NR 507
WEEK 8 EDAPT
CNS BRAIN DISORDERS
SEIZURES AND EPILEPSY
, 1
CNS Brain Disorders and Dermatological Conditions
Seizures are uncontrolled neurons firing in the brain. This
random neuron activity can be caused by a lot of different
things. What results is a loss or change of consciousness
that could be life-threatening if the patient’s airway or
body is not protected from injury. Everyone can have a
seizure, but when the cause is irreversible or requires
chronic treatment, it becomes a seizure disorder called
epilepsy. Seizure prevention depends on the cause and
triggers.
After completing this module, you will be able to:
• List some of the pathophysiologic factors causing seizures and epilepsy.
• Describe the characteristics and types of seizures.
• Discuss risk factors and prevention strategies for seizures.
• Review common testing and treatments used to find and treat seizures.
Seizure Pathophysiology
Seizures are caused by the increased activation or
decreased inhibition of neurons in an area of the brain, causing
random electrical signals across multiple neuronal
pathways. Gamma-aminobutyric (GABA) are inhibitory neurons
that may be defective or influenced by other mechanisms. This
causes neurons to depolarize in a disorganized manner, which
may cascade through neuron depolarization across many of the
major neurons, first in the brain and then across the body.
While the mechanism for seizure activity is not always clear, it
may be caused by:
• A change in permeability of the neuronal membrane: this can affect sodium and calcium channels
within the neurons.
• Neurotransmitter imbalances: a defect in the inhibitory neuron.
• Reduced ability of neurons to exercise inhibitory control: by excitatory neurotransmitters over-
powering inhibitory neurons (GABA).
Epilepsy is a disorder that is due to one or more chronic conditions in the body. It is characterized by disturbed
nerve cell activity in the brain. This leads to recurrent seizures. Seizures may occur due to brain trauma that
leads to disturbed and uncontrolled nerve activity in the brain. It is important to differentiate between
epilepsy and seizure.
Seizure is a condition that occurs due to excessive and uncontrolled neuronal activity in the brain. The
uncontrolled neuron activity can be generalized or localized to one area of the brain. For example, it can be
localized just to the area that perceives the touch sensation. Whether it is generalized or localized, the
, 2
excessive neuronal activity lead to the seizure. The type of seizure will depend on the area of the brain
affected.
Mechanisms of Seizure Development
Normally there exists a balance between the excitation and inhibition of neurons in the CNS. Neuronal activity
is regulated by acetylcholine (ACH) and gamma-Aminobutyric acid (GABA). Neurons are synchronously active
at the same time when they are not supposed to be.
The term active denotes neuron firing where they are
sending electrical signals from neuron to neuron. A
microscope view of a neuron will demonstrate that
each electrical signal that passes through it are just
ions floating in and out through protein channels (see
diagram below). The ion flow is controlled through
neurotransmitters. Neurotransmitters bind to the
receptors to tell the cell to either open the ion
channels to relay the chemical message (excitatory
neurotransmitters) or close the ion channels to inhibit
the electrical message (inhibitory neurotransmitters).
Phases of Seizures
During a seizure, clusters of neurons in the brain become temporarily impaired. Seizures develop in a group of
neurons when there is hyperexcitability and usually happens in two phases:
1. Initiation phase: Some neurons become hyperexcited and start to have excess neuron discharges. One
of the most important reasons relates to the body’s sodium level as in the case of hyponatremia.
2. Propagation phase: Normally the neurons that have
neuronal discharges are surround by a zone of
inhibitory neurons called the zone of
hyperpolarization. This zone prevents the spread of
excessive neuron discharges to other parts of the brain.
But due to some abnormality in the brain, as in the case
of decreased sodium levels, the zone of
hyperpolarization gets depolarized that allows the
spread of neurons to other parts of the brain.
In the diagram below, the electrical activity in the normal brain
is displayed. Seizures can be partial or generalized in terms of the
extent of the neuronal discharges. In a partial seizure, a
portion of the brain is involved. During a generalized seizure, the
neuronal discharge encompasses the entire cerebral cortex.
Etiology of Seizures
To remember seizure etiology, use the
acronym Vitamins D:
, 3
Types and Classifications of Seizures
Generalized seizures: Generalized seizures usually start at one place in the brain and due to widespread
neuronal networks, they spread through that whole cerebral cortex. The main characteristic of a generalized
seizure is that there is spread of the seizure. One of the major structures that helps in the spread is the corpus
callosum. It connects the right and left-brain hemispheres and because of this the seizure spreads to the other
hemisphere of the brain.
Below are the different types of generalized seizures. Match each type to their proper characteristics. Click the
type of generalized seizure and then click the correct characteristics. Click again to deselect.
