EMS Neurological Emergencies - Seizure Disorder Pathophysiology

The pathophysiology of seizures involves complex changes in the electrical activity of the brain, leading to abnormal synchronization of neuronal firing and the generation of seizure activity. 

While the precise mechanisms underlying seizures can vary depending on the type of seizure and the underlying cause, there are several key components involved in the pathophysiology of seizures:

Neuronal Hyperexcitability: Seizures are characterized by abnormal, excessive, and synchronous neuronal activity in the brain. 

This hyperexcitability can arise from various factors, including changes in ion channel function, neurotransmitter imbalance, or alterations in neuronal connectivity.

Ion Channel Dysfunction: Ion channels play a crucial role in regulating the flow of ions (such as sodium, potassium, calcium, and chloride) across neuronal cell membranes, which is essential for maintaining normal neuronal excitability and function. 

Dysfunction of ion channels, either through genetic mutations or acquired alterations, can lead to abnormalities in neuronal excitability and contribute to seizure generation.

Imbalance of Excitatory & Inhibitory Neurotransmission: Normal brain function relies on a delicate balance between excitatory and inhibitory neurotransmission. 

Excitatory neurotransmitters, such as glutamate, promote neuronal activation, while inhibitory neurotransmitters, such as gamma-aminobutyric acid (GABA), dampen neuronal activity. 

Imbalances in the relative levels or function of these neurotransmitters can disrupt the normal inhibitory control of neuronal firing and contribute to seizure generation.

Aberrant Synchronization of Neuronal Firing: Seizures result from the abnormal synchronization of neuronal firing, leading to hypersynchronous activity within neuronal networks. This synchronized firing can spread rapidly throughout the brain, resulting in the characteristic clinical manifestations of seizures.

Network Dysfunction: Seizure activity often involves multiple brain regions and networks. 

Abnormalities in the connectivity and communication between different brain regions can facilitate the propagation of seizure activity and contribute to the generation of seizures.

Excitotoxicity & Neuroinflammation: Prolonged or recurrent seizure activity can lead to excitotoxicity, a process in which excessive release of excitatory neurotransmitters, such as glutamate, results in neuronal damage and cell death. 

Additionally, seizures can trigger neuroinflammatory processes, further exacerbating neuronal dysfunction and contributing to seizure generation.

Structural & Metabolic Factors: Structural abnormalities in the brain, such as tumors, vascular malformations, or cortical dysplasia, can disrupt normal neuronal circuitry and increase the likelihood of seizure activity. 

Metabolic disturbances, such as hypoglycemia, electrolyte imbalances, or mitochondrial disorders, can also trigger seizures by affecting neuronal function.

Overall, the pathophysiology of seizures involves a complex interplay of genetic, molecular, cellular, and network-level processes that lead to abnormal neuronal excitability and synchronization. 

Understanding these mechanisms is essential for developing targeted therapies aimed at preventing or controlling seizure activity.

Further Reading:

Bledsoe, B. E., Cherry, R. A. & Porter, R. S (2023) Paramedic Care: Principles and Practice (6th Ed) Boston, Massachusetts: Pearson

Huff, J.S. & Murr, N (2023) Seizure. Treasure Island, Florida: StatPearls Publishing https://www.ncbi.nlm.nih.gov/books/NBK430765/ Accessed April 24, 2024

Peate, I. & Sawyer, S (2024) Fundamentals of Applied Pathophysiology for Paramedics. Hoboken, New Jersey:  Wiley Blackwell

EMS Neurological Emergencies - Seizure Disorder Causes

The causes of seizures can vary widely and may depend on factors such as age, medical history, genetics, and environmental influences. 

Here are some common causes and risk factors associated with seizures:

Epilepsy: Epilepsy is a neurological disorder characterized by recurrent seizures. It can have various causes, including genetic factors, brain injury, infections, developmental disorders, and structural abnormalities in the brain.

Traumatic Brain Injury: Head injuries, such as those sustained in motor vehicle accidents, falls, or sports-related injuries, can lead to seizures. Traumatic brain injury (TBI) can disrupt normal brain function and increase the risk of seizures.

Brain Tumors: Tumors in the brain can cause seizures by interfering with normal brain activity or increasing intracranial pressure. Seizures may be a presenting symptom of a brain tumor.

Strokes: A stroke, which occurs when blood flow to the brain is disrupted, can lead to seizures, especially if the stroke affects certain areas of the brain responsible for regulating electrical activity.

