitory surround.
What does the the evolution of focal seizure to generalized (bilateral) involve
Involves a loss of hyperpolarization and surround inhibition.
understand the electrophysiological basis for tonic phase and clonic phase
In tonic phase- GABA mediated inhibition disappears where as glutamate mediated AMPA and NMDA receptor activity increases
In clonic- GABA mediated inhibition disappears gradually returns leading to a period of oscilliation.
What happens as GABA mediated inhibition breaksdown during tonic phase
Action potentially propagate to a distant neurons, leading to spread of seizure activity from focus to distant sites in the brain.
Describe underlying conditions or environmental perturbations that can trigger epileptic seizures
Pre natal injury
CVD
Brain tumors
Head trauma
infection
hemorrhage
drugs
metabolic disturbances (hyperventilation, blood gas, PH, hypoglycemia)
sleep deprivation
stress
withdrawal from AEDs
Identify drugs that aggrevate or increase seizure risk
-alcohol
-theophyline
-CNS stimulants
-bupropion
-oral contraceptive
-withdrawals from depressants
-clonzapine