• Generalized tonic-clonic seizures: there is wide-spread and uncontrolled neuron activity in the entire
cerebral cortex. These occur in 10% of patients who have epilepsy. There is excessive neuronal
discharge in the motor nerves through the brain.
o Tonic-clonic phase (lasts 10-20 seconds): Due to the excessive discharge of neurons in the
motor nerves that results in:
▪ the muscles of the body become contracted. without any relaxation.
▪ loss of consciousness.
▪ ictal cry. This is a typical sound produced by the tonic contractions of the laryngeal
muscles and muscles of expiration.
▪ respiratory impairment that results in cyanosis.
▪ tonic contraction of the jaw muscles that can cause tongue biting.
▪ Increased sympathetic activity. This will cause increased heart rate and blood pressure
o Clonic phase (lasts one minute): continuous discharge of neurons gets interrupted. It is
characterized by small durations of relaxation. This occur because of inhibitory mechanisms of
the brain to try to control the wide-spread neuronal activity. The patient will exhibit spasms and
jerking. This is perceived as violent shaking of muscles.
o Post-ictal phase (lasts one to two hours): this stage is characterized by confusion,
unresponsiveness and muscle flaccidity. Following the post-ictal state, there will be a return to
normal state of consciousness.
• Generalized tonic seizures: this seizure is characterized by unconsciousness and muscle rigidity.
• Generalized clonic seizures: this seizure is characterized by muscle spasms.
• Generalized absence seizure: this seizure is most common in children. It is caused by a genetic
abnormality. They are characterized by sudden and brief loss of consciousness without muscle tone
and last for only a few seconds. There is no associated post-ictal confusion.
Post-Seizure Symptoms
1. Post-ictal confusion.
2. Paralysis that affects the arms and legs that is usually limited to one side of the body (Todd’s paralysis
or paresis). It can last on average 15 hours and subsides completely by itself within two days. The exact
mechanism behind Todd’s paralysis is not well-known but may be due to temporary but severe
suppression of activity of the area of the brain affected by the seizure.
Overall, in generalized seizures, it involves both hemispheres of the brain where the patient will lose
consciousness briefly or over a long period of time. If the seizures do last for a long period of time (> 5 minutes
with ongoing seizure) or the individual has multiple seizures without returning to normal in between, this is
called status epilepticus. It is characterized by a clonic-tonic type sub-seizure. It can also be caused by other
types that don’t involve convulsions. This situation is considered a medical emergency and can be life
WEEK 8 EDAPT
CNS BRAIN DISORDERS
SEIZURES AND EPILEPSY
, 1
CNS Brain Disorders and Dermatological Conditions
Seizures are uncontrolled neurons firing in the brain. This
random neuron activity can be caused by a lot of different
things. What results is a loss or change of consciousness
that could be life-threatening if the patient’s airway or
body is not protected from injury. Everyone can have a
seizure, but when the cause is irreversible or requires
chronic treatment, it becomes a seizure disorder called
epilepsy. Seizure prevention depends on the cause and
triggers.
After completing this module, you will be able to:
• List some of the pathophysiologic factors causing seizures and epilepsy.
• Describe the characteristics and types of seizures.
• Discuss risk factors and prevention strategies for seizures.
• Review common testing and treatments used to find and treat seizures.
Seizure Pathophysiology
Seizures are caused by the increased activation or
decreased inhibition of neurons in an area of the brain, causing
random electrical signals across multiple neuronal
pathways. Gamma-aminobutyric (GABA) are inhibitory neurons
that may be defective or influenced by other mechanisms. This
causes neurons to depolarize in a disorganized manner, which
may cascade through neuron depolarization across many of the
major neurons, first in the brain and then across the body.
While the mechanism for seizure activity is not always clear, it
may be caused by:
• A change in permeability of the neuronal membrane: this can affect sodium and calcium channels
within the neurons.
• Neurotransmitter imbalances: a defect in the inhibitory neuron.
• Reduced ability of neurons to exercise inhibitory control: by excitatory neurotransmitters over-
powering inhibitory neurons (GABA).
Epilepsy is a disorder that is due to one or more chronic conditions in the body. It is characterized by disturbed
nerve cell activity in the brain. This leads to recurrent seizures. Seizures may occur due to brain trauma that
leads to disturbed and uncontrolled nerve activity in the brain. It is important to differentiate between
epilepsy and seizure.
Seizure is a condition that occurs due to excessive and uncontrolled neuronal activity in the brain. The
uncontrolled neuron activity can be generalized or localized to one area of the brain. For example, it can be
localized just to the area that perceives the touch sensation. Whether it is generalized or localized, the
, 2
excessive neuronal activity lead to the seizure. The type of seizure will depend on the area of the brain
affected.