Infections: Infections of the central nervous system, such as meningitis, encephalitis, or brain abscesses, can trigger seizures. These infections can cause inflammation and damage to brain tissue, leading to abnormal electrical activity.

Genetic Factors: Some seizure disorders have a genetic component, meaning they run in families. Mutations in certain genes can predispose individuals to develop epilepsy or other seizure disorders.

Metabolic Disorders: Metabolic imbalances, such as low blood sugar (hypoglycemia), electrolyte abnormalities, or kidney or liver failure, can provoke seizures by disrupting normal brain function.

Drug or Alcohol Withdrawal: Abrupt discontinuation of certain medications, especially anti-epileptic drugs or benzodiazepines, can trigger seizures. Similarly, alcohol withdrawal syndrome can lead to seizures in chronic alcoholics.

Toxic Exposure: Exposure to certain toxins, such as lead, carbon monoxide, or certain chemicals, can impair brain function and induce seizures.

Developmental Disorders: Some developmental disorders, such as autism spectrum disorder or cerebral palsy, are associated with an increased risk of seizures.

It's important to note that not all seizures have a clear identifiable cause, and in some cases, the cause may remain unknown (idiopathic). 

Proper evaluation and diagnosis by a healthcare professional are necessary to determine the underlying cause of seizures and guide appropriate treatment and management strategies.

Further Reading:

Alexander, M. & Belle, R. (2017) Advanced EMT: A Clinical Reasoning Approach (2nd Ed). Hoboken, New Jersey: Pearson Education

Bledsoe, B. E., Cherry, R. A. & Porter, R. S (2023) Paramedic Care: Principles and Practice Volume 2 (6th Ed) Pearson.

Mistovich, J. J. & Karren, K. J. (2014) Prehospital Emergency Care (11th Ed). Hoboken, New Jersey: Pearson Education

Online Resources:

EpilepsyU

EMS Neurological Emergencies - Seizure Disorder Classification

Seizure disorders can be classified into several types based on their characteristics and underlying causes. 

Here are some common types of seizure disorders:

Generalized Seizures:

Tonic-Clonic Seizures: These seizures involve loss of consciousness, muscle stiffening (tonic phase), followed by rhythmic jerking of the limbs (clonic phase). They can be associated with convulsions and may result in injuries. Formerly known as Grand Mal Seizures.

Absence Seizures: Absence seizures typically occur in children and involve brief periods of staring or "spacing out." The person may appear to be unaware of their surroundings and may not remember the seizure afterward. Formerly known as Petit Mal Seizures.

Myoclonic Seizures: These seizures involve sudden, brief muscle jerks or twitches, often affecting the arms and legs. They can occur in various epilepsy syndromes.

Atonic Seizures: Atonic seizures cause sudden loss of muscle tone, leading to the person collapsing or falling ("drop attacks"). These seizures can result in injuries due to falls. Also known as Drop Attacks.

Partial (Focal) Seizures:

Simple Partial Seizures: These seizures affect a specific area of the brain and may cause twitching, sensory changes, or other symptoms without loss of consciousness.

Complex Partial Seizures: Complex partial seizures involve altered consciousness or awareness, with or without automatisms (repetitive, purposeless movements) and other behavioral changes. They may start as simple partial seizures and progress to affect larger areas of the brain.

Focal to Bilateral Tonic-Clonic Seizures: Focal seizures that spread to involve both hemispheres of the brain, resulting in generalized tonic-clonic activity.

Other Types:

Febrile Seizures: These seizures occur in young children as a result of fever, typically between the ages of 6 months and 5 years. They are usually brief and do not cause long-term harm.

Psychogenic Non-Epileptic Seizures: Some seizures may mimic epileptic seizures but are not caused by abnormal electrical activity in the brain. These may be due to psychological factors or other medical conditions.

It's important to note that within each type of seizure, there can be variations in presentation and severity. Proper diagnosis and classification of seizures are essential for determining appropriate treatment and management strategies. 

Further Reading:

Alexander, M. & Belle, R. (2017) Advanced EMT: A Clinical Reasoning Approach (2nd Ed). Hoboken, New Jersey: Pearson Education

Bledsoe, B. E., Cherry, R. A. & Porter, R. S (2023) Paramedic Care: Principles and Practice Volume 2 (6th Ed) Pearson.

Mistovich, J. J. & Karren, K. J. (2014) Prehospital Emergency Care (11th Ed). Hoboken, New Jersey: Pearson Education

Online Resources:

EpilepsyU