Mon. 11/02 - Epilepsy Flashcards
What is epilepsy?
- Chronic neurological disorder characterized by recurrent seizures – hyperexcitable, “irritable” neurons
- One seizure is not epilepsy
What is the neurological substrate of seizures? / Define seizure
Generally neurons fire in specific patterns and in a sort of synchrony. Seizures are the upset of this balance.
Seizure is an episode of sudden, transient disturbance in cerebral excitation, neurons firing rapidly in synchronized bursts.
What is generalization of seizures?
Neurons firing all at the same time
A focus (group) of neurons is hyperexcitable, which can affect other populations of neurons
Differentiate seizures and convulsions:
Convulsions indicate a seizure, but a seizure doesn’t always include convulsions.
True or false: all seizures include a loss of consciousness
False
The population more prone to fever seizures:
Young children
What increases the likelihood of a fever seizure?
How fast the fever increases in a febrile episode
Seizure Classification (3)
Focal (partial)
Generalized
Unknown = anything that does not fit into the other two categories
Sub-types of partial seizures (2)
Simple
Complex
Characteristics of Simple Seizures (4)
- Focal area,
- Unilateral motor or autonomic responses, including convulsion
- Full consciousness
- Difficult to catch/ recognize
Characteristics of Complex Seizures (3-4)
- Focal area,
- Bilateral, resulting in a wide variety of manifestations and bizarre behaviors
- Altered consciousness
(75% originate in the temporal lobe)
What neurological pattern could a generalized seizure follow?
Can start as a partial and spread via the thalamus to affect the entire brain.
Subtypes of Generalized Seizures (7)
- Absence
- Myoclonic
- Tonic -clonic
- Clonic
- Tonic
- Atonic
- Status epilepticus
Describe the two phases of tonic- clonic seizures
Tonic Phase: rigid body, clenched jaw and hands, sustained contraction of all muscles
Clonic Phase: begins with rhythmic jerky movements ending with relaxation of all body muscles
True or false: Tonic-Clonic seizures are associated with major convulsions of the entire body and loss of consciousness.
True
Describe Absence seizure/ Typical Symptoms
Sudden, brief loss of consciousness
motor signs may be absent or may range form rapid eye-blinking to symmetrical jerking movements of entire body
Describe Myoclonic seizure / Typical Symptoms
Sudden, brief “shock-like” contraction (single or multiple) of the muscles in the face and trunk or in one or more extremities;
consciousness may be impaired
Describe Clonic seizure / Typical Symptoms
Rhythmic, synchronized contractions throughout body; loss of consciousness
Describe Tonic seizure / Typical Symptoms
Generalized sustained muscle contraction throughout body; loss of consciousness
Describe Atonic seizure / Typical Symptoms
Sudden loss of muscle tone in the head and neck, one limb or throughout the entire body
consciousness can be maintained or lost briefly
What causes seizures? (6, 7 from G and F, 4 more from Dr. T)
Head injury Fatigue Hypoglycemia Changes in electrolytes Fever (febrile seizures) & illness (infection) Missed medication
From Goodman and Fuller:
- Stress
- Poor nutrition/ skipped meals
- Flickering lights
- Allergies
- Lack of sleep
- Anger, worry, fear
- Heat and humidity
Dr. T also listed congenital, birth trauma, anoxia, and genetic as causes
What is the major role of the thalamus in epilepsy?
-Is the path to the cortex
-If the hyperexcitability affects the electrical activity of the thalamus, this has widespread effects to the cortical areas.
Name the only thalamic nucleus that does NOT project directly to the cortex.
Nucleus Reticularis
What type of cells are found in the Nucleus Reticularis
GABAergic
How does Nucleus Reticularis modulate the activity of the other thalamic nuclei?
The nucleus reticularis, while consisting of inhibitory interneurons, actually works by disinhibition, so it has an overall excitatory effect. This is an example of how a GABAergic cell can have overall excitatory effects.
This nucleus is essential for initiation of movement.
Nucleus reticularis is very impotant in mov initiation -> convulsions in seizures
Name the three antiseizure drug strategies:
- Increase the activity of CNS inhibitory neurons
- Decrease the activity of CNS excitatory neurons
- Stabilize the opening and closing of Na+ or Ca++ channels
Which neurotransmitter is targeted to decrease the activity of excitatory neurons?
Glutamate (excitatory)
Glutamate receptors are a favorite pharmacological target to decrease excitability.
Name the two types of glutamate receptors
- NMDA
2. AMPA
What type of channel does the NMDA receptor open?
Ca++ channels causing depolarization.
What does hyper-excitability lead to?
Hyper-excitability leads to prolonged NMDA receptor activation and large increases in intra-cellular calcium concentration. During the seizure, the neurons will fire continuously (tonic phase). The seizure ends when repolarization of the membrane occurs (clonic phase).
What type of channels do AMPA receptors open?
Na+ channels also cousing depolarization
Which neurotransmitter is targeted to increase the activity of inhibitory neurons?
GABA - Major inhibitory neurotransmitter
What type of channels do GABA receptors open?
Cl- channels causing hyper-polarization
What is the mechanism of GABA receptors?
increase inhibition
What are the barbiturates and benzodiazepines effect over GABA receptors?
Both increase the inhibitory effects of GABA
Barbiturates serve as GABA agonists.
Benzodiazepines work by increasing the amount of chloride that can flow through the channel, so help to further hyper-polarize and increase inhibition.
Can barbiturates and benzodiazepines be prescribed together?
Yes, but definitely don’t drink with these!
What effect does positive ion (Ca++ and Na+) entry have on a neuronal membrane?
Depolarization
True or false: Sodium and calcium channels (not glutamate receptor associated ones), are another pharmacological target for control of seizures.
True
What are the 3 major pharmacological targets for control of seizures?
- Glutamate receptors
- GABA receptors
- Ca++ and Na+ channels
How do you think dehydration could lead to seizure activity?
Dehydration will increase the Na+ concentration inside the cell, increase depolarization (excitation) and precipitate the seizure.