Mechanisms of Seizure Development
Normally there exists a balance between the excitation and inhibition of neurons in the CNS. Neuronal activity
is regulated by acetylcholine (ACH) and gamma-Aminobutyric acid (GABA). Neurons are synchronously active
at the same time when they are not supposed to be.
The term active denotes neuron firing where they are
sending electrical signals from neuron to neuron. A
microscope view of a neuron will demonstrate that
each electrical signal that passes through it are just
ions floating in and out through protein channels (see
diagram below). The ion flow is controlled through
neurotransmitters. Neurotransmitters bind to the
receptors to tell the cell to either open the ion
channels to relay the chemical message (excitatory
neurotransmitters) or close the ion channels to inhibit
the electrical message (inhibitory neurotransmitters).
Phases of Seizures
During a seizure, clusters of neurons in the brain become temporarily impaired. Seizures develop in a group of
neurons when there is hyperexcitability and usually happens in two phases:
1. Initiation phase: Some neurons become hyperexcited and start to have excess neuron discharges. One
of the most important reasons relates to the body’s sodium level as in the case of hyponatremia.
2. Propagation phase: Normally the neurons that have
neuronal discharges are surround by a zone of
inhibitory neurons called the zone of
hyperpolarization. This zone prevents the spread of
excessive neuron discharges to other parts of the brain.
But due to some abnormality in the brain, as in the case
of decreased sodium levels, the zone of
hyperpolarization gets depolarized that allows the
spread of neurons to other parts of the brain.
In the diagram below, the electrical activity in the normal brain
is displayed. Seizures can be partial or generalized in terms of the
extent of the neuronal discharges. In a partial seizure, a
portion of the brain is involved. During a generalized seizure, the
neuronal discharge encompasses the entire cerebral cortex.
Etiology of Seizures
To remember seizure etiology, use the
acronym Vitamins D:
, 3
Types and Classifications of Seizures
Generalized seizures: Generalized seizures usually start at one place in the brain and due to widespread
neuronal networks, they spread through that whole cerebral cortex. The main characteristic of a generalized
seizure is that there is spread of the seizure. One of the major structures that helps in the spread is the corpus
callosum. It connects the right and left-brain hemispheres and because of this the seizure spreads to the other
hemisphere of the brain.
Below are the different types of generalized seizures. Match each type to their proper characteristics. Click the
type of generalized seizure and then click the correct characteristics. Click again to deselect.
• Generalized tonic-clonic seizures: there is wide-spread and uncontrolled neuron activity in the entire
cerebral cortex. These occur in 10% of patients who have epilepsy. There is excessive neuronal
discharge in the motor nerves through the brain.
o Tonic-clonic phase (lasts 10-20 seconds): Due to the excessive discharge of neurons in the
motor nerves that results in:
▪ the muscles of the body become contracted. without any relaxation.
▪ loss of consciousness.
▪ ictal cry. This is a typical sound produced by the tonic contractions of the laryngeal
muscles and muscles of expiration.
▪ respiratory impairment that results in cyanosis.
▪ tonic contraction of the jaw muscles that can cause tongue biting.
▪ Increased sympathetic activity. This will cause increased heart rate and blood pressure
o Clonic phase (lasts one minute): continuous discharge of neurons gets interrupted. It is
characterized by small durations of relaxation. This occur because of inhibitory mechanisms of
the brain to try to control the wide-spread neuronal activity. The patient will exhibit spasms and
jerking. This is perceived as violent shaking of muscles.
o Post-ictal phase (lasts one to two hours): this stage is characterized by confusion,
unresponsiveness and muscle flaccidity. Following the post-ictal state, there will be a return to
normal state of consciousness.
• Generalized tonic seizures: this seizure is characterized by unconsciousness and muscle rigidity.
• Generalized clonic seizures: this seizure is characterized by muscle spasms.
• Generalized absence seizure: this seizure is most common in children. It is caused by a genetic
abnormality. They are characterized by sudden and brief loss of consciousness without muscle tone
and last for only a few seconds. There is no associated post-ictal confusion.
Post-Seizure Symptoms
1. Post-ictal confusion.
2. Paralysis that affects the arms and legs that is usually limited to one side of the body (Todd’s paralysis
or paresis). It can last on average 15 hours and subsides completely by itself within two days. The exact
mechanism behind Todd’s paralysis is not well-known but may be due to temporary but severe
suppression of activity of the area of the brain affected by the seizure.
Overall, in generalized seizures, it involves both hemispheres of the brain where the patient will lose
consciousness briefly or over a long period of time. If the seizures do last for a long period of time (> 5 minutes
with ongoing seizure) or the individual has multiple seizures without returning to normal in between, this is
called status epilepticus. It is characterized by a clonic-tonic type sub-seizure. It can also be caused by other
types that don’t involve convulsions. This situation is considered a medical emergency and can be life
