Seizures Signs and Symptoms, Causes, Classifications

Seizures Signs and Symptoms, Causes, Classifications

Definition:

Seizures are characterized by an excessive, hypersynchronous discharge of cortical neuron activity, which can be measured by the electroencephalogram (EEG). In addition, there may be disturbances in consciousness, sensory motor systems, subjective well-being, and objective behavior; seizures are usually brief, with a beginning and an end, and may produce post-seizure impairment.

Signs and symptoms: of generalized seizures may be minor or major.

 Absence seizures: present as alterations of consciousness (absences) lasting 10 to 30 secs.

»Staring and loss or reduction in postural tone are typical. If the seizure takes place during conversation, the individual may break off in midsentence.

»Enuresis and other autonomic components may occur during absence seizures.

Myoclonic seizures: present as involuntary jerking of the facial, limb, or trunk muscles, possibly in a rhythmic manner.

Clonic seizures: are characterized by sustained muscle contractions alternating with relaxation.

 Tonic seizures involve sustained tonic muscle extension.

 Generalized  tonic–clonic seizures cause sudden loss of consciousness.

The individual becomes rigid and falls to the ground. Respirations are interrupted.The legs extend, and the back arches; contraction of the diaphragm may induce grunting.This tonic phase lasts for about 1 min.

 Atonic seizures: are characterized by a sudden loss of postural tone so that the individual falls to the ground. They occur primarily in children.




Cause:

Some seizures arise secondary to other conditions. However, in most cases, the cause of the seizure is unknown.

Primary (idiopathic) seizures have no identifiable cause:

This type of seizure affects about 75% of people with epilepsy.

The onset of primary seizures typically occurs before age 20.

Birth trauma, hereditary factors, and unexplained metabolic disturbances have been proposed as possible causes.

Secondary seizures (symptomatic or acquired seizures) occur secondary to an identifiable cause.

Disorders that may lead to secondary seizures include:

»Intracranial neoplasms

»Infectious diseases, such as meningitis, influenza, toxoplasmosis, mumps, measles, and syphilis

»High fever (in children)

»Head trauma

»Congenital diseases

»Metabolic disorders, such as hypoglycemia and hypocalcemia

»Alcohol or drug withdrawal

»Lipid storage disorders

»Developmental abnormalities

»Age at seizure onset is associated with specific causes.



Classification:

Partial seizures (seizures beginning locally

Simple partial seizures (consciousness not impaired)

»With motor symptoms

»with somatosensory or special sensory symptoms

»with autonomic symptoms

»with behavioral symptoms

 Complex partial seizures (with impairment of consciousness)

»Starting as basic halfway seizures and advancing to debilitation of awareness

»Without automatisms

»With automatisms

»With impairment of consciousness at onset

»With no other features

»With features of simple partial seizures

»With automatisms

Partial seizures (simple or complex), secondarily generalized

Generalized seizures (bilaterally symmetric, without localized onset)

Absence seizures

True absence seizures (petit mal)

Atypical absence seizures

Myoclonic seizures

Clonic seizures

Tonic seizures

Tonic–clonic seizures (grand mal)

Atonic seizures

Unclassified seizures:

Complex partial seizures: are accompanied by impaired consciousness; however, in some cases, the impairment precedes or follows the seizure. These seizures have variable manifestations.

»Purposeless behavior is common.

»The affected person may have a glassy stare, may wander about aimlessly, and may speak unintelligibly.

»Psychomotor (temporal lobe) epilepsy may lead to aggressive behavior (e.g., outbursts of rage or violence).

»Postictal confusion usually persists for 1 to 2 mins after the seizure ends.

»Automatism (e.g., picking at clothes) is common and may follow visual, auditory, or olfactory hallucinations.



Pathophysiology:

Seizures reflect a sudden, abnormal, excessive neuronal discharge in the cerebral cortex. Any abnormal neuronal discharge could precipitate a seizure.

»Normal firing of neurons: which usually originate from the gray matter of one or more cortical or subcortical areas, requires the following elements:

»Voltage-dependent ion channels: are involved in action-potential propagation or burst generation.

»Neurotransmitters: control neuronal fi ring, including excitatory neurotransmitters, acetylcholine, norepinephrine, histamine, corticotropin-releasing factors (CRFs), inhibitory neurotransmitters, _aminobutyric acid (GABA), and dopamine; therefore, normal neuronal.

Gross anatomy of the brain

Image source:Gross anatomy of the brain

Neurotransmitters; and glucose, oxygen, amino acids, and adequate systemic pH.

»People with epilepsy may be genetically predisposed to a lower seizure threshold.

»A diencephalic nerve group that normally suppresses excessive brain discharge may be deafferentated,

hypersensitive, and vulnerable to activation by various stimuli in individuals with epilepsy.

»During seizures, there is an increased use of energy, oxygen, and, consequently, an increased production of carbon dioxide. Because of the limited capacity to increase the blood flow to the brain, the blood supply may be oxygen deficient. The ratio of supply to demand decreases

When the seizure episode is prolonged, leading to increased ischemia and neuronal destruction. Thus, it is crucial to diagnose seizures and treat them as soon as possible.

»Abnormal electrical brain activity occurring during a seizure usually produces characteristic

Changes on the EEG. Each part of the cortical area has its own function, and the clinical presentation of a seizure depends on the site, the degree of irritability of the area, and the intensity of the impulse.

»Seizure activity may include three major phases.

»A prodrome may precede the seizure by hours or days.

»Changes in behavior or mood typically occur during the prodrome.

»This phase may include an aura—a subjective sensation, such as an unusual smell or flashing light.

»The ictal phase is the seizure itself. In some cases, its onset is heralded by a scream or cry.

»The postictal phase takes place immediately after the seizure.

»Extensor plantar reflexes may appear.

»The patient typically exhibits lethargy, confusion, and behavioral changes.



Conclusion:-

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