Understanding Seizures and Their Causes

Seizures

• Seizures are abnormal, uncontrolled electrical discharges from a group of neurons in the cerebral cortex.
• This leads to abrupt and temporary alterations in cerebral activity.
• Seizures are a symptom of underlying central nervous system (CNS) dysfunction.
• Severity and presentation vary depending on the site of the discharge in the brain.

Theories on Causes of Seizures

• Neuron membrane alterations
• Imbalances in ion distribution
• Decreased activity of inhibitory neurons
• Structural changes
• Neurotransmitter imbalances

Seizures in Canada

• Approximately 1 in 100 Canadians have epilepsy.
• First seizures typically occur before age 20.
• Seizures after age 20 are often due to structural changes, trauma, tumors, or stroke.

Broad Categories of Seizures

• Unprovoked seizures: Cause unknown, often associated with epilepsy
• Provoked seizures: Secondary to an underlying cause such as infections (e.g., HIV, bacterial meningitis, and others), head injury, etc.

Focal vs. Generalized Seizures

• Focal seizures involve one hemisphere of the brain. They can be further categorized by whether or not consciousness is impaired during the seizure.
  • Focal seizures without impairment of consciousness: May be localized or widespread within the hemisphere. Characterized by no loss of consciousness or responsiveness and can have motor, sensory, or autonomic symptoms. The initial part of the seizure can be recognized as an aura.
  • Focal seizures with impairment of consciousness: Begin in one hemisphere and rapidly spread to the other, often originating in the temporal lobe. May cause loss of consciousness and awareness as well as hallucinations and illusions. These seizures may also present automatisms (e.g., repetitive movements or behaviors) and confusion, which can last after the seizure has ended (post-ictal state).
• Generalized seizures involve both hemispheres of the brain at onset. These seizures are typically accompanied by unconsciousness and symmetrical motor activity on both sides of the body. There are six broad categories of generalized seizures.

Types of Generalized Seizures

• Absence seizures: Characterized by disturbances in consciousness, but no convulsions. Typically occur only in children. Manifestations include blank stares, being motionless and unresponsive, and often brief loss of contact with the environment.
• Atonic seizures: Characterized by a sudden loss of muscle tone. Manifestations may include jaw slackening, drooping limbs, and falling to the ground.
• Myoclonic seizures: Characterized by brief, involuntary muscle contractions. The contractions can be bilateral or confined to the face, trunk, or extremities. The seizures are often triggered by cerebral stimuli.
• Tonic-clonic seizures: Characterized by a tonic phase (muscle contraction and extension of extremities) followed by a clonic phase (rhythmic bilateral contraction and relaxation of extremities). Unconsciousness often occurs during the tonic phase and continues until the post-ictal phase. They are typically major motor seizures and may have a vague warning sign (focal seizure) beforehand.

Diagnostic Tests for Seizures

• Neurological exam
• Electroencephalogram (EEG)
• Computed tomography (CT) scan or magnetic resonance imaging (MRI)
• Lab tests

Treatment for Seizures

• Protect from injury during a seizure.
• Reduce seizure activity through pharmacological means.
• Medications vary depending of the type of seizure
• Surgery may be an option if medications are not effective.
• Neurostimulators are also used in some cases.

Complication: Status Epilepticus

• Prolonged seizure activity, lasting 30 minutes or more.
• Can lead to respiratory failure and death if not treated immediately through airway maintenance and medications.
• Identification of the underlying cause (e.g., tumors) is essential for appropriate treatment.
• It is a medical emergency.

Prognosis for Seizures

• With medication treatment:
• Seizures may be eliminated in about one-third of individuals.
• Seizure frequency may reduce in a significant portion.
• About sixty percent of patients who remain seizure-free can discontinue antiepileptic medication.
• Sudden unexpected death in epilepsy (SUDEP) is a rare but significant complication with an unknown cause